A friend just got a QR Caliente and was out on a test ride. When he was going down a good hill, the bike started to shake violently when he hit about 40MPH. He was on the bullhorns, there was no strong cross-wind, he was using regular low profile spoked wheels, and the wheels appear true.
Any ideas? He’s ready to send the bike back.
check his headset, maybe loose
.
Wheels or headset.
It may go away at 45+ 
A friend just got a QR Caliente and was out on a test ride. When he was going down a good hill, the bike started to shake violently when he hit about 40MPH. He was on the bullhorns, there was no strong cross-wind, he was using regular low profile spoked wheels, and the wheels appear true.
Any ideas? He’s ready to send the bike back.
It’s not the headset, the wheels, the frame, or any other single component. It’s sometimes called speed wobble, and it is described here.
I had the same thing with my Cervelo, just about the same speed too…
I swapped out -
Headsets Bars Wheels (x4) Forks (x3)
There was just some odd thing with the frame that makes it want to shimmy at speed. Never did solve it (and that bike is now in a box).
One other thing to consider…a death grip on the basebar!! If you tense up you don’t allow the bike to track with normal minute changes. Your tense grip tends to make the bike wobble at high speed and gets worse the tighter you grip the bars. Before changing equipment try totally relaxing. I’ve had 2 bikes do this and as soon as I relaxed the wobble was gone. This is especially true with a new bike you are not used to yet. This occurred on my brand new Look 596, until I relaxed and has not happened since.
changing tires seems to make the biggest difference to me in where the resonance point occures. The easiest solution… go faster.
Did he put both his knees against the toptube? That, and relaxing my grip made my speed wobbles go away.
whats the stem length on the bike?
Check the alignment of the rear tire in the horizontal droupouts. I had the same issue on my 04 Caliente on the worlds toughest 1/2 course in Auburn on the long downhill to the bridge. Thought I was going to die for sure,
The adjustment screws were off and the rear wheel would not align in the horizontal droupouts. I had to remove the adjustment screws and insert them from the dropout side the get the tire straight (thanks to Herbert for the advice).
Not a single speed wobble in 4 years and many many miles.
Dave
When I was riding with a buddy in Austin we started going down this awesome hill. I stayed in my aerobars at about 55 mph and he got up to about 40 and stated wobbling and almost ate shit. When he finally made it to the bottom I told him that he is too tense and his knees are sticking out like an old cowboy. After relaxing and putting his knees against the top tube, the wobbles disappeared.
Just like Zipp said (unless there is something wrong with the bike), relax. You can’t fight the bars on a decent. Let the bike go. Get in the aero bars and relax. I was decending down that hill in Kona right after you hang the left off of the Queen K going up to Hawi when my bars started to shake violently at 51 mph when I was on the cow horns. I quickly jumped over to the aero bars and relaxed (I used to race and crash motorcycles going twice as fast as this, so this was no big deal ) and I hit a smooth 51 again after hitting the brakes.
the Caliente in and of itself is more than likely not the culprit. lots of factors combine to create the wobble, potentially with any bike/rider combination. many of us here have experienced nearly going to visit our maker. don’t mess around with trying to change the bike, change the rider technique.
learn to “unweight” the saddle a bit, loosen the grip, and maybe try to bring a leg up against the top tube a little.
isn’t it fun to go fast?
I have a Lucero and it did the same with the stock Real Design 60mm wheels. No problem when I switched over to Zipp wheels. It is scary when it happens.
" It’s not the headset, the wheels, the frame, or any other single component. It’s sometimes called speed wobble, and it is described here."
x2
mm
Ill advise to check the opposite as well.
When I worked on and raced motorcycles, have the headset too tight caused the bike to be unstable at speed. Its like any little bump or torque was transferred through the chassis rather than the bars and your hands.