bitdivision Posted July 11, 2015 Posted July 11, 2015 So last year I crashed my 2001, low-sided it in a corner causing it to flip. Crash caused a bent rear subframe and slightly bent front fairing stay (amongst other things). New subframe was installed, and bike was on the road again. Ever since then I've noticed a slight wobble at speed when there's a bump in the road. Also seems to happen on sharp deceleration. Doesn't cause a tank slapper or anything, but it feels a bit unstable. It doesn't seem to happen at low speed as far as I can tell, but it might be that I'm just used to it now. Researching this kind of thing, it looks like there are a few things that could be wrong: Head bearings (replaced last year with tapered). I haven't checked the torque on these recently, possibly could be loose? Forks bent. No, checked with run-out gauge. Wheel bearings. Doesn't seem to be any play. Tire pressures. At spec, PR3s installed. Frame bent. Don't think this is the case, measured the wheel alignment as per haynes manual and found no difference, but wasn't particularly accurate. I'm not sure if this is all in my head, or if there's actually a problem. Am I missing something basic? Quote
bitdivision Posted July 11, 2015 Author Posted July 11, 2015 Bent rim? Haven't seen anything obvious but I'll have a close look. Quote
Member Contributer FJ12Ryder Posted July 11, 2015 Member Contributer Posted July 11, 2015 It's also possible that the wheel could be slightly twisted within the forks. You might try loosening the axle pinch bolts and axle bolt, then use the front brake and your weight to compress the forks a couple times. See how that works. Quote
TNRabbit Posted July 11, 2015 Posted July 11, 2015 Check head bearing torque. Wih the front off the ground, should require about 5-10 lbs of force from the fork tube to move the fork. Quote
bitdivision Posted July 11, 2015 Author Posted July 11, 2015 Thanks for the replies. It's also possible that the wheel could be slightly twisted within the forks. You might try loosening the axle pinch bolts and axle bolt, then use the front brake and your weight to compress the forks a couple times. See how that works. Did think of this. Forks have been off three times since the crash and I've always tried to settle them as much as possible. Check head bearing torque. Wih the front off the ground, should require about 5-10 lbs of force from the fork tube to move the fork. I'll need to do this. From past experience it's definitely less than 5 lbs. Hopefully that'll sort it out. Quote
checksix Posted July 11, 2015 Posted July 11, 2015 Front tire worn and/or out of balance (missing wheel weight) ? Quote
Member Contributer GP Paul Posted July 11, 2015 Member Contributer Posted July 11, 2015 You ride over 70 mph? What kinda hooligans have we got on this website anyhow? Quote
bitdivision Posted July 11, 2015 Author Posted July 11, 2015 Front tire worn and/or out of balance (missing wheel weight) ? Nope, it's a little worn but it's not missing the weight. Quote
Member Contributer Switchblade Posted July 11, 2015 Member Contributer Posted July 11, 2015 Bent frame ? Quote
bitdivision Posted July 11, 2015 Author Posted July 11, 2015 Bent frame ? Could be. As I said above I measured it as per Haynes. No issues with wheel alignment that I could tell Quote
Member Contributer Switchblade Posted July 12, 2015 Member Contributer Posted July 12, 2015 The easiest way to check the fork is to loosen the pinch bolts on the top tree and the lower tree and then grab each fork tube and try to twist it, if the do not spin them got bent fork, you do not need to take the wheel off, it is not super accurate but you can tell if they are bent without taking everything apart. Quote
Member Contributer BusyLittleShop Posted July 12, 2015 Member Contributer Posted July 12, 2015 In short...Deceleration Shimmy = front tire problems... (annoying)...Wobble = front end problems... (could grow into the dreaded tank slapper)Weave = rear end problems... (annoying)... DECELERATION SHIMMY You might have experienced a deceleration shimmy and it's normal...some bikes may shimmy decelerating through the 45 mph range... keepingyour hands on the bars should arrest most of the front end shimmy...some bikes shimmy more than others and it's no big deal with yourhands on the bars in the critical speed range... your bike should beimmune at speeds above 45 mph...Deceleration shimmy is chiefly the product of non OEM or a worntires... it ain't the product of tire cupping... but low pressure orloose steering head bearings defeat the tire's corrective efforts... because every bike has this instability... it is held in check bydamping forces created mainly by the tire's self-correctingtendencies... STEERING HEAD BEARINGSIf your steering head bearings are too tight the bike will weave andnot seek it own center... if you're steering head bearings are looseyou'll notice a pronounce clunk during braking... I don't use torquefigures rather I raise the front wheel off the ground and tighten thesteering head bearings until the bars lock then I back off the nutuntil the bars free wheel with a slight drag... with this method youfind that sweat spot and avoid over tightening and under tighteningeven if you upgrade to taper roller bearings...WOBBLE or HEAD SHAKEAny bike my be induced into a head shake... head shakes happen underacceleration as the front tire hits a bump or finds a rut... a slightdisturbance in front tire alignment occurs and the rider feels thehead shake... and if the rider stays loose on the bars they seldomgrow into the dreaded tank slapper... steering dampeners don't curethe head shakes rather they lessen the degree the rider feels...perhaps it's best to hold back adding stuff until you have yourtechnique sorted out... Quote
bitdivision Posted July 12, 2015 Author Posted July 12, 2015 The easiest way to check the fork is to loosen the pinch bolts on the top tree and the lower tree and then grab each fork tube and try to twist it, if the do not spin them got bent fork, you do not need to take the wheel off, it is not super accurate but you can tell if they are bent without taking everything apart. Yep, it's definitely not bent fork tubes. I've measured them with a run-out gauge. In short... Deceleration Shimmy = front tire problems... (annoying)... Wobble = front end problems... (could grow into the dreaded tank slapper) Weave = rear end problems... (annoying)... Thanks Busy. I'm guessing it is loose steering head bearings. I'll go out and check the torque as soon as the rain lets up. Quote
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