I bought the bike of my dreams last year, a Seven Alta. It comes in at just over 16 pounds. I love the bike, but I had a scary experience recently while riding in Big Bend National Park in Texas.
I was descending out of Chisos Basin — a long, winding and very fast descent — when I picked up a front-end shimmy that got progressively worse. I was convinced I was going down but managed to bring it to a stop. I’ve been hesitant to let it loose on descents ever since.
The owner of my LBS theorized that a slightly loose front hub was at fault. There was also a fairly significant crosswind hitting the bladed spokes. Do you think there is anything inherently wrong with my bike that would cause this shimmy to happen again? — Larry M.
Jim Langley Replies: Your e-mail made my day, Larry, because 25 years ago, on my cross-country tour, I rode up to Chisos Basin and down the very hill you’re talking about.
What a beautiful place! I almost decided to stay there and work for a few months because it was so relaxing and peaceful, and because the riding was so epic.
I don’t think there’s anything inherently wrong with your Seven. Speed wobble is one of those cycling phenomena that many roadies experience sooner or later.
I’m not a physicist, but as I understand it, speed wobbles are basically vibrations. Once one begins, it gets worse due to harmonics. You might have seen a video of the bridge in Washington that self-destructed after a strong wind started it swinging faster and faster. That’s harmonics at work.
Speed wobble is known to happen to motorcycles, too, so you can find quite a few hits on the subject if you search on Google. Uncle Al has addressed the issue, too, here at RBR.
In your case, the loose hub may have contributed. But I think it was probably a gust of wind or rough pavement that set the front end into a slight oscillation that accelerated and scared you to pieces.
When wobble happens, you need to take quick action before you disintegrate like that bridge.
On most bikes, you can stop the vibration immediately by clamping your knees against the top tube, which braces and stiffens the frame.
If the top tube is too low for that (as in a compact frame), you can still press one leg against it. In fact, some riders routinely descend that way to prevent wobble from beginning.
I assume your shop checked for all the usual suspects — loose headset, loose spokes, bad tire, misaligned wheel, too-high saddle (which affects weight distribution).
If so, I think that future wobbles will be rare. And using the knee-against-the-frame technique should damp it quickly if it happens.
FROM MATT C.: Jim, you’re absolutely right that vibration is a downhiller’s enemy. Skis, bikes, airplanes — wobbles can wreck your whole day. Damping a bike frame with the legs is a good fix.
Larry’s stability woes could be cured by some technical fixes. Without knowing his frame size or his body size, I’d guess that he’s taller and bigger than the average 5-foot-6, 130-pound climber. He could try switching to a fork with less rake to increase the trail; increasing his tire width; or adjusting his weight distribution with a longer or shorter stem.
But if he loves to go downhill and the bike still has a vague, floating feeling at speed that compromises his descents, he should re-think the titanium choice. Geometry helps, but ultimately a bigger diameter and thicker gauge (less flexible) top tube would stiffen the bike.
I really wanted to like titanium but couldn’t get the ride I wanted for the price I was willing to pay and had a custom carbon frame made for half the cost of a Seven. I’m sure that the folks at Seven would want to help before Larry took a radical step like a different frame.
Jim Replies: Thanks for the input, Matt. I didn’t want to suggest that anything was wrong with Larry’s Seven in respect to its construction, but several people have suggested that the frame tubing might be too thin and light for him. That can happen when a person insists on the lightest bike when they shouldn’t.
From Uncle Al: Shops can make mistakes, especially when there’s a customer hounding them about their lightweight dream machine.
Some shimmy problems come from how a rider “sits the bike.” A big-butt rider with a small upper body can have poor weight distribution, i.e., too much weight on the rear wheel, which turns the front wheel into a shopping cart wheel.
A short riser stem can make the problem worse. I see a lot of riders making that modification after they’ve been properly fitted to a bike, once they discover they are neither youthful nor flexible enough to look like the pros do. That’s a factor a company like Seven, for whom I have tremendous respect, can’t factor in.
From Greg K.: Larry didn’t specify much about his weight or the rest of the components on his bike, nor the details of how his bike was built. The heavier Larry is, or the larger the frame or lighter the tubing, the more likely Larry is going to see this wobble again. Other flexible components in the front end (fork or front wheel) could help induce the wobble.
To isolate the source of the problem, Larry will need to experiment with his bike. Perhaps it was a loose headset, but I expect he will find the frame or other components are too light and flexible for his size/weight. After checking the headset, he should try a different front wheel. If the wobble persists, it’s either the fork or frame.
From Leon S.: Can’t you stop a wobble by either slowing down or speeding up? Isn’t it the constant speed that allows the oscillations to amplify?
