I was doing hill repeats last night with my tri club. A short 1 km climb that gradually get steeper and steeper as you get to the top. Coming back down you really take off and there is a 45 degree curve to the right near the bottom of the steep section where you may hit close to 60 kph, there are also some small potholes on the steep section near the curve. The fifth time coming down the hill, the back of my bike began wobbling just as I entered the beginning of the curve. I managed to feather the brakes to hold the speed, but couldn’t take the curve as sharp so I ended up the left side of the road before the wobble stopped. Luckily no cars were coming toward me. It’s the first time it’s happened to me and I was not too happy about it. Couldn’t see anything wrong with the bike, but it’s in the shop this morning for a full check of the frame and rear wheel. It’s my road bike, a TCR composite.
Here’s my question - are there bikes that never get speed wobbles?
Yes, bikes with the proper rake and trail will not have speed wobble. I’ve found most mechanics know rake or trail but not both. Recommend you revisit your specs and see what is the proper rake and trail for your bike.
I learned this the hard way at a hilly race. Came down the “big one” and lost all my water bottles and barely held it together. Think Beloki with a good ending. The bike was going back and forth to 45 degree angles.
No, there aren’t any bikes that “never” get speed wobbles, any bike will wobble given the right (or wrong) conditions. The trick is to recognize when you are getting that wobble, and to do something to alleviate the wobble, e.g. slide back in the saddle, relax grip on the bars, clamp top tube between your knees, etc.
Sounds like “death wobble”. I’ll let one of the engineers explain the dynamics but it’s an oscillating effect between certain riders and frames. The “cure” is loosen the white knuckle grip, place a knee against the top tube and unseat your weight a bit.
Yes, it is more common among certain frames and there have been a number of complaints about earlier medium size aluminium and carbon TCR frames. Quite a few posts on various roadie forums about this. Apparently Giant corrected the problem on later frames. I owned an early aluminium TCR size medium and it wobbled horribly on steep decents. No other bike I’ve owned was that bad.
Another rarer possibility could be an assymetrical carbon fork, never a problem in the days of steel forks because they could be cold set to near perfection. There is a good article about this on the Calfee site.
I’ve been told that the steel Lemonds and Eddie Mercyx MX Leader never wobble.
But the OP stated a rear wobble - usually a death wobble is the front wheel. I am wondering, given what he said about potholes, if he didn’t get into a bad pavement patch that started the back wheel hopping. I have hit this on both road bikes and motorcycles, and it is a totally different phenom than a front wheel oscillation. Feathering the brakes was exactly the right thing to do. In morocyling you can pick the bike up a bit and lean your weight out more to imporve your contact patch, but road bikes really don’t allow this too well.
Since you mention the rear wheel it probably wasn’t speed wobble that you experienced. I know someone on a Cervelo P3 that just experienced a crash from speed wobble. My understanding is that all bikes will suffer from it but you might not.
Thanks for replying everyone. I did think the speed was a little on the low side for what I would think of as a speed wobble. It was definitely the rear wheel wobbling. The first thing I did was check to see if a spoke had broken. I was a little upset with myself that I hadn’t tried clamping the top tube with my knees, but it did happen pretty fast and I thought more about what I might end up hitting had I gone right off the road.
Just not sure now if I can “trust” that frame at speed anymore.
In December I had my first “death wobble” and did not really know what it was. My coach wrote it off as not having the front skewer tightened enough. Then it happened again 2 more times in the next month. It really is a very scary event and I have been lucky thus far tht it has not caused a crash. In all three cases my speed was above 38-40 mph. I feel your pain in not trusting your frame but for me personally, I am not willing to write off a $3000 bike yet.
Also, I checked out the link on the motorcycle videa and had a very real flashback. Scary stuff.
Here’s my question - are there bikes that never get speed wobbles?
Sure – the ones that are properly designed. Don’t expect to find many of them (if any) in the current industry.
What you experienced was a frame resonance, fundamentally due to a flawed frame design that allows such an undamped resonance at a frequency that can be excited by a combination of factors. Yes, you can mitigate the occurence, even provide some damping, but the fundamental problem is still there: the frame has a design flaw.
The bike industry is essentially selling toys to hobbyists, and as long as this goes on you will never be able to buy a bike engineered to the same standards as, say, a car or motorcycle.
I remember developing a wobble at about 120 on my Ducati. Most puckered my butt has ever been. Some schools of thought are to drop the hammer and power through it. Others say sit upright become a sail and slow down. Any moving vehicle can get one no one is immune.
