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Power2Max MTB Power Meter

55K views 229 replies 28 participants last post by  WR304 
#1 ·
As my Powertap hub has died I've been trying to consider what may be a good replacement. The Power2Max MTB power meter looks like a possibility. One nice thing about it is that it uses an accelerometer for cadence so you don't need a cadence magnet attached to the frame for it to work.



https://www.power2max.de/europe/en/Produkt/power-meters-en/rotor-3d-mtb/

DCRainmaker review of road version:

https://www.dcrainmaker.com/2013/01/power2max-power-meter-in-depth-review.html

Has anyone tried one and how does it hold up in bad weather? Riding in the UK getting soaked is unavoidable.

For my bike I'd probably go for a Rotor 3D crank (alloy rather than carbon crank arms so can be welded and modified) in a triple chainset version with a 169mm q factor, allowing me to keep my current setup of 44/33/23 front chainrings.

I have to use a modified left hand crank as I'm unable to use a normal length crank due to my knee not bending. I also use Rotor Q ring oval chainrings. Would a modified crank and oval rings result in inaccurate power readings?

This picture shows my current modified crank, which is used with a Shimano Deore XT chainset. I'd have to get a new one made to match the Rotor cranks. It has a 75mm crank length and a 50mm swing crank. The right hand crank is a standard 175mm crank with no alterations.

Swing crank explanation:
https://www.highpath.net/highpath/cycles/swingcrank.html

The swing crank allows you to pedal without bending your knee as much as normal.





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#55 ·
I did three hours on the bike today and there were no power spikes. It seems to be a rare occurrence if you manage a particular action. I think it's something like freewheeling, starting pedalling and stopping pedalling again, or a fast downwards movement of the crank with very little load on possibly.

I have a Chris King PF30 ceramic bottom bracket fitted but because I'm using a Shimano Hollowtech II crank with a 24mm diameter spindle (instead of a PF30 crank with 30mm diameter spindle) I have to have the 24mm plastic reducers installed. The Shimano crank uses a plastic preload bolt which I didn't feel was up to the job of holding the adjustment. The plastic bottom bracket reducers would keep developing free play that you could feel as the crank slopping around. I'd have to repeatedly adjust it every few weeks which was really annoying.

At the same time as the new crank my friend had a new preload bolt made. Instead of being plastic this one is made from aluminium and uses a 10mm allen key to adjust the preload. This is similar to the metal preload bolts that you get with other manufacturers cranks (Rotor, SRAM etc) and should be up to keeping the bottom bracket in adjustment.



It's not power meter related but I've got a new SRAM X0 Type 2 rear derailleur on now as well. The drivetrain is so much quieter over the bumps with a clutched rear derailleur.:)
 
#56 ·
The aluminium preload bolt worked better than the original plastic one but I was still unhappy with the bottom bracket reducers in the Chris King PF30 bottom bracket. It was staying in adjustment but water getting in the gap between the plastic reducer and steel bottom bracket axle was causing the axle to rust badly.

As part of the refresh to fix the most pressing issues with my bike (new suspension pivot bearings, fork and brain rear shock service, new headset) I replaced the Chris King bottom bracket with a Praxis conversion bottom bracket. This eliminates the need for plastic reducers when using a 24mm diameter Shimano crank in a PF30 frame.

https://praxiscycles.com/conversion-bb/



My bike with the Power2Max custom crank mark two fitted. My winter shoes have been rubbing on the crank, taking some off the black paint off the crank arm.



Riding today the new Praxis bottom bracket seemed ok. The real test is seeing how well it lasts over the winter. My previous Chris King PF30 bottom bracket did 883 hours/ 12,851 miles and the bearings in that were still just about acceptable.
 
#57 ·
I didn't have the Power2Max power meter last winter so it's only really now that I've been doing any riding in the cold with it.

One of its main features is temperature compensation. Whenever you stop pedalling and freewheel the power meter automatically re-calibrates itself to take account of changes in temperature, so that in theory the power readings will stay consistent throughout a ride, even when there are large swings in temperature.

I've been reading this thread on the subject with interest:

BikeRadar.com ? View topic - Power Meter Temperature Drift, Or Sharp Decline In Fitness?

I got home early enough to fit in a quick ride this afternoon before it got dark. As it was a Friday I didn't feel like navigating the town traffic so went straight up a climb into the hills. Because I was in a hurry the bike went immediately from being indoors (around 14c/ 58f room temperature) to out and riding. In the valley it was around 9c/48f but it was much colder on top of the hills (around 5c/41f).

As I was riding uphill I rode for around 12 minutes with no freewheeling whilst the temperature dropped significantly at the same time.



