Trek ABP affected by 30t chainring?- Mtbr.com
Results 1 to 16 of 16
  1. #1
    mtbr member
    Reputation:
    Join Date
    Aug 2005
    Posts
    1,689

    Trek ABP affected by 30t chainring?

    Does it feel different to those that converted? Was optimized for 32t likes lots of designs? I just want to understand the trade offs before I go forward.

  2. #2
    mtbr member
    Reputation:
    Join Date
    Oct 2004
    Posts
    7,068
    It will be interesting to hear from the suspension experts on this. Hard to believe that 2t will matter a whole lot (though it may matter which particular Trek bike you are most interested in).

    If you don't get much input on this, you might try posting in the suspension forum.
    Whining is not a strategy.

  3. #3
    Cassoulet forever !
    Reputation: 20.100 FR's Avatar
    Join Date
    Jan 2004
    Posts
    2,260
    You probably won't feel any difference.

    With a smaller front ring, you get a tad more anti squat, and a tad more pedal feedback. Trek suspension have medium anti squat, so you can go smaller without problems. That might even be a good thing.

    Notice that last year Remedy 29 was a single ring, and that it is now a double. And that in the EWS leov was rocking a single ring and that Moseley used a double. All with the same pivot location...
    Frenchspeaking 29"ers community site http://VingtNeuf.org

  4. #4
    meow meow
    Reputation: b-kul's Avatar
    Join Date
    Sep 2009
    Posts
    10,621
    i have had a 32 and a 30 tooth chainring on both my remedy and fuel ex. there is probably some slight changes the size makes but i couldn't feel one (and I'm pretty picky about how my bike rides).

  5. #5
    I Tried Them ALL... SuperModerator
    Reputation: Cayenne_Pepa's Avatar
    Join Date
    Dec 2007
    Posts
    6,597

    ZERO Difference....

    I had a 30t round and now 32t oval and ABP is still rockin'....
    "This is a male-dominated forum... there will be lots of Testosterone sword-shaming here" ~ Kenfucius

  6. #6
    mtbr member
    Reputation: sherwin24's Avatar
    Join Date
    Jul 2010
    Posts
    485
    Switched between a 32 and 30T when I had my Remedy. Never noticed any difference other than climbing was easier with a smaller CR. Did run a 38T a couple times on real smooth stuff and couldn't tell then either, but had it in trail mode anyway.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Aug 2005
    Posts
    1,689
    Thanks for all the feedback. I used to run a 1x9 and loved it, but lived in Central Texas. Now I am back in the mountains, I want the simplicity, but also know a double is a safe bet.

  8. #8
    Cactus Cuddler
    Reputation: tehllama's Avatar
    Join Date
    Jul 2013
    Posts
    1,808
    If one of the silly-wide gearing cassettes is an option (9-44T or similar), those can obsolete most 2x10 drivetrains in terms of gearing range, the tiny 9T cog (does require an XD driver hub) means that a 30T chainring gets you farther than a typical 36/11 would.

    As far as an anti-squat delta for that small a chainring difference (it's about 4.5mm vertically) - really pretty trivial, and going to matter less in terms of climbing technical singletrack less than even one tiny shim washer in the shock's compression stack being moved to a different point. I'd downsize and not even thing about it.

  9. #9
    I hate that name.
    Reputation: blunderbuss's Avatar
    Join Date
    Jan 2004
    Posts
    1,643
    Echo what others have said. 32 to 30 shouldn't affect the suspension any differently. I use my 22 (Remedy, 11-36 cassette) for any kind of climbing with no issues.
    Worked at Trek/Fisher dealer 2008-2013. Only a little biased.

  10. #10
    mtbr member
    Reputation: gambo2166's Avatar
    Join Date
    Dec 2004
    Posts
    395
    I have a 28t (Im big and fat)on my 2016 Fuel Ex with no effect.

  11. #11
    mtbr member
    Reputation: Robg68's Avatar
    Join Date
    Oct 2013
    Posts
    498
    I switched to a 30 tooth single on my Fuel and rode all last year and never noticed or had a problem or anything strange.

  12. #12
    mtbr member
    Reputation:
    Join Date
    Feb 2012
    Posts
    378
    Running a 30t on my Ex 29 and it's still amazing. :^)

  13. #13
    mtbr member
    Reputation: Lone Rager's Avatar
    Join Date
    Dec 2013
    Posts
    7,643
    ABP is a feature that helps decouple the effects between braking and suspension movement. It is unrelated to anti squat, pedal bob or any effect a different size chainring may have.

  14. #14
    Cactus Cuddler
    Reputation: tehllama's Avatar
    Join Date
    Jul 2013
    Posts
    1,808
    Any four-bar linkage setup will do that, and ABP is just the acronym Trek has chosen for their axle concentric rear pivot, pedal direction control linkage four-bar setup (most similar to SplitPivot) with a 'floating' lower shock mount which is cantilevered off the front of the chainstay.
    Even Trek engineers (note, not marketing people) will straight tell you that it's impossible to decouple braking or pedaling inputs from suspension behavior, and the kinematics that establish those instantaneous leverage ratios and torques applied are always a compromise around achieving desired characteristics while minimizing undesired side effects.

