Jay_B Posted February 9, 2015 Posted February 9, 2015 Maybe someone has experienced this before or can point me in the right direction... Last weekend during Berg en Dale race while coming down the first big descent going into the cradle my bike starting snaking under me, initially I thought my quick release had come loose and when I stopped and checked everything was still tight... got going again and same thing happened further down the hill, again check and nothing is loose or seems to be broken. This proceeded to happen every downhill after that. My initial though was that something was wrong with my back wheel, so send it in to get checked and nothing can be found that is wrong, wheel is still true and everything. Take it out again over the weekend and again it happens. The confusing part is, the bike snakes only on a downhill when coasting, as soon as the shaking and wobbling starts to set in if I start pedalling it will go away and it happens whether im on the brakes or not. So I though its still my wheels and contacted the distributer to tell him what is happening and arrange to send them back to him to be inspected. In the interim I put my aluminium training wheels back on and went for a ride this evening and the same thing happened - downhill, freewheeling and bike starts snaking. So now I am led to believe that there is an alignment issue that has come about in my frame, I have checked all the welds and cant see any cracks. Has anybody had an experience like this or can you please point me to someone or somewhere that I can take my bike to get the frame checked out properly for any misalignment problems that could be causing this? Thanks and sorry for the long post.
Baaisikilist Posted February 9, 2015 Posted February 9, 2015 Pivot bearings on a road bike...?Is everything right n tight headset wise...?
porqui Posted February 9, 2015 Posted February 9, 2015 Check your headset. See if it happens when you apply rear brakes only.
MAK Posted February 10, 2015 Posted February 10, 2015 Certain bike frames have a resonance frequency which causes this oscillation. It's very easy to cure, simply clamp your knees against the top tube when it happens [usually at a particular speed].This stops the oscillation and stabilizes the frame.
Malpiet Posted February 10, 2015 Posted February 10, 2015 Pivot bearings on a road bike...?Is everything right n tight headset wise...?it does not sound like the OP is using a road bike.
King_Crispy Posted February 10, 2015 Posted February 10, 2015 it does not sound like the OP is using a road bike. Berg and Dale a mtb race?Go back and read OP's post again.
Jay_B Posted February 10, 2015 Author Posted February 10, 2015 Just to clarify I am talking about my road bike and not MTB... sorry for not stating that in the initial post.Check your headset. See if it happens when you apply rear brakes only. Headset is still tight and all in order. I have watched my front wheel really closely when it happens and there is no movement there. The problem happens whether I have the brakes on or off. Certain bike frames have a resonance frequency which causes this oscillation. It's very easy to cure, simply clamp your knees against the top tube when it happens [usually at a particular speed].This stops the oscillation and stabilizes the frame. Yup I am aware of that but this isn't a resonance frequency coming through the frame... the back wheel feels as if its completely loose and wants to slide out from underneath me. And once it sets in even when I apply the brakes to slow down it carries on until I have come to a complete stop or start to pedal. If it was a resonance frequency occurring at certain speeds it would go away once I start to slow down under that speed.
Eugene Posted February 10, 2015 Posted February 10, 2015 My friend bought a Merida and he had similar problems. Turns out the one stay was shorter than the other. He got a new one under warranty.
Thomo Posted February 10, 2015 Posted February 10, 2015 My friend bought a Merida and he had similar problems. Turns out the one stay was shorter than the other. He got a new one under warranty. Thank goodness for quality checks ...
Jay_B Posted February 10, 2015 Author Posted February 10, 2015 My friend bought a Merida and he had similar problems. Turns out the one stay was shorter than the other. He got a new one under warranty. That's my thinking as well... that one of my chain stays have bent out of alignment and when I am pedalling the torque in the wheel is pulling it all straight again. Unfortunately I don't have a warranty anymore on the frame and my wedding is in a few weeks so no spare cash for a new one
grego12 Posted February 10, 2015 Posted February 10, 2015 I had a similar problem on my MTB a long while back. The bike would start to wobble and shake dangerously on a downhill. If I pedalled it stopped. I had tubes in the wheels with sludge in them. Sludge had formed a solid ball in the tube which was throwing the balance off. Now I doubt you have sludge in a road bike, but may be worth it to check...I know some guys do have it in their tubes
Jay_B Posted February 10, 2015 Author Posted February 10, 2015 I had a similar problem on my MTB a long while back. The bike would start to wobble and shake dangerously on a downhill. If I pedalled it stopped. I had tubes in the wheels with sludge in them. Sludge had formed a solid ball in the tube which was throwing the balance off. Now I doubt you have sludge in a road bike, but may be worth it to check...I know some guys do have it in their tubes Don't have sludge but have checked the balance on the wheels and there is no heavy spots...
David Marshall Posted February 10, 2015 Posted February 10, 2015 It sounds like a shimmy. Plenty info if you google "shimmy " or "high speed shimmy" can be caused by anything on the bike - including rider tension or shivering. History is important - like are you new to the bike or have you changed anything? - wheels, tires etc. To check frame alignment is fairly simple. Take the wheels off and then wrap the bike in string sort of mirror imaging the path of the string on both sides of the frame eg through dropouts - around head tube and back and so on. With a ruler measure the distance of the frame to the string on each side at the same place. You will soon see if it is the frame.
Long Wheel Base Posted February 10, 2015 Posted February 10, 2015 Don't want to sound funny but have you ridden another bike to see if its you or the bike? There is a guy in my club that its common knowledge to stay FAR away from him, especially on downhills. The dude cant ride in a straight line and it gets worse on faster decents . He is a bit of a novice but still what iv seen happen to him on the downhills sounds similar to your problem. He just needs to learn to relax a bit and get used to bunch riding. You know the guys that always seem to be involved in the accidents.
Recommended Posts
Archived
This topic is now archived and is closed to further replies.