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  1. #26
    dru
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    You don't need to count the cogs inside. The hub uses various combinations of those cogs to produce the ratios that Baker listed. The ratios X whatever of the 7 sprockets you choose determines the effective gear.

    As Baker said the 18T gives 13.2, 18, 24.5

    And, as Baker said, count the number of teeth on the sprocket on the hub.

    When you have that # multiply it by .733, 1, 1.364 to get your three 'gears'

    For instance, using the 22T gives you 16.126, 22, 30.008....

    Drew
    occasional cyclist

  2. #27
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    Quote Originally Posted by GT *in-use* View Post
    Thanks for your answer BUT the Nexus 3 has the cogs inside the hub. Cannot see the cogs, cannot count the teeth unless the hub is completely disassembled and opened hence my question...
    An internal gear hub, such as the Nexus 3, uses a planetary gear system to determine its ratios. It doesn't have cogs like you find on a freewheel or cassette. The Shimano specs that show a range of available cogs to use with the Nexus 3 are actually talking about the single rear cog that can be switched out. I have rear cogs ranging from 18t to 22t that will fit on my Nexus 3, but only one can be fitted at a time. Changing the rear cog is simple. Doing so will change all three gears of the hub to be either higher or lower. There isn't a way to change individual gears in the hub, though that would be nice.

    You can use a gear calculator to compare the gear ratios in the Nexus 3 to cassette cogs. Here is one that I use, as it displays the results in a nice graph:

    kstoerz.com | visual drivetrain comparison tool

    You change the IGH field to Nexus Inter-3 when entering your data.

    I used to have a Nexus 3 mated to a 700c wheel. With a 39t chainring and 19t rear cog, the three gear ratios in the Nexus 3 were equivalent to using 26t, 19t, and 14t cogs on a cassette (also with a 39t chainring and 700c wheel).

  3. #28
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    Maybe he meant to ask how many pawls are inside the hub - as in how quickly will drive engage?

  4. #29
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    Quote Originally Posted by dru View Post
    You don't need to count the cogs inside. The hub uses various combinations of those cogs to produce the ratios that Baker listed. The ratios X whatever of the 7 sprockets you choose determines the effective gear.

    As Baker said the 18T gives 13.2, 18, 24.5

    And, as Baker said, count the number of teeth on the sprocket on the hub.

    When you have that # multiply it by .733, 1, 1.364 to get your three 'gears'

    For instance, using the 22T gives you 16.126, 22, 30.008....

    Drew
    Got it... got it now! Sorry Baker I did not get it the first time!

    Quote Originally Posted by scooby214 View Post
    An internal gear hub, such as the Nexus 3, uses a planetary gear system to determine its ratios. It doesn't have cogs like you find on a freewheel or cassette. The Shimano specs that show a range of available cogs to use with the Nexus 3 are actually talking about the single rear cog that can be switched out. I have rear cogs ranging from 18t to 22t that will fit on my Nexus 3, but only one can be fitted at a time. Changing the rear cog is simple. Doing so will change all three gears of the hub to be either higher or lower. There isn't a way to change individual gears in the hub, though that would be nice.

    You can use a gear calculator to compare the gear ratios in the Nexus 3 to cassette cogs. Here is one that I use, as it displays the results in a nice graph:

    kstoerz.com | visual drivetrain comparison tool

    You change the IGH field to Nexus Inter-3 when entering your data.

    I used to have a Nexus 3 mated to a 700c wheel. With a 39t chainring and 19t rear cog, the three gear ratios in the Nexus 3 were equivalent to using 26t, 19t, and 14t cogs on a cassette (also with a 39t chainring and 700c wheel).
    Great link!
    Took me a while to understand the concept but I stand corrected!
    Thanks

    Quote Originally Posted by Corporal Punishment View Post
    Maybe he meant to ask how many pawls are inside the hub - as in how quickly will drive engage?
    Thank you for sharing and trying to make me look less stupid!
    I was confused but corrected.

  5. #30
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    No worries GT *in-use*, this stuff isn't straightforward when you move from a regualr drivetrain over to IGH...
    baker

  6. #31
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    Shifter question

    So, would the SA thumb shifter work with this hub? I would like to set one of these Nexus up on a drop bar bike and don't like the idea of their twist shifter on the bar end.

    Thanks, Matt

  7. #32
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    Quote Originally Posted by MattyT View Post
    So, would the SA thumb shifter work with this hub?
    No.

    Quote Originally Posted by MattyT View Post
    I would like to set one of these Nexus up on a drop bar bike and don't like the idea of their twist shifter on the bar end.
    If you're so enamored with the Shimano hub you've named one of you children Nexus, there are ways to use a drop bar shifter with this hub. Probably more straightforward though just to use a Sturmey three-speed hub from the AW-NIG family on that drop bar bike, then you'll have a choice of factory classic trigger, modern trigger, thumb, twist, bar end, braze-on downtube or seatpost shifters.

