Chain growth

mrfmilo
mrfmilo Posts: 2,250
edited October 2010 in MTB workshop & tech
Getting my first full sus frame in the next few days... can someone explain chaingrowth or link to a good article?

Thanks

Comments

  • Anonymous
    Anonymous Posts: 79,667
    Why do you want to know about it, and what exactly do you want to know?

    Basically, almost every single full suss bike available today have chain growth when the suspension compresses. This means that the distance from the BB to the rear axle increases as the suspension compresses.
    Like I said this is true for almost every single bike available, although some have significantly more growth at the start of the suspension stroke, which then eases off into the mid stroke.

    The reason they do this is so that any effort you put through the cranks tries to pull the rear wheel down, or extend the suspension.
    This is done to counteract your weight shift compressing the suspension.

    On a well designed bike (results may differ depending on rider position and weight as well) the idea is that the suspension extension due to pedalling power exactly counters the suspension compression effect of your downward momentum, keepig the suspension stable.

    Too little chain extension can lead to bobbing.
    Too much can lead to noticeable kickback on the pedals - but again this can vary depending on rider weight.
  • mrfmilo
    mrfmilo Posts: 2,250
    Why do you want to know about it, and what exactly do you want to know?

    Basically, almost every single full suss bike available today have chain growth when the suspension compresses. This means that the distance from the BB to the rear axle increases as the suspension compresses.
    Like I said this is true for almost every single bike available, although some have significantly more growth at the start of the suspension stroke, which then eases off into the mid stroke.

    The reason they do this is so that any effort you put through the cranks tries to pull the rear wheel down, or extend the suspension.
    This is done to counteract your weight shift compressing the suspension.

    On a well designed bike (results may differ depending on rider position and weight as well) the idea is that the suspension extension due to pedalling power exactly counters the suspension compression effect of your downward momentum, keepig the suspension stable.

    Too little chain extension can lead to bobbing.
    Too much can lead to noticeable kickback on the pedals - but again this can vary depending on rider weight.

    Just wanted to know what it is really. So cheers for that :) Is chain sizing diferent on full sus, to compensate for chain growth?

    All the drivetrain from the Norco is going on the new frame, but will I need a new chain?
  • nicklouse
    nicklouse Posts: 50,675
    in some cases yes you will need to take it into considerateion.

    remove shock/air and fully compress with the chain big and big. (held by a wire etc) and see is the sus will go through all its travel. if no add a link or risk blowing up a mech or a hanger/mech/wheel.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Anonymous
    Anonymous Posts: 79,667
    As Nick says, it may be worth checking. However most bikes only have a small amount of chaingrowth, so you should be ok.
    Chances are that you WILL need a new chain though. It's not likely that it will be the same length for both bikes (although not improbable)
  • mrfmilo
    mrfmilo Posts: 2,250
    Thanks nick/yeehaa. So compress the sus fully with the chain on yes...? :oops: :lol:

    Yeehaa my frames suspension is similar (or identical) to yours, it's a Quake 7.2 :)
  • Anonymous
    Anonymous Posts: 79,667
    Oooooh, QUAKE :D
    I like Quakes, a lot!

    Well, on my Wolfridge, which as you say shares a very similar suspension behaviour to yours, there is a total of about 11.5mm of chain growth at full compression.
    Since the quake has more travel, i would expect the travel/growth curve to be similar, yielding slightly more growth when yours is fully compressed. Maybe as much as 15mm (the chain growth eases off in the mid-stroke on these bikes, then ramps up again, I'm guessing this is to aid bottom out resistance).

    So, in thac case, I'd suggest adding a whole link to be on the safe side, or measure it as Nick suggests.
    To measure the chain, run it round the biggest chainring, and bigggest sprocket, WITHOUT going through the rear mech - just directly round the cogs.
    Then add one complete link (inner and outer).

