Results 1 to 21 of 21
  1. #1
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    31

    Tire touching seat tube when bottoming out

    Has anybody encountered this problem?
    Every time I bottoms out during a jump or a bit of harsh landing (1-2ft drop to flat) the rear tire slightly touches the seat tube.

    I run Shimano 778 XT wheels with Conti RQ 2.2 Tubeless on the rear wheel.

    I checked the space from the tire to the seat tube when the rear shock is flat out and there is about 10mm of space, so its looks like some kind of flex at the rear or something with the deformation of the tire during harsh landing

    Any advice?
    Thnx,
    Tal

  2. #2
    www.derbyrims.com
    Reputation: derby's Avatar
    Join Date
    Jan 2004
    Posts
    6,788
    The knobs of some taller tires can occasionally buzz the front derailleur cable upon hard bottoming with no damage and normally doesn't rub the seat tube paint but it is a bit startling to hear the cable buzz. If you don't have the Lopes Link, which started to be shipped with new Mojos in '09, the swingarm flexes more than ideal and allows a little more bottom travel range and hard cornering flex. Also double check that your link bolts aren't loose.

  3. #3
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    262
    The rub also happened to me on my 2009 Mojo SL, 2.25 Schwalbe Fat Albert rear tire, with Lopes link, after some seriously hard riding. It turned out to be loose link bolts. Not one, all of them. They have all been re- torqued with blue loctite . I now check them judicously. I also went with a bolt on rear axle for my Easton AM Havocs.
    Last edited by lml427; 03-22-2010 at 07:25 PM.

  4. #4
    mtbr member
    Reputation: Yody's Avatar
    Join Date
    Jan 2008
    Posts
    2,937
    my 2.4's used to buzz the seat tube all the time, I have a 2010 SL with a lopes link. I had to put a clear protective sticker right in the spot, it quickly turned black from buzzing so much. I ended up putting a 2.24 on the rear and don't buzz at all ever, anymore.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    31
    thanks,

    I ride Mojo SL 10, in use for about two weeks now, I'll double check the link bolts.

    Yody, what tire are you running on the rear wheel?

    What rear tires are recommended, from anyone experience, for light AM use that do not rub the frame?

  6. #6
    mtbr member
    Reputation: Yody's Avatar
    Join Date
    Jan 2008
    Posts
    2,937
    The WTB Mutanoraptor 2.24 is what I'm runningi now, I feel its an excellent rear tire for AM use, I'm sure there are many other good ones that won't rub as well. I also ran a weirwolf 2.3 that didn't rub. Only the Mutanoraptor 2.4 (not the smaller 2.24 one) has rubbed but its a pretty bulbous high volume tire.

  7. #7
    mtbr member
    Reputation: getbusyliving's Avatar
    Join Date
    Mar 2007
    Posts
    417
    Quote Originally Posted by Tal Kadouri
    What rear tires are recommended, from anyone experience, for light AM use that do not rub the frame?
    I run Specialized Eskar Control 2.3 in rear and never buzzed it (and really like it). Also never had problems with Kenda Nevegal 2.35's, but they're slow tires.

  8. #8
    meh
    Reputation: clewttu's Avatar
    Join Date
    May 2007
    Posts
    1,068
    I had a Nevegal 2.35" that I just swapped to a 2.4" UST Nobby Nic, no rubbing from either, but i have to say, NN destroys the Neve in every category, its seems as versatile as the Mojo so far

  9. #9
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    31
    Thanks, I will check the tires option. I also noticed that the rear wheel can flex quite a bit towards the chainstay, will a thru bolt axle will help? what kind of axle will fit a shimano 778 wheel?
    Tal

  10. #10
    Ride More Work Less
    Reputation:
    Join Date
    Jun 2006
    Posts
    372
    Tal,
    Recently someone found that they had a shock that was too long, allowing too much travel and the tire buzz. You should verify your shock length.

  11. #11
    meh
    Reputation: clewttu's Avatar
    Join Date
    May 2007
    Posts
    1,068
    fairly certain you cant change it out on those wheels

  12. #12
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    31
    thanks guys,

    I checked the shock:
    boost valve 10' RP23
    shock dimensions: eye to eye = 7.875", Shaft length = app. 2.3", full travel = 2"

    from what i see in the ibis site at the tech section http://www.ibiscycles.com/tech/ - should be OK...

    I guess its the tires - I hope the buzz will disappear as I wear the tire a bit
    Tal

  13. #13
    Happy when not-last.
    Reputation: MinskyBA's Avatar
    Join Date
    Jun 2006
    Posts
    221
    Check to be sure the bolt through the lower shock pivot isn't bent. I had to get the Ti bolt because I had bent the steel one, you may have the same issue if your tire's big enough.
    All your base are belong to ME.

  14. #14
    T.W.O.
    Reputation: mimi1885's Avatar
    Join Date
    Aug 2006
    Posts
    8,011

    New question here. Uh Oh!

    How about the first Gen Mojo would the tire contact with the seat tube when bottom out. I'm using kenda nev 2.35 rear. I remember reading about occasional contact between tire and seat tube here on the forum. I kinda accepted it. Seems like it should not happen at all. would up grade the link solve the problem? Thanks

  15. #15
    Turn off the TV
    Reputation: SMT42's Avatar
    Join Date
    Nov 2006
    Posts
    241
    No upgrading link will not help the issue. I have a regular mojo and get some tire rub on hard landings. I run 2.2 Purgatory and have had no real issues it stops after the tire wares a bit

  16. #16
    Grams Light Bikes
    Reputation: pastajet's Avatar
    Join Date
    May 2006
    Posts
    2,279
    Bigger tires can cause the issue to happen, but it is frame and sometimes frame size dependent, I have 3.5 years on my Mojo, and have used the fattest tires that fit and have hit the bumper on the shock (got max travel) and never hit the seat tube nor cable, although if the cable end sticks out to much I have buzzed that.

  17. #17
    T.W.O.
    Reputation: mimi1885's Avatar
    Join Date
    Aug 2006
    Posts
    8,011
    Mine is a small. Is that it? I increase the air a bit to control the bottoming, it hasn't happen in a while now. I do wish it doesn't happen though.

  18. #18
    Turn off the TV
    Reputation: SMT42's Avatar
    Join Date
    Nov 2006
    Posts
    241
    If the rear triangle is the same size on all bikes how would frame size matter? Seat tube angle? I think it has to do with the height of the tire and there is no standard for this in the bike industry. I think the bike was developed with 2.1 tires in mind and we have all gravitated toward bigger. My frame is medium, I have been riding it since Sept 2007, I had no issues untill using the Specialized Purgitory 2.2 which are tall, I like them and am on my second rear with no perceptable damage. The rub goes away as the tire wears down.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    57
    I recently discovered the same problem on mine when I installed Crossmarks 2.35, so I ordered the lopes link suposing that would fix it, installing the lopes link I found the lower shock bolt was bent.
    Titanium bolt set on order

  20. #20
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    57
    My bad, Crossmarks were 2.25. Previously ran Larsen 2.1

  21. #21
    mtbr member
    Reputation:
    Join Date
    Jul 2008
    Posts
    945
    I have the same problem with a Specialized Purgatory 2.2 in back . I have done it enough that there is a small wear patch in the clear coat on the seat tube and part of the cable stop for the front derailleur cable is worn down. It is disconcerting, and definitely comes from some sort of flex in the rear triangle (if you take all the air out of the shock and fully compress the bike there is about 5-10mm of space) on hard landings. However, I doubt it will damage the structural integrity of the bike. I may try to find a shorter tire--racing ralph or panaracer CG anyone?

Posting Permissions

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