Slowtwitch Forums: Triathlon Forum: High Speed Wobble at IMC on decent

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Slowtwitch Forums: Triathlon Forum:
High Speed Wobble at IMC on decent

GrahamK

Aug 26, 08 10:42

Post #1 of 13 (668 views)

High Speed Wobble at IMC on decent	Can't Post

Folks. I raced IMC over the weekend and nearly had the crash of my lifetime decending from twin lakes back to Penticton. Doing about 40mph a big cross wind hit me and next thing I know my P3SL and Hed3's are shuddering back and forth like crazy. It took all my strength to hold the bars, lock my kegs to the cross bar, and crank the brakes on to slow the bike and wobble down. I have never had a Hed3 wobble before over many years of riding. Anyone else ever have a Hed3/P3SL combo wobble?

Thanks, Graham

tomd

Aug 26, 08 10:44

Post #2 of 13 (664 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

are your wheels true?

Old and Haggard

Aug 26, 08 10:51

Post #3 of 13 (648 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

http://draco.acs.uci.edu/rbfaq/FAQ/8h.5.html
-----------------------------------
Ken Lehner

"reread klenher [sic] and pretty much skip the rest." - desert dude 5/25/2008

Robert@Newton

Aug 26, 08 11:19

Post #4 of 13 (619 views)

Re: High Speed Wobble at IMC on decent [Old and Haggard] [In reply to]	Can't Post

Graham, it wasn't you. There were some GNARLY crosswinds on both descents. I damn near lost it coming down from Richter at 52 MPH, and I was on the hoods. I heard similar comments from at least a dozen other athletes.

GrahamK

Aug 26, 08 12:39

Post #5 of 13 (527 views)

Re: High Speed Wobble at IMC on decent [Robert@Newton] [In reply to]	Can't Post

Thanks. I was starting to think I needed to seriously consider moving to a deep dish rim style wheel like a Zipp. Are Zipps just as prone to this or is the tri spoke a bigger problem as each blade passes through the fork?

Robert@Newton

Aug 26, 08 12:43

Post #6 of 13 (512 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

FWIW, I was on 808's and now wish I'd had 606's

HH

Aug 26, 08 14:15

Post #7 of 13 (463 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

It's the H3s. Search on here, I've previously posted as have others.

I've ridden thousands of miles and have only had a frightening wobble develop one time -- on H3s, at high speed (40 mph), and after sudden crosswind gust (from a passing tractor-trailor truck). Still ride the H3s, but won't ride them on very windy days, and also careful when riding downhill if subject to gusts.
.

Hoegaarden wishes and Super Record dreams, HH

cliogrrl

Aug 26, 08 15:14

Post #8 of 13 (425 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

I had a bad wobble during Ride the Rockies with a 404 on the rear. I talked to the Mavic guys in the demo tent afterward, and they suggested that deep rims are a bad idea on fast descents. I used one of their demo wheels afterward and had no more problems.

cuds

Aug 26, 08 15:59

Post #9 of 13 (402 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

I had a 404 front and 808 rear, and the same thing happened to me. I thought for a moment I was a goner, but I got slowed down and stayed upright. Drives me crazy... work so hard up that damn hill just to have to go down it like a little girl lol.
______________
cuds is retired.

Roadndirt

Aug 28, 08 11:24

Post #10 of 13 (319 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

I have had the same problem in the past. Very scary, needed to use knees also to brace bike and get back under control.
I changed my headset and it solved the problem. It never recurred.

canuck8

Aug 29, 08 0:07

Post #11 of 13 (214 views)

Re: High Speed Wobble at IMC on decent [HH] [In reply to]	Can't Post

In Reply To

You can include me in this thread with HED H3 Carbons.

Twice during IM and once during a half ...all on decents.

Have since realised it was due to the rear wheel being out of true.

Hed was very helpful ,and it will be sent back within the very near future.

Terry

" Dream big and strive to separate yourself"
Chris Lieto...Oct. 2006

bmas

Aug 29, 08 5:16

Post #12 of 13 (179 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

"Shimmy that concerns riders the most occurs with hands firmly on the bars and it is rider generated by muscular effect whose natural response is the same as the shimmy frequency, about that of Human shivering. Descending in cold weather can be difficult for this reason. The rider's "death grip" only enhances the incidence of shimmy in this situation. Loosely holding the bars between thumb and forefinger is a way of avoiding shimmy when cold."

This is the last paragraph in the article cited by klehner. I suspect this death grip is the problem in most high speed wobbles. Happened to me a couple of times when I was nervous on a fast descent. Hasn't happened since I've learned to relax and loosen the grip.

-----------------------------------------------------------
"Every time I see someone on a bicycle, I fear less for the future of the human race." HG Wells

JimH

Aug 29, 08 6:18

Post #13 of 13 (152 views)

Re: High Speed Wobble at IMC on decent [GrahamK] [In reply to]	Can't Post

Have the same problem on my roadie. The only way it goes away is being really light on the drops and weight to the back. If I'm on the hoods, hang on.

Jim