When I got to the top of the hill there is a false flat. I was still trying but the power meter was saying that I was only doing 136 watts! That was clearly wrong as I wasn't going that gently. When the display stayed at that level I decided it was time to try freewheeling. I then freewheeled for a few seconds to try and re-calibrate the power meter (long enough to let the head unit power display go to zero) and sure enough when I started pedalling again the power meter was showing 159 watts, rather than 136 watts, for the same perceived effort. That's quite a big difference.

Here's a zoomed section of the graph showing my power output at the top of the hill after 12 minutes of pedalling, freewheeling to re-calibrate, and then the higher power output afterwards:



The main thing to remember I think is that the Power2Max needs you to deliberately freewheel from time to time, especially near the start of a winter ride, otherwise the automatic temperature calibration won't happen and your power numbers will start drifting significantly as a result.:)
 
#58 ·
I had a clear strategy for today's ride. This time I would try and freewheel every 5 minutes or so at the beginning of the ride, in order to allow the Power2Max to re-calibrate and adjust to the changes in temperature. It was a different route, with some flat before the first climb of the day, so do-able.

I waited until 11.45am to find the warmest part of the day when the roads would hopefully be a bit less icy (it was 50/50 whether to just do some turbo training and not risk it). First thing it had been a hard white frost and frozen but it was beginning to thaw and up to 4c /39f by the time I set off. Even so, as I turned out of the drive onto the main A road, which was in the shade, headed towards the traffic lights and then started braking lightly the back wheel locked up immediately.:eek: Point taken. It was slippery as anything so I stuck to the main roads.

This graph shows the first 30 minutes of the ride. The drops to 0 watts of the yellow power trace show where I was freewheeling, for several seconds each time to allow the Power2Max to re-calibrate. Around every 5 minutes seemed about right. On the 9 minute climb I freewheeled at the bottom but then rode up it without any freewheeling, the longest period of pedalling. The power looks ok to begin with but the final few minutes of the climb (after 9 minutes of pedalling continuously) are maybe lower than I would expect. Apart from that one section I was freewheeling roughly every five minutes and there was nothing obviously wrong with the power readings that I was seeing in between.:)



Some temperature notes: I leave my Garmin Edge 500 head unit stood outside for 20 minutes or so before setting off. This allows the temperature, barometer and satellite lock to sort itself out fully before I begin riding. This is why the temperature begins at 4c (rather than the much higher room temperature).

I keep the bike inside before setting off however. Leaving the bike outside would be better for the Power2Max calibration (as it would begin at outdoor temperature and not have to adjust itself so much) but I feel it's a little nicer on cold days to have the bike contact points (saddle and grips) start off warmer, rather than freezing cold.:)
 
#59 ·
I had a 2900 watt power spike today. I'd been riding along the canal towpath and stopped to open a five bar gate. The bike was leaned up and pushed around for close to two minutes as it was a stiff latch. When I set off the very first pedal stroke registered as a big power spike before it re-calibrated as I freewheeled.

All I can think of is that moving the bike around or leaning it up whilst doing the gate might have affected the calibration somehow. It was the only spike in the 3 hour 49 minute hour ride, no other anomalies in the file before or after.



These occurrences are very rare which is why when they do happen I've been posting them here. The rest of the time the power meter has been trouble free, impressively surviving being used throughout the UK winter with no drama.:)
 
#61 ·
Which chainrings are you going with?

My Power2Max is the older classic version. The newer Power2Max Type S power meter has a 110/60mm BCD spider for the double chainring version and a 104mm BCD spider for the single chainring version. There are lots of 104mm BCD narrow - wide rings available but the 110/60mm BCD of the Power2Max Type S double chainring spider is intended for Rotor chainrings, either the no-q round rings or oval q-rings.

110/60mm BCD chainring sizes currently available in the Rotor rings that will fit the Power2Max Type S double crank spider:

No-Q Rings (Standard Round Chainrings)
Outer Ring 42T, 40T, 39T, 38T, 36T
Inner Ring 26T, 24T, 22T

https://www.velotechservices.co.uk/shop/Vprod4.asp?cat=31

Q-Rings (Oval Chainrings)
Outer ring 40T, 38T, 36T
Inner Ring 27T, 26T, 25T, 22T

https://www.velotechservices.co.uk/shop/Vprod4.asp?cat=67

For making sense of offroad power data I feel it's worth having a seperate speed sensor on the bike. This gives you a more reliable speed trace than relying on GPS, so that if you wish to you can zoom right in and look at your power on a particular section in detail, using the speed trace as an anchor to identify exactly where you were on technical stop start sections and obstacles (accelerating out of a switchback, riding over roots etc). Without a decent speed trace this is far harder to do.