    What ABP enables engineers to do is that they can dial a remarkably low amount of brake jack in via keeping the brake rotor relationship to the calipers pretty constant across the travel [not actually that important at high speed], but more importantly through use of the floating lower shock mount that reduces instantaneous leverage ratio over small bumps, and shocks with dampers like the Re:Aktiv which can run with effectively more low speed compression because of how speed sensitivity is available with regressive damping -- the braking torque that has to be applied somewhere on a nearly foot-and-a-half lever arm in order to have a rear brake can be oriented with minimal resulting unloading of the suspension [i.e. predominately parallel with the seat-stay positioned linkage].

    So, ABP is related to anti-squat properties, resulting pedal bob, and both of those are also affected by chainring size... but the difference between a 32T and 30T chainring is probably about one click worth of adjustment on the shock difference in terms of pedaling characteristics, with the smaller ring actually producing more antisquat in the more stump-puller gears, and basically negligible in the higher gears. Since Trek does a really good job of setting up the custom tunes on the shocks, there's no way a rider within three sigma of average is going to have any issues with that setup on either chainring, so it's mostly moot.

  15. #15
    mtbr member
    Reputation: Lone Rager's Avatar
    Join Date
    Dec 2013
    Posts
    7,643
    Quote Originally Posted by tehllama View Post
    Any four-bar linkage setup will do that, ....
    Will do what? ABP mounts the caliper to a seatstay that moves up and down with much less rotation than does the chainstay, so the while braking, the suspension can move without trying to rotate the wheel, and vice versa.

  16. #16
    Cactus Cuddler
    Reputation: tehllama's Avatar
    Join Date
    Jul 2013
    Posts
    1,808
    There are Split Pivot iterations (I'm thinking of a couple Devinci examples, but I doubt they're alone) that do that too - and in a video Dave Weagle specifically explains why he's doing that, and it has very little to do with those traits when the bike is static.

    Basically brake jack only exhibits negative traits when doing trials stuff, or at speed. Losing traction at speed is arguably the worst of those, and the rotation of a caliper with respect to rotor while braking through undulations that will cycle the bike through its travel [thinking gnarly braking bumps are the best example here] is pretty negligibly different from a seatstay link mounted brake caliper.

    If you want to check for yourself, helpfully VitalMTB has videos of every TestSessions bike they had cycling through travel [and the music selection is amusing for this task]. You'll notice that the seatstay located link is rotating single digits of degrees with respect to the chainstay, so that difference in braking performance isn't going to be discernable to anybody withot a data acquisition kit on the bike (and even then questionably repeatable). What that location does allow is a brake caliper location which orients the braking force (i.e. transmitting the torque from decelerating the wheel to the frame of the bike) cause less suspension extending force than many rivals - hence active braking pivot, because the suspension is allowed to remain more neutral under braking which keeps it active over small stuff.

    The simplified explanation you have is the one the marketing group uses - intuitively it makes sense, and probably sells some bikes. While my engineering degree is in the 'wrong' field, I can still deduce that when the bike is actually rolling with any meaningful speed the far more important part is the direction of the torque applied via braking with respect to the main pivot and rear pivot. The engineering staff at Trek are very up front about this, but that doesn't take away from what they've been able to pull off with this bike. The Trek does a great job of managing this whole deal, and I suspect that a big part of achieving that behavior without compromising the pedaling platform/small bump sensitivity compromise has to do with the cantilevered floating shock mount and the Re:aktiv damper [while most FSR/Horst derivatives leverage the non-rear axle concentric rear pivot to elicit those behaviors].

    ABP doesn't operate in isolation from the four-bar layout chosen, which why I'm willing to dive down this rabbit hole in this particular thread is that those little adjustments to where the big input torques are supplied from [relative to the pivot points] do make a difference, but it's quite small. The direction those forces are applied from make a bigger difference, but in the case of going to smaller chainring the small delta in direction and location of the applied force to the chain ends up exerting a greater anti-squat torque when in the lower gear-inch regions of the cassette, and a negligible impact when going quicker. If anything, for a rider like myself (above the target weight for the shock's LSC tune, who values efficiency over small bump absorption when pedaling in low gear) who wants the lower gears, the changes in pedaling behavior are ones I'd consider to be positive ones, even for climbing technical singletrack.

Similar Threads

  1. Front end stiffness affected by burliness of headset?
    By Honda Guy in forum Bike and Frame discussion
    Replies: 2
    Last Post: 10-25-2015, 03:40 PM
  2. Replies: 4
    Last Post: 09-10-2013, 04:47 AM
  3. Is suspension air pressure affected by elevation change?
    By PeytonP in forum Downhill - Freeride
    Replies: 18
    Last Post: 08-14-2012, 12:31 PM
  4. Will new chain and chainrings be affected by used cassette
    By hozzerr1 in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 6
    Last Post: 01-12-2012, 02:26 AM
  5. Replies: 47
    Last Post: 06-14-2011, 03:57 PM

Members who have read this thread: 1

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.