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Speed Wobbles !

Old 06-06-22, 07:13 AM
  #26  
LarrySellerz
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Originally Posted by _ForceD_ View Post
Since it was a school bus…as mentioned above…you should contact the school bus/student transport company, or maybe the school department (I suppose a complaint to the police wouldn’t hurt either). Give them all the info you can about the bus with regard to location, time of day, and the bus number if you happened to notice it. If you were safely on the shoulder/bike lane the bus should not have come that close to you…and/or slowed and waited until it was safe to pass you. They might be able to determine who the driver was and take appropriate action.

Dan
24 inches is plenty, don't try to get some poor bus driver fired..
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Old 06-06-22, 07:48 AM
  #27  
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I've had the wobblies twice on different bikes. Both times I was cold and shivering a bit on high mountain descents. The first time was minor enough. I solved it by doing squats out of the saddle to warm up. It was snowing/raining at the time. The second time was more immediately dangerous, definitely a Code Brown. I had also just been passed (safely) by a car in a crosswind. Knees clamping the top tube and rode it out to a lesser grade, stopped and warmed up in the sun. Both bikes had been stable on those descents several times before, in all sorts of wind conditions.

I congratulate the OP on knowing not to brake.
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Old 06-06-22, 08:30 AM
  #28  
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Originally Posted by LarrySellerz View Post
don't try to get some poor bus driver fired..
Who said try to get them fired?

Dan
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Old 06-06-22, 08:41 AM
  #29  
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Had a frame built up by a LBS which did not include a fork from the manufacturer, so they added what they was appropriate. Every time I hit 35+ MPH I would go into a wobble. Had the bike checked out by the shop for true wheels, frame irregularities, etc. They could fine nothing but the wobble continued. Finally took the bike to a high end, Euro-shop where they checked out the bike and suggested changing out the fork as a trial. Bam - that was it. The old fork developed a resonance which the new carbon fork did not. Problem solved.

Just another thing to consider if anyone develops a wobble.
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Old 06-06-22, 10:59 AM
  #30  
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Glad you survived to tell the story. My advice is to take the lane at high speeds. Bus won't pass and the bike lane does not give much maneuver room on the curb side.
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Old 06-06-22, 09:16 PM
  #31  
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Had a speed wobble today after I hit a pot hole at 38 MPH, I remembered the mantra to loosen the grip on the bars, rather than a death grip and hitting the brakes, and it worked. The wobble resolved itself and had a terminal speed of 43 before rudely interrupted by a traffic light.
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Old 06-07-22, 09:10 AM
  #32  
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Unloaded, 2017 Cannondale FSI 2 Schwalbe Marathon Supreme 29x2 tires, Carbon Rims, Flatbar. 2 large Water Bottles. I’m 6 foot, 240 and ride Cross Country 500 miles a month mostly in the Hills above and around Santiago Canyon Road, peddling up and back from Anaheim. The headset was rebuilt to specification. A run thru at the Shop found the front Spokes were under-Tensioned and both Wheels were set straighter. They were really close already. My front tire was 6 months old but had a good sized Screwhole in it that I had a 1/2 inch round patch on from underneath. Since replaced the Front tire. Wow! They really went up in price.
The Frame is as stiff as they come and the back rim is held on by a Thru Bolt. The Front Bearings are huge on a Lefty and show no play whatsoever. Like I had mentioned, it never happened before and I ride that stretch every other day. This Bike is really is built like a 25 pound Carbon Fiber Tank.
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Old 06-07-22, 01:31 PM
  #33  
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Originally Posted by Bendopolo View Post
Unloaded, 2017 Cannondale FSI 2 Schwalbe Marathon Supreme 29x2 tires, Carbon Rims, Flatbar. 2 large Water Bottles. I’m 6 foot, 240 and ride Cross Country 500 miles a month mostly in the Hills above and around Santiago Canyon Road, peddling up and back from Anaheim. The headset was rebuilt to specification. A run thru at the Shop found the front Spokes were under-Tensioned and both Wheels were set straighter. They were really close already. My front tire was 6 months old but had a good sized Screwhole in it that I had a 1/2 inch round patch on from underneath. Since replaced the Front tire. Wow! They really went up in price.
The Frame is as stiff as they come and the back rim is held on by a Thru Bolt. The Front Bearings are huge on a Lefty and show no play whatsoever. Like I had mentioned, it never happened before and I ride that stretch every other day. This Bike is really is built like a 25 pound Carbon Fiber Tank.
go find a school bus to pass you, on the same hill, at the same speed, at the same proximity, to test the wheel adjustments ... hehe only kidding. I only chimed in because I had front wheel shimmy on a fast downgrade with my rear rack overloaded, with a DIY rear rack extension, thereby changing the center of gravity. used to have to grip the top bar w/ my knees, get up on the pedals & off the saddle, etc. but it can be scary & certainly no way to ride. but I started being smarter with the loading & eventually changed bikes. it was old anyway. from what I've read, one can be going along OK & then something happens like hitting a rock or whatever & that sets the bike into a wobble. but for me, on that bike, I'm sure over loading the back, took too much weight off the front, so it didn't take much for the wobble to start. & flying in the upper 20s didn't help. this is the bike. I added a DIY front rack to get rid of the wobble, which worked, but the rack I made was DIY & kinda s*cked, (p-clamps on front fork kept sliding down so rack rubbed on tire) so I started bringing stuff to work w/ my car so I didn't have to carry EVERYTHING on the bike. w/o the huge load, on the ridiculous rear rack extension, I got rid of the wobble. don't know why the photo has the saddle angled like that. didn't ride it like that

