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Thread: PowerTap Disc

  1. #126
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    Here's a picture showing the post ride reports available on a Garmin Edge 500 when using a Powertap. These are the only two screens per ride, plus you can view the same for each manual lap.

    As you can see there isn't much information. It doesn't tell you a great deal on the head unit beyond the basics. No Normalized Power, TSS, IF time in power zones etc.

    That doesn't really matter when you're downloading the data but as I had posted a few pictures of the CycleOps Joule 2.0 head units reports previously it's something to compare.

    My CycleOps Joule 2.0 has gone back under warranty now.
    Attached Thumbnails Attached Thumbnails PowerTap Disc-garmin_edge_500_ride_reports.jpg  


  2. #127
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    So what are the recommended Edge 500 settings for maximum accuracy when using a Powertap? I seem to have problems with grade and cadence not displaying accurately, and when I stop/start the timer, the Edge will sometimes perform weirdness, like failing to record anything other than time for a portion of the workout.

    Also, how often should I perform a calibration of the Powertap? I use the calibration function on the Edge before every ride, but I don’t know the ins and outs of things like torque and auto calibrate.

  3. #128
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    Quote Originally Posted by lassiar View Post
    So what are the recommended Edge 500 settings for maximum accuracy when using a Powertap? I seem to have problems with grade and cadence not displaying accurately, and when I stop/start the timer, the Edge will sometimes perform weirdness, like failing to record anything other than time for a portion of the workout.

    Also, how often should I perform a calibration of the Powertap? I use the calibration function on the Edge before every ride, but I don’t know the ins and outs of things like torque and auto calibrate.
    I'm using the 2.80 firmware on my Garmin Edge 500.

    The main issue with the Garmin Edge 500 seems to be problems caused when using the GPS "courses" feature to provide a route that you follow. The general advice seems to be that if you never use "courses" then you're less likely to have any data file corruption.

    With a Powertap hub all the automatic features of the Garmin Edge 500 should be turned off. Here are my settings:

    System Menu
    Auto Power Down - OFF

    Bike Settings Menu:
    Auto Lap - OFF
    Auto Pause - OFF
    Auto Scroll - OFF
    Start Notice - OFF

    Data Recording
    Cadence - NON-ZERO AVG
    Power - ZERO AVG
    Recording Rate - 1 Second (although it doesn't matter with a Powertap because it automatically records at 1 second intervals)

    Under the Named Bike Option -

    Bike Details
    Wheel Size - CUSTOM and use a manual tyre circumference so that the GPS isn't involved. You have to be careful with a Powertap as the rear tyre compresses when you sit on the bike so the tyre circumference will be less than the uncompressed tyre circumference. Whenever you fit different tyres this needs changing. Don't leave it on auto.

    ANT+ Spd/Cad - OFF The speed and cadence both come from the Powertap hub so there's no need for any additional sensors. This setting should be disabled.

    ANT+ Power - YES
    Under the Calibration menu Auto Zero should be TICKED

    Garmin Power Meter Calibrate Screen
    There are two parts to the Powertap calibration menu on the Garmin Edge 500. The naming is slightly misleading as when you click on calibrate it isn't actually calibrating the Powertap. What it's doing is zeroing the torque offset of the head unit. By having Auto Zero ticked it will do this automatically when you stop pedalling during a ride. This is worth enabling as the Powertap hub's torque offset will often move during a ride. By repeatedly zeroing the torque offset to match this it should keep the power readings consistent.

    In order to check whether the calibration of the Powertap hub is accurate you can use the bottom number on the calibrate screen. When you press down on the crank arm this number changes to show how much torque is being measured.

    This Cyclepowermeters.com link explains how to carry out the calibration test. You'll need some weights to hang from the crank arm in order to check the readings.

    http://www.cyclepowermeters.com/powe...check-76-c.asp

    Garmin Edge 500 Display Settings Whilst Riding
    When riding there are three Power options available for the display - Power, Power - 3s Avg and Power - 30s Avg. This is the amount of smoothing on the power numbers. You need some smoothing because the power display is all over the place otherwise if you're viewing the unsmoothed power readings.

    Power - 3s Avg is the one I have shown. It's still a bit jumpy (frequently +/-20 watts each way every time the display updates ) but that's the best option available. It can be a bit annoying when the display can't make up its mind how hard you're going. A 5 second display smoothing is easier to make sense of for pacing.

    Cadence from a Powertap hub is virtual cadence. Without any smoothing on the numbers Powertap virtual cadence won't give you accurate readings. Whenever you see it giving you junk cadence numbers on the screen that's why. If you look at my ride history in post #126 you can see that it shows a maximum cadence of 177rpm, much higher than I actually pedalled at during that ride. All that virtual cadence is good for is looking at average cadence post ride.

