S Calipers

[overman]

Looking through the posts on a set of S Calipers just sold has my attention... The owner is selling the S's to upgrade to A's for track use.... Which Caliper is the best for track use, the S's or the A's??

[Bill Verburg]

Answer , it depends

S is lighter
A is stiffer

For folks w/ a sensitive foot stiffer will be more desireable.

[overman]

Makes since, Thanks Bill. Wouldn't the S dissipate heat better?

[Bill Verburg]

Wouldn't the S dissipate heat better?

Al and iron will both radiate the heat at the same rate, Al. will conduct it faster but to where?

The rotors job is to temporarily store and later get rid of the heat generated during braking.

[island911]

A temporary heat storage, eh?

Diverting more of the thermal energy, that has made it's way to the back of the pad, into the caliper body, has got to be better than letting it heat the fluid. (local boiling)

As you said, this isn't (generally) a steady-state event.

Also, A caliper body has a spinning wheel recirc'ing air all around it's surfaces.

I can't see how the iron A caliper can compete in that regard.

[Bill Verburg]

The caliper isn't supposed to get hot, rubber parts get very unhappy in short order.

[island911]

Originally posted by Bill Verburg
The caliper isn't supposed to get hot, rubber parts get very unhappy in short order.

Yep!

. . .and brake fluid isn't suppose to boil.

I'm just saying, it's an advantage to give heat a prefered path away from the brake-fluid. . . should the pad be especially thin, or whatever.

[Bill Verburg]

Yes, and the prefered path is through the rotors. A great deal of effort is spent insulating the fluid and caliper body from heat. Newer designs pump air through the pistons.

the lightness is the #1 attribute of alumiinum, if they were meant to dissapate any substantial portion of the heat they would have fins like they did in the old days, but technology has moved on. As I intend to.

[island911]

I would agree that the lightness is the #1 attribute the alumiinum S.

However that doesnt mean it's the ONLY possitive attribute.

As to 'fins of the old days;' they were'nt so successfull. You really have to consider the air flow when incorporating fins. (waht does the increase in surface area, of the fin, cost in reducing air flow ...) Note, the minimal fins, out-board only, on the 930 caliper.

As to "moving on" ... The question is simply between the A & S caliper. I believe the S has more than just a weight advantage.

[Tom F2]

The S uses a thicker pad to insulate the caliper from heat and, I guess, to get longer wear.

[overman]

Gentlemen... Thanks for the feedback.