Hey MR_tin
*Was it cold by the last time down? That will make you shiver just a bit and make you wobble. It can also be from being a bit scared, you tend to shake just a bit and it will give you the death wobble. I know this as I had a TT this last weekend and we had a fast descent with a very strong cross wind and with an H3 and a disk it was a hand full and I got the wobble, but I knew it was just because I was a bit freaked out by the wind, I cooled my self down and it stopped. * Dan…
Umm, even motorcycles get speed wobbles. That’s why high end sport bikes use steering dampers.
In my five years of motorcycle racing I never experienced, saw, or heard of any uncontrolled high-speed wobble; in my four years of bicycle riding I have experienced it a couple of times, have seen a friend crash due to it (and end up in a 3-week coma), and heard numerous stories about it.
Steering dampers are not there for frame resonances.
There are reasons for speed wobble that are simply physics. One of the reasons that it is more common on a bicycle than a motorcycle is that moto’s are considerably heavier. They are also designed around greater stability at high speed. etc etc. Bicycles are also much more sensitive to rider input, by virtue of lower mass.
One of the functions of a damper is to assist in controlling otherwise uncontrollable oscillations of the front wheel. There is a reason you see them on sportbikes and not on touring bikes.
I ride down a major 80+ kph hill every morning & have only had the death wobble 2 times which I beleive was due to overinflation of my tyres changing their profile - try keeping them at the lower mid end of the recommended pressure?
It did take a long while to really trust the bike again though, being on a bike at 80 wearing lycra with a shake bad enough to lose both my water bottles was really REALLY not somthing I want to repeat.
There are reasons for speed wobble that are simply physics
I am a theoretical physicist.
One of the reasons that it is more common on a bicycle than a motorcycle is that moto’s are considerably heavier
No. The reason is that the resonant frequencies of a frame are way above the low-pass filter frequency of the suspension – that’s why full-suspension mountain bikes do not exhibit high-speed wobbles no matter how light they are. In the absence of a suspension, road bikes are very susceptible to road excitations, and that’s why they really need to be designed with extreme attention to detail (theoretical analysis, FEA, testing, etc.) – but they are not, and that’s why I’m saying that the bike industry is still in an embryonic state (Honda in the '70s knew how to critically damp their frames to get any desired effect they wanted; Trek in the 21st century still doesn’t get it).
One of the functions of a damper is to assist in controlling otherwise uncontrollable oscillations of the front wheel
No, the function of a damper is to provide a little more stability to a steeply raked front suspension (and that’s precisely why you might see them on a sportbike but not on a tourer); you would never get uncontrollable oscillations if you disabled the damper.
I remember developing a wobble at about 120 on my Ducati
Colour me surprised… This is the first time in my life that I hear of a high-speed wobble on a motorbike… A Ducati no less… You’re sure it wasn’t an ordinary tank-slapping thing?
I presume there was nothing otherwise wrong with the bike?
I’m willing to bet that the excitation was due to aerodynamics, not road imperfections – you didn’t try to wheelie at that speed, right?
I had a Pantah 600 for a brief period (does that date me?), but 115 was the highest I ever saw on its quite optimistic speedometer, and at those speeds it always felt rock solid (too solid! – I had trouble turning it).
I’ve experienced several death wobbles myself (I ride a P3 Alum.) The last one was at the Baja 1/2 in June about 64 KPH. Almost soiled the chamie on that one. I’d had a few before and strong armed my way out of them. Was then told that this was the exact opposite of what I should be doing. So in Baja I relaxed AND, as I’d been told to do - peddled out of it. The bike came around but my nerves took another 10 miles.
If it happens to me again, I’ll try the knee on the top tube, sit out of saddle trick.
well, in theory there is no difference between theory and practice… no offense, but I’d prefer to get advice from an engineer, frankly…
It’s true that no suspension bike should get a wobble, but any road bike can get a wobble, theory notwithstanding. Mostly it’s due to the rider more than the frame, so I am not convinced there’s any way to design a frame to prevent it. Given the varieties of fork, wheel and rider that might end up on that frame, it’s an incompletely specified problem.
Unweighting the saddle and loosening up on the bars will usually fix it. I’ve managed a death wobble at 25 on dead flat ground, by hitting a patch of mud in the shadow, then clenching the bars (and butt) in reflex. On the other hand, I’ve descended most road passes in Colorado on this same bike (Paramount) without any problems.