Road bike speed wobble
 

I have an '04 Litespeed Siena. It used to get twitchy around 75kms/hr and then the integrated headset went south. Got a new, traditional style headset last summer through warranty.

So... yesterday I was going down a nice hill at around 65kms/hr and I got a speed wobble strong enough that it was a bit scary. I want to go fast. I want my bike to go fast. With the bars unweighted (i.e. sitting back and letting go) I've gotten a speed wobble as low as 45kms/hr.

Headset is adjusted correctly
Wheel bearings are adjusted correctly
Tires are on straight and the wheels are true.

Any ideas? I've got the stock carbon forks. Is there a chance they're too flexy? (I weigh ~160lbs)
What about the head tube? Think that's screwed up somehow?

Thanks for any help!

The newest issue of Bicycle Magazine says, in a short piece, that wobble is weird and no one knows shy it happens, but the best thing to do is to press your knees hard against the top tube to break the wave action, and it will stop.

I found an article by Jobst Brandt on Sheldon's site that says pretty much the same thing...

He suggested that holding the bars too tight can increase the problem. Hard to force yourself hold on loosely though when you're wobbling at that speed!

I have heard the knee thing and used it a bit.

However, the point i wanted to make is that out of the 10 or so bikes I own ( TI, steel, alu, etc.), I have experienced a wobble problem :eek: at least once with every bike I have gone fast down hill in :( . I am convienced that it is a combo thing involving: road surface, weight distrabution, wind, speed.....get the point. :cry:

Next time you feel a wobble, don't mix another drink :beer:

If you want to experience real wobble, try riding downhill on a 1960 Capo road bike (full double-butted Reynolds 531, long wheelbase, "spaghetti" stays) with a rear Pletscher rack loaded with textbooks. :) I think the wobble most of us have experienced at least once is a resonance phenomenon, and the variables are the rider's weight, the headset bearings, the trueness AND DISH/centering of the wheels, tire eccentricities, and frame stiffness. When wobble occurs, we are probably driving a complex mass-on-a-spring system into one of its resonant modes, and the knee-against-the-top-tube trick, which I have successfully used myself, will shift the system's resonant frequency whilst providing direct damping.

One question going back to the original posting; how did you manage to replace an integrated headset with a traditional type?

A frame with a headtube made for an integrated (or zero stack) headset won't accept the conventional press-in cup and race headset so how did you do it?

I was wondering that too! Is there even a way to go from integrated to internal? I thought Chris King tried to make some sort of conversion to do that, but it was not successful.

It is quite possible to go from integrated to traditional, but unfortunately I won't be providing you with the easy answer you're looking for; You have to cut off the old head tube and weld on a new one. :)

Litespeed did mine for me under warranty when my integrated headtube failed.

D'oh! Guess that wasn't the answer I was hoping for. :) Glad that Litespeed took care of you.

I just re-read my original post and to clarify it was actually the bearing "cups" pressed into the headtube at Litespeed (supposed to be an integral part of the frame) that were the problem, not the headset itself.

Does this wobble only happen at certain speeds like between 55 and 65km or does it happen all the time after you pass 65km?

If it happens only in a small about 5km range of speed and goes away above or below that then you have a harmonic imbalance; its the same thing that occurs when a car tire is not balanced correctly.

So now the question becomes what did you do recently to change the balance of the tire? Did you have a flat and while replacing it did not put the tire back in the same position on the rim as it was when it came off? Did you recently put a new magnet for a computer on the front wheel? If so where is it now? Make sure the magnet is opposite of the valve stem. Then try moving the tire 1/4 a turn on the rim and retest, and note if anything changed, if so but you still have a wobble just at a different speed then move the tire again another 1/4 th a turn in the same direction you moved it the first time and retest.

Otherwise do what Sheldon Brown and Jobst Brandt says.

But I've personally never experienced a wobble except one time when I put the computer magnet right next to the valve stem...duhh! And I've ridden speeds approaching 70mph.

I wonder when they changed your headtube out if they changed the angles, which would have changed the trail, therefore the handling of the bike - particularly at speed.

Litespeed used a "Zero-Stack" headset design which has separate shallow cups pressed into the flaired top and bottom of the headtube as bearing seats. A true "Integrated" headset has the headtube ends machined to accept the bearings directly and has no inserts.

BTW, Litespeed attempted to make their first frames of this type compatible with both Cane Creek and Campy bearings and they fit neither properly. They had a lot of warranty work and finally settled on the Cane Creek design. It's also instructive to note that by 2006, they had gone back to the conventional headset design for almost all of their frames.

Wobble has to do with Frame Flex and fork flex (mainly fork)

Dont believe me, go and look at some of the wobble crashes on Youtube MotoGP or the Superbikes, and those frames are stiff as boards.

