Crashes I nearly bought the farm due to the dreaded high speed wobblies.

Discussion in 'Travelling, Commuting & Safety' started by motorbikemike45, Jun 8, 2011.

  1. I was in an unfamiliar to me area when I started down a very steep and long hill on my e-bike. The speed was exhilarating as the speedo went past 45mph. Then the front wheel/fork/handlebar began to oscillate out of control. I had had this happen before when I hit some uneven pavement at 70+ on my old and somewhat worn out Harley years ago. A friend I was riding with talked me into taking my hands off the bar and riding it out, slowing with the rear brake. It worked!

    I had "the death-grip of fear" on the hand grips and my arms were absolutely rigid. It took a real mental effort to relax my hands and arms somewhat, but doing that and slowing the bike using both front and rear brakes cured the wobble and I survived.

    It is sort of a difficult thing to do, but learning to ride without a death-grip on the grips and your arms relaxed will give you much greater control of your bike. Once the osillation begins, you have only a second or two before you are on your way to the pavement. Part of the cause of the wobblies is overcontrol by the rider, relax and enjoy the ride.
    Last edited: Jun 8, 2011

  2. Happy Valley

    Happy Valley Active Member

    That and hitting 45mph heh, glad no mishaps ensued, you did well to keep it together at that speed, be careful out there.
  3. I have tightened the steering tube bearings, which had worn in and gotten loose on this new(ish) bike. I'm a bit ashamed it had skipped my notice as I usually check things over more carefully. A bad lesson relearned, over and over.
    Last edited: Jun 8, 2011
  4. MikeJ

    MikeJ Member

    Hi MotorbikeMike45 -

    I know this is an old thread, but pertinent to me. I had the same description of front wheel wobble happen to me at about 27 mph on a smooth street. I slowed down as did you, and the wobbles stopped.

    My front fork is a RockShox Dart 2, with 100 mm of travel. I invite other readers who experienced this wobble to reply with comments to prevent future front wheel wobble. I'm thinking that if the wobbles should happen again, that fork is being replaced with a fixed, heavy duty fork. My Haro fixed fork never wobbled even as I passed through 42 mph on it going downhill.

  5. Richard H.

    Richard H. Member

    Yes and good general advice to bring it up. Suspension forks made for what is ostensibly called "mountain bikes" were never specced for high speed travel over a smooth surface, especially low/medium duty forks or any quality fork for that matter that has wear. I've over-hauled many bike suspension forks and the slider bushings become worn and develop play which produces the slight oscillations or wobble that extrapolates at the wheel axis during high speed. Cheapy bicycle suspension forks were never made to close tolerances to begin with. Riding in dirt, one can get away with a certain amount of play because the tire, usually a knobby, tends to purchase better on any ridge or rut in the trail and the rider is attuned to making constant small corrections. Not so at speed on pavement. These are NOT motorcycle forks that were specced accordingly. Just another chapter in the book of why a bicycle is just a bicycle. (often during these discussions someone will mention the Tour de France and how riders hit 60mph on the road course there conveniently overlooking that paid professional riders on a $8000 hand made bike with a chase van full of identical replacement is following, and serious crashes sometimes involving death is not uncommon)
  6. Cavi Mike

    Cavi Mike Member

    Interesting concept of letting the bars go and slowing down. My old Ducati Monster used to tank-slap over 90 but you had to pull the handlebars as hard as you could to keep it under control. The lighter you held them, the worse it got. Then again, that was a sport-bike, not a cruiser.
  7. The_Aleman

    The_Aleman Active Member

    I also have RockShox Dart 2 100MM on my bike, but I have never once encountered speed wobble. I have nearly 5000 miles on the bike and have gone up to 40MPH.

    I'm also relatively tall and lean over the bars slightly, too. My bearing preload is also slightly excessive, because I like a bit of drag.
  8. MikeJ

    MikeJ Member

    I will try again. Maybe I had a not-tight-enough axle or maybe the headset was loose. They will be more closely examined and triple checked. I don't recall other riders having wobble problems, so I have to assume my setup had a hidden flaw in it. Testing will be in a few days. I will post the results after that time.

  9. Richard H.

    Richard H. Member

    Something I always keep in mind with forums and online venues is that is that much of what gets passed on is anecdotal. One person uses a component and reports having satisfactory results with it but that does not necessarily make it universally applicable. There are too many variables and conditions that remain unremarked. Keeping your own counsel is a good idea and apply commonsense when considering what a manufacturer's design parameters were when building something meant to be pedaled by an average rider at 12 to 15 mph max and never specced to have an engine attached.
  10. The_Aleman

    The_Aleman Active Member

    I totally agree with you, Richard, but speed wobble is something that can be dialed out, for the most part. It can occur at any speed, not just speeds exceeding what's typically attained on a bicycle. As a longtime pedalhead, I've seen speed wobble in many forms and at many different speeds. Once you understand it, you can avoid it.

    There are several factors involved in speed wobble on bicycles. Assuming the tire is mounted and aired up correctly, wheel is true, the forks are straight, much of what's left is weight transfer. If you have most of your weight over the rear axle of the bicycle, speed wobble is more likely to happen. Of course, some bicycles just have a bad headtube angle - something that's much more likely on poorly-designed frames - and combined with sitting too far back, can make speed wobble much more likely too.

    The RockShox Dart 2, like most suspension forks, are definitely more loose than rigid forks. If you are getting speed wobble, they could make things worse. Increasing your bearing preload will help, but doublecheck all your components. Maybe even rethink your riding posture. Wikipedia has a lil article on speed wobble, too:
  11. MikeJ

    MikeJ Member

    Here is another thought, sure to poke somebody to ask, "Just why?".

