Scary moment on ride yesterday

[deluz]

I am just starting to get into longer and hillier rides after a year off due to health problems. Yesterday I did a moderately hilly ride (1900 ft) that I have done probably a hundred times before. One section of the ride has a long twisty descent through a canyon that can get pretty windy. It is a narrow road with high speed car traffic. Yesterday the wind was gusting and part way down the front wheel started oscillating back and forth and I had to put on the brakes.
I was riding my new Tarmac SL8 with 40mm BTLOS wheels. On previous rides I had noticed the wheels catching the wind but nothing serious like this.
The rims are GX40 22mm internal width and thought this shape rim is supposed to be less subject to catching the wind.
I am not wanting to change wheels and decided not to ride this road anymore since I am 67 and wanting to have less risk as a crash could be disaster.

[mass_biker]

Wow. I’ve been “caught” by gusts before. Not fun.
For reference - which road in North County SD? See you’re from Encinitas and I do a fair amount of riding up there when visiting in laws so am curious.
MB

[deluz]

Originally Posted by mass_biker

Wow. I’ve been “caught” by gusts before. Not fun.
For reference - which road in North County SD? See you’re from Encinitas and I do a fair amount of riding up there when visiting in laws so am curious.
MB

It was the Elfin Forest - Del Dios Hwy loop.
The incident occurred heading west on Del Dios Hwy.
Gusty winds are typical there and combined with the narrow road and high speed traffic I am no longer interested in doing it. Elfin Forest is really good though. It used to be a rough road but it has been repaved and is super smooth. Next time I will probably just do an out and back on Elfin.
Another favorite is doing loops through Rancho Santa Fe. Lots of quiet scenic hilly roads with low traffic.

[AngryScientist]

I'm sure they do a lot of "reverse engineering" - but I'm not convinced these much loved off brands like BTLOS have enough design prowess as the big guys like Campag, Zipp, etc to design the best wheel shapes, especially for something like managing side winds.

That said, if your typical riding has a lot of up and down with gusty winds involved, 40mm wheels are not the right tool for that job.

I'd stick to something lighter and shallower if I were you.

Glad there was just a scare, not a crash!

[deluz]

I will admit I was pushing it down that hill and could have gone slower.
My other bike has 30mm rims also BTLOS that I could use in these situations.
When I was deciding on these wheels I was debating whether to go 35 or 40mm and now I think I would have gone 35mm if I did it over.
For most riding I think 40mm will be ok but I will see how it goes.

[mass_biker]

I do Elfin Forest a fair amount - down from San Elijo, left on Elfin Forest to the end, and then either back up over S. Twin Oaks to DoublePeak via Barnham, Country Club etc. It’s rare that I do Del Dios, and when I do it, I usually go westbound towards RSF after Elfin Forest. The descent is fast, but between the traffic and the winds, it is unnerving. Now, I’m riding a pretty old bike (Ksyrium clinchers) on it, but I too get blown around a bit - the last time I did that (Del Dios) I swore I wouldn’t do it again for those reasons. I also had a bad experience on Gopher Canyon Rd (that steep descent eastbound towards Old Highway 395). Not as much traffic, but the same combo of downhill + canyon + winds = not great. Glad you are ok!

[stackie]

I wasn't there, but could that have been a speed wobble? You said new bike, windy... maybe you were a bit tense? or maybe something up with wheels or build.

40mm not that deep especially if you are comparing to 35. I don't know your height or weight, but 40 not that deep.

Just tossing out ideas.

Jon

[deluz]

Originally Posted by stackie

I wasn't there, but could that have been a speed wobble? You said new bike, windy... maybe you were a bit tense? or maybe something up with wheels or build.

40mm not that deep especially if you are comparing to 35. I don't know your height or weight, but 40 not that deep.

Just tossing out ideas.

Jon

That is possible. I was down in a tuck gripping tightly on the bars.
Previously just felt the bike being pushed around which is no big deal, not the wobble that I experienced that day.

[deluz]

Originally Posted by mass_biker

I do Elfin Forest a fair amount - down from San Elijo, left on Elfin Forest to the end, and then either back up over S. Twin Oaks to DoublePeak via Barnham, Country Club etc. It’s rare that I do Del Dios, and when I do it, I usually go westbound towards RSF after Elfin Forest. The descent is fast, but between the traffic and the winds, it is unnerving. Now, I’m riding a pretty old bike (Ksyrium clinchers) on it, but I too get blown around a bit - the last time I did that (Del Dios) I swore I wouldn’t do it again for those reasons. I also had a bad experience on Gopher Canyon Rd (that steep descent eastbound towards Old Highway 395). Not as much traffic, but the same combo of downhill + canyon + winds = not great. Glad you are ok!

Double Peak is a bitch of a climb. I am not in shape to do it right now. Maybe in a few more months. Another super steep one in that area is Coronado Hills Dr. if you have not done it.

[tellyho]

Can't really see the value of 40mm wheels. I don't go fast enough for it to make a difference.

[mass_biker]

Originally Posted by deluz

Double Peak is a bitch of a climb. I am not in shape to do it right now. Maybe in a few more months. Another super steep one in that area is Coronado Hills Dr. if you have not done it.

I’ll have to scope it out next time I’m out there. Although the 52/36 + 11/28 gearing that came stock on this bike works for most of the rides I like to do in SD - including most importantly, Palomar! - I think some lower gearing would be advisable from what I’ve heard about Coronado Hills, Washingtonia etc. (all the roads in the neighborhoods that lead up to little Mt. Whitney there) a lower range would be advisable.

[deluz]

I can't imagine doing it with 36/28
Found this nice video showing these roads.

https://www.youtube.com/watch?v=MjN2VrQZKmQ

[unterhausen]

Every bike has a speed it will shimmy at. The better ones only shimmy at speeds you will never reach. But I can see how deep rims will hurt a bike's shimmy characteristics.

[Mark McM]

Originally Posted by unterhausen

Every bike has a speed it will shimmy at. The better ones only shimmy at speeds you will never reach. But I can see how deep rims will hurt a bike's shimmy characteristics.

^^^ This. Wind can blow a bike off to one side, but a wobble is usually a shimmy - however, a sudden gust of side wind has been known to trigger a shimmy. Once a shimmy is triggered, it will usually continue until the bike slows below the critical speed.

[smontanaro]

If this happens again, it might be worth a try to dampen the vibration with one leg, just tip it a bit toward the center of the bike and lean it gently against the top tube. In my experience that is generally sufficient to change the harmonic frequency enough to calm things down.