There was an interesting picture of Alban Lakata's bike from the 2015 Cape Epic. He has an SRM power meter and in the background of the shot you can see his ANT+ speed sensor mounted on the rear wheel also:



https://www.bikeradar.com/mtb/gear/article/pro-bike-alban-lakatas-canyon-lux-cf-43865/
 
#62 ·
Man WR304 I have nothing to add to this discussion but I just wanna say thank you, you post are always so detailed and well though that are a pleasure to read. You have contributed so much to this forums that they should give you a trophy.

I don't write here much but I always visit the forums and try to read your post, I've gained so much insight from your post in my short career MTBing that I really feel in debt to people like you.

Again thanks a lot.
 
#63 ·
I went with Rotor round chainrings, in 38/24. It's a little annoying to get locked into Rotor chainrings due to the unusual BCD, since they're about 50% more expensive than comparable SRAM/Shimano stuff. I guess it's a drop in the bucket though relative to the cost of the whole setup .

I agree with you completely on not relying on GPS for speed/distance data. I run a Garmin magnetless speed sensor.
 
#64 ·
Power2Max do seem to like non standard chainring bolt layouts for their MTB spiders. I had to order a custom middle chainring from Fetha in Australia to fit on my Power2Max Classic due to its rotated layout. That chainring is still going strong and working well. The teeth are getting hooked but should last a few months yet.

I got a low battery warning for the power meter whilst riding today. The battery warning appears as an alert filling the Garmin Edge 500 head unit screen and you have to press the Enter button to cancel it so it's hard to miss. Since last replacing the Renata CR2450N battery in late October 2014 I'd done 294 hours riding, a little less than with the first battery. Riding in the cold reduces battery life so it was probably to be expected.

I took the crank off the bike and replaced the battery seated at a table so that there was no danger of losing the three small screws for the battery compartment (last time I dropped one of the screws and it took lots of searching on the floor to find it again! ). It all looked very clean and dry inside and went back together with no drama.:)
 
#65 ·
I realised that I haven't actually posted much offroad power data recorded with my Power2Max in this thread.

Here are a few extracts from today's ride. The full ride was 37 miles with around 24 miles of that being offroad on a mixture of surfaces and terrain, some open grassland, some rutted tracks used by motocross bikes, some farm tracks and some byway (dirt road). I'd made a few changes to the bike's suspension settings and had my act together for once. I rode everything cleanly apart from about 10 metres of muddy ruts.

Common - Grass Surface



This graph shows a section of the ride where I was riding over the common. This is open grass land interspersed with a few humps, natural worn paths and small dropoffs to ride off for fun.

The main thing that the power meter shows here is that riding on grass is hard work. The increased rolling resistance meant that as soon as I turned off from the tarmac road my speed dropped and I was having to put out 200 watts just to ride at a steady 10mph on the flat. Where there was a small rise to get up onto a rocky path you can see how I put in a short burst at 300 watts, lasting just a few seconds. As soon as I was on the path, which has lower rolling resistance than the grass that I had been riding on, my power drops but my speed increases straight away. What you can use this type of information for is to decide your lines. If you have a choice between riding on grass or a firmer surface (hardpacked dirt, gravel etc) trying to stay off the grass is likely to see you travelling faster for the same or less effort.

Short Steep Hill - Deep Gravel



This graph shows a section of the ride where I was riding up a short steep rise, the steepest part being 20% gradient. This took me 47 seconds at an average power of 290 watts.

Along with being steep I was climbing on a deep loose gravel surface so traction was a real concern. For this climb I was seated right on the nose of the saddle in bottom gear. On the steepest 20% gradient section I was doing 394 watts at an average speed of 5.4mph. If you look at the blue speed trace you can see how on this steep section my speed was dropping. If this had been much longer I would have been in trouble!

Fortunately the gradient eased so I got a quick rest, my power dropping to 225 watts, before the final push to the gate at the top. Although this final part was only 12% gradient it also had the loosest deepest gravel so I was back up to 302 watts.

On this graph I have the green cadence trace displayed. The cadence gives an insight into my technique when trying to get up this steep hill whilst also maintaining traction on a loose surface. To avoid breaking the wheel free with big torque spikes (from too much downstroke pressure by my stronger right leg) in the gravel I was revving at a high cadence, over 100rpm on the steep sections. I'd guess that if you could see my pedal force through the entire stroke that would see a smoother application of torque than if I was pedalling at a lower cadence.