    Strange readings from the % grade display onscreen whilst riding is probably going to be a Garmin Edge 500 bug.

    https://forums.garmin.com/showthread.php?t=13404

    It's not a display item that I've had displayed to look at so far. I'll try it tomorrow. When I'm struggling up a hard hill in bottom gear I usually don't want to know steepness. The elevation data recorded by the Garmin Edge 500 barometric altimeter appears roughly correct when downloaded into WKO+ 3.0 though. Compared to the CycleOps Joule 2.0 the amount of altitude gained over the same 1.5 mile climb is within 20ft or so. There's always going to be some variation with barometric altimeters so that's about as close as you'd expect.

    Never pressing the start/stop button is the safest way to ensure that your data will be ok. Press the start/stop button once when you set off and only press it again when you finish the ride so that the timer runs continuously. I did that today and it got rid of any bad data this time. It takes a little effort going through the file in WKO+ afterwards and cutting out the stationary time but it's worth it to avoid any errors.

  4. #129
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    The Garmin Edge 500 has been working fairly well. It's survived several very wet rides and is still working. There haven't been any Powertap dropouts or strangeness either. I've been leaving the timer running and manually editing the data post ride. The % grade display on my head unit seems about right. It lags a little but the displayed gradients are close to what the actual hill steepness is.

    One notable issue with the Garmin Edge 500 is that the rubber flap which covers the mini USB port isn't as tight as it was. Whenever you connect it to the computer the flap is pushed back hard each time by the USB cable. After less than a fortnight the rubber flap is already becoming a loose fit. The USB port itself isn't waterproof so you can't let it get wet as it will break the head unit. I'm going to have to start taping it in position so that the unit is sealed properly. They should have used a waterproof mini USB port like the Joule 2.0 really.

    Garmin Edge 500 GPS Trace
    WKO+ 3.0 doesn't have that many options for looking at GPS data. You can use it to adjust the altitude profile of the ride route or export the GPS trace into Google Earth. You can export either the entire ride or just individual sections. WKO+ 3.0 doesn't have the Garmin Connect option of being able to move your cursor over a particular point of the map to view power output, speed etc at that point. The GPS isn't really something that's a big priority for me but one thing I quite like doing is to look at the GPS trace of where I went in Google Earth and then trying to spot any alternative routes nearby using the satellite view and Googe Streetview. I've found a few nice byways doing that. You can see the lines running cross country on the satellite and then zoom in for a look at where they start and end.

    The actual accuracy of the Garmin Edge 500 GPS trace is quite variable. It takes 30 seconds to a minute for the satellites to lock on at the beginning of a ride. A good tip is to turn the head unit on and leave it somewhere open to the sky before you start riding so that you don't have to wait for it. Riding in the UK the GPS accuracy is usually shown as being between 10-16ft in open areas. Under treecover the displayed GPS accuracy declines to 25ft+. It's ok for looking at where you went on a map but if you spend much time in woods then it doesn't seem that reliable. In woods I wouldn't trust the GPS speed reading to give any sensible information. A speed sensor looks like it's essential.

    You can overlay multiple rides onto a single Google Earth map which gives an idea of how well the GPS works for tracking your position. It's normally quite good but sometimes the trace will go completely wrong with loops in the trace or veering off wildly, even though it's the same route as previous rides. The picture below is an example of how the GPS accuracy varies. This is the data from four seperate rides travelling along the same main road. All four of the blue GPS traces were travelling in the same direction (from right to left and riding on the left hand side of the road.) The yellow line overlaid is the position of where I would have been actually riding each time.

    You can see how the blue GPS traces wobble around under the tree cover but as soon as I get out into the open countryside they become more accurate and follow the path of the road better. That's what it's like most of the time, apart from when it gets confused where the trace will go way off course.

    Pictured below: Garmin Edge 500 GPS trace typical accuracy comparison between riding under treecover and in open countryside along a straight main road.
    Attached Thumbnails Attached Thumbnails PowerTap Disc-garmin_edge_500_gps_trace_accuracy.jpg  


  5. #130
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    Best Power Outputs In WKO+ 3.0
    By default it's quite hard to track your best power outputs in WKO+ 3.0. The dashboard summary shows your best best 1 minute, 5 minute and 20 minute power for each week/ month but that's all. If you want to see any other best power outputs then it means digging through individual files.

    You can easily add a report to the dashboard which shows all your best power outputs though. I used the same periods that Poweragent displays, although you can use any period.

    1. In order to create this open the dashboard in WKO+ 3.0. Click on the Options button at the top right of the screen. Options - Add a Chart to this Page - Performance Management Chart. This adds a new PMC chart to the dashboard.

    2. Click on Options at the top right of the new chart and select Customize this Chart which will bring up a new dialogue box.

    3. On the first General page change the title to "Best Power Outputs" and change the date range to "Custom thru today". I've used 01 Jan 2011 to today so that it shows all of this season.

    4. Click on the Details tab and then delete all the existing items (CTL, ATL and TSB).

    5. Click on "Add" and add the power periods that you want to view. The picture below shows how this appears. Type in the title for the power period (5 seconds, 10 seconds etc), Content is Mean Maximal, Channel is Power, Duration is the period that you want, Units are watts but you could also do w/kg.

