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Front-end stability question(4 posts)

Front-end stability question5ive
Mar 31, 2002 11:54 AM
I've hada 52cm Pinarello Prince for 6 months. It's a lovely bike and I really like the way it handles at higher speed. However, at slower pace I find steering a bit too twitchy for my taste. Every tiny input on my handlebar is translated at an instance without any delay. I'm wondering if anything could be done to stablize the front-end without changing out the fork or affecting the current setup I have too much. Could moving back the saddle and adding more weight to the back of the bike improve stability? How about getting a longer or shorter stem or raising the bar hieght? Any help will be appreciated. FYI, I'm running 100cm stem with 42cm bar and my sitting position is bit forward than normal with my short femurs. Thanx.
Thick question...Leisure
Mar 31, 2002 5:59 PM
There are a lot of variables we can't see without having you in front of us. First off, did you get professionally fit when you bought it? About what height are you? If you have short femurs for your height and are riding a much more compact frame than most in combination with a short cockpit (esp. a 100mm stem), I can see you riding tall without as much weight going into centering your handlebars. Swapping stems doesn't change handling on road bikes the extent it does on mtbs, but in combination with moving the seat back you might get a more noticeable improvement. Try a 130mm stem, the height won't make much of a difference. Changing your fork may not make a big difference; my feeling is a fork's weaknesses surface at speed, not going slow. Then again, I never really have felt like we finally resolved the whole "fork rake" issue. Eh, who knows.
Twitchy steering:guido
Mar 31, 2002 8:40 PM
Sounds like your Pinarello has a steep headtube angle, 73.5, 74, 74.5 degrees?

I have a bike like that. It requires a light touch on the handlebars when going slow, and every now and then still surprises me at stop lights. No matter what fork is used, the twitchy steering will still be there if the steering angle is steep. The more vertical the steering axis, the quicker the steering. How far the front wheel is in front of the steering axis doesn't affect it.

A longer stem would provide a longer steering lever and dampen response somewhat, but still requires a light touch, because it places the weight of hands and forearms further over the front wheel. If the stem is way lower than the saddle, twitchy steering could be caused by too much upper body weight on the bars. Raising them a little might rotate upper body weight back toward the rear wheel, enabling that feather touch on the front.

If the saddle set back is optimal for your femurs, but you feel positioned a little too forward, a low stem could be the reason. 52 cm. frame is pretty small, too. If the saddle is jacked way up, are the handlebars a tad low? Is the frame too short?

Well positioned fore-aft, a steep steering angle will eagerly follow your slightest command, but you have to get used to it. As you experienced, high speed handling is very stable. The faster the front wheel is spinning, the more it acts like a gyroscope, and the "harder" it steers.
Dang, you're good!5ive
Apr 1, 2002 6:18 AM
Guido, thanks for your input. You're right on the money about my bike and position. First, my Prince does have a steepish headtube angle. Pinarello never publish this info for some reason, but everyone agrees it's somewhere around 73.5 degrees. I was especially impressed when you said "If the saddle set back is optimal for your femurs, but you feel positioned a little too forward, a low stem could be the reason." My saddle to handlebar drop is a little more than 3 inches. I've always liked riding this way and I guess, like you pointed out, this is partly to blame for less than ideal weight distribution over my bike. I'll try out some of your suggestions. Thank you. You've been very helpful.