Byway (Dirt Road)



This graph shows me riding along a 10 minute section of byway (dirt road). This road surface consists of hard packed gravel / mud. If you compare my power output to riding on grass there's a big difference. Here on hard pack I'm averaging 13.6mph at just 137 watts average power. On the grass in the same ride it took a much higher power output of 200 watts to average just 10 mph.

You'll often see generalised comments about how riding offroad power output is always very bursty with big swings in power output and cadence. This really depends on terrain however. Where you live and the trails you ride makes a big difference to what your power files will look like.

If you're riding here in the Cotswolds a lot of the offroad riding is on farm tracks and bridleway. It can be muddy, bumpy and rutted but in terms of the effort and power output required this type of terrain is mostly about constant efforts. The bike's full suspension may be getting a hammering but when you see the power output on a graph it's steady. Decent fitness is a big factor.

In the graph above you can see how I'm pedalling along this byway at a 92rpm cadence. I freewheel a few times and have to brake for a lunatic pheasant. Apart from that it's a steady pace. There isn't a great deal going on, and that's the whole point of this graph. On longer duration mountain bike rides in particular don't automatically expect every part of the ride offroad to be a mass of power spikes. It isn't always like that, especially if you're doing fire road and dirt road sections. Smooth singletrack can often be similar in terms of power output too. This sounds incredibly obvious but is an important thing to remember at the same time.:)
 
#66 ·
Dcrainmaker has posted a review of the Power2Max Type S road power meter.

https://www.dcrainmaker.com/2015/03/the-power2max-type-s-power-meter-in-depth-review.html

Scroll down to the section on power balance and his 84% / 16% left - right balance whilst pedalling with just one leg picture. Those balance percentages seem strangely familiar to me. All he needed to do was unclip his left foot and pedal with the right leg instead and it would look just like one of my rides.:lol:



In the comments section there are some posts about battery life and also power readings. When I've had a Power2Max power meter low battery warning appear on my Garmin Edge 500 I've replaced the battery at the end of the ride before riding again. I wasn't sure how much life was left after the warning. Battery warnings are sometimes conservative so I thought there might have been quite a bit. Reading the comments someone says that they had a low battery warning, and then the power meter shut down an hour later. It's probably best to be safe than sorry and assume that if there's a low battery warning it needs a new battery.

The comments posts about having power readings slightly lower on the Power2Max (2 to 7% lower compared to other brands) were interesting. There are several posts about this, including one that mentions not just lower steady state readings but also substantially lower peak power values from a Power2Max than a Powertap hub. That matches up with my peak power curve and the lower power values in Post #44 of this thread too.

Quoted from comments section of dcrainmaker Power2Max Type S review:

----------------------------

"Have you experienced the Power2Max reading a slight bit lower than other power meters (i.e. Quarq or Computrainer)? Both myself and a friend moved to Power2Max Type S units from Quarq. Subjectively I felt like the Power2Max read about 5% lower than the Quarq. My friend felt the same thing and he compared it to his Computrainer which reinforced our hypothesis. Just wondering if anyone else has experienced the same thing. Of course, I understand that it really doesn't matter and that precision is more important than accuracy." Michael Post #35

----------------------------

"I am a fellow Power2Max user as well (Campagnolo Type-S) and have had my unit for nearly 7 months like another user above. In my case I am coming from a Powertap PRO+ and my power values have consistently been ~5-7% lower for steady state efforts and 150-200 watts lower for peak sprint values. Admittedly, it took a while to adjust since the ego was suffering from initial confusion but all was well when I finally managed to test both units at the same time on one bike.

Prior to riding with both units, I was "killing" myself on efforts trying to replicate my Powertap readings. Now all is well with my "fudge" factor. I just needed collect more data from the new power meter."
Dan Post #36

----------------------------

"I went from SRM to P2M and found between 1.5-2.5% (lower) difference in power, depending on the time being measured across. I now use a rough 2% 'rule of thumb' when comparing back to any SRM power." Nick Post #37

----------------------------
 
#67 ·
I got my P2M up and running last week. I only did a couple of trail rides with it so far, but the data so far is very interesting to say the least. Tons of hard efforts in the 30 second - 1 minute range, but I barely sustain 220W normalized for 20 minutes. The trails here are tight and twisty, and not a ton of elevation so the claims and descents are short and steep. I guess the power numbers make sense based on the terrain. Here are a couple of pictures of the P2M with Rotor Rex 3 cranks on my Specialized Epic.

Bicycle tire Mode of transport Bicycle part Spoke Bicycle


Tire Bicycle tire Bicycle frame Wheel Bicycle wheel
 
#68 ·
Thanks to bloodninja for letting me post some of his power data.:)

When you first get a power meter I think it's a good idea to just ride with it for a few weeks. As you build up a stock of ride files you'll start to create a picture of your own riding and abilities. Don't get hung up on trying to use training zones or sticking to particular power outputs until you have a good handle on what you can and can't do in terms of power output.