    On the right hand side Show Bests is how many points are displayed. If you wanted to see your 10 best 20 minute power outputs for 2011 then you'd enter 10 in this box. Choose a colour, Format - line, Symbol - square, Line Style - thin solid and that's the first one done.

    6. Click "Add" again and repeat the process for each power period that you want to look at. The ones I have are: 5 seconds, 10 seconds, 30 seconds, 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, 60 min, 90 min and 120 min.

    7. Once you've finished click on Apply and the chart will be created. You can drag it around on the dashboard by holding down the left mouse button and dragging it to a new location.

    Double left clicking on the chart on the dashboard makes it full screen so that you can see it better. By moving your mouse cursor over the individual points you can see what your best power outputs were and when they occurred. If you look at my chart below for example you can see that most of my power bests were in June and July 2011. There were hardly any power bests in January and February. When you have a full season of data to look at this chart will help to show where your best form was.

    Pictured below: Adding a Best Power Output chart to the WKO+ 3.0 dashboard
    Attached Thumbnails Attached Thumbnails PowerTap Disc-wko_power_chart_1.jpg  

    PowerTap Disc-wko_power_chart_2.jpg  

    Last edited by WR304; 08-07-2011 at 11:54 AM.

  6. #131
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    In the Garmin blog post about their new pedal based Powermeter there are also some details about new features being added to the Garmin Edge 500 and Edge 800 head units. Apparently they're going to be updated so that they can display normalized power, intensity factor and TSS:

    Garmin Brings Power to the People with Vector

    "Get an ‘Edge’ on the competition: For users already using a Garmin Edge® 800 or Edge 500 cycling computer, adding a Vector power meter will take their training to the next level. Not only will the Edge display total power, left and right leg power, and cadence, it will now also display in real-time the widely adopted power metrics from TrainingPeaks™: Normalized Power (NP ™), Intensity Factor (IF ™) and Training Stress Score (TSS ™). The Edge 800 adds a new interval summary page to enhance the power-based training experience.

    “Vector’s easy-to-own design has the potential to make power-based training more accessible and usable by a broader range of athletes,” said Hunter Allen, founder of Peaks Coaching Group and widely regarded as a leading expert in training with a power meter. “In addition, by integrating the TrainingPeaks metrics of Normalized Power, Intensity Factor and Training Stress Score directly into the Edge head units for real-time display, Garmin continues to demonstrate a strong commitment to advancing power-based cycling tools.”
    Garmin blog

  7. #132
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    Quote Originally Posted by WR304 View Post
    In the Garmin blog post about their new pedal based Powermeter there are also some details about new features being added to the Garmin Edge 500 and Edge 800 head units. Apparently they're going to be updated so that they can display normalized power, intensity factor and TSS:

    Garmin Brings Power to the People with Vector

    "Get an ‘Edge’ on the competition: For users already using a Garmin Edge® 800 or Edge 500 cycling computer, adding a Vector power meter will take their training to the next level. Not only will the Edge display total power, left and right leg power, and cadence, it will now also display in real-time the widely adopted power metrics from TrainingPeaks™: Normalized Power (NP ™), Intensity Factor (IF ™) and Training Stress Score (TSS ™). The Edge 800 adds a new interval summary page to enhance the power-based training experience.

    “Vector’s easy-to-own design has the potential to make power-based training more accessible and usable by a broader range of athletes,” said Hunter Allen, founder of Peaks Coaching Group and widely regarded as a leading expert in training with a power meter. “In addition, by integrating the TrainingPeaks metrics of Normalized Power, Intensity Factor and Training Stress Score directly into the Edge head units for real-time display, Garmin continues to demonstrate a strong commitment to advancing power-based cycling tools.”
    Garmin blog
    i really hope they start making axles for other pedals. i think i would spring for this setup x2 if they made a Crank Brothers pedal spindle....
    My wife's website....
    Allison Mann

  8. #133
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    The Powertap 160mm brake rotor works fine with 2011 Shimano M988 XTR Trail brakes. I'm still using the Hope mounting bracket from my previous Hope Tech X2 brakes and everything lines up properly without needing any tweaks.

    The lever action and feel of the 2011 Shimano M988 XTR Trail brakes is quite different to my previous Hopes. I was actually quite nervous today whenever I had to do any braking. The XTR brakes are genuinely a one finger brake - all it takes is to gently tickle the brake lever and you're stopping rapidly. I was finding them quite grabby today though. That's probably down to new pads with old rotors, plus needing to practice with them more. The Hope Tech X2 brakes in contrast modulated nicely but always needed two fingers on the lever, along with quite a bit of hand pressure for big stops.

    Looking at the braking deceleration from today's ride I wasn't really braking very hard (the maximum deceleration was only -2.39 m/s2 which is gentle) but that was largely because I was being cautious and trying to get a feel for where the brake's bite point was.

