Originally Posted by moguljunkie
I've gotten into biking more this summer, and just hit 39 mph yesterday. I can't imagine going much faster, because the bike was not very stable at that speed -- in fact, when I started to pedal at one point, I thought for a second I might lose it. The road wasn't the smoothest in the world. Could it be that or is it more likely my Trek 2100 is not suited for higher speeds? Do you have to spend a lot for a bike with some high-speed stability?
Any decent road bike is more then capable of hitting some scary-fast speeds -- it's more a question of the riders nerve once the speedometer creeps above 40 or so then anything else.
I find the secret to high speed is a matter of relaxing and letting the bike flow. I find the bike will shake a bit on all but the smoothest roads; death-gripping the bars or the saddle between your legs just causes the shaking to be worse. I don't use a totally loose "la-de-dah" grip, but I'll definitely let the bike bounce around a bit and I use my legs and hands to keep the bike within an "acceptable range".
On seriously potholed / frost-heaved roads -- well, that's where nerve really comes into play. Sometimes it's just not worth letting it rip. Taking a spill at high speed isn't something you want to even remotely contemplate.
Getting your weight distributed over the tires correctly is also pretty important. Too little weight on either tire is going to cause that wheel to slide pretty easily, which is definitely a
: moment. The steeper the descent, the more you have to get your butt hanging back over the saddle. Look at pictures of MTB'ers descending -- they'll practically be sitting on the rear wheel to keep traction on it. Gravity takes care of keeping weight on the front. If your bike doesn't fit very well though it can be difficult to find a happy medium where both tires are tracking well.
Experience! On a familair hill that you feel safe on, you just have to let it go sometimes. Smooth roads really help build confidence.
All that said... There can be physical issues with the bike itself that could make it inherently unsafe for high-speed descents. i.e., if the wheel drop-outs are slightly mis-aligned and the wheel just sits in the frame crooked, you could be in for a scary experience. Frames can become mis-aligned as well, especially if they've been crashed hard. If you think that something really is wrong, then you can take it to a shop and have them measure just how "straight" your bike is. I doubt a quality manufacturer like Trek though would let something really bad slip through their quality controls though.