When you first get a power file of a route that you don't know and haven't ridden the first thing is to try and get a mental picture of what it represents. GPS makes this a lot easier. I like to look at the map with power overlaid as a colour coded line.



This shows bloodninja's mountain bike ride on 04 April 2015. "First lap was warmup. Second was Lakeview Loop twisty, rooty, and moderately technical singletrack. The third lap was fire roads and some pavement. The last lap was smoother "flowy" singletrack."



From the map you can see how there are some clear differences. The singletrack sections are twisty with lots of bends, there's a lot of white (0-20 watts which is freewheeling or soft pedalling) and also quite a lot of Red (greater than 450 watts which is sprinting or trying very hard). The middle fireroad/ road section in contrast is more constant with visibly less freewheeling, although still some hard efforts.



The next thing I like to do is look at an overview of the elevation profile. Here I've zoomed in on just Lap 2 Lakeview Loop.



There's not a great deal of elevation change or any major climbs. That doesn't mean it's flat though! You can see from the elevation how it's constantly up and down, like a saw blade. That gives an insight into what the power output is likely to be like here. Tight and twisty with constant small rises is unlikely to see a steady state power output. Below the elevation you can see bloodninja's power output. Each time there's an uphill rise there's also a 20 second to 1 minute power spike at 300 to 360 watts.

This shows a pie chart of the power distribution for just the 10.5 miles of the Lakeview Loop.



What I look for is the amount of time spent freewheeling or soft pedalling. 0-20 watts is typically freewheeling and anything below 100 watts is soft pedalling. Here there's 23 minutes 12 seconds (33.9%) of the time spent below 100 watts on a 1 hour 2 minute loop. The aim is always to minimise this. If you're not putting down as much power as you're physically able then there's potentially time to be gained.

On difficult terrain there's not much you can do about having some time below 100 watts. This is where improvements in technical skills and line choices will show up. Equipment choices - tyres, full suspension etc can make a difference too. Fit chunkier tyres with more cornering grip and you may be able to pedal through more corners and accelerate earlier. Dial in the bike's full suspension and you may be able to keep pedalling over the roots or take a more direct line through the obstacles. If you see that time spent below 100 watts reducing thats a sign of progress in your riding.

At the other end you have the time spent above 450 watts. This was 5 minutes 52 seconds (9.3%) for the Lakeview Loop. This is where you were trying hard and it represents the peaks of the frequent 20 seconds to 1 minute efforts. When you're doing lots of these efforts for several hours it can take it out of you sprinting repeatedly. For pacing offroad this is where the power meter can come in useful. If you have the Garmin display showing with 3 second smoothing you can double check your effort on these rises. 30 seconds or over uphill is long enough that you can usually manage a quick glance at the Garmin. If it's showing too high a number on these short bursts early on you can then back the intensity down to a more sustainable level, saving your energy for later in the ride. Alternatively, if you look down and see the power numbers are too low part way up a rise it's a sign to try harder.

This shows the summaries for Lap 2 (Lakeview Loop singletrack), Lap 3 (fire road/ tarmac road), Lap 4 (tight singletrack) excluding cool down.



If you look at your heart rate it gives a good idea of how hard you rode each hour. You went hard on the Lakeview Loop and then the remaining two hours were at a steady pace. Without knowing your plan for the ride that appears to be how it went. If you'd planned to do the entire ride hard then the pacing was way off.

The most notable thing here is your cadence. There is a big difference between Lap 2, where you were trying hard, and the rest of the ride. For Lap 2 trying hard you averaged 90 rpm cadence for an hour whilst at lower intensities you were only averaging around 82rpm, including on similar terrain during lap 4 for an hour on the tight singletrack at 81rpm. That's a big difference in pedalling cadence which you want to have a think about. I'd do some more rides and see if that pattern continues.
 
#69 ·
This is a great analysis and gives me so much to think about. Thank you so much WR304. I test myself from time to time on the Lakeview loop, since it's pretty representative of a Cat 3 race around here. I intended to go 90%+ there and then make the rest of the ride zone 2. If you look on Strava though, you can see that I went for a PR on the Green loop the first time around. I was feeling good after the fire roads, so I figured I'd go for it.

I think it's pretty common for my cadence to be 90 or higher when I'm trying hard, and 80 or so when I'm pacing myself. I see the same thing on my trainer rides, and my really hard intervals are even over 100.

