They help to lessen the approach angle under throttle. Push the track away from the steep rail profile.
The theory is solid and for the price it definately doesn't hurt. I didn't regret running them, they seemed to help the sled stay on top a little better in the deep....it's one of those things that's tough to say how much it helps, but I guarantee they don't hurt. Designed to wrok with stock 8t drivers only.