    Update: The grabby brakes were down to the pads needing some time to bed in. After another few rides the initial bite when the pads first touch the rotor is feeling much smoother. It also helped spending some time with a tape measure making sure that the reach and lever travel was even between the left and right levers. The left hand lever (rear brake) was out a bit further than the right hand lever (front brake) as a result of my fiddling with the adjustments and not getting them quite the same.

    The brakes are working well now and I've been gradually moving my brake points back towards the corners again. I always like to give it a while to build confidence before pushing too hard but they're feeling good so far. There currently isn't any brake squeal either, even riding in the rain today which is a nice surprise. My previous Hope and Avid disc brakes could always be relied upon for plenty of brake squeal in the rain.


    Pictured below: Shimano M988 XTR Trail brake caliper with Powertap brake rotor.
    Attached Thumbnails Attached Thumbnails PowerTap Disc-powertap_xtr_brake_caliper2.jpg  

    Last edited by WR304; 09-20-2011 at 02:55 PM.

  9. #134
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    Looks like Cycleops is already selling its new version of Powertap Pro for mountain bikes:
    (I can not post any links since I'm new to the forum, but go directly to Cycleops site).

    I'm curious wether someone has had any experience with the new model and would share thoughts about it. Something I would like to know is wether this model enjoys the architectural improvements announced by Cycleops, like the separation of the "electronics" from the hub structure per si, thus allowing for servicing the system without having to send the entire wheel back to them.

    Regards,
    Fernando

  10. #135
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    Quote Originally Posted by laudares View Post
    Looks like Cycleops is already selling its new version of Powertap Pro for mountain bikes:
    (I can not post any links since I'm new to the forum, but go directly to Cycleops site).

    I'm curious wether someone has had any experience with the new model and would share thoughts about it. Something I would like to know is wether this model enjoys the architectural improvements announced by Cycleops, like the separation of the "electronics" from the hub structure per si, thus allowing for servicing the system without having to send the entire wheel back to them.

    Regards,
    Fernando
    The new 2012 mountain bike Powertap hub is the Powertap Pro. There doesn't seem to be an MTB version of the lightweight 2012 Powertap G3 hub. In UK pricing from cyclepowermeters.com the 2012 Powertap Pro disc hub is £825 GBP (plus an extra £39 GBP for the brake rotor), which is £120 GBP less than the previous MTB Powertap disc hub cost.

    http://www.cycleops.com/en/products/...category_id=22

    The 2012 Powertap Pro still uses the old style heavy hub body but according to this Bikeradar.com article the internal electronics within the 2012 Powertap Pro hub have been updated. There would be enough room in the hub for the Powertap G3 electronics module to fit so it might be replaceable also.

    "The PowerTap Pro is meant for those with cost in mind when buying a power meter. While considerably heavier at roughly 425g, it offers the same features that offers a ± 1.5% accuracy and the same style external transmitter, which comes with the same ease of serviceability as the G3 model. All of this, however, is packaged in the larger old style hubshell." Bikeradar.com

    CycleOps New PowerTap G3 And Pro, Head Units And Wheels - BikeRadar

    If you look in the specifications on the Cycleops site it says that the Powertap Pro hub uses 1 x CR2032 battery, rather than the 2 x 357 batteries that the older Powertap hubs use so it must be slightly different internally. CR2032 batteries are what the Powertap G3 hub uses too. The Powertap G3 electronics module would fit easily into the space beneath the cover of the Powertap Pro hub. It's mostly empty space under there in the old style Powertap hub. You can see the battery and electronics of the G3 hub in these DC Rainmaker pictures. :

    DC Rainmaker: First look at the new CycleOps Joule and Joule GPS, PowerTap hubs, PowerCal, and VR software


    Pictured below: 2012 Powertap Pro MTB disc hub

    Powertap G3 electronics module
    Attached Thumbnails Attached Thumbnails PowerTap Disc-2012_powertap_pro_disc_hub.jpg  

    PowerTap Disc-powertap_g3_electronics2.jpg  

    Last edited by WR304; 10-05-2011 at 04:12 PM.

  11. #136
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    CycleOps have finally released a new firmware update for the CycleOps Joule 2.0 head unit. Apparently it adds a new screen but could be a little problematic updating to the new firmware.

    Weight Weenies • View topic - joule new firmware 14.072 update

    My suggestion for trying to do the update via the Poweragent software updater would be to make sure you have the head unit connected to a Windows XP pc first. If you try and do the update connected to a Windows 7 64 bit PC the intermittent connection issue is sure to make the firmware update fail.

    My CycleOps Joule 2.0 that filled with water was replaced under warranty but I haven't used the new one. It's sitting in a box as the Garmin Edge 500 has been ok.

    Something to remember with the Garmin Edge 500 is to regularly clear out the contents of the "activities" folder from time to time (every week or so). If you have too many ride files in there it really slows down the time it takes to load ride histories.

  12. #137
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    Last edited by WR304; 10-31-2011 at 04:18 PM.

