Road Cycling - Going Downhill

I have been riding now for 6 weeks. I don't get to ride often and when I do get to ride, I usually go 25-30 miles. I climb okay and I like to sprint on the flats.

My problem is going downhill. I am not a daredevil, but not a wimp either (3 little girls at home, can't afford to be dead). My max speed going downhill is 25 mph....I usually sprint on flats faster than this (26-29 mph).

My road bike starts to shake around 24 mph going downhill. I am not nervous, so that is not the reason. Also, I had my LBS do a tune up and a realignment...alas, no better.

What is the best way to position yourself going downhill?

Thanks,
29 :rolleyes:

Hi,
what do you have for a bike; and could you describe the shake a little better?

sometimes clamping your thighs around the top tube will
dampen the vibrations (osscilations really) to the point
of killing the shaking.
How old is your bike? If its new (as in 6 weeks or so) it
should not behave this way.

Check that your wheels are all the way in the dropouts,
I've seen this cause bad shaking before.


Marty

My ride is a 2003 Specialized Allez. I bought it new 6 weeks ago.

29

29,

I'd go back to the shop and ask them to check wheels,
alignment etc. your bike should NOT shake at 25+ mph
on a downhill. Something is wrong here, it should be up
to the shop to rectify it.

Marty

could be reflectors on wheels.

A brand new quality bike should be stable at 50mph; something's wrong. Have the dealer fix it.

Could it be bad positioning on the bike causing the front end to unload a bit or too tight a grip on the bars causing unintentional steering input?

Originally posted by djbowen1
could be reflectors on wheels.
I don't think road bikes this days come with reflectors. At least I haven't seen any at my store. ;)

Originally posted by Chuvak
I don't think road bikes this days come with reflectors. At least I haven't seen any at my store. ;)

They do come with reflectors although many people have the sense to remove them. ;) And I was told that bikes sold mostly pre-assembled from the factory need to be sold with reflectors mounted but bikes that are built frame-up don't. Or something like that. Regardless, I still get a bag of reflectors everytime I've left the store with a bike.

It could be the bike or the rider (no offense at all, 29). If you're nervous enough at higher speeds, you'll tense up and start to do too much steering with the bike. That could be at least part of it; you'd have to tell us if that was the case. As for positioning, locking your knees or thighs around the top tube does add a lot of stability to your descent, regardless of speed. It's a good way to feel better about the fact that you're flying down a hill. If your shop has checked everything over and all's lined up well, I'd look at your riding style and how relaxed or tense your upper body is while descending.

Originally posted by khuon
They do come with reflectors although many people have the sense to remove them. ;) And I was told that bikes sold mostly pre-assembled from the factory need to be sold with reflectors mounted but bikes that are built frame-up don't. Or something like that. Regardless, I still get a bag of reflectors everytime I've left the store with a bike.



That reminded me of something else. When I was a newbie in cycling I left the clear plastic spoke protector on. It stayed there until I was into the first day of my first BRAG tour and I'm between SAG stops, when the stupid thing decided to jam itself between the freewheel and the downstays. I had to wait for a service vehicle to come by with pliers to get it out.

What does the spoke protector look like? I have a relatively new bike and am new to this stuff so I think I need to know. Any other tips for a relatively new bike?

I'm still trying to relax my hands. Might need to move the handlebars or something. AAH!

It's a large, usually clear, plastic disc about 6 to 8 inches in diameter. It fits on the rear hub between the spokes and the largest cog. The purpose for it being there is that if you should shift to far up, or the derailleur goes too far to the inside, it will hit this disc, and not get jammed into the spokes. It was more frequent on friction shifters than indexed ones. Being made of plastic they tend to break easily, and in my case, pick the most unfortunate time to do so. And I guess that someone once sued a bike company because he didn't adjust his equipment right and he jammed the rail into the spokes, and so now everyone gets one, just like those bumps on the inside of forks. (But I think I have found a solution for this! I'll post soon!)

bumps on the inside of forks?

Originally posted by thomspins
bumps on the inside of forks?