In a straight line these forks flex cos the shocks on the front flex forwards and backwards.

Watch them in slow mo as they go around a corner. Twitchy.

Wheel balancing
 

Wheel balancing? Similar to on an automobile, when an unbalanced wheel spins fast, it will create a resonant shimmy. Factors affecting this will be how much out of balance the wheel is, and how fast it is rotating. With you bike in a stand, you may notice that when you spin the wheels, they come to a stop at the same orientation, often with the valve stem at the low spot. This is because the valve stem is usually the heaviest part of your tube. Since there is a slightly heavier spot in your tire, depending on how much heavier it is in relation to the rest of the wheel will determine at what speed, and how much, it will shake.

To prove this point, with your bike in a stand, get the derailleurs in highest gear, and get the cranks turning by hand as fast as possible. Stand back and let the wheel spin freely. At a certain speed, as the wheel begins to lose momentum, the entire bike, and possibly work stand, will shake in resonance with an out-of-balance wheel.

Or I could just be rambling, but this is the only logical explanation I can think of.

It's a harmonic vibration, and it's even got a name.....the Death Wobble. My bike does it between 52 and 58 mph dropping a big honking hill, and smooths out again when I cross that upper threshold.

check that your brakes are aligned properly too. If you are braking hard and your pads make contact at different times (out of line) this can put force to the left or right and contribute to the problem.
Another thing is how you sit on the bike. Your weight distribution across the machine.

Litespeed used to have a Customer Forum on their web site and the topic of speed wobble came up frequently after they went to the zero stack headset and the house-branded "Real" fork that came standard on their bikes for a couple of years. I don't know it it was coincidental or if the fork was truly a contributor.

I'm about 150 lbs have three Litespeed, a 55 cm '96 Catalyst, a 57 cm '05 Firenze and a 57 cm '06 Tuscany. The Catalyst has a threaded Kestrel EMS Pro fork and the other two have threadless Easton EC90SLX forks. All three forks are carbon and the Eastons have carbon steerers. All the headsets have conventional press-in cups.

Not one of these bikes has ever shown the slightest tendency to speed wobble and there is a hill near my house that I routinely hit 45 mph (73 kph) going down.

What? I've had misaligned brakes in the past and never had a vibration as long as the pads didn't contact with the wheel when not braking; in fact I test rode a bike once where the brakes stuck with one pad slightly rubbing one side of the front rim and it never vibrated either just made a squeaking sound.

And your weight distribution wouldn't cause a problem either unless your sitting with you butt completely off the saddle to either the far left or right...who does that while riding? Or perhaps, though I've tried it so can't say for sure, but if you sat on your top tube thereby shifting most of your weight onto the front wheel you could have a problem...though probably mostly with the family jews :eek: !!!

Most vibration problems are related to harmonic imbalance as I pointed out earlier, this can be due to computer magnet in the wrong place or an imperfect tire which you can compensate for by moving on the rim bit by bit till the vibration goes away. Even tire liners can cause a harmonic imbalance, but again that can be compensated simply by moving the tire bit by bit.

Some vibration problems are mechanical and harder to defeat, like worn headsets, wheels are out of wack and hubs, misaligned or poorly made forks and frames, some may be impossible to correct if the frame is at fault; in these instances the knees against the frame is your only option while riding. Some frame manufacture in trying to cut frame weight didn't put enough support material at the joints where the tubes join together, either the butts were not thick enough or the internal lugs were too thin, the welds were not done right etc and this caused the frame to flex too much and it also would cause frame vibration at certain higher speeds. Less expensive AL frames use welds with voids in the welds which makes the frame weaker at the joints, more expensive AL frames use void free welds; less expensive AL frames are not monitored closely for accurate frame alignment and the list goes on.

More Wobble Problems
 

Froz Posted"Most vibration problems are related to harmonic imbalance as I pointed out earlier, this can be due to computer magnet in the wrong place or an imperfect tire which you can compensate for by moving on the rim bit by bit till the vibration goes away. Even tire liners can cause a harmonic imbalance, but again that can be compensated simply by moving the tire bit by bit."