  13. #138
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    Coffee King (CK) pointed out that wheelbuilder.com now have a Powertap 142x12mm axle conversion kit available. The conversion kit allows you to use your existing Powertap hub with newer bikes such as the Specialized Epic and Trek Superfly 100 which have 142x12mm thru axle rear dropouts.

    Once converted the Powertap hub can also still be used with standard 135mm QR rear dropouts by simply swapping the end caps.

    Wheelbuilder PowerTap MTB 142mm x 12mm Axle Conversion

    There isn't any mention of warranty on the product page so it would be worth checking what implications this has before ordering. I'd guess that swapping the axle will probably void any existing warranty on your Powertap hub.

    Pictured below: Wheelbuilder.com 142x12mm axle Powertap hub conversion kit
    Attached Thumbnails Attached Thumbnails PowerTap Disc-wheelbuilder_powertap_142x12_conversion.jpg  


  14. #139
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    My Wheelbuilder.com 142x12mm Powertap conversion axle arrived a while ago but I hadn't got round to doing it until now. My new bike is getting close to being ready so I decided it was worth swapping the axles over.

    Bearings
    The first thing to note is bearing sizes. The Powertap MTB disc hub original bearings are:

    Non Drive Side bearing: 6802 2RS 15 x 24 x 5 mm
    Original Drive Side and freehub bearing: 6902 2RS 15 x 28 x 7 mm (three bearings, one in the hub and two in the freehub)

    The conversion axle comes with an Enduro 17 x 28 x 7 mm bearing included. It also comes with 2x 142mm end caps and a single 135mm non drive side end cap (you re-use the original 135mm drive side end cap). I used SKF bearings as replacements for the other bearings.

    Replacing the bearings in the Powertap hub is quite straightforward. Tap out the old cartridge bearings and press new ones in. For the 17mm inside diameter drive side bearing we used a headset press to make sure it went in square. Everything went well initially - speed readings, torque offset etc were all fine on the hub after replacing the bearings. The wheel bearings and freehub span freely when not fitted in a frame.

    Axle Left-Right Free Play
    It was only when the wheel was mounted into the frame and the skewer tightened down that it became clear there was an issue. As the wheel skewer was tightened the freehub was binding, so that the wheel became a fixed wheel. It became apparent that there was roughly 0.6mm of left-right free play in the axle after the hub bearings had been pressed in. Not good.

    After taking it apart, checking the axle width measurements and that the bearings were pressed in properly it's not clear where this 0.6mm of play is coming from. The conversion axle width length and assembly appear to be correct. Both the bearings were pressed fully home. I'm wondering if possibly the Powertap hub had left - right play with the original axle too (I don't remember any but didn't check before pulling it apart). You wouldn't notice with the original axle as the endcaps and skewer clamp everything down so that the freehub is held in place against the drive side bearing.

    Freehub and Axle Design
    The big difference between the original axle and conversion axle is the drive side design where the freehub body sits. On the original 15mm Powertap axle the drive side bearing slides onto the axle and then a sleeve goes inside the freehub body. The end of the sleeve presses against the drive side bearing and acts as a spacer, so that the freehub body is always kept roughly 0.5mm from the drive side bearing. The drive side bearing is pressed into the hub so the freehub body is unable to move inwards towards the bearing, even if there was play in the hub axle.

    The conversion axle is different. It uses a 17mm inside diameter bearing slid onto the axle and then the freehub sleeve is machined into the axle as a step. This means that the drive side bearing and freehub body will still have a 0.5mm gap between them (when the drive side bearing is pressed against the axle shoulder and the freehub body is put in place). This gap is empty space however (rather than the 0.5mm of solid metal sleeve that holds the freehub body and drive side bearing apart with the standard axle). So long as there is no axle play the machined step holds the freehub in its correct position.

    Because there's 0.6mm of free play in the axle as you tighten the wheel skewer it pushes the hub axle across towards the non drive side however. Once that happens the machined step that should hold the freehub body in place is out of position and the freehub body is free to move inwards, resulting in it binding on the hub.

    With the original axle design this problem wouldn't occur. The reason that it's been done I think is because the axle has to be much thinner in order to take a 12mm skewer through it. With a 12mm inside diameter and 15mm outside diameter the axle would be weaker than the thicker original Powertap axle so the additional material reinforces the axle, making it less likely to snap.

    My hub isn't sorted yet. This conversion might have been smoother starting with a brand new hub. The bearing shoulder to shoulder measurements of the two axles are identical so I'm wondering if the problem is with the hub itself. Powertap hubs are made of seperate parts so maybe something had stretched or slipped over time? My 2010 Powertap hub had done 10,343 miles/ hours 698 hours from new, although the original bearings were all still smooth and in good condition. The plan now is to try putting a 0.6mm spacer on the inside between the axle shoulder and non drive side bearing as a way of removing the axle play. I'm hoping that will sort it.

    Pictured below: Powertap internal parts and widths compared to Wheelbuilder conversion axle
    Attached Thumbnails Attached Thumbnails PowerTap Disc-powertap_wheelbuilder1.jpg  

    PowerTap Disc-powertap_wheelbuilder2.jpg  

    Last edited by WR304; 01-22-2012 at 04:04 PM.