    In comparison to Shimano and SRAM IGHs, Sturmey hubs have the additional advantage in NA of parts support.

    JD

  8. #33
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    I use a Sturmey Archer S-RF3 on one of my drop bar bikes. The SA bar-end shifter works great. Makes for a great drop bar commuter bike.

    I used to have a Nexus 3 wheel, but didn't use it on this bike. I couldn't find a satisfactory shifter arrangement. I ended up selling the wheel to cover the cost of the new SA hub.

  9. #34
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    Quote Originally Posted by scooby214 View Post
    An internal gear hub, such as the Nexus 3, uses a planetary gear system to determine its ratios. It doesn't have cogs like you find on a freewheel or cassette. The Shimano specs that show a range of available cogs to use with the Nexus 3 are actually talking about the single rear cog that can be switched out. I have rear cogs ranging from 18t to 22t that will fit on my Nexus 3, but only one can be fitted at a time. Changing the rear cog is simple. Doing so will change all three gears of the hub to be either higher or lower. There isn't a way to change individual gears in the hub, though that would be nice.

    You can use a gear calculator to compare the gear ratios in the Nexus 3 to cassette cogs. Here is one that I use, as it displays the results in a nice graph:

    kstoerz.com | visual drivetrain comparison tool

    You change the IGH field to Nexus Inter-3 when entering your data.

    I used to have a Nexus 3 mated to a 700c wheel. With a 39t chainring and 19t rear cog, the three gear ratios in the Nexus 3 were equivalent to using 26t, 19t, and 14t cogs on a cassette (also with a 39t chainring and 700c wheel).
    In most european countries the actual gearing components inside the hubs are whats called cogs. And in a derailleur system i guess the rear end are cogs too, kinda, but the internals of a planet gear system are more cogs than a derailleur system if you ask me, purely linguistically speaking. If you say "cog" to someone in europe they immediately refer to the internal parts of planet gear stuff in 99.5% of the cases I'd guess.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

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  10. #35
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    Quote Originally Posted by car bone View Post
    In most european countries the actual gearing components inside the hubs are whats called cogs. And in a derailleur system i guess the rear end are cogs too, kinda, but the internals of a planet gear system are more cogs than a derailleur system if you ask me, purely linguistically speaking. If you say "cog" to someone in europe they immediately refer to the internal parts of planet gear stuff in 99.5% of the cases I'd guess.
    You make good points, linguistically speaking. I tend to think of the chainring and external cassette gears as sprockets, but most people around here call them cogs.

    It would be great is if one could replace the cogs inside an IGH to change the ratios. I have my S-RF3 geared where I like it, but that was done by changing the external sprocket (42 front/20 rear). If I could fine tune it, I would make the ratios a bit closer. Wishful thinking, I know...

  11. #36
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    anyone know the cable pull distance(measurement) between gears?
    thxs

  12. #37
    dru
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    I really doubt you'd find it here. Maybe Shimano has it published somewhere?
    occasional cyclist

  13. #38
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    its actually quite easy, use a paint marker, put a dot on the cable and measure the distance. or measure the lever movement.
    i would do it if i had one in front of me.
    i'm wondering if its close to a front 3 spd (sram) shifter.

  14. #39
    dru
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    My worry would be inaccuracy. That kind of stuff needs to be spot on, as in tenths of millimeters.
    occasional cyclist

  15. #40
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    Then put a locking bead or 2 on it and measure. Its easy to measure 0.1mm. I have a feeling +- 0.5 mm or so is passable on 3 sp ones. Or even much more. Seems to me its like 3 different positions so this can't be that hard honestly to get something working.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  16. #41
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    i was thinking a dial indicator on the lever, if the cover can be removed. i've never seen one in person, so i don't know.
    cable stretch and housing compression is more than 0.1mm. And considering the instructions say to put the yellow indicator between the two yellow lines... doesn't sound too precise to me.

  17. #42
    dru
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    You're right about the margin of error, but you are also trying to get a shifter from something else to work. The hub might be a bit picky about that. If you find that it works let the forum knw, by all means.
    occasional cyclist

  18. #43
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    Sturmey-Archer AW family
    1-2: 7.4mm
    2-3: 11.2mm

    Sachs/SRAM T3
    1-2: 7mm
    2-3: 13.8mm

    Sturmey Archer RS-RX3:
    1-2: 8.6mm
    2-3: 15.0mm

    Sorry, don't own a Nexus 3 so I've never measured the cable pull on one. Because of all the different factory shifters available and being able to get spare parts, most the gear heads are into Sturmey 3s.

    jd

  19. #44
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    I actually purchased a Sturmey Archer thumb shifter, to attempt using it with a Shimano Nexus 3. I haven't had a chance to set it up, but I will let you know if it works.

