Forum home Mountain biking forum MTB workshop & tech

Lateral movement in frame?

jolmesjolmes Posts: 144
edited April 2013 in MTB workshop & tech
Hey guys

Just after some advice really, I have a 2008 SC blur lt, not the newest model but the previous one (05-08) and i bought it 2nd hand from a guy who said it was in perfect working order. Now I'm not the most aggressive rider in the slightest and have only used it a couple of times but it appears to have developed some lateral play in the frame. By this I mean the rear triangle is moving a lot more than it should be, however the all the pivots bolts and bushings are tight and plush to the correct torque etc, its extremely visible when moving the cranks a touch, you can see the frame bend inwards towards the middle...

is it time for a new frame?

Posts

  • cooldadcooldad Posts: 32,599
    Define 'bend inwards' better. New bearings maybe.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • jolmesjolmes Posts: 144
    standing prone, with both brakes held firm and pressing slightly on the pedals, the whole rear triangle and the cranks/chainrings from the bb flexes around 3/4s -1 inch either side with no movement from the shock.

    If that makes sense, kinda hard to explain
  • The RookieThe Rookie Posts: 27,802
    Standing is upright, prone is laying down - clarify standing prone please!

    I think your saying the frame is flexing due to chain tension which will be trying to pull the driveside of the rear wheel forwards and hence moving the BB shell part of the frame to the left as it does so?

    Some play is normal, as is some flex, but that sounds like new bearing/bush time.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • jolmesjolmes Posts: 144
    Haha sorry yeah I meant standing still, god knows why I wrote prone...

    The flex is happening even without the chain on the bike, even taking the rear wheel off it still occurs, the rear triangle still has too much play in it. Tried all sorts of variables and it still seems more flexible than what it should be. A mate also has a BLT1 and his is quite rock solid, he also suggested a bearing/bush change.

    Thanks TB
  • The RookieThe Rookie Posts: 27,802
    jolmes wrote:
    The flex is happening even without the chain on the bike, even taking the rear wheel off it still occurs, the rear triangle still has too much play in it.
    Now I'm confused, which way is the flex? without a chain there is no sideways load so the only movement is up and down, so where is the flex then?
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • supersonicsupersonic Posts: 82,708 Lives Here
    if you stand on the pedal in its lowest position you get a lateral force into the BB which flexes the frame. is it this?
  • njee20njee20 Posts: 9,613
    if you stand on the pedal in its lowest position you get a lateral force into the BB which flexes the frame. is it this?

    That was what I was understanding? If so that's not really an issue, you can get several inches deflection from most frames doing that, road, MTB, hardtail, FS!
  • supersonicsupersonic Posts: 82,708 Lives Here
    Yep, all my frames move quite a bit when I do it!
  • jolmesjolmes Posts: 144
    I'll try upload a video of it. I did speak to another guy who owned a pre 08 blur and he had a similar issue, replacing the bearings worked a treat and anti seize on the lower and upper link removed the squeak from the frame was his advice.

    TB/SS - the flex is sideways , sitting on the bike and looking down, pedal near the top and pushing slightly, the bb area moves around an inch sideways, with the brakes on. I've done the same thing on a lot of other bikes recently and not seen anything like it, only other LT1 riders mention it...

    It also got worse the more I was riding it yesterday after a few runs, the last run I thought it was going to shake loose completely. Kind of difficult to explain without showing or filming but cant seem to get a good video of it atm.

    I've ordered some bearings for it and gonna replace the bushings at the same time too.
Sign In or Register to comment.