  15. #140
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    Rotor options

    What are the rotor options? Do you have to use their branded rotor with the correct # of holes, or are there other options?

  16. #141
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    Quote Originally Posted by jared_j View Post
    What are the rotor options? Do you have to use their branded rotor with the correct # of holes, or are there other options?
    You have to use their two-piece rotor. It has a different number of holes, larger center bore and the aluminum carrier is not in plane with the rotor.

    Morgan

  17. #142
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    Quote Originally Posted by WR304 View Post
    After taking it apart, checking the axle width measurements and that the bearings were pressed in properly it's not clear where this 0.6mm of play is coming from. The conversion axle width length and assembly appear to be correct. Both the bearings were pressed fully home. I'm wondering if possibly the Powertap hub had left - right play with the original axle too (I don't remember any but didn't check before pulling it apart).
    Here's a picture confirming that the problem is with my Powertap hub, rather than the conversion axle or bearings. The hub width (inside of bearing to inside of bearing) is 52.69mm. Both axles are 52.07mm wide (shoulder to shoulder), explaining why there was play. I think it's very likely that the original Powertap axle must have had some left - right play in also.

    Looking at the conversion axle I think that the way to fix the issue would be to put a 0.6mm spacer between the non drive side axle shoulder and bearing, making the axle width match the hub width. In order to make sure that it isn't possible for the axle to move I think a spacer is needed inside the non drive side endcap of the hub too. This takes up all the free space inside the non drive side endcap that the axle is currently able to move into. Essentially making the axle longer.

    The additional spacer in the endcap would neutralise any left - right axle play once the entire hub is tightened down. The non drive side endcap presses against the bearing so the axle would be unable to move out of position once the wheel skewer has been tightened. The changed design of the conversion axle means that it's crucial for the axle to stay in exactly the right place. The original Powertap design is much more forgiving of any differences.

    Pictured below: My Powertap hub width 52.69mm (inside of bearing to inside of bearing) doesn't match the width of the axle 52.07mm (shoulder to shoulder), resulting in the 0.6mm of left -right play which is causing the freehub to bind once the skewer is tightened.

    The design of the conversion axle means that there's a gap between the non drive side axle and endcap. If there's any play in the axle (as with my hub and its 0.6mm of left-right play) this gap allows the axle to move into the endcap and out of position.
    Attached Thumbnails Attached Thumbnails PowerTap Disc-powertap_hub_width_axle_difference.jpg  

    PowerTap Disc-powertap_bearing_axle2.jpg  

    Last edited by WR304; 01-24-2012 at 03:42 PM.

  18. #143
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    It's been a few weeks but I finally have my 142x12mm thru axle Powertap hub working.

    It spent a few weeks at my mate's factory waiting for the new 0.6mm spacer washer to remove the play. That spacer was made and installed last week to correct the bearing width problem. Everything seemed good with free spinning bearings and no binding from the freehub, except that the torque tube zero offset was reading 369 when I checked it. Anything beyond a zero offset of 512 +/-5 means the hub has an issue.

    Because I've been using a Garmin Edge 500 head unit and my 2010 Powertap SL+ MTB disc hub had an older firmware version (meaning that it only displays the Powertap hub's ANT+ ID, rather than the hub's torque zero offset) I hadn't checked the zero offset since last summer when my Joule 2.0 broke. There's a chance my 16 month old hub may have had an issue which I wasn't aware of, even before I started pressing new bearings into it.

    Powertap Service
    Fortunately, the Powertap UK service centre is just down the road so I took it there to be fixed. It was quite interesting to see how they did it. The Powertap hub is in two parts. You have the hollow shell and hub flanges, but then literally everything inside the hub is part of a single unit which unscrews. Broken torque tube unscrewed - in the bin - new torque tube fitted.

    For pressing the 142x12mm axle conversion bearings in and out of the torque tube they used a vertical press. A combination of supporting spacers underneath the torque tube and a flat spacer against the bearing made sure it went in square. With all the correct tools it was done easily.

    For assembly they recommended using a layer of Contralube 770 Connector Lubricant on all the internal electronics of the hub, especially on the connection where you plug the battery pack into the hub. I've always put waterproof grease around the seals but not on the connector itself. After riding in very wet conditions or with a lot of condensation they recommended taking the hub's black plastic cover off to let it all dry.

    Contralube 770 Connector Lubricant : Lubricants & Butane Gas : Maplin Electronics

    Once the hub had been assembled it was then calibrated accurately and adjusted using a custom wheel jig which had a weight hung from a metal bar integrated into the jig. The new torque tube began with a zero offset of 500 and after calibration was adjusted to the correct 512.

    I'm very grateful to them for sorting out the hub out whilst I was there. I'd been expecting to have to leave it. My Powertap hub is now at the wheelbuilder being built into a 29" rim to go on my new bike.