I have to give some more thought to the amount of time that I spend coasting or soft pedaling. One of the things that struck me while I was riding was how often I'm in a relatively flat section, feeling like I'm moving pretty fast, but only putting out 90 watts. I can put out 150-180 watts and still recover between the hard efforts, so why not push it a little more on the flats? On the other hand, maybe I should conserve as much energy as possible so that I can go as hard as possible on the climbs where there's more time to gain. I'll definitely be paying attention to the amount of time I spend under 100W, but also avg speed vs NP for the loop. I also expect that I'll make up a little time as my handling improves to where it was last fall. I've only ridden outside a handful of times so far this year.

The map with color coded power output is great. Is that using Rubitrack? I wish it were available for windows.
 
#70 · (Edited)
The colour coded map is from rubiTrack for IOS on iPad. For an easy to use analysis program I think it works really well.:)

rubiTrack for iOS by Markus Spoettl
https://appsto.re/gb/YQNfR.i

You can have various different map types overlaid. I usually use the Open Street Map overlay but satellite imagery can give a good idea too. Where your ride was in woodland a lot of the offroad riding around here is over farmland. That affects your power output and the pattern of the ride.

Here's an aerial view of a short section of my ride from today. This is over fields and then along a farm track. The first part is grassy field then you have a farm track, then it turns into singletrack path as it goes through some trees (muddy) before you rejoin the farm track. Because you're tending to follow field boundaries there aren't that many bends.



I averaged 154 watts for this 1.5 mile section and wasn't going flat out. I've done it far quicker in the past. There's a big section of downhill on farm track where I was freewheeling that I could easily have pedalled.

There are two short sharp rises where you can see my power jump. The second one in particular is steep on rough rocks. I was in bottom gear sitting right on the nose of the saddle up there.

Edit:

Here's the graph of the same section in WKO+ 3.0 with the same parts of the route highlighted. You can see how the power output varies between different parts of the



To try and give a visual idea of how this appears when riding I found a picture I took of the steep rise on the farm track at the end of this graph. This is where I was in bottom gear (taking the right hand track as it has the fewest loose rocks).:)

 
#71 ·
Here are some offroad climbing and descending power graphs from today's ride. It was a nice day but still muddy in places. I did 3 hours (40 miles) on what is quite a hilly route with a mix of off road and road sections.

This satellite map and WKO+ 3.0 graph shows my power output riding around some fields and then going down a byway descent. This track had large farm tractors on it recently making for a rough surface over their tracks.





For the first section of the descent I rode on the middle between the ruts at 18.6mph. It was quite rough washboard and the full suspension was doing its job here. There's a steep turn at one point which I took slowly at just 3.7mph before accelerating back up to speed, still staying on the centre section between the ruts. Partway down it was muddy and loose rocks too, muddier than I'd expected where the tractors had churned it up. If you look at the gradient trace on the attached WKO+ 3.0 graph you can see how this was a flatter section. On this section I was picking my way through at low speed (8mph) but pedalling to make sure I wouldn't get the front wheel hung up in the holes or deep mud.

After that it opens out and I could get off the brakes until the descent flattens off. Once I'd turned off the byway back onto the road there is a short steep road climb and then a road descent immediately afterwards. I've included them as although they aren't offroad sections they appear on the map above.

This satellite map and WKO+ 3.0 graph shows my power descending a byway on quite a rough surface and then climbing back up the other side.





Rain water has eroded gulleys across the path on the descent and they're full of gravel so you have to lift the front wheel over them and criss cross from side to side to find the best line. This is where the satellite map can help explain what was going on. I set off confidently on the open section at 17mph, prepared to let the brakes off and the bike run but you can then see where I reached the small wooded part I slowed right down to 4.4mph. Under the trees there was lots of deep mud. I took the dry line but it was right next to a small wall. I was only half pedalling keeping the pedal up high and lifting it back up at mid stroke, not wanting to pedal full circles in case I grounded my pedal on the wall I was that close. After that it opened out again so once past the worst of the eroded gulleys I was back up to 20mph.

After a long time stuck trying to cross the main road I then began the climb up the other side. This is on a track that has loose rocks on it (similar to the picture in the post before this one). It starts off steep, flattens off mid way up and then steepens again towards the top. I went up here fairly hard, averaging 253 watts for 3 minutes 47 seconds up the 0.5 mile climb. I need to do a proper full gas effort up this climb sometime (My best power output for five minutes this year is 309 watts). I reckon I can do it quicker.