Jim Replies: Speeding up is what the motorcycle guys say to do. I’ve never had luck doing that (which isn’t always possible on a bike, of course) or slowing down. I’m not saying that it won’t work on certain bikes, but in my experience a wobble will continue until you interfere with it by bracing the frame.
I’m definitely not an all-knowing expert on this subject. Maybe no one is. I just know that the knee trick is one of those things that seems to work in all situations, so that’s the advice I give people.
From Rick: I saw a Bob Roll piece on speed wobble last year. He was testing a Litespeed and showed that every time he took his hands off the handlebar, the front end wobbled. I have friends that have Litespeeds and some of them say the same thing. I must surmisethat, in the case of Litespeeds, it’s bad geometry.
Jim Replies: It might be geometry. It could also be that the frame has tubing too light for the person riding it. I have a frame like that. It’s okay for me, but if I let my 200-pound friend ride it, watch out! Lots of people buy bikes based on weight, and it can lead to handling problems if the frame’s too light for their weight.
From John B.:I’ve experienced speed wobble problems twice. I’m convinced that crosswinds were the reason, just as they were for the Tacoma Narrows Bridge that you mentioned. Clamping the top tube with my knees didn’t seem to work, but zig-zagging across the road seemed to do the trick. Fortunately, a driver saw that I was in trouble and didn’t try to pass. I have heard three possible solutions, but I haven’t tried them:
1. Change position on the bike (move forward, back, up or down) to change the natural frequency.
2. Pedal to disrupt the natural frequency.
From Ron M.: I have been riding a 1990 Merlin since new and never had a shimmy. Last year, I did some major upgrading, and a part of that was Campy Eurus wheels with bladed spokes. Since then, I have experienced some uneasy tracking in fast descents. The bike tends to drift and shake a little when I get any crosswind. The only thing I can attribute this to is the bladed wheelset. I’m strongly considering going back to a set of 32-spoke Mavics.
Jim Replies: If you wanted to test your theory, you could drive to a hill with both pairs of wheels. Ride down on the Eurus that seem to make the bike shake, then switch to standard wheels to see if there’s an improvement. If so, you know which wheels to be riding.
From Dan: I thought I was the only rider who experienced speed wobble, as it’s happened with every road bike I’ve ever owned (four so far). My most recent episode was just this last Saturday while on a fast (40 mph is fast for me), somewhat curvy descent. I believe I am at least part of the cause as I tend to get nervous sometimes and this causes me to stiffen my upper body, especially my arms.
Another factor may be the low spoke count in my front wheel (Rolf Sestriere). I am planning to get stiffer wheels and try the knees against the top tube. A more relaxed upper body should also help. A friend says I just need to do more high-speed descents until I’m more confident.
Jim Replies: In my experience, only the occasional bike will wobble. So, I wonder if something else is wrong in your situation.
One contributor is a seat that’s too high. This makes it hard to put enough weight on the pedals, and that can decrease a bike’s stability. Because all four bikes have wobbled, I wonder if you always set the seat height the same. It could be the common denominator and worth checking.
If it’s not the seat, try relaxing as your friend recommends. It’s helpful to shrug your shoulders frequently to release the tension that builds up in your arms and neck. I try to do it every 15 minutes. Exhaling through your mouth and breathing in through your nose helps, too. And try standing every now and then.
From Bill B.: Bladed spokes that are slightly twisted will provide a “propeller” effect that can cause a front wheel to wobble at high rpm, like over 20 mph. I would speculate that a wobble not caused by bladed spokes is caused by the wheel being slightly out of true. Also, the destructive force behind harmonics (e.g., the bridge in Washington) is known as an “anharmonic oscillation.”
From Fil B.: You state that shimmy is caused by harmonics. It’s actually resonance — an increase in vibration amplitude when an input matches a natural resonant frequency of the frame.
From Dan N.: I had a wobble problem on a brand new bike. Now when descending, I push down on the handlebar to ensure there’s some weight going to the front wheel. I’ve never had the problem again. I think many riders mimic pros who have a relaxed “cool” appearance as they descend the mountains. But we don’t really know their techniques.
From Robert H.: Your response to Larry was correct, Jim. Aside from tightening knees to the top tube, a looser grip on the handlebar works to reduce the wobble. Unfortunately, when a wobble begins at speed, the natural tendency is to grip the bar tighter in order to gain control. That does not help.
From Gary B.: Your column brought back memories of a ride on which I was sure I was going to die. It was 1989 and I was on day one of the Great California Land Rush, a two-day ride from San Francisco to Los Angeles. I was on the final stretch into San Luis Obispo, riding down the Cuesta Grade on Highway 1, and I was humping it — around 62 mph.
That’s when my front wheel hit a piece of gravel. A harmonic oscillation developed almost instantly. The shimmy was so bad I could not let go of the drops to grab for the brake levers. On top of that, the bike was veering all over both southbound lanes. I had one 18-wheeler on my butt and another ready to pass.
