D
Doug McLaren
Guest
So, I'm riding to work today, on the most scary part of my ride -- 0.6
miles over a bridge on a pretty busy highway with 65 mph traffic. 12"
of unridable curb. (Alas, any other options are miles out of my way.)
It's slightly downhill, so I usually get a pretty good speed going,
perhaps 35 mph if I pedal 25-30 mph if I don't. It's perfectly
straight, and perfectly flat -- no turning, no bumps. It scares me,
but it's usually over in about a minute, so I do it.
Today I'm not pedalling, right in the middle of the lane, and I'm
crouched down on the lower handlebars (no aerobars or anything like
that) and my odometer says my top speed was 28 mph, so that's probably
what my speed was. And then the steering starts oscillating back and
forth, at about 2 Hz. It starts weak, but turns into a pretty strong
oscillation in about two seconds, and I'd say I was a second or two
away from a serious crash. I hit the brakes, and as I slow, the
oscillation goes away.
I stop and walk the bike somewhere safe, and check it out. Wheels are
well secured, steering column is tight, etc. I can't find anything
wrong. I ride it slow at first, no problems, and the later I'm going
down another hill (in a much safer place) and hit 30 mph and no
problems (but so ready to hit those brakes!)
It's a Giant OCR2 2003 or so -- aluminum frame, fork. It's pretty
much stock, except that it has 700x28c tires, and a luggage rack. And
interrupter brake handles, but I wasn't on the top part of the bars
this time. (This might be relevant -- I do most of my riding with my
hands on the top part of the bars. I don't race, I just ride for
exercise, fun and to get from point A to B.)
The bike is pretty new to me, but I'm not the first owner. I've
personally only got about 70 miles on it now. No problems like this
before, but this was probably the fastest I'd been on it until today
too.
This part of my ride makes me nervous, and so I might have been
holding on tighter than usual, but I doubt I was actually shaking
(well, I was after ...)
I've found a number of pages that talk about this --
http://www.sheldonbrown.com/brandt/shimmy.html
http://en.wikipedia.org/wiki/Speed_wobble
.... but I don't really know what to do about it. I was pretty close
to losing it, and if I had, it would have been very bad.
One of the articles suggests putting a leg against my top tube, which
I'll try, but is there more that can be done? Something that doesn't
rely on me remembering to ride the right way?
--
Doug McLaren, [email protected]
Marge, this ticket doesn't just give me a seat. It also gives me the
right, no, the duty, to make a complete ass of myself. --Homer Simpson
miles over a bridge on a pretty busy highway with 65 mph traffic. 12"
of unridable curb. (Alas, any other options are miles out of my way.)
It's slightly downhill, so I usually get a pretty good speed going,
perhaps 35 mph if I pedal 25-30 mph if I don't. It's perfectly
straight, and perfectly flat -- no turning, no bumps. It scares me,
but it's usually over in about a minute, so I do it.
Today I'm not pedalling, right in the middle of the lane, and I'm
crouched down on the lower handlebars (no aerobars or anything like
that) and my odometer says my top speed was 28 mph, so that's probably
what my speed was. And then the steering starts oscillating back and
forth, at about 2 Hz. It starts weak, but turns into a pretty strong
oscillation in about two seconds, and I'd say I was a second or two
away from a serious crash. I hit the brakes, and as I slow, the
oscillation goes away.
I stop and walk the bike somewhere safe, and check it out. Wheels are
well secured, steering column is tight, etc. I can't find anything
wrong. I ride it slow at first, no problems, and the later I'm going
down another hill (in a much safer place) and hit 30 mph and no
problems (but so ready to hit those brakes!)
It's a Giant OCR2 2003 or so -- aluminum frame, fork. It's pretty
much stock, except that it has 700x28c tires, and a luggage rack. And
interrupter brake handles, but I wasn't on the top part of the bars
this time. (This might be relevant -- I do most of my riding with my
hands on the top part of the bars. I don't race, I just ride for
exercise, fun and to get from point A to B.)
The bike is pretty new to me, but I'm not the first owner. I've
personally only got about 70 miles on it now. No problems like this
before, but this was probably the fastest I'd been on it until today
too.
This part of my ride makes me nervous, and so I might have been
holding on tighter than usual, but I doubt I was actually shaking
(well, I was after ...)
I've found a number of pages that talk about this --
http://www.sheldonbrown.com/brandt/shimmy.html
http://en.wikipedia.org/wiki/Speed_wobble
.... but I don't really know what to do about it. I was pretty close
to losing it, and if I had, it would have been very bad.
One of the articles suggests putting a leg against my top tube, which
I'll try, but is there more that can be done? Something that doesn't
rely on me remembering to ride the right way?
--
Doug McLaren, [email protected]
Marge, this ticket doesn't just give me a seat. It also gives me the
right, no, the duty, to make a complete ass of myself. --Homer Simpson