930 calipers - magnesium?

[bkreigsr]

This year at Sebring I got into a discussion with a rep from Performance Friction about 930 brakes and he mentioned that only a very few of the 930 calipers were made of magnesium, and those for only for one or two years.
Is that the case? Are the capliers that were made for the 917 the only magnesium ones?
How can I determine if my two sets are magnesium? ....or should I automatically assume some other aluminum alloy?
Bill K

[wildcat077]

My guess is that magnesium calipers would have been crazy expensive and made exclusively for race cars,but then again Porsche has been known to build wilder things !

Cheers
Phil

[GeorgeK]

Magnesium on a street driven car is a very bad idea in the long term.
Suffice to say that if the calipers display no signs of aggressive corrosion, they are not Mg, but rather the std aluminum alloy.

[Bill Verburg]

Until 1970 all Porsche including 917 used ATE aluminum calipers
the 917 used 4x 34mm w. ventilated 12" disks 60cmcm Textar v 1431 pads

from 1970 on the JW entries switched to more efficient Girling 4x42mm aluminum calipers

the Girlings originally were al. saddle al pistons and steel bolts w curved vane non perforated disks but evolved to al saddle al pistons and Ti bolts w/ al centering bushes and curved vane perforated disks

Eventually after trying various Girling and and ATE offerings Porsche decided to make their own(Brembo) which were used on the Group 7 cars, these had al saddle, al cylinder, Ti bolts 4x 42mm al pistons(there were some experimental mg pistons)

[roblav]

Magnesium would be a horrendous material to use for calipers! Who was the Performance Friction rep?

PF does produce some very nice brakes though.

[tharbert]

Magnesium burns and it's much more brittle than Fe or Al. I would think the limitations of Magnesium would exclude it from even experimental brake calipers.

[bkreigsr]

I don't remember his name, (Ken maybe), but he had some nice videos of the new 996 GT3 RSR calipers and rotors as they went around several circuits of a road course. The videos showed how much deflection and distortion even the best made calipers undergo and the temp range (ambient - 1,400F) of the rotors in a hot lap.
Perhaps someone else that was at the 48 Hours in Feb can chime in.

[djpateman]

I know of a few sets of magnesium calipers, but only in the 908 style. I think they were used for hillclimb cars or some such application where extreme weight savings trumped service life.

[HelmetHead]

I was under the impression that the 77-79 930's had similar brake calipers to the 917 and they were the larger "Lockheed" magnesium calipers with floating rotors with smaller fins and Porsche name.

[bkreigsr]

Maybe 78-79, but my 77 930 came over with alum 'S' calipers front, and steel (M?) rears.
Bill K

[GeorgeK]

78-79 930s had floating rotors, which are very expensive. There is legend that the very first few 3.3 930s had 917 type calipers, because the Brembos were not ready, but I have never seen any, nor heard of any substantiating data. Most likely urban legend.

[boba]

The 917 calipers were used on the 1973 2.8 RSR and were also used on the 1974 3.0 RS. The 1974 3.0 RSR used a caliper of similar configuration with a different fin arrangement. These calipers had the configuration that was used in the construction of the Turbo calipers with a more modest fin arrangement.

917/2.8RSR Caliper on a '74 3.0 RS



1974 3.0 RSR Endurance caliper



Turbo Caliper



Zuffenhaus reproduction 917/2.8 RSR calipers



Zuffenhaus Caliper on a brake dyno test

[irl]

Awesome thread.

[Steve@Rennsport]

Nice pics, Bob!!!

[Bill Verburg]

Lockheed brakes were tested, Girling and Lockheed were considered to be considerable better than ATE, both were rated equally w/ the ATE @360lb-ft of brake torqu was 73% as good Additionally the Girling was 2kg lighter. Lockheed were not used for series cars because the Girling pads had 20% greater pad material.

mg was tried but only in the caliper pistons where it was found to be not up to par and thus not used in any racing environment