    Pictured below: Contralube 770 connector lube for the Powertap internal electrical connections
    Attached Thumbnails Attached Thumbnails PowerTap Disc-contralube-770.jpg  


  19. #144
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    My 2012 Specialized Epic 29er is finally up and running. The Powertap hub with its 142x12mm conversion axle seems to be working fine so far. Just like any other Powertap hub but with the correct spacing for the frame.

    I had it built into the original Roval Control 29 rear rim that came with the bike for now.

    The picture below shows the updated calibration screen on my Garmin Edge 500. The 2010 hub internals were an older firmware version and the Garmin Edge 500 only displayed the hub's ANT+ ID before. With the new hub internals the Garmin Edge 500 shows the zero offset of the hub in the calibration screen. Much more useful. A value of 512 is the normal calibration you'd expect if your Powertap hub is working properly.

    Pictured below: Garmin Edge 500 Powertap calibration screen. Powertap hub installed in 142x12mm 2012 Specialized Epic 29er frame
    Attached Thumbnails Attached Thumbnails PowerTap Disc-powertap_calibration.jpg  

    PowerTap Disc-2012_epic_new3.jpg  

    PowerTap Disc-2012_epic_new4.jpg  


  20. #145
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    The converted 142x12mm Powertap hub has been working well. No problems at all with it so far. The data from it seems comparable to all my previous data.

    It's quite interesting doing a direct comparison to see how my new 2012 Specialized Epic 29er compares with my previous 26" 2010 Specialized Epic. I swapped nearly all the parts over so that apart from the frame, fork and the bigger wheels they're the same bike.

    My mountain bike is my only bike nowadays so it gets used for road rides as well as offroad. One issue that I discovered today is that the longer wheelbase of the Epic 29er makes it harder to draft a roadbike closely when riding in a paceline. I was out for a ride by myself when some guys from the road club caught me up. They'd been out on the clubrun and were heading home. It was into the wind so we were riding through and off in a paceline.

    One thing stood out immediately. When riding with other riders you automatically fall back into the patterns that you've learnt over all the years of road racing and riding. That means staying tight to the rider in front for the maximum slipstream effect. Only with the Epic 29er the front wheel sticks out so far you can't get that close to the bike ahead. My front wheel was almost touching the rear wheel of the rider in front but he was still a long way away. This was also repeated in the other direction. I could see that when a rider was behind he was tending to overlap wheels in order to try and get closer.

    The graph below is an 18 minute extract from the ride showing riding in a paceline on the road. The highlighted areas show where I was working hard on the front, and then recovering in the slipstream of another rider. You can see how I'm putting in a big effort to maintain the speed, but only for 20-60 seconds each time before the next rider rotates through so I get a rest.

    Aerodynamic issues are more exaggerated using a mountain bike. You can't miss how much less effort it takes for a road or time trial bike to travel at the same speed. I was lucky on Sunday that it was into the wind and only about 21mph average speed. When the speeds get up to near 30mph you have so much aerodynamic drag on the mountain bike that trying to come through for a turn on the front is almost a waste of time. It's ok following wheels but as soon as you pull out from the rider in front at 30mph it's like hitting a wall. If you look at the graph of yesterday's ride you can see that where the blue speed trace was highest at 30mph I made sure I was sitting in. I only came through once we were going up the slope and the speed had dropped. Something I've learnt from getting dropped repeatedly in the past.

    If you look at the end of each work section you can see that the rotation was generally fairly smooth without too many big speed or power jumps. There aren't too many big spikes at the end of each work section. What you can get sometimes if a rider goes through too hard at the beginning of a turn is that they open up a gap and the rider who's been on the front has to sprint to try and get onto the wheel. That shows up in the power graph as a big spike at the end of each turn. It's either a sign of bad technique by the rider going through, or a sign that you're tiring. If you're trying to work with other riders it's better to go through just slightly faster than the lead rider, hold your line so that you don't chop their front wheel and allow them to ease across into your slipstream.

    Pictured below: Riding in a road paceline.
    Attached Thumbnails Attached Thumbnails PowerTap Disc-power_output_paceline.jpg  

    Last edited by WR304; 03-19-2012 at 12:45 PM.

  21. #146
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    Quote Originally Posted by WR304 View Post
    With the new hub internals the Garmin Edge 500 shows the zero offset of the hub in the calibration screen. Much more useful. A value of 512 is the normal calibration you'd expect if your Powertap hub is working properly.
    I have the old disc hub (I've been riding it for a few years) and I just updated my hub with the ANT+ updater so it would work with my Garmin 500 and on the same screen you show I have "Current Calibration -9031" which isn't even close to 512. I don't think this is my hub ID, it shows a different number for that something around 52000 I think.

    Should I be worried about my torque tube?

  22. #147
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    So I've been sitting at home thinking about my -9031 number, hoping that it's not supposed to be saying 512 since that seems like a big difference...

