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Speed wobble !!
Speed wobble !!
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crash
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09 Oct 2012 20:41 #1
by crash
Hi Guys, great sportif at week end,
Had a major speed wobble, as witnessed by a few club members. Have any you experienced this and or have any tips to avoid it ?(other than a fresh pair of shorts!)
The above link shows the type of thing a speed wobble is ,
When I stopped and checked the bike over we could find no reason for the wobble, spokes were tight ,wheels true and properly fitted !!
My Speed was not high perhaps 38mph
Crash
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09 Oct 2012 23:56 #2
by alec
Hi Crash,
New bike, maybe a little livelier at the front end than your old one - probably less front wheel track - descending - in a descending crouch? Possibly not an issue with your previous bike but is it possible you only had two point contact where both pedals count as one contact and both hands on the bars count as another? No firm contact with saddle or cross bar near down tube? These sorts of wobbles feel like front wheel wobbles but are often actually the unconstrained rear end of the bike picking up an oscillation. If that's the case you can control them by gripping the saddle with your thighs or sitting down to re-establish 3 point contact - pedals, bars,saddle. It might not be this, but it might be. Next time we're out together I can demonstrate inducing a downhill wobble and controlling it.
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Di2vid Lindsay
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13 Oct 2012 21:31 #3
by Di2vid Lindsay
I saw this in person and it was exactly how that video showed it, scary...
Ash, when descending try gripping the toptube with your knees too, that could help (4 anchor points then)
I like shiny things
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crash
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13 Oct 2012 22:38 #4
by crash
Hi David, im glad u witnessed it,i have to say it "Felt" like it went on a lot longer than the clip and felt loads more scary , but ive done a load of google research and yep it seem nip up the butt and grip that top tube baby , at least tomorrow we are going uphill ! Ill get it sorted soon and then moto on !!! see ya tomorrow
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geoffrey smith
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14 Oct 2012 18:31 #5
by geoffrey smith
its your head set..worn bearings,but what do i know..G
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14 Oct 2012 18:36 #6
by alec
Brand new bike G, first ride.
How's the hols going? Brass monkeys here this morning.
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geoffrey smith
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15 Oct 2012 09:16 #7
by geoffrey smith
back home on Saturday..quick 100kms on Sunday..cold in the morning (09.00hrs),warm by lunch time..was the old bike a heavy weight ????...new bike carbon ???............G
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15 Oct 2012 10:09 #8
by feef
its your head set..worn bearings,but what do i know..G
I was going to suggest that as it's often the cause for similar wobbles on motorcycles, but I wasn't sure if it would have the same effect on something lighter like a bicycle as the loads are lower.
When a passenger of the foot, hooves in sight, tootel the horn trumpet melodiously
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geoffrey smith
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15 Oct 2012 12:16 #9
by geoffrey smith
according to Archimedes..its all about load on the bearings...he just invented the screw..G
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crash
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15 Oct 2012 18:52 #10
by crash
Hi geoff
old bike trek1500, as you know, new bike full carbon Felt ar3 aero frame
I plan to get a pro bike fit ( as your not back until xmas !) I still have the trek, so have checked lots of measurements , all about same, however i notice the saddle is quiet a way back on the new bike, which puts weight further back?
Glidiing down some gentle hills I have made the bike wobble and then nipped the x bar which works but not had another proper resonating wobble to test that theory
C rash
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geoffrey smith
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15 Oct 2012 19:23 #11
by geoffrey smith
hi there A,,ah at last i know your problem,,,you need at least 120mm stem..you need to put your elbow a on the peak of the saddle,,with your forearm stretched your fingers should be half way along the stem.adjust saddle either way... worked for Maureen my wife luvvy...see ya xmas..G..........
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Speed wobble !!
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