Also called "Lawyer Tabs" They are the protrusions on the dropouts on your front fork, that make it necessary to unscrew your quick release a lot before removing the wheel... really there to keep your front wheel attached to the bike in the event you did not tighten your QR enough

Jeff

Twenty nine: a little looseness in the headset will result in wobble. There is an allen bolt inside the top, try tightening it up a bit.. (Headset is accessed from the fork end of the stem and is the part you see looking down at the stem from the riding position )

Thomspins: nubbins on the tips of the front fork where the wheel is clamped on, in the good old days, you flipped the QR lever, lifted the bike up and the front wheel.... just fell out.... Someone in New Jersey failed to close his QR and the wheel .... fell out... while riding. Don't recall the settlement but the result was nubbins on the inside of the fork tips that retain the wheel in place til the QR is unscrewed 3-5turns on all bikes ever since. Also known as lawyer lips. They can be filed off. Steve

Originally posted by pointyhead
It's a large, usually clear, plastic disc about 6 to 8 inches in diameter. It fits on the rear hub between the spokes and the largest cog. The purpose for it being there is that if you should shift to far up, or the derailleur goes too far to the inside, it will hit this disc, and not get jammed into the spokes. It was more frequent on friction shifters than indexed ones. Being made of plastic they tend to break easily, and in my case, pick the most unfortunate time to do so. And I guess that someone once sued a bike company because he didn't adjust his equipment right and he jammed the rail into the spokes, and so now everyone gets one, just like those bumps on the inside of forks. (But I think I have found a solution for this! I'll post soon!)

erm...we're supposed to remove this?!

i'm new at this too, so i have no idea. but i looked at mine, and it's not coming off without me either breaking it to pieces or removing my cogset.

does everyone remove this? do i look like a geek with it on? i must know!

I noted that this discussion was hanging out there unanswered - please help the newbies.

Well, mine started to come off by itself. I was a few miles into the Bicycle Ride Across Georgia, when the darn thing broke loose and jammed itself in my cogs and chain. Thankfully, the sag wagon came by and the roaming mechanic finished breaking it away using needle-nose pliers. I recommend removing it before it breaks on its own and does major damage.

We all look like geeks to somebody! If the spoke protector isn't bothering you, it's not worth the effort to take it off.

someone seems to have resurrected an old thread!

i wasn't too concerned about my spoke protector, just being a bit silly. i figure if my chain comes flying off, my Spokes will be Protected (hence the name). chewing up a couple of spokes with the chain during a ride seems just as bad as chewing up some spokes with the chain protector. but hey, what do i know?

maybe i'll paint it pink to draw more attention to it. streamers on the end of my bars are next...

I have a 2 month old Trek 5200 and just got going 39 MPH down a hill over the weekend and no shaking what-so-ever. I'd definitely have your LBS check it out.

Teski

The so-called "dork wheel" that keeps the derailleur out of your spokes is not necessary IF your derailleur stops are set right. (No offense on the 'dork wheel' monker; it's a holdover from my shop days.)

Interestingly enough, I notice a wobble in my new Orbea on the same 50 mph downhill that was steady as a rock on my old Cannondale. Nothing that makes me feel out of control, but it's interesting.

If all the mechanics of the bike check out, then it could possibly be that going certain speeds cause the bike to reach an unstable resonance frequency because of the combined mass of the bike and the rider and wind/road conditions.

By simply changing positions on the bike, you could change where the unstable frequency lies.

When I start to feel a hint of a wobble, I either sit a little forward or backwords, or even get off in the saddle while staying in the drops. I try to do all this while slightly squeezing the top tube with my knees and/or quads.

I've found these methods have increased my confidence, but admittedly, I'm a speed weenie and have on the guts to max out at 40mph for only a little while---then I start to rise up and act like a parachute or feather the breaks. However, be carefule when you do this at speed, because that in and of itself can cause instability.

Even though I'm relatively new to riding, I don't have any ambitions to go faster than that (40mph), unless I'm in the flats---but when's that ever going to happen?

Anyhow, good luck!

Check the latest "Tech Talk" on velonews.com Zinn covers in some detail.