Frame or Wheel Flex?

OTimms
OTimms Posts: 14
edited March 2012 in MTB general
Hi there, I have a 2012 Genesis Core 50 and recently took it for a week long thrash round Wales with my Bro. The bike's absolutely great 95% of the time and the 120mm Reba front forks are mega for trail centre riding and natural XC, the only problem I have is with the rear end!!

I know it's a hardtail but I can definately feel flex in the rear on the fast downhill sections. Initially I thought it might be the lightweight wheels, but it gets so bad that it's losening my 9mm QR and needs re-clamping every hour or so.

I've checked the wheel, which is true and not dished, so all I can assume is it's the frame!

Question is, am I getting to the limit of the bike's capabilities or does this happen with all hardtails? (for context: the speeds I'm talking about are black route stuff and we hardly ever get passed by other riders) Even so, at £1300 I would expect the bike to be pretty robust?!

Any advice welcome!

Comments

  • supersonic
    supersonic Posts: 82,708
    What QR skewer is it?
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  • danlikesbikes
    danlikesbikes Posts: 3,898
    You would expect an element of frame flex to be expected from any frame, though can't imagine that it would be so excessive.

    As for the QR's coming loose that could be caused by movement in the frame but sounds unlikely that you are getting that much movement that it is causing them to come loose if they are fitted correctly in the first place. You might want to swap them over and try a different set and see if it is an error with them as could easily be solved?
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  • OTimms
    OTimms Posts: 14
    Supersonic - it's the basic Shimano one that came with the bike, can't tell you anymore than thatt!
  • supersonic
    supersonic Posts: 82,708
    These are usually the best too! Very odd for it to come loose like this, and I have not heard of other problems with this frame.

    I would try another QR - also check the dropouts are straight and the wheel axle is not bent (turn the axle in you fingers and look for any osciallation)
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  • .blitz
    .blitz Posts: 6,197
    A couple of mates have HTs and I notice they flex whenever I'm following them. One is a Voodoo Bokor the other is a Spesh Rockhopper. Standing beside the bikes you can hold the seat tube/post and flex the top of the back wheel a cm or two side to side. Difficult to see what's wrong nothing is loose but it still moves.

    My Rize is a lot worse though. The chainstays are supposed to be doing all the work but the plastic seatstays make it quite easy to twist the back wheel. The Voltage is made out of scaffolding but the back wheel can still be persuaded to move sideways.
  • 1mancity2
    1mancity2 Posts: 2,355
    All frames flex and so do they wheels they have too but your skewer coming loose is a worry, mine has done it in the past and it was down to a bent axle as SS as already pointed out.
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  • YeehaaMcgee
    YeehaaMcgee Posts: 5,740
    OTimms wrote:
    so bad that it's losening my 9mm QR and needs re-clamping every hour or so.
    My guess in that case would be that you're not tightening the QR levers anywhere near hard enough.
    You should styart to feel resistance when the lever is in line with the wheel axle, 90 degrees from fully closed.
    You should tighten the nut on the other side until this is the case.
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  • sloppycowpat
    sloppycowpat Posts: 349
    are the cones/ bearing covers and axle all tight and correctly lined and spaced?
    worst moment ever...
    buzzing down twisting single track then.... psssst BANG!!!
  • OTimms
    OTimms Posts: 14
    Hi all, thanks for the comments.
    I should say, that I'm used to spannering bikes and do all my own maintenence, that's why I'm so perplexed by the problem.

    YeeHaMagee- the skewer should be tight enough, I'm close to hurting my palm to get it stuck!!

    The cones etc are all tight too...
  • bluechair84
    bluechair84 Posts: 4,352
    So, if you stand the bike and push / pull against the wheel and seattube, what do you feel? Is the tyre too big for the rim and rolling around? are the spokes all tight (though I'm sure they'd let the wheel buckle before you'd notice any flex)? Can you change the hub to a 10mm bolt thru?
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  • OTimms
    OTimms Posts: 14
    Bluechair84 - thanks. Tyre should be ok it's only a Mountain King 2.2''

    I would be interested to swap the rear for a bolt thru', something I might try... ta
  • 1mancity2
    1mancity2 Posts: 2,355
    OTimms wrote:
    Bluechair84 - thanks. Tyre should be ok it's only a Mountain King 2.2''

    I would be interested to swap the rear for a bolt thru', something I might try... ta

    Recently done that on my bike and it does feel alot more secure.
    Finished, Check out my custom Giant Reign 2010
    Dirt Jumper Dmr Sidekick2

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