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Wheel Traps
Well, what would you call them?

By: James R, Davis



As agile as we know our motorcycles are there are times when two wheels simply are not up to the tasks we present to them - unless we know HOW.

For example, assume you are riding along and notice that there is a trough in the middle of the road extending for as far as the eye can see. It also just happens to be about four inches wide and about one inch deep. Like a magnet, that trough sucks your front wheel into it, the rear wheel obligingly joins it and suddenly your wheels are trapped. You cannot steer out of it.

OK, OK, I can hear it now: 'Get real!'

Fine, so it's not down the center of the road. It's along side and some people would call it a rain gutter.

Or it is down the middle of the road, but it only has one side - they resurfaced the road, one lane higher than the one next to it.

Or you eased off the pavement and there was about a one inch drop to the apron beyond.

Or you are on a surface street and pull over to the curb and your front tire slides right up against the curb, parallel to it.

You get the picture. There are all kinds of traps out there that we don't normally have to deal with but that can be encountered at any time, and you will have no choice but to deal with them.

In every case I described above the problem is that you must either ride up and over one side of the obstacle or you must turn away from that obstacle - both of which turn out to be more difficult than first expected.

The problem, of course, is that you often simply cannot turn your wheel because it *IS* trapped. An effort to turn away from the curb that your front tire is hugging finds that the rear edge of the tire must push against the curb in order for the front edge to turn away from it. A mere one inch of height is sufficient to stop you cold - your bike will fall over before you can turn the wheel.

In this particular case you have no choice but to stop completely, lean the bike away from the trap, and walk the bike free.

  • Never get within 6" of a raised surface that runs parallel to the direction you are moving!

If the surface is only 1" high you can ride over it without much concern so long as you approach it at any meaningful angle. (Greater than 20 degrees.)

Anything higher than about 1" and you must put as great an angle of attack to it as possible. Ideally you want to cross over it with a 90 degree (perpendicular) angle.

  • Always approach a trap that you must cross over with more than a 20 degree attack angle.

It is not so much that you should fear that your front tire will fail to get over the trap, it is that you must be concerned about getting your rear tire over it. What happens if your attack angle is low is that you instinctively turn your front wheel into the trap to get over it, so it does, but your rear tire, having a lower attack angle, slides along the trap rather than going over it. This immediately twists your bike into the turn and presents an ever increasing attack angle for that rear tire. At some point (quickly) the attack angle will be sufficient and the rear tire will grab and ride over the obstacle. Unfortunately, while it was sliding along you and your bike turned the front wheel in the direction of the slide. Thus, when that rear tire grabs it is analogous to the classic conditions of a highside. About 2/3s of a second later you will hit the ground.

  • Before trying to ride over a trap that is relatively close to you, turn away from it and then towards it in order to build the largest attack angle possible.

About 1/2 second before your front tire hits the obstacle, accelerate. That unloads your front shocks. At the same time shift your weight to your pegs and lift your butt off the seat. When the rear tire hits the trap the rear-end of the bike will get quite a vertical jolt - possibly enough to throw you off the seat and cause you to have to fight for control if you have not already raised that derriere.

Copyright © 1992 - 2020 by The Master Strategy Group, all rights reserved.
http://www.msgroup.org

(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)

     
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