    I will try a few rides with the shocks currently installed. They are great shocks on a smooth road doing 25 mph in a frame with heavy rider but no 30 pounds of engine, tank, etc. I will tighten its nuts and bolts before doing higher-speed engined runs.

    But if the wheel wobbles at any speed below 40 mph, its days as the shocks which Rock Shox sold are done. I intend to remove the spring and drain the oil out of the product. I will then insert the sliding tubes in the housing, and slide the tubes almost all the way down. Then I plan on drilling quarter-inch holes, several of them, through the tubes and insert bolts. The intent is to prevent any motion relative to the tubes. Essentially, the shocks I have now will become fixed hard forks. There will be no chance of reversing this.

    Why? If tolerances for shocks that are good on a non-motorized bike result in wheel wobble on a motorized bike, I will just do away with the the tolerances. Radical idea? Probably. But a new front fork that I like costs over $100. AND the lower head bearing needs replacing, which means I borrow a special bicycle shop tool, or the wrenchers which I have little faith in, must install the new bearing.

    Some readers will say, "You will destroy the shock!" Yup, they will be re-purposed. I have no other bike to put the unaltered shocks on, and I am not giving them away. If my concept works, I saved $100. If it fails, I will spend the $100 then. But there is no way I am going to risk scraping my old hide on any paved road.

    I hope the tightening of axle, stem, preloading, and maybe a stiffer spring, will do the job.


    Added Later - I read earlier today that Harley sells some device to place on their Dyna Glide shocks for what they readily acknowledge as the Dyna Glide Wobble. How or why the device works is a little beyond me at this moment. But I did realize that the tiny bit of flex in forks at high speed is the cause of some pretty good tumbles. Solid front forks remain an option until testing is done and evaluated.
    Last edited: May 10, 2012
  12. 2stroker

    2stroker New Member

    I was going down a steep hill about a year ago and my back tire started to wobble and locked up on me. I slide for about 60 ft and the bike kept falling over and i had to kick my self back up straight so i didn't crack my head open. The bearings fell out and it was all over with after that. By the time it was done with the tire was folded over. My dad thought i hit a curb cause the tire was folded in half. Keep your bearings greased is the point of this post.

    I have a rim from the 50's with a grease fitting for the bearings its sweet. I dont have to take my wheel off to grease em just hook up the grease gun.
  13. reb1

    reb1 Member

    High speed wobbles hapen due to weight being in the wrong place. A common cause is placing weight two far forward. A handlebar bag on a road bike is a bad idea. The geomitry of the frame and fork is very different between different models of bicycles. Yes taking your hands of of the handlebars will put less weight forward and cause the wobble to stop. A safer way is to use a knee against the top tube or grasp it with one hand and the wobble will stop. Notice the speed at witch it happens and keep below this speed to avoid it. Frame damage or improper alignment could also have some bearing on what causes it. I purchase my wife a mountain bike shortly after we were married. It was not a cheap one. The front wheel was damaged from shipping so the manager traded a front wheel from a same model. A couple of months later we were comming down a windy canyon road and I heard a scream. She was so scared of the wobble she almost did a head on with an comming traffic. I managed to get next to here and grabed her seat rail and slowed her down. She was in no condition to listen or react while the wobble was going on. After we stopped I coached her on how to stop the wobble and to keep below the speed where it happened if posible. I got here to create the situation one more time and obsereved her take the appropiate action to stop the wobble. We pedalled to the shop where I purchased it. I couldn't see any visible damage to frame or fork and the shop where we purchased had no frame tools. The owner contacted Nishiki and they traded out the bicycle a week later. We never had the problem again. If you look up this issue on the web. You will find very little on loose bearings or worn shock forks being the cause.
  14. Happy Valley

    Happy Valley Active Member

    I think that's simply because it's is not very well understood. Better yet, ask a seasoned, knowledgeable (rare) bike mechanic.

    A misaligned frame is fairly easy to do a quick check with the simple string method but issues with a bad frame will usually make themselves plainly apparent at slow speeds as well.
  15. darwin

    darwin Well-Known Member

    I bought a new 650 dual purpose m/c and it had knobbies on it. Well I was going on the freeway with those grooves cut into the road for traction
    [?] doing about 70mph. Wobbles hit me and I thought I was going to die it was so bad. Next time I'm putting 70/30 street tires on the bike, its long gone now but next couple of years will get another. I never knew they made street/dirt tires till I checked into it.
  16. MikeJ

    MikeJ Member

    Hi All -

    I am happy to report that my current build exceeded 30 mph today with NO wobbling front wheel.

    I tightened a couple of spokes, a few nuts and bolts, and added 5 turns of preload to the shock spring. The ride is stiffer, but the results are what I am looking for.

    Am going to prep for a 30 mile ride yet tonight, maybe a 100-miler tomorrow if weather is good.

    Many thanks for all your inputs!

  17. jaguar

    jaguar Well-Known Member

    Consider also that the steering angle is steeper on a bicycle than on a motorcycle (around 30 degrees) which makes it more "twitchy". Since I am a speed freak I take into consideration that angle when buying a bike. If you install longer forks then that increases the steering angle. Also a fork that places the axle more forward make the front end more stable.
  18. zwebx

    zwebx Member

    malvern star can take alot of speed ( i have tested it w/o a motor up to those speeds) and i would much prefer it to my crappy old kmart bike at 20mph
  19. MikeJ

    MikeJ Member

    A couple days ago: Took my bike up to 40.2 mph / 56 kph without wobbles. Going downhill with a 30 mph tailwind. Backed off my engine throttle and just coasted. Credit a highly tensioned front fork and more detail to tightening up nuts, bolts, headset, tire pressure, etc., for the safe ride. Also had added counterweights to front wheel to balance it.

    40 mph while under only engine power? No thanks, I will pass.
    Last edited: Aug 1, 2012