'69S v '85 Carrera brakes

[Patronus]

My friend has a 69 S and I have a '85 Carrera, both completely stock. We were doing some work on our cars a few days ago, and while the wheels were off, we wanted to examine the progress in brake technology between 1969 and 1985. I was suprised to see that these two cars use the same brake pads!! Perhaps there are differences you can't see with the naked eye, but they are the same size. Surely the heavy Carrera required bigger brake pads than the very lightweight (and OLD) 1969 'S'? We didn't check the rear pads, but from what I could see from the outside, they didn't differ much either.

The Carrera had a much thicker rotor, for heat reasons, but I would have thought more would have happened between 1969 and 1985 than a thicker rotor and pressure bias system. I mean, compare the '85 Carrera's brake pads with that of a 2001 Carrera (also 16 years later) - they are much, much bigger and that's notwithstanding all sorts of other electronic gatgetry that makes it stop faster.

By no means am I disappointed with my car's brakes, just very surprised to see the small difference over 16 years. Or did more changes take place than meets the eye?

By the way, The little S is a real sweety, it is surprisingly fast and nimble. And the brakes are not too shabby either!!

[Jim Smolka]

The front 'A' Calipers have been essentially the same for years. Some 911S had Alum calipers. The A calipers for the Carreras were thicker (bigger spacer). The M calipers (rear brakes) are essentially the same expect on the Carrera they had the thicker spacer and larger pistons as compared to the earlier M calipers. The Carreras also had a proportioning valve set for 30 Bar as to help keep the rear wheels from locking up.

[Patronus]

The 2.0S in question does have aluminium calipers. Must do wonders for heat dissipation. As far as I know Porsche went away from aluminium for their calipers because of the stresses involved, but now I see that the Boxsters have aluminium calipers too. A different type of aluminium, or just a stronger design?

[jmohn]

The short answer is, of course, there's much more to brake performance than just the size of the pads. Wil Ferch (I think it was Wil?) did a nice write up on brake performance if you care to search for it. Essentially, if you can create enough clamping force and disipate the heat quickly enough, a small pad/rotor combination can perform equal to a larger pad/rotor that is less efficient. Rather than just enlarging the sytem, I think Porsche increased it's efficiency. My suspicion is, if you tested their efficacy, your Carrera brakes would perform equivalent to your friends '69.

Jerry M
'78 SC

[pu911]

One subtle difference is the S calipers use a slightly thicker pad 13mm Vs 10mm. It is my understanding that the S caliper flex alot for serious racing. Brakes may not have changed alot of the years but the improvements in tires has been huge. God bless those engineers and chemists.
Phil

[Wil Ferch]

JerryM:
Thanks for the stab at a plug, but unfortunately I didn't write anything on brake performance as to the type you mention. I think the acknowledged brake master on these pages ( or Rennlist?) is Bill Verburg, among others.
---Wil Ferch

[masraum]

From one point of view smaller pads can be better than bigger pads if you are using an aggressive pad compound that requires some heat to get going. A smaller pad will concentrate it's heat in a smaller area heating up faster. Also, pad material changed in that 16 years, so maybe the pad material caught up with the rest of the brakes.

I think the 911 brakes were still the benchmark, even in the 80's (and stil today?).

Too, weren't the S brakes the better brakes in their time?