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  1. #1
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    Untrue wheel? "bent" rear? Or something else...

    I never posted this before but ever since I got the Mojo which is about 4 months ago, I noticed instantly that the rear wheel isn't centered between the SS or CS. I didn't really think anything of it since it's not rubbing, but the offset is pretty obvious.

    I don't think it's the wheel for a coupla reasons. First, it was centered on my old bike....that's probably the biggest reason. And 2nd, if a wheel was untrue it would "wobble" between the SS/CS which it doesn't. Is there some way that the entire wheel can somehow be offset to the left (the tire is closer to the left SS/CS)? There is probably a 3mm gap between the left SS and the tire....and at least double that space on the RT. The gap differences on the CS are even more obvious. There is probably only 3 mm clearance on the left side and maybe 1/2 inch on the right. When I spin it, the wheel spins very straight....meaning it doesn't "wobble". I can't think of any way that the entire wheel can be offset to the left unless the rear of the Mojo isn't totally true. Correct me if I'm wrong.

    My wheels are very stout (King's 3X laced to 823's, brass nipples, straight gauged spokes) and since they were perfectly fine on my old bike, I can't believe that it's the wheels that's the problem.

    I wish I could take pix but my camera is busted

    I haven't tried to take the rear apart but I have checked all the pivots and they're solid (the shock bolt was loose but it's now tight and the problem persists).

    I'm thinking it's the rear end since it's been this way ever since I built the bike.

    Think I should have Ibis take a look at it? I didn't buy it from an LBS....private sale.

  2. #2
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    a little off

    On my new SL frame the drive side seat stay is a bit closer to the downtube than the non-drive. Small but something I noticed. I think they all are that way. Probably because I'm so anal and every past Ibis I have owned, back to #214 , has been just absolutely flawless as far as frame alignment is concerned. Chalk it up to the vagaries of mass production in a far away land. Or maybe they've built it that way for a reason....

    Before worrying about that I would check that the hub is snug. No contamination on the axle/dropout interface. Is the axle sitting true in the dropout. Howz the dish? Check it twice, no 3 times. Maybe your old bike was off. Is your tire symmetrical?(I've run into this) Beads seated?

    I haven't finished my build so I can't compare. The boys at Ibis can come back and say 'it's a flowing organic form and therefore not symmetrical' and we'd all be happy.

    Does it ride straight? Does the center of the rim intersect the center of the seattube??

  3. #3
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    My rear wheel is within 1mm of true dish (I build my own wheels) and it's tire has less clearance on the left side chain stay and seat stay, closer to the chain stay. The wheel alignment looks true to the frame by eyeballing from the sides of the wheel to the sides of the frame. It sure rides easy with no hands on the street and it feels "true".

    I think this asymmetrical clearance is common on all the Mojo's. There's a lot of tight clearance in the dw-link design to deal with, and there's designed asymmetry in the swing arm so it may be that tire clearance and side-to-side stay strength have a bit of an “organic” result.

  4. #4
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    Quote Originally Posted by derby
    My rear wheel is within 1mm of true dish (I build my own wheels) and it's tire has less clearance on the left side chain stay and seat stay, closer to the chain stay. The wheel alignment looks true to the frame by eyeballing from the sides of the wheel to the sides of the frame. It sure rides easy with no hands on the street and it feels "true".

    I think this asymmetrical clearance is common on all the Mojo's. There's a lot of tight clearance in the dw-link design to deal with, and there's designed asymmetry in the swing arm so it may be that tire clearance and side-to-side stay strength have a bit of an “organic” result.
    If that's the way it's supposed to be....meaning designed that way, then I'm not worried about it. I'm definitely not an engineer so if there was some reason for the asymmetry, I'll rely on Ibis to know exactly what they're doing. I just didn't want a lemon rear end.

    I'll have the wheel trued, have them check the dish and see what happens. It definitely rides straight....my riding skills probably don't help

    I'll check to see if the wheel is centered behind the seattube. I imagine it should be but never eyeballed it.

    if other Mojo'ers could chime in and let me know if the tire is supposed to be asymmetrical between the stays, that would be great. Or better yet.....Hans or Tom. Thanks......

  5. #5
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    Same here: closer to the left chain stay than the right chain stay when measured right behind the bottom bracket. I was measuring to the rim instead of the tire to take that out of the equation. My dish is true.

    Eyeballing the seat tube says that the wheel is centered and straight with regard to the frame ... for all I can tell by eyeballing.

  6. #6
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    man i was thinking of posting this same question a few weeks ago...i noticed it too...the rear wheel is definetly closer to the left (non drive side) chain stay. it's noticable without measuring it. my wheel is true too.

    i took notice because there's obviously tire rub (2.35" fat alberts) on that left chain stay because the paint keeps getting chipped right on the edge where the brake guide is. 2.35" tires touching chainstays for an AM bike?!

  7. #7
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    I just checked the bike...the whole wheel is offset to the left. When I eyeballed the wheel, it's not centered over the seat tube. It should be right? I imagine that the seat tube should be the "center" of the bike....at least laterally. It's very noticeable.

    Could the wheel be that off? Since most people have experienced the same thing, I imagine that the bike is designed to have less clearance on the left but mine seems to be abnormal. I'll have to bring it in somewhere to check I guess.

    Yo crappy..

    We should compare the differences.....swap wheels to see what the heck is going on.

  8. #8
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    i know where this is going to go...first swap wheels, then girlfriends, etc. just letting you know i'm not down with the swingers lifestyle but yeah we should swap the wheels to see.

    just to clarify, the rub i was talking about isn't when the bike is still. obviously there's clearance...but during riding the tire probably rubs on the stay because the paint is rubbed raw/chipped at that closest point.

    none of this effects performance i'm guessing, but maybe it does and i can justify that crash off of that skinny due to the leftward tire placement! think about it, if the rear isn't centered, then any skinny would be trouble right?

  9. #9
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    Rear Wheel Alignment

    Hello all,

    The tire is supposed to be centered within about 2mm, though it's hard to check due to the shape of the swingarm. Also, it's sensitive, since any error is multiplied by two visually, that is, 1mm off center = the tire on one side 2mm closer to the chain stay than on the other side.

    An easy way to check is to flip the wheel over and see if the gap issue changes sides. If it does, it's probably the wheel, if not, it's the swingarm.

    I would guess that there is a little bit of clearance in the dropout slot / axle contact area and the chain tension is pulling the wheel over a little bit.

    If it bugs you and you want it to be closer to perfectly centered, here are some things you can try:

    Loosen the quick release, then center the wheel with a slight shift of the axle location. You can tighten the quick release in that position (it needs to be tight to hold it)

    or

    do a very careful, small and gradual amount of work with a rat tail file to allow the wheel (axle) to sit perfectly when the wheel is centered and up in the drop outs. You check it, file, check it, file and repeat until it's dialed. I don't recommend this unless you are patient and methodical about it. You do not want to ruin the drop out(s).

    Take care,

    Hans

  10. #10
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    Quote Originally Posted by hanssc
    Hello all,

    The tire is supposed to be centered within about 2mm, though it's hard to check due to the shape of the swingarm. Also, it's sensitive, since any error is multiplied by two visually, that is, 1mm off center = the tire on one side 2mm closer to the chain stay than on the other side.

    An easy way to check is to flip the wheel over and see if the gap issue changes sides. If it does, it's probably the wheel, if not, it's the swingarm.

    I would guess that there is a little bit of clearance in the dropout slot / axle contact area and the chain tension is pulling the wheel over a little bit.

    If it bugs you and you want it to be closer to perfectly centered, here are some things you can try:

    Loosen the quick release, then center the wheel with a slight shift of the axle location. You can tighten the quick release in that position (it needs to be tight to hold it)

    or

    do a very careful, small and gradual amount of work with a rat tail file to allow the wheel (axle) to sit perfectly when the wheel is centered and up in the drop outs. You check it, file, check it, file and repeat until it's dialed. I don't recommend this unless you are patient and methodical about it. You do not want to ruin the drop out(s).

    Take care,

    Hans
    Thanks....I'll try flipping the wheel. That makes total sense....shoulda thought of it before If I can discern from that test if it's the wheel (what I'm hoping), then it's all good. And if that doesn't work, I'll try recentering the axle. I definitely do not want to try filing away at the dropouts! :O
    Last edited by ddraewwg; 01-17-2008 at 05:57 AM.

  11. #11
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    Quote Originally Posted by crapaccount
    i know where this is going to go...first swap wheels, then girlfriends, etc.
    i wouldn't worry about him wanted to swap for your fiancee... i'd worry about him going brokeback on you. not that there's anything wrong with that.

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