Originally Posted by AdrianM

Back in the day...the SST series sedans had 4mm diff balls...thats really big. In testing Schumacher R&D found that smaller diff balls gave a diff more limited slip action. This means is you ever lift a rear wheel smaller diff balls send more power to the wheel on the ground than big diff balls. Thats a good thing.

Schumacher ended up going with the smallest balls they could easily source in Europe...2.5mm.

3/32" (2.4mm) balls from associated will not fit. The width of the center of our diff pulley is designed to let a little of a 2.5mm ball peek out either side. With a 2.4mm ball the diff rings will be too close to the center of the diff pulley and that messes everything up.

That said there is no reason to run anything over than U2459 T/C diff balls. They are THE BEST. Over the last 6 years that I worked at Schumacher we tried every kind of diff ball from every place you can imagine and nothing worked as well as out tungsten carbide 2.5mm balls.

I think ceramics have a lower coefficient of friction against the steel rings than tungsten balls. As a result ceramics tend to slip easier and this chews up diff rings faster.