Last edited by rumrunn6; 06-07-22 at 01:34 PM.
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Old 06-07-22, 02:40 PM
  #34  
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That’s funny about the seat. I posted a picture of my SS on the Beach Cruiser Forum and my chain was a little droopy from an on the road repair. They were merciless!
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Old 06-07-22, 03:13 PM
  #35  
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One thing about your story is that if you actually do have speed wobble or shimmy, it's generally made worse by moving your weight back. I'm not sure if that was really what happened, since the air from the bus could have just been pushing you around. Clamping your knee on the frame was a good idea though, that generally gets things back under control. I have had a couple of bad cases of speed wobble that were caused by me shivering. I kept having to remind myself to put my knee on the top tube.
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Old 06-09-22, 07:00 AM
  #36  
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I've had wobbles on descents on loaded touring bikes. First was on a certain bike with handlebar bag and rear panniers, then later on the same bike with different bags in the same configuration. Later on a different bike with four panniers and handlebar bag, then that bike again with handlebar bag and towing a B.O.B. trailer.

The first occurrence became a tankslapper while the others were less severe, but it's really hard not to whiteknuckle at times like that.
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Old 06-09-22, 07:22 AM
  #37  
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Originally Posted by 50PlusCycling View Post
I've experienced wobbles on bikes and motorcycles, and they can be scary. They are a kind of gyroscopic thing in which destabilizes the wheel when it tries to move to a different phase. Wheels spin smoothly in equilibrium when they are perfectly vertical or horizontal, if they are anywhere in between these positions they try to push back to equilibrium, in certain situations they fluctuate between phases. The effect amplifies itself as the wobble increases. To minimize the potential for this problem, keeping the wheels true and in balance is important. Another possible cause is fork/frame misalignment, or a loose headset.

You can balance the front wheel with a cycle computer magnet which attaches to a spoke. Normally when you spin the wheel, it will stop with the heaviest side down. Attach the magnet to a spoke opposite to the heavy side. Moving the magnet closer or further away from the hub can fine tune the balance. When the wheel is balanced, it should stop turning in random positions. Heavy grease in the headset and tightening the bearings enough to add a little resistance when turning the fork can help. Motorcycles use dampeners and/or stabilizers for the same effect.
with a motorcycle a simple tweak can make a difference - reduce shimmy / wobble

up preload on rear shock and / or increase compression damping
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Old 06-09-22, 07:24 AM
  #38  
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Originally Posted by rsbob View Post
Had a frame built up by a LBS which did not include a fork from the manufacturer, so they added what they was appropriate. Every time I hit 35+ MPH I would go into a wobble. Had the bike checked out by the shop for true wheels, frame irregularities, etc. They could fine nothing but the wobble continued. Finally took the bike to a high end, Euro-shop where they checked out the bike and suggested changing out the fork as a trial. Bam - that was it. The old fork developed a resonance which the new carbon fork did not. Problem solved.

Just another thing to consider if anyone develops a wobble.
same geometry with the new fork ?

( same amount of trail ? )
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Old 06-09-22, 07:30 AM
  #39  
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Originally Posted by beng1 View Post
This is a problem with bike design that nobody is talking about, the trend to market road-bikes with more sporting geometry that makes the bikes twitchy.

There is really Zero reason for a road-bike to have to steer very quickly. A mountainbike going slow in tight trails has a lot more use for quick steering geometry, but a road-bike, on roads designed for multi-ton motor-vehicles, is never going to run into turns so tight that it has to have the ability to turn any more quickly than those motor-vehicles because it is almost always going to be going much slower than they are on the same roads, get it ???

But instead of making road-bikes that are very stable, they make them very quick-steering and twitchy, and on top of the quick geometry they are making the frames as light as possible so they are not going to be as stiff as they would be if they had more material in them, and the result is the higher the speed, the less safe they are to ride.

An old water-pipe framed Schwinn Continental with very laid-back steering tube geometry, which would give it a lot of "trail", will handle better at high speed than a modern bike with "racing" geometry. Also heavier wheels are more stable at speed due to the gyro effect, super-light wheels do nothing but help in the first few car-lengths of acceleration, after that they have no advantage over a heavy wheel in most riding. And of course the fashion trend to sell non-pros "aero" handlebars used in time-trials, which give much less control than standard drop-bars, also make it hard to control a bike in an emergency.