    You could do this with the suspension at full suspension compression, OR, you should be ok by measuring at rest and adding an additional full link, which will allow for an inch of chain growth.
  • mrfmilo
    mrfmilo Posts: 2,250
    Yeah, perfect travel for my trails/riding :D Got some nice red bling on the way soon aswell 8)

    Oh right, I thought it'd be more than 11.5mm :lol: I'll measure it and stick a powerlink it, see how that goes.

    Cheers!
  • Anonymous
    Anonymous Posts: 79,667
    mrfmilo wrote:
    Yeah, perfect travel for my trails/riding
    PMSL! :lol:

    QThe quake is a very, very hardcore machine!
  • mrfmilo
    mrfmilo Posts: 2,250
    mrfmilo wrote:
    Yeah, perfect travel for my trails/riding
    PMSL! :lol:

    QThe quake is a very, very hardcore machine!

    What...? :? I mean it's not a full on 9 inch DH beast, slightly lighter and less travel, just right for me.
  • Anonymous
    Anonymous Posts: 79,667
    sorry, I thought you were joking :oops:
    It might not have 9" of travel, but it is raced as a DH bike by Shaums March. It's pretty much ideal for lift assisted bikeparks.
    It does pedal very well, but it also carries a lot of heft.
    Think more crazy freeride than trail bike. I mean, the lighter duty Attack trail makes an ideal megavalanche bike, and the Wolf ridge has been ridden in the Crankworks slopestyle event.

    They all ride like, and feel as though they have far more rear end travel.

    I really wanted a Quake, but I decided that I wanted to replace my old do-everything bike first. I might still get a quake later on for alpine DH trips and the like.
  • mrfmilo
    mrfmilo Posts: 2,250
    Nope :lol: I know it's abit of a beast, but I like big bikes :wink: Have ridden one and it felt really nice compared to Stinkys/Big Hits etc. and pretty much all reviews are very good.

    Trying to build it up lightish, but strong - I like hitting big stuff, just 'cos i'm 13 doesn't mean I only need 2 inches travel :lol:

    Hopefully visiting Gawton/Tavi soon, and Fort William next year :D
  • Anonymous
    Anonymous Posts: 79,667
    It will be awesome at Fort Bill!
    I've even met someone who rides XC one one, and had his fully triecked out with XTR cranks, X.0 mechs, carbon bars and post etc etc etc! :lol:
    He was fully aware it wasn't your typical XC race bike, and weighed about 4 times as much as one, but he mostly did freeridey things, but decided that XC racing looked like a laugh :lol:
  • mrfmilo
    mrfmilo Posts: 2,250
    What the hell..?! :lol::lol: That's like kitting out a Top Fuel with Saint :lol: Oh well, if he likes it...

    Will be posting pics soon :D:wink:
  • Anonymous
    Anonymous Posts: 79,667
    He claimed that he swapped parts out for trips to France and Whistler, to more heavy duty stuff, but swapped it for the lightweight parts for pretty much all UK trail riding.
    I have to say, I like the way he was thinking! :lol:
  • mrfmilo
    mrfmilo Posts: 2,250
    Fair enough :P but if he can afford that, can't he just buy another frame/bike?
  • Anonymous
    Anonymous Posts: 79,667
    probably, but we all know big bouncy bikes are the most fun.
  • supersonic
    supersonic Posts: 82,708
    If you can tell me the exact year and model, I can tell you the exact max chain growth.
  • nicklouse
    nicklouse Posts: 50,675
    or you can download "linkage" and find out yourself :wink:
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • supersonic
    supersonic Posts: 82,708
    Lol, I have the Pro version so have a bigger database ;-)
  • nicklouse
    nicklouse Posts: 50,675
    but all you need is a photo of your bike :wink:

    the Pro version? Ie the one you pay for rather than the free one.

    Or did you go the whole way....
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • supersonic
    supersonic Posts: 82,708
    Yeah, paid for a version as has better features and more bikes. Needed it for when doing the sus feature for WMB.