shind3

Is there a definite answer to this? I am also curious.

Slowcrash_101

I'm guessing the loaded pin gets hotter and expands more than the trailing pin, and the slots are to help keep the pin from seizing in it's bore.

freq

I'll buy that logic.

Old thread ....... different chassis but still relevant.

shind3

Yeah, all the pins at the leading* edge of the caliper on all corners seem to be perfectly cylindrical. I guess it also helps keep the caliper square to the rotor as sort of an 'anchor' point for the rest of the assembly. But I don't buy the 2nd half of that. Why doesn't this cylindrical pin seize then? When properly greased it moves just the same as the grooved one. Why not put cylindrical pins in all locations? Would that improve brake feel as the caliper stays a bit more square to the rotor? Should lessen pad retraction after braking finishes?

*Leading edge is on top for rear calipers and bottom for front calipers (S2000).

Polaris0352

Does the grooved pin rotate in the caliper bracket when it's all fitted together? It may be for alignment of some sort.

zeroptzero

Yes it rotates.

shind3

Well, not 'when it's all fitted' together... The M10 bolt keeps enough clamping pressure against the flange on said pin to keep it from rotating.

The grooved pin has the same OD as the solid pin and you can put either in either hole. (that's what she said...)

Read on page 10. Bosch used to use grooved pins in both locations until 2002 in this HD sliding caliper. Then they switched to using one solid pin and one pin with a rubber bushing. Ditching the grooved pins entirely.
http://www.bosch-mobility-solutions....ide_Manual.pdf

And on the other hand, BMW guys run this and get better brake pedal feel as compared to their (worn?) stock rubber bushings. It is effectively running a solid pin in both locations.
:: ECS Tuning :: Introducing the ECS Performance Caliper Guide Bushings

So, who's going to be brave enough to run solid pins in both locations in an S2000?