Derby Talk

Hi all,

After our second place finish last weekend, my son and I are already plotting our reven...er...comeback next year.

One question I had was with regard to the camber angle on the rear wheel. A lot of the tools out there seem to be set at 2.5 degrees negative camber, and that's approximately what we've used bent axle-wise the last two years.

However, I see a lot of folks who drill their holes angled at 3 degrees as well. This seems to also be an accepted angle.

On the one hand, there is a part of my engineering mind that says you want the least amount of camber possible that will still move the wheels out towards the heads of the axles and keep them there throughout the run, because the more evenly distributed the weight is across the axle the more efficient the system will be.

But 2.5 and 3 degrees seem to be the most commonly used angles. Is this because somewhere in there happens to be an optimal angle that balances the outward force with the bore tilt etc?

Maximum Velocity seems to have done an experiment way back when that showed a mild but statistically irrelevant gain as angle increased. I'd love to run experiments, but alas, I have no off season access to a track.

So, what do you like to run on your rears? Have you noticed any effect of different cambers on a 3 wheel RR configuration?

Andre

I think as long as you're somewhere between 2.5 - 4.5, you're fine.

When I bend axles by hand, I think I usually end up around 4 degrees. If I use a drill jig and straight axles, it sets my axles right at 3. The Derby Worx RR tool will set them at 2.5 degrees.

Conversely, I think the camber on the front wheel makes more of a difference. The original DW "recipe" for rail riding suggests 1.5 degrees of positive camber. I go for a lot more than that. I prefer closer to 7 degrees of positive camber on the DFW axle. My working theory is that a more severe angle on he DFW axle gets you closer to have rolling friction instead of sliding friction both surfaces that the DFW wheel needs to contact (track and rail).

I think the 2 1/2 degree angle has probably been learned from experience. I agree with your thinking from what just happened to me. I say "I" because this is a car I'm building for our Sponsor race. All my wheels were set with 1 1/2 degree cant and the right rear wheel showed toe-out. I don't know if a 2 1/2 degree cant with the additional pressure on the axle head would have showed the misalignment.