I am sure a number of cyclists have been killed or maimed after losing control at speed on what is being sold today as a "performance" road bike.
agree - amount of trail is significant

I was fortunate to learn this from a friend that was a frame builder

surprisingly (to me at least) - some of the old vintage high-end road bikes were the worst offenders
.
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Old 06-09-22, 10:37 AM
  #40  
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Originally Posted by t2p View Post
same geometry with the new fork ?

( same amount of trail ? )
Yup, but from a different manufacturer - Wound Up. Don’t know if they are still in existence
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Old 06-09-22, 10:51 AM
  #41  
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Originally Posted by beng1 View Post
An old water-pipe framed Schwinn Continental with very laid-back steering tube geometry, which would give it a lot of "trail", will handle better at high speed than a modern bike with "racing" geometry.
Good stuff.
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Old 06-09-22, 11:22 AM
  #42  
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Originally Posted by LarrySellerz View Post
24 inches is plenty, don't try to get some poor bus driver fired..
I've had my share of close passes. never got thrown into a death wobble because of it
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Old 06-09-22, 11:41 AM
  #43  
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Originally Posted by beng1 View Post
This is a problem with bike design that nobody is talking about, the trend to market road-bikes with more sporting geometry that makes the bikes twitchy.

There is really Zero reason for a road-bike to have to steer very quickly. A mountainbike going slow in tight trails has a lot more use for quick steering geometry, but a road-bike, on roads designed for multi-ton motor-vehicles, is never going to run into turns so tight that it has to have the ability to turn any more quickly than those motor-vehicles because it is almost always going to be going much slower than they are on the same roads, get it ???

But instead of making road-bikes that are very stable, they make them very quick-steering and twitchy, and on top of the quick geometry they are making the frames as light as possible so they are not going to be as stiff as they would be if they had more material in them, and the result is the higher the speed, the less safe they are to ride.

An old water-pipe framed Schwinn Continental with very laid-back steering tube geometry, which would give it a lot of "trail", will handle better at high speed than a modern bike with "racing" geometry. Also heavier wheels are more stable at speed due to the gyro effect, super-light wheels do nothing but help in the first few car-lengths of acceleration, after that they have no advantage over a heavy wheel in most riding. And of course the fashion trend to sell non-pros "aero" handlebars used in time-trials, which give much less control than standard drop-bars, also make it hard to control a bike in an emergency.

I am sure a number of cyclists have been killed or maimed after losing control at speed on what is being sold today as a "performance" road bike.
the video of a crash posted in the 'Crashing techniques and styles' thread reminds me of a quick handling bike with a low amount of trail ... twitchy ... nervous ...

( might not be the case with that bike - but the front tire knifing under / subsequent crash reminded me )
.
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Old 06-09-22, 11:50 AM
  #44  
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Glad to hear you made it back under control. That's some scary shii.
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Old 06-17-22, 08:34 AM
  #45  
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I had it happen twice on my then "hand built" Trek. Eastern Washington long downhill. The bike just started oscillating WILDLY. I had never experienced anything like it. I was terrified. I was gently tapping the brakes, trying to slow the monster down. It was shaking, again, WILDLY. Friends behind me thought I was done. Somehow I managed to bring it under control. Got off and shook for a bit - I was oscillating wildly for a few minutes. Looked over the bike and there was nothing obvious. One friend suggested hugging the top tube with the thighs if it even happened again. It did, same bike on another hill on another ride. The "thigh" hug worked. Had that bike for years and it only happened those two times. Again, absolutely terrifying.
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Old 06-17-22, 03:38 PM
  #46  
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Originally Posted by _ForceD_ View Post
Who said try to get them fired?

Dan
You said "appropriate" action.

Larry was thinking you meant firing the guy, I was thinking about rewarding the driver for not hitting the cyclist, and the A&S crew was thinking about a flogging with a subsequent visit to a re-education camp.
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Old 06-17-22, 03:41 PM
  #47  
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Originally Posted by rsbob View Post
Yup, but from a different manufacturer - Wound Up. Don’t know if they are still in existence
After sales began to decline, they eventually Wound Down.
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Old 06-18-22, 10:27 AM
  #48  
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Originally Posted by t2p View Post
the video of a crash posted in the 'Crashing techniques and styles' thread reminds me of a quick handling bike with a low amount of trail ... twitchy ... nervous ...

( might not be the case with that bike - but the front tire knifing under / subsequent crash reminded me )
.
Jerome's wheel was totaled when it touched Jeffs, he would have crashed on any bike with that wheel
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Old 06-18-22, 09:05 PM
  #49  
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You can create your one wobble, all you do, as you're riding at say 20 mph, is to use one arm to slap the side of the handlebar, that should make the bike wobble, that's basically what happened to your bike, when that bus went by, the rush of the air "slapped" your handlebar and set up the wobble.

It seems like you did a great job of getting the bike under control, but just in case this happens again you can cut the wobble shorter. First thing to do is not grip the bars hard, relax; then brace the top tube with your legs; then gently slow down while only using the back brake to do so.
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