Frame balancing for high speeds?



R

-RB

Guest
I'm interested to learn if there is info out there about precision
frame and wheel balancing for high speed descents. I recently hit
58MPH on a descent and experienced a slight wobble beginning at
probably the moment I hit 58. At least that is my guess, I was not
watching my speedo. However, when I first felt the wobble I applied a
little brake and it promptly stopped so I figure it started at my max.
speed. I'd like to know this won't be a problem in the future,
especially if I can take an active part in assuring my bike is in
complete balance.

I have plans for next summer that will include Mount Ventoux and Carson
Pass descents. I want to come home in one piece. If anyone knows of
such work please forward me the info on it to [email protected]. In case
you're wondering, or it's important, my ride is a 00' Trek OCLV 5500.

Thanks in advance,
-RB
 
-RB wrote:
> I'm interested to learn if there is info out there about precision
> frame and wheel balancing for high speed descents. I recently hit
> 58MPH on a descent and experienced a slight wobble beginning at
> probably the moment I hit 58. At least that is my guess, I was not
> watching my speedo. However, when I first felt the wobble I applied a
> little brake and it promptly stopped so I figure it started at my max.
> speed. I'd like to know this won't be a problem in the future,
> especially if I can take an active part in assuring my bike is in
> complete balance.
>
> I have plans for next summer that will include Mount Ventoux and Carson
> Pass descents. I want to come home in one piece. If anyone knows of
> such work please forward me the info on it to [email protected]. In case
> you're wondering, or it's important, my ride is a 00' Trek OCLV 5500.
>
> Thanks in advance,
> -RB


http://www.faqs.org/faqs/bicycles-faq/part4/section-23.html
 
T

Tim McNamara

Guest
"-RB" <[email protected]> writes:

> I'm interested to learn if there is info out there about precision
> frame and wheel balancing for high speed descents.


Yup. It's a waste of time.

> I recently hit 58MPH on a descent and experienced a slight wobble
> beginning at probably the moment I hit 58.


That's called a "shimmy." Read up on it in the FAQ and/or search this
group's archives at Google for many ad nauseum discussions of shimmy.

If your bike shimmies at 58 mph it's not much of a problem, the places
you can go that fast are pretty few- Phil Liggett's exaggerations at
the Tour day France notwithstanding.
 
A

A Muzi

Guest
-RB wrote:

> I'm interested to learn if there is info out there about precision
> frame and wheel balancing for high speed descents. I recently hit
> 58MPH on a descent and experienced a slight wobble beginning at
> probably the moment I hit 58. At least that is my guess, I was not
> watching my speedo. However, when I first felt the wobble I applied a
> little brake and it promptly stopped so I figure it started at my max.
> speed. I'd like to know this won't be a problem in the future,
> especially if I can take an active part in assuring my bike is in
> complete balance.
>
> I have plans for next summer that will include Mount Ventoux and Carson
> Pass descents. I want to come home in one piece. If anyone knows of
> such work please forward me the info on it to [email protected]. In case
> you're wondering, or it's important, my ride is a 00' Trek OCLV 5500.


If anything, a properly aligned frame with round wheels will
be more, not less, provne to shimmy than a crooked frame.

This may help:
http://draco.acs.uci.edu/rbfaq/FAQ/8h.5.html

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
 
M

Mike Jacoubowsky

Guest
> I'm interested to learn if there is info out there about precision
> frame and wheel balancing for high speed descents. I recently hit
> 58MPH on a descent and experienced a slight wobble beginning at
> probably the moment I hit 58. At least that is my guess, I was not
> watching my speedo. However, when I first felt the wobble I applied a
> little brake and it promptly stopped so I figure it started at my max.
> speed. I'd like to know this won't be a problem in the future,
> especially if I can take an active part in assuring my bike is in
> complete balance.
>
> I have plans for next summer that will include Mount Ventoux and Carson
> Pass descents. I want to come home in one piece. If anyone knows of
> such work please forward me the info on it to [email protected]. In case
> you're wondering, or it's important, my ride is a 00' Trek OCLV 5500.
>
> Thanks in advance,
> -RB


I wouldn't worry too much. The "shimmy faq" will give you quite a bit of
helpful information, but what I think it leaves out is a bit of common
sense. Specifically, shimmy is a function of the bike *and* rider together.
Without thinking about it, you've learned to ride in a way that doesn't
create or enhance shimmy. But that's at relatively-normal speeds. Two things
happen at speeds "off the charts." First, people aren't going to design a
frame that's specifically meant to be super-stable at speeds that people
aren't likely to hit (such a design would likely compromise handling at more
moderate speeds). Second, because such speeds are so unusual, the rider
doesn't have experience in knowing how to ride at such speeds. The fear,
uncertainty & doubt (probably a whole lot of adrenalin, basically) doesn't
help matters.

As for Ventoux, I don't recall there being many stretches of that road where
you could hit such high speeds. Carson pass, with a tail wind, is another
matter entirely. Be very, very careful when doing so; a flat at 55mph can be
more excitement that you would want to experience.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
 
R

-RB

Guest
Thank you gentlemen. I feel more at ease after reading the FAQ's page,
and Mike's response. I'll see you in the spring at tune up time Mike.
I have to confess after reading Brandt's last paragraph, I was cold
when I first dropped down Carson. In fact I told my buddy I wasn't
sure if it was the bike or me. I know it happened twice in the same
stretch. The first time I relaxed my grip and concentrated on my
breathing. However, very shortly thereafter I had the shimmy again.
So, it still could have been me that initiated it, but I understand
better how it all works now.

Incidentally, had a brief encounter with Brandt last year. I was
climbing up Highland Road from Corrolitos with a couple of slow riders.
Brandt came riding by while I was giving the guys a quick brake.
Brandt stopped to chat a moment. I thought at the time, "That is one
old guy still hanging tough." He still wears old wool bike clothes and
no helmet, just like when he was in his early years. I later visited
some websites that had photos of Brandt in France way back in the
seventies. He's still riding the same dang yellow bike that was in the
photos too, it's huge compared to my 54cm. I also thought, wow, "He's
tough, but what a dinosaur". He was a bit of a smart ass too. One of
the guys with me was also an old smart ass Jewish guy at
sixty-years-old. When the topic came up about our route, I thought
these two old guys could have easily dismounted and start throwing
blows once the one-upsmanship started flying. It was almost hilarious,
like a couple of old pissid off New Yorkers. Two rude old farts
puffing up and arguing out in the middle of nowhere. It was a funny
moment.

Thanks again for the info,
-RB