How to make a road bike less twitchy?
February 3, 2010 7:22 PM   Subscribe

Does the types of handlebars change the handling of a bike? I have a 80's Lotus International road bike. It's my commuter, grocery getter, and all-weather bike. However, it does not handle grocery-loaded pannier bags nearly as well as my "nice bike" surly cross check does, which is my century bike and my touring bike. I don't want to lock the surly outside of the store or subject it to the daily wear and tear. I am thinking about making changes to make my Lotus handle more stable-ly. Is there anything i can do? Different handlebar? wider tires? longer stems?
posted by atetrachordofthree to Grab Bag (7 answers total) 1 user marked this as a favorite
You might need a different front fork. The rake and trail affect stability and steering.
posted by procrastination at 7:26 PM on February 3, 2010

I concur with the fork hypothesis.
My touring bike (ugh i know) has the same issue as your lotus, and I ascribe it to a very slightly bent fork...
Depending on where you are, it may not be too difficult to switch out the fork with something a little more raked. Just make sure it's dead even.
posted by Cold Lurkey at 8:18 PM on February 3, 2010

Fork geometry dictates the degree of self-steer that a bike has.

Wider bars and longer stems reduce the effect of your control inputs.

Heavier tires means more inertia in the front end.

Yes, roughly speaking, all of these changes will make your bike "less twitchy", in differing ways. Choose your poison.
posted by randomstriker at 9:02 PM on February 3, 2010

Fourthing "fork", and maybe tires, but probably fork.
posted by talldean at 9:07 PM on February 3, 2010

Another thing that changes handling is the stem. Pointing up versus down, there is a difference.

Perhaps you could match the stem angle and the fork rake of the surly on the lotus?
posted by GregorWill at 12:48 AM on February 4, 2010

Move the center of mass forward, as close to the bottom bracket as possible. The further backward the load you're carrying is, the more twitchy the bike will be. Even an inch or two will make a difference.

Another thing you can do is increase the trail, which is basically the pivot point of the front wheel. If you imagine the front wheel as a lever, pushing the balance point forward is akin to expanding the leverage. So, increase your fork rake.

This wikipedia article on bicycle and motorcycle dynamics is informative.
posted by luckypozzo at 7:31 AM on February 4, 2010

Here's a helpful spreadsheet to calculate trail factors - Anvil Bikeworks Trail Calculator

Plugging in the Cross Check's geometry (around my guess of 28mm tires) of 72deg HTA with 44mm of rake, the resulting trail is 63.9. Work backwards off of your Lotus' geometry and see what rake you would need to reach the same trail value.
posted by stachemaster at 5:00 PM on February 4, 2010

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