Determine Salisbury diff angles

[wesg]

I'm on the drivetrain team for this year's car, and I'm investigating the ramp angles for the Salisbury diff. I understand how the angles affect performance, but does anyone have a good way of determining the best combination?

First post of many!

[wesg]

I'm on the drivetrain team for this year's car, and I'm investigating the ramp angles for the Salisbury diff. I understand how the angles affect performance, but does anyone have a good way of determining the best combination?

First post of many!

[Alan]

Probably the most fundamental thing to consider will be the engine torque while driving and coasting. Gear ratios and final drive ratio will need to be factored in. Beyond that the approach you take will depend a lot on what sort of data you have available.

If you guys used a Salisbury before that is a good starting point. Rear wheel speeds will give you part of the story but it is better to have driveshaft torque data to go along with that. If you are starting from scratch, I would look at some typical tire loads during cornering, use whatever tire data you have available, and see if you can determine how much "locking" you want from the diff. Come up with a diff spec to achieve said locking and hope for the best. If you can afford to build some ramp combos with more or less locking under drive and coast, track testing will point you in the right direction.

A word of caution. I ran the diff dyno while I was at Forsythe and these things are huge can of worms. I guarantee you whatever amount of locking you calculate/design into your diff will not be what you physically measure on a dyno. But if you can get an understanding of how your diff works, it is a huge tuning tool.