The oscillations were so bad that my taillight’s mounting bracket snapped and sent it flying. There was no shoulder, only a knee-high guardrail with a 100-yard slope of rip-rap below. I was sure that I was going down under one or both of the semis, but I managed to put a death grip on the top tube with my knees. Seconds passed like hours. But somewhere down the slope, I was able to get the bike under control.
I ride a custom-built 68-cm Reynolds 531 frame and always wondered if the frame size had anything to do with it. I rarely will ride above 40 mph now.
Andrew Learned says
I appreciate these comments as I too just experienced this phenomenon going 47 on a downhill. I too thought I was going to die so I appreciate your help in rebuilding the confidence to get back on the saddle. My question, which didn’t seem to be addressed above, is I was riding 80m carbon wheels and I’m wondering if they are the culprit. Usually, I ride on flats in Florida and they work great there; I know to be on the lookout for crosswinds (there was none this day), but I was in a pack and curious if maybe the turbulence of the peloton had something to do with it. Thank you again for your article above. -Andrew
Add me to the list. Was doing about 50 k done a rough road when the bike just started to rock and roll like a bronco at The Calgary Stampede. I had already put myself in the ambulance and arrived at the hospital. Luckily I did all the wrong things and survived. But now I stay as loose possible and keep my weight on the bars. Legs ready to grip the top tube. Thanks for the info
I had one on Friday 13th September, on fast, narrow downhill descent, ended badly 6 ribs, 3 vertebrae and punctuated lung, also busted hand ligaments.
Had one or 2 wobbles before but 1st one on Spesh Allez, the top tube trick and moving hands and weight didn’t work this time,
John Clark says
I experienced my first oscillation two years ago on a hill I’d descended many times. I loved hitting the top and trying to crank out enough power to ascend the following hill. This day I was really psyched because they’d finally put a new top coat on the road. Just after I noticed how the new pavement sucked into old cracks in the road I started to shimmy and pull hard toward the embankment at just under 40 mph.
All I saw was the swamp water I was about to drown in.
I grabbed the brakes, tensed up, and wrestled the bike to a stop. Then I went home and started researching the event. I’m sure it was me cranking hard while hitting a rut that caused it but I found I was on an undersized bike and also carried a trunk on my bake rack to carry necessities on frequent longer, unassisted rides.
After trying for months to get over a new found anxiety on the bike I decided it was time to check my bike fitting before a 540 mile ride around Lake Ontario. My bike was great if I were 5’8” or so. (Surprise!) So I was fitted to a Trek 720 and made my ride around the lake but still would feel, or think I felt, a wobble from time to time.
I was finally returning to a greater level of comfort on an 80 mile ride with a friend. We got to a descent I was familiar with and had enjoyed in years passed. Traffic in the on coming lane, traffic behind me, rough shoulder and another oscillation. Not as severe but equally as nerve wracking with the large amount of hostile traffic and the knowledge that the bike my decide to pull into the line of cars.
I’m now back to being anxious on descents which I had previously seen as a reward for climbing those darned hills!
John G says
The times I have experienced wobble were when I had heavy panniers on the back and none on the front. My riding position and body type are also rear biased. Experienced touring friends have suggested distributing weight with front panniers.
Soooooo many variables! Yes, I’ve heard weight distribution impacts the ride. I’m thinking since I’m not a racing type rider that I should stick with a big old metal frame and slightly wider, more rigid tires and rims. I’ve got a Trek 720 light touring bike. (It has clip on waterproof sacks on each fork. Not a fan.) But weight distribution is now something I consider more thoroughly.