    I went and hung a 20lb weight from my pedal with the crank parallel to the ground and the chain in 22f 34 rear and on the calibration screen on the edge 500 for torque it said 25.62. If I calculate what it should say using this:


    torque = M g L Nr / Nf,

    where M g = weight of bucket with water, L = crank length, Nf = teeth on front ring, and Nr = teeth on rear ring.

    I get 213lb in which is within about 6% what the powertap is showing. This is fine as I was going for a ballpark number anyway. My measurements were pretty sloppy, it was a 20lb kettle bell still in it's packaging which my park tool fish scale said weighed 19lb 12oz and my bathroom scale said was 20.0lb, additionally I didn't use a level on the crank arm (small angle approximation and all...meh)
    Last edited by litany; 04-19-2012 at 12:00 AM.

  23. #148
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    Quote Originally Posted by litany View Post
    I have the old disc hub (I've been riding it for a few years) and I just updated my hub with the ANT+ updater so it would work with my Garmin 500 and on the same screen you show I have "Current Calibration -9031" which isn't even close to 512. I don't think this is my hub ID, it shows a different number for that something around 52000 I think.

    Should I be worried about my torque tube?
    What was your torque offset before you updated the hub to ANT+?

    Because you have an older hub the Garmin Edge 500 probably isn't going to display anything useful in the calibration field. It needs a Powertap hub with one of the latest firmware versions for the Garmin Edge 500 to be able to show the Powertap hub's torque offset.

    Do you know anyone with an ANT+ Cycleops head unit? (either a LYC or Joule). If you can pair that with your hub then the Cycleops head unit should show what your hub's torque offset is.

  24. #149
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    Quote Originally Posted by WR304 View Post
    What was your torque offset before you updated the hub to ANT+?

    Because you have an older hub the Garmin Edge 500 probably isn't going to display anything useful in the calibration field. It needs a Powertap hub with one of the latest firmware versions for the Garmin Edge 500 to be able to show the Powertap hub's torque offset.

    Do you know anyone with an ANT+ Cycleops head unit? (either a LYC or Joule). If you can pair that with your hub then the Cycleops head unit should show what your hub's torque offset is.
    I didn't check before converting it to ANT+, I didn't know how or even think to do it. Since I dont have anything but Garmins I ended up following these instructions I got from Saris for using my yellow CPU to get the zero offset.

    Here are the steps to get the calibration reading on your Wireless PowerTap w/ yellow CPU:



    1. Ensure you have transmission by spinning the wheel. The transmission icon on the top left of the CPU should be present. If you cannot get transmission, re-learn the hub ID, check the batteries of hub and CPU, and battery holder in the hub.

    2. Once you have transmission, press and hold MODE and SELECT until you enter the Setup screen. This screen will display after "clr".

    3. Using the SELECT button, navigate to the "t" on the middle line, then press MODE

    4. Press MODE three more times so you arrive at the 3rd test screen

    a. Top Line = The Offset (difference between Middle and Bottom lines)

    i. Ideally this is “0”. If it is not “0”, push and hold SELECT until it becomes “0”

    ii. If this does not go to “0” you may need a new wireless CPU

    b. Middle Line = Raw Torque Value

    i. 500 – 524 is the acceptable range, meaning your hub is reading with +/- 1.5% accuracy

    ii. If it’s anything outside this range, you may need us send your hub/wheel for repair

    1. We will need to issue you a Return Authorization # before you can send it in

    c. Bottom Line = Calibration of CPU

    i. 500 – 524 is acceptable range (same as middle line)

    My values were

    Top: 0
    Middle: 492
    Bottom: 492

    Waiting to see what Saris has to make of these numbers.

  25. #150
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    492 is a bit low. One thing to try would be changing the batteries again as that can affect the torque offset. Saris can manually recalibrate the hub which might be enough to sort it out.

    If the hub is a few years old there might be a problem though. If you look at the picture in Post #106 that's the torque tube part of the Powertap hub. It's a one piece unit without much that can be easily replaced. If there is something wrong with the torque tube then they might recommend a new torque tube. If they decide to do that then the best bet is to ask for all the hub internals to be replaced at the same time in order to eliminate any other possible issues.

    I think that my Powertap hub might be drifting out of calibration. It started off at 512 at the end of February 2012, it was up to 518 a few weeks ago and reads 523 today. The problem with that is it raises the question of whether the power values the hub is reporting are accurate. Have I really been setting personal power bests for the last few months or not?

    Today was my best 20 minute FTP test result ever, including 10 min 40 seconds at an indicated 285 watts average power for the climb section of the route. I equalled my best FTP test time up the hill from last year (10 min 41 seconds average power 267 watts 15 June 2011). Considering that the June 2011 time was set using slick tyres and I was using knobbly tyres today it is possible that I was putting out more power today.

    On the climb today I saw a red top in front a few bends ahead, thinking it was a bike I dug in to try and catch them, only to realise it was a runner! I was going flat out and it took some doing to catch them. I was doing 7mph and they were only 1-2 mph or so slower than that. I passed them before the top, just. It was the final minutes of the FTP test and I was puffing like a steam train by that stage.

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