    I kind of just went for it, thinking all I would need to do is get 2nd gear lined up, and that it would be OK if the shifter overshoots 1 and 3...not too sure it's going to work, but I can't stand the grip shifter.

  20. #45
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    Quote Originally Posted by sriracha View Post
    I kind of just went for it, thinking all I would need to do is get 2nd gear lined up, and that it would be OK if the shifter overshoots 1 and 3...
    Overshoots, yeah. Undershoots, not so much.

    As you say: you gotta line up 2nd gear accurately. If you don't get 2nd lined up, your three-speed hub can have a short and very unhappy life.

    The Shimano 3-speed bell crank has an indicator on it for 2nd gear alignment. Of course the other two gears are found at cable slack and cable taut - conditions your shifter of choice has to achieve.

    One approach with a three-speed is to use a many-speeds indexed shifter (DT, bar end, brifter, dual paddle) and set one of the middle index positions to 2nd gear. This acurate shifter index position can be found when riding by counting clicks, visual observation, looking at the shifter's indicator (were applicable) or feel.

  21. #46
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    Quote Originally Posted by smokey_z View Post
    It's been a little short of a year and a half since I put the nexus 3 speed hub into service. I thought I would follow up with how the hub has been performing.

    I have been riding the hub for my commute to work for almost a year and half. It's about a 18 mile round trip, with a mix of flats and small hills. I live in Portland, where it happens to rain quite a bit throughout the year, except July through September. My original goal in building this bike was to have a very low maintenance commuter that didn't feel like a tank to ride. Since I've built it, I have done very little maintence, except oiling the chain, changing tires, and adjusting brake pads. Recently I noticed that the 3 speed hub was making an intermittent click/ creak, so I decided to check it out.

    What I found right away was that the drive side of the hub had been contaminated with water and dirt. The non-drive side looked pretty much like I expected, the originally white grease had turned to a neutral grey color from the natural breaking in process of metal to metal contact. On the drive side, the outer most bearings, cone and retainer were covered in rust, with little grease remaining. The color difference is pretty obvious. The bearings and retainer need replacement, possibly the cone and cog carrier.
    So while this hub offers some higher performance features in terms of weight and the clutch, it lacks the type of seals that are needed for year round riding in the pacific northwest. At the least there should be a double set of seals on the drive side to reduce water ingress. I plan to rebuild the hub with new bearings and see how it performs, however I doubt it last more than one or two more winters before the entire hub is shot.
    wondering if you considered regular (once a month?) oiling of the hub? I've got one built as a commuter wheelset and I am planning to just inject heavy suspension oil (30wt) down where the shift pin goes and just let it seep out slowly. I put 5ml in at a time and so far have had any leak onto the rim (I'm using disks so it wouldn't matter anyway). Suspension fluid shouldn't be too hard on any seals in the hub I hope as otherwise it would eat your fork seals?

  22. #47
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    Quote Originally Posted by dru View Post
    My worry would be inaccuracy. That kind of stuff needs to be spot on, as in tenths of millimeters.
    lol

  23. #48
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    Quote Originally Posted by sriracha View Post
    I actually purchased a Sturmey Archer thumb shifter, to attempt using it with a Shimano Nexus 3. I haven't had a chance to set it up, but I will let you know if it works.

    I kind of just went for it, thinking all I would need to do is get 2nd gear lined up, and that it would be OK if the shifter overshoots 1 and 3...not too sure it's going to work, but I can't stand the grip shifter.
    Any luck yet?

  24. #49
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    Well I used an old right hand Shimano thumb shifter and its working fine

  25. #50
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    Regarding the Nexus SG-3D55: I have recently set one up on my daily commuter.
    - It's brand new, and at this point has seen less than 400km.
    - I have been careful to make sure the indicator rod's yellow line has always been squarely in between the yellow lines when in 2nd gear.
    - The hub has had essentially no problems shifting. (It has mis-shifted perhaps ten times, my own fault due to not tightening a grip shifter on the handlbars properly, so i didn't fully get to 3rd)
    - I have recently noticed a high-pitched squeaking from the hub when in 3rd gear and putting a fair bit of effort into pedalling. I thought the sound came from my cheapo pedals at first because it only happened when i was putting force through the drivetrain.
    - I wonder if this may have to do with the weather. It's recently gotten to about -10C where I live, and I wonder if this is affecting the hub's grease.
    - FWIW, I am on 3rd gear the majority of the time, with the two other gears as lower gears.

    I am mildly concerned... Can I live with this as some kind of "breaking in" process, or should I open up the hub and replace its grease with Shimano's blue mineral oil/ATF fluid/something else?

    I hate the idea that something is destroying itself inside the hub.

    I guess I am OK with the idea of replacing the hub's oil on a regular basis.

    If i replace the grease with oil, any suggestions for what to use other than Shimano's blue stuff?

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