Big Ring Bob says
Many years ago, I traveled to Medford, OR and did a ride that as I recall was called “Dead Indian”. It was basically a logging road that went to the top of Siskiyou Pass. We took I-5 back into Ashland, OR (one of the few places bikes are allowed on an Interstate). On the descent, I drafted a semi. On a rented bike with a metal frame (~1986) I experienced “wobble”. The first time was at about 42 mph, as I continued to accelerate, it smoothed out and started again at about 54 mph, this time a little more intense, with further acceleration the bike became smooth again until we hid slightly more than 62 mph. With each instance, the faster the velocity, the more aggressive the vibration. This time I chickened out and backed out of the draft. Definitely a harmonic phenomenon, and anything that changes the tuning, leg against the frame, taking your butt off of the seat, can solve the problem. With the wisdom of my old age, I now recognize the foolishness of the exercise, but has become one of the more unforgettable experiences I have had on a bike
Sorry to report but squeezing the top tube doesn’t always stop the wobble, but often can slow it down. I have been dealing with speed wobble for over 25 years on multiple high end bikes. My most terrifying episode was going down from a ski resort at about 50 mph when it hit. My sons, who were following in a car, said that my back wheel was jumping back and forth about a foot left and right. The violent oscillating continued until I got the bike nearly stopped. I am 6’ 165 lbs with very long legs for my height. I ride a 61 cm steel bike now, with “a fist full” of seat post showing. I am positive that up canyon or cross winds can initiate the wobble. We frequently ride a mountain with a 6+ mile descent with 6-9% grades in places. Most times there is no problem at 35-50 mph. However- add a little uphill wind and let the panic begin. It happened again last week and I told my riding buddy that it is discouraging to not be able to enjoy the descent at all after a 3,000’ climb! I had to use nearly every trick in the book to control it. I learned a new one in this article and comments (push down on bars) and will try it next time. Light grip, weight on the pedals and squeezing the top tube does not make for a fun ride down when you can feel the wobble trying to start. I’m hoping that the gravel bike I have on order will solve the problem for me. (Stiff CF frame, 40 mm tires and new bar layout)
John Clark says
I keep hoping someone replies with THE answer. Cycling has lost a lot of its enjoyment for me between occasional wobbles and aggressive drivers. At 56 I hope to have many more peddling years ahead but it takes a lot longer to recover from minor crashes. I might be done.
Brian McLaughlin says
My new lightweight carbon bike makes me really nervous at moderate speeds – feels like my steering is floating around and I experienced a heart pounding road wobble last week, which is why I’m here today.
Has anyone tried a headset dampener on their road bike? I rode a steel framed racing bike back in the 80s that had a crude dampener in the headset but it did the job and I never had road wobble despite many high speed descents.
I thought those dampers were just hype but I’ve become much more curious. I know there are new versions out there on the internet. I’m considering buying an old Raleigh ten speed that I wanted back in the 70s. That old metal beast won’t shake.
John P says
I experienced the dreaded speed wobble today riding down Rabbit Ears pass (eastbound) in CO. I was doing something slightly in excess of 35 mph at the time it started. I’ve experienced it before, but it’s been quite a few years, and it has only happened to me on carbon fiber frames. I was fortunate to be able to stop it by gripping the top tube with my legs and playing with my brakes, front and rear, on and off, on and off, and bringing the bike to a complete halt. However, it is scary as all get it. It does make me not want to descend very fast.
In our search for a lighter load and supposed easier ride with lighter bikes we might be creating a situation that means enjoyment. I’m too old to fall of my bike on the pavement. I won’t bounce like I used to, I’ll crack, splinter, or snap. And my old skin won’t get road rash it’ll just peel off. I’m going in search of a 70s metal frame. Or, since I’m cheap, maybe I’ll avoid going down hills.
D. Martin says
I had never experienced this phenomenon until putting new tires on my 2013 Specialized Tarmac Expert (28mm Grand Prix, previously rode 25mm Vittoria Rubino Pro) and having a “fitting”, changing to a more upright riding position. Since then I had several episodes of severe shimmy on moderately high speed descents, usually with a strong cross wind and/or rough pavement. Once, unable to negotiate the turn, crossing into the oncoming lane, fortunately no one coming. Add me to the list of those no longer willing to bomb the descents like I used to, now riding the brakes to keep speed checked.
Had a pretty gnarly speed-wobble today descending Fountaingrove Parkway in Santa Rosa. I ride a 64cm Diverge Comp E5 and I started wobbling in a right-hand curve as I snuck up on 55 mph. I was tucked down in the drops and got tossed from the bike lane through the right lane into the left lane before I got it back under control. Not fun!
Jim P says
Wow, glad I’m not the only one who’s experienced this level of terror. I have a slight hand tremor and thought it was all me. Wondering if lowering the seat post before a descent would make a difference. (All my rides are up paved roads to a ski resort and back down, so once I’m descending, I no longer need to pedal.) Any thoughts appreciated.
John C says
In one of the earlier posts in this thread a couple people spoke about more weight on the front rim so dropping the seat would seem to remove weight from the forks. This thread is a pretty good discussion on these oscillations with a wide range of corrections sadly it’s trial and error. Good luck!
Make sure the top side of ahead stem(or spacer above) is 3 mm above the steer tube. In my case it was apparently well mounted, but I realized that the to cap of the ahead stem was not shallow, but rather deep and slightly touching the steer tube. Just changing the spacers configuration in order to gain 1 mm solved the problem completely. Now the top cap does not touch the inner tube. Going that fast on a bike was never a good idea.
Had a similar terrifying wobble, pictured hitting an adjacent ditch already and was promptly saved from this event by simply not panicking or even pressing hard on those pedals. Nonetheless, panicking is also a factor that one might need to avoid in these situations and just keep everything on a straight line.