Just after this climb I was riding some singletrack in the woods and got a muddy section completely wrong, falling off straight into a bramble bush. I was sat there on the ground picking all the thorns out of my arm, hands and side, blood everywhere from the cuts. Some things never change... I got back on rode the rest of the section cleanly and made it round the rest of the ride in one piece.:)
 
#72 ·
WR304, I sure am impressed with what you're able to do with one good leg. Glad you were able to get back up and finish the section after you fell into the bush.

Your analysis of the ride is great. You really broke down every part of the ride. I want to do that, at least for races and hard training rides, after I spend some time gathering data first. I have a Kindle Fire and PC, so I guess I can't use rubiTrack. Too bad, because that map feature is great.
 
#73 ·
The problem with only having one working leg is that it's a case of either clear a section or fall off. There's no bail out option as my left leg just gives way. I try not to take too many risks but falling off is part of the sport. It's always going to happen sometime. In general I rely on the bike to get me through unscathed. It's amazing how much stuff it can plow through without much rider input.

I was feeling a bit sore to begin with on today's ride so I stopped now and then to take some pictures on the way out. The first part of the ride was fairly low key and then I did some higher intensity efforts on the way back.

Being able to represent power data in a way that is useful, so that you can take that data, critique it and improve your riding as a result isn't always easy to describe in words. What I thought I'd do would be to take photos of particular sections and then put some notes on the pictures.:)

This picture shows a section of byway with a river crossing. The green line and arrows show my direction of travel. I came down the hill across the bridge, weaved between the concrete bollards and then accelerated away afterwards.



A view over the bridge showing the bollards and opposite bank:



This is the WKO+ 3.0 graph with the same notes so that you can see my power output at the highlighted points in the photograph. I was trying hard throughout here.



If you look at the photo and the green line the first thing to note are my line choices. That green line twists and turns several times. On the opposite bank I came right down towards the river, which is deep loose gravel, before turning across towards the bridge. This shows in my power output and speed. Where I had been doing 21 mph I was now braking, 0 watts and down to 8mph. I put some pedal strokes in to get up and over the bridge at 182 watts and 8mph before another right - left turn between the bollards at 0 watts at 5.5mph. On the exit I was back up to full power heading towards the gravel slope away from the river crossing.

This is where the photo and power data together hopefully shows where there is room for improvement through line choice. You can see from the power data that I was slow approaching the bridge, slow over it and slow on the bridge exit too. As soon as you see all that time at 0 watts, turning slowly on loose gravel and weaving between bollards at 5.5mph that raises an immediate red flag. Is this the best way to ride this bridge? Probably not.

On a mountain bike good line choice is everything. In the bridge photos above you can see the opposite bank. There's a second higher track that I didn't ride today. This is hardpacked dirt, not loose gravel, so will have higher grip. It also gives a straight line onto the bridge, cutting out the turns. This should be a faster entry line. On the exit of the bridge nearest to the camera, instead of turning right then left between bollards it is possible to go to the far left side of the small bush, giving a straight line without needing to turn between the bollards. You can see the path as the dark mark in the grass on the photo. By using that alternative line it should be possible to save several seconds on just this one bridge.

This picture shows a section of bridleway on a rocky farm track. It starts off slightly downhill, there is a short sharp 14% gradient rise and then the track continues gradually uphill at around 3.5% gradient. Out of picture there is then a descent down to another farm gate.



This is the WKO+ 3.0 graph for this section.



What this tries to show is how power output responds to the terrain. I set off freewheeling from where I had taken the photo, I then try quite hard at 15mph and 241 watts, a short pause in power weaving between puddles and then I blast up the short steep rise. Here my power output averages 325 watts at 8.7mph on the steepest section, although it's near the end of the ride and it feels harder than that. I then keep working hard up the 3.5% gradient slope, 179 watts at 11mph until I reach the top and begin the descent to the gate.

From the power trace the main thing to look at is my power output on the 3.5% gradient slope. You can see how it isn't a straight line, instead my power output is gradually dropping throughout as I near the top. That's a bit where I could have done better. That drop in power output will show on the display as you're riding. I should have responded to this drop in power by upping the pace but I didn't. I had my thumb on the trigger shifter but didn't press it.

My explanation for this is the short sharp power burst at the bottom. It doesn't look much but if you put a really hard effort in the result is that you then have to recover from that effort at some point. Sometimes showing restraint on the short sprints can pay off with higher power outputs later on. Here for example if I'd gone up the steep section a little easier I might have then felt able to ride the following 3.5% gradient slope at a higher power output than I did today. It's all about parcelling out your effort for maximum effectiveness.

These two pictures don't have any power data attached. I've included them as they're representative of the farm tracks that a lot of my riding is on. There are ruts from the farm vehicles which are usually deep and full of water. You then have a central section that the motocross bikes and mountain bikes use. The motocross bikes in particular create a third rut. This is why I like Specialized Ground Control tyres as they work well on this type of mud, whilst still performing on hard pack gravel and rocks too.



This picture shows a bridleway path around a field boundary. It's dried mud, full of horse hoof prints and tractor tracks. Riding on this stuff is rough enough to get the bingo wings flapping and dentures loosened. There aren't any large bumps but it's a constant beating and takes some effort to keep going. On this section today I averaged 201 watts for just 12 mph speed!

 
#74 ·
My bike has been making nasty creaking noises for the last month or so, whilst pedalling in just the 23T granny ring originally but increasingly in the 33T middle ring also. There was no creaking in the outer 44T chainring. It started off intermittent but by today it was sounding horrendous.

Despite taking the crank off, checking all the chainring bolts (at the end of March they seemed fully tight), trying a different rear wheel (in case it was the freehub or cassette) etc I couldn't track it down.

It was sounding so bad today that when I got home I decided to check the chainring bolts again. This time when I went to check the alloy chainring bolts holding the two outer chainrings together the head of the first chainring bolt sheared off immediately with only minimal pressure! I carefully unfastened the other three chainring bolts. Of those two appeared fine but the third was close to breaking too. This bolt had a long split running round it and the head was only loosely attached. That explained why I'd been getting creaking. Two out of four of the alloy chainring bolts had failed.



The reason that these bolts were what was causing creaking in the granny ring is that on my Power2Max triple chainset the granny ring bolts onto a carrier that is in turn bolted in place by the same chainring bolts that hold the two outer chainrings on. All the torque from the granny ring goes into the carrier and those four bolts.

I've replaced the four alloy bolts with steel bolts now. Hopefully that will have cured the creaking.:)
 
#76 ·
Sorry to hear that it didn't fix it WR304. Trying to track down creaking is the worst. Did you eliminate seatpost and suspension linkage as possible causes?

That reminds me... I think due to the type of aluminum used in the Rotor no q rings, if there's even the slightest bit of grit on my chain it makes a sound like my drivetrain is getting chewed up. It makes me feel the need to clean my chain thoroughly after every single outdoor ride...which I guess really isn't a bad thing.
 
#77 ·
With my custom crank it could potentially be the lockring thread holding the spider on or even the crank spindle itself that is creaking. You then have all the usual problem areas bottom bracket, suspension, saddle etc

Today it was sounding bad in both the granny ring and middle ring, but I was also getting occasional creaks when hitting bumps. It's not consistent, sometimes I can be putting a lot of effort in and the bike isn't creaking. Next thing I'm soft pedalling and it's creaking like mad.

When riding it all feels fine though. Apart from the noise the bike is working normally and I've been going well fitness wise, setting some new climbing personal bests and also power personal bests at the weekend.
 
#78 ·
I tried a different crank today (instead of the power meter crank) and the bike was creaking as badly as ever. The creaking wasn't from the power meter crank. It's a really dry "cracking" sound of creak. A carbon fibre creaking sound that comes and goes when I'm pedalling.

So far I've replaced the seatpost, seatpost collar, saddle, pedals, and bottom bracket with brand new parts, greased the SRAM X0 rear derailleur clutch, tried using a different crank, tried an entire different rear wheel with no joy.

There isn't a great deal left. It's looking like maybe there could be something going on with the pressfit carbon fibre bottom bracket shell (this bike is on its fifth press fit bottom bracket) or maybe a rear suspension pivot bearing where it is pressed into the carbon frame (this bike is on its third set of pivot bearings).
 
#79 ·
My bike has been in and out of the bike shop several times to see if they could find this creak. As I only have the one bike I've been riding it in between. Although it was noisy the bike was riding fine.

Yesterday I'd been out on the club ride. The bike had been relatively quiet all ride. I was on the way home through town when I rolled up to some traffic lights. From an almost stationary start (with both feet on the pedals) I put in my best 20 second sprint of 2015, 565 watts maximum power and an average of 462 watts for 20 seconds.



Unfortunately laying down that "awesome" sprint was more than the bike could handle. It's only a few minutes home after that but the creaking following that sprint was horrendous!

When I got home I could see why. Something in the lower rear suspension pivot bearings has broken and failed completely. In the picture below the large gold allen bolt bolts through and secures the bearings. This is normally recessed and flush with the edge of the swingarm. You can see the ring of dirt where its normal position would be but it is now protruding from the frame. There's a ton of play in the rear triangle. Rock the rear wheel by hand and those lower pivots are wobbling freely. Not good.

Ironically enough it was booked in for all the rear suspension pivot bearings to be replaced tomorrow anyway.

 
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