I read your posts on the thread re:front end wobble. I started riding a
Specialized AL bike with a Carbon front fork. It is real fast and stable on descents and in cross winds.
I purchased a Look carbon 555. I have two sets of wheels. One set is my commuters, multi-spoked wheels built by Joe Young (see Sheldon Brown) and I have a set of Easton Ascent 2's, . With either set I got severe wobble at about 40 MPH. I destroyed my look 555 in an accident (it was on top of my car) and purchased a Look 585, carbon. I have the same problem. I looked at my magnet positions, I never thought about that aspect, and they are just by dumb luck-opposite my valve stems. It happens in slight cross winds and of course bad cross winds are just scary.
I ride enough to wear out a few sets of tires a year and the new tires still give me the severe wobble. I spoke to Look-they told me they have never had this complaint.
What do you think?e

There are lots of reasons for this problem, however you stated that this occured on two different bikes and on two different wheelset, so this leaves out the obvious mechanical problems most people come up with like: loose head set, loose or broken skewer, loose wheel bearings/cones, cracked frame etc. This maybe be due to the way the frame was manufactured not having enough or strong enough support at the joints in an effort to save weight. I've never had this problem and I've been close to 65mph on many different steel lugged frame bikes, and friends I knew that rode either steel or large diameter AL frames never had the problem either unless it was one of the mechanical problems I listed then it would go away once it was repaired.

Now Jobst Brandt said in effect that It is a well recognised problem with bicycles at high speed. There is nothing wrong with the bikes; any bike can do it given the right circumstances. It has to do with the dynamics of forward motion and the gyroscopic forces of wheels. It happens rarely with MTBs because these generally operate on rough surfaces, at moderate speeds using knobbly tyres. All these factors militate against frame resonance, which is the culprit. The smoother everything is, the more likely it will happen. It is said that the shivering of a cold road rider can set it off because human shivering is very close to the natural resonance of a bike frame!

I'm not so sure about that, but I'm not an expert either!! Reason I'm not so sure about Jobst Brandt's thoughts is because I use to live in California and use to race and train back in the mid 70's to mid 80's all over the mountains of southern Cal and neither I nor my friends ever had to worry about a high speed wobble...unless a mechancal problem occured which would be fixed and then no problems; and we routinely reached speeds of over 50mph coming down mountains. So I think Jobst Brandt is skirting a bigger issue that seems to effect carbon fibre bikes the most, and maybe thin walled welded, not lugged, steel frames, and older small tube diameter AL frames, neither of which are supported well at the joints.

Regardless whether my theory is right or wrong, and seeing that you can't do anything about the construction of your bike, or about gyroscopic forces, then you have to try a few things the next time the wobble occurs. First try unweighting your seat, this means stand up on the pedals; sometimes this works. If this doesn't work then go back onto the seat and try clamping the top tube with your knees and legs as tight as you can; this usually works. The reason this works is because instead of the bike having the necessary reinforcements at the joints, you supply that reinforcement with your legs! That's why I disagree with the gyroscopic force idea; and thats why it rarely happens to MTB's because they have beefier frames (and I've known people to reach over 50 on those in California mountains).

Froze-I appreciate your taking the time to give me such an in depth response. I read in part of this thread about riding through wobble. I live in Salt Lake City and most of my training rides include allot of climbing and the gratifying descents you earn by making the climb. I don't know if I have the guts to let the bike continue to accelerate through a wobble but I may try it-I will forward a few words from Elvis and Major Taylor to you if it doesn't work. These wobbles require a cross wind to fire up, but I have found it does not take much of a cross wind to make the problem occur.
I am a 5'9", 54 year old, 160 pound person so I am fairly average in stature and weight. I may think that some of these frames a just too gossamer but the pro's ride them and I don't think the manufacturers would produce them if they were inherently unstable.
It is interesting to note that you referred to thin tubbed aluminum frames being sometimes problematic. My Specialized has a very large diameter front tube. Other than the wobble, my carbon bike is so soft to ride, it is really comfortable. I have ridden Lotoja (206) miles/day for the last three years. Once on the Aluminum bike and twice on the Carbon bike;my body definitely enjoys the comfort of the carbon in that ride.
It is also interesting to note that I had a Wobble Naught professional fit done on my first Look bike-as far as comfort and the elimination of sore neck and shoulders, numb hands, sore knees and keester that fit was miracle stuff. The Wobble Naught did however wobble. Oh well thanks for listening to my ramblings and again thanks for the advise, I will send you a report of my application of some of your ideas about squeezing the top tube and standing.

Try different tire pressures. If that doesn't fix it, you might have your chain on backwards.


OK, I'm kidding about the chain, but I'd be interested in hearing if tires or tire pressure has any effect.

I've used the knee-on-top-tube bit successfully before, too, but ISTR that another answer is: something in the complex equation at that moment has got to change.

Stand up slightly. Shift your weight slightly. Knee against the tube. Something. Instinct still has me doing the knee thing, but ... if I can break that habit ... I'll try something else next time.

I was referring to older small diameter AL tubing (not made like this anymore for reasons I suggested and other reasons) and not the thin large, or fat, tubed frames which I don't think have had issues, but not sure.

Please let us know if you survive the wobble descent and what worked to control it. If you die just e-mail me when you get to where your going :eek: