rsbob 

Used 60mms rims front and rear and on a 1 mile 6-8% descent today. I was cruising along at 45 MPH when a box truck doing about 40 MPH (a WAG) uphill upset the airstream suddenly throwing me into a high speed wobble. I was able to slow it down as the wobble became more pronounced just before I stopped. The hill’s speed limit is 35 and there was a car behind me (thanks Varia) the whole time. When I got out of the lane, which I took on the way down, to the shoulder, the car creeped past me making sure I was all right. I have been down this hill several times at speed with no issue but there were also no box trucks.

Wonder if anyone else has had this happen? Is there an inherent danger with deep section rims at higher speeds? Thoughts?

rm -rf

I've only had a couple of speed wobbles over all my years of riding. ( Riding just a typical road bike with low profile rims.)

They were each caused by sudden troubles that got me to grab the bars with a death grip and stiff arms. The oldest one was an unexpected sharp blast of side wind on a fast downhill. A more recent one was unseen gravel on an otherwise good road downhill. It's crazy how the initial wobble keeps going for a long time!

I googled my old comment, and located one of the threads. from 2009! The comments are still relevant.
Severe high speed wheel wobble

rsbob 

On another thread SierraRider commented that with his 45s he was doing 55 and was hit by a side wind gust which put him into a wobble as well. It appears that deep section rims may have more of a tendency to be affected by sudden wind changes at speed.

I too had a speed wobble on my Fondriest using 25s and old fashioned aluminum rims which developed a wobble any time I exceeded 40 MPH, it was cured with a new fork. Had many very interesting/clenching moments before the change.

I may switch the front wheel to a 35mm in the future when I know I will be doing fast descents as insurance.

Silver02M5

I have experienced the same with sudden, strong crosswinds on my 40mm carbon wheelset. It never happened with my old alloys, so it is most certainly the fault of the wheels.

Carbonfiberboy 

I once had a bit of trouble riding a long descent at about 50 and being passed by many vehicles doing maybe 60, while using only slightly deep alu rims. That was on my spare bike, a CAAD9. Didn't a a real speed wobble, just a terrifying lot of wiggling. I never used it for that sort of a ride again. Never had a problem on my Trek. This thread maybe has me giving up the idea of getting deep rims. I do a lot of fast descending on somewhat busy roads.

Iride01 

Have you ridden the bike enough with low profile rims to know that the speed wobble doesn't happen with them in similar circumstances? I've only had one or two bikes that ever gave a death wobble. Both were old style geometry with long head tubes and just normal for their day non-aero rims.

Maybe I'm just not fast enough anymore! <grin>

datlas 

I suspect the high-speed wobble is more related to a sympathetic/driven vibration that may not necessarily be caused by the deep section wheels per se.

In any case, it's scary and reminder to grab frame with your knees for stability etc.

79pmooney

+1 In many cases, the frame + rider geometry, stiffness, etc. has a harmonic resonance. The wheels or traffic or whatever are just the starters. (Tuning forks are quiet until they are hit.) My best bike with me on it has the tendency. Deepest rims it has ever seen are Velocity Aeros; not very deep. If I am strong, confident (and 15 years younger/fearless) speed wobbles simply aren't an issue. But even early on, I struggled on a cold wet ride with steep, narrow roads of poor pavement I didn't know. Now at 70, it starts around 40 mph. By contrast, the old racing bike I just picked up is rock solid at any speed this old man is ever going to go. I bet I could put rather deep rims on it and never have an issue; not that I am going to.

rsbob 

If I were to do it over again, 32 on the front and 55-60 on the back. That should take care of it.

88ss

I would bet the heavier weight of deep rims adds to the tendency of a bike to stay in a speed wobble once it is there.

TakingMyTime

I have no direct experience with high profile rims. I do know that my carbon Canyon seems to get blown around a little more than my other bikes just due to the lightweight nature of the bike.