One reason is to give you the option of some very good bearings that run true, smooth, and fast. These are high quality bearings that have the best shields in them for the purpose. The inside bearing gets a metal shield and the outer bearings get rubber shields to keep out the dirt. These are easy to tell the difference as one shield is black and the other is orange red. These are oiled bearings. We have numerous cars that have had a single set of these bearings in place for over 6 months now and they are still very smooth.
The second reason is that we have seen a lot of people use clutch bearings in this pinion position and this is not correct. A clutch bearing has looser tolerances so that when it heats up, it is in tolerance and tight. The pinion will never heat up this much to heat up the bearing and thus when using clutch bell bearings, you are adding unnecessary wear and tear to your ring and pinion.
TLR347000 HD Pinion Bearings provides 2 of each size so enough to do your entire car.
Good luck at the races and have fun out there!
