rb4u

Interesting thread about the difference in caliper construction, you may want to read this:

http://forums.racingbrake.com/showthread.php?t=1337

TrackDays247.com

It looks as if the new caliper designs are an improvement in caliper braking function, etc - but real world service / usability takes a HIT

JasonAndreas

And here's the patent?

est8esq

I am admittedly a technical moron, so please forgive the ignorance? Been reading through this thread and like Tom Hanks in the movie, "Big", I still don't get it??

My GT3 is mostly for track. Bottom line, I need to make swapping pads as easy as possible, trackside. So, for a guy like me who has been known to hurt himself w/ only a screwdriver, would these pins make it easier and do they make them for both front and back?

Lastly, does anyone out there know of a good aftermarket pad that's been made yet? I TOTALLY don't care about squeal or noise. The squeaking can crack glass for all I care. Just want "bite" and longevity as my only parameters.

RacingBrake

Take a look on RacingBrake 6 piston calipers, among them the large 6-pot is developed to replace GTR's stock 6 piston calipers;

Hard Anodizing Finish:


Red Powder Coating Finish:


they are made from forged aluminum alloy, and bolt together with 12.9 grade bolts for the ultimate strength and stiffness.

Even with the same top load on pads, RB design is simpler and easier, one center bolt and two side pad pin bolts all all you have to work (from front) with, not from inside, and no pins to punch.

GTR/Brembo calipers with center mount two piece rotors:


RB caliper with RacingBrake center mount two piece rotors


Compare how the pad sits in the caliper and notice the pad overhang on OE set up and pad is not centering to pistons (=taper wear) vs. RB set up with pad inside the caliper and centering around the pistons for a more positive and effective hydraulic pressure applied to pads.

orthojoe

Well, since this thread was revived, anyone care to guess why the bars were placed on the calipers now that Sam has proven that the brake pads still taper with the 'improved' design?

008

Having swapped my pads a few times now on my C2S, I'm really not concerned about the change.

TrackDays247.com

A stud setup would be so much better than removing a bolt each time

JasonAndreas

Greatest increase in rigidity for the least production cost? From the production patent linked above.

"A brake caliper for a disk brake system of a motor vehicle, has a caliper body Which is cast from a light metal alloy or from light metal, With a skeleton structure arranged inside the Caliper body. The material of the skeleton structure has a higher modulus of elasticity than the material of the caliper body. The skeleton structure is cast into the caliper body so that the caliper body encases the skeleton structure."


"By virtue of this type of construction, the skeleton structure extends through all the load-bearing components of the caliper body, to be precise through the cheeks and through the Webs for connecting the cheeks.As a result, the cheeks and the Webs are even stiffened in each case in themselves by the longitudinal members or by the cross-members of the skeleton structure leads to a stiffening of the entire caliper body, that is to say, in particular, also of the connections between the cheeks via the Webs."

Petevb

I'll hazard an educated guess: I think the decision was driven largely to allow for a larger pad size.

The 991 GT3 has nearly a 10mm longer pad that the 997 (or CTS-V shown above). All else being equal this should improve brake performance, reduce pad wear, etc, probably important factors given that the brakes originated on the 918. The downside is that longer pads seriously impact stiffness, as flex increases to the cube of the unsupported length.

If you look at the design of the bridges, they not only have much more cross sectional area than the metal pin designs so probably better stiffness despite lower modulus material, but as a system the bridges also look quite stiff in bending, where the metal pin with connections won't really be able to take bending loads.

Thus my suspicion is that this design allows them to go to a bigger pad without increasing flex and hence hurting pedal feel. On the fronts, anyway, though if you have a higher stiffness to weight design it must be tempting to use it all around. The requirement to remove the caliper in is an unwelcome side-effect. Of course that's been par for the course for lots of cars, BMWs, etc, for a while.

At least that's my blink. $.02

BGB Motorsports

I haven't ready any of this thread and probably should but I get a lot of inquiries from you folks about a caliper stud kit for the new brakes; if I'm being redundant, let me know.

For the longest time, big time brake companies like Brembo and PFC have been obsessed with caliper flex under heavy braking and turning in the Cup cars, RSRs, etc.

The bridge was an attempt to address that but if someone wants me to measure and retrofit another caliper we can. Should I be trying to fit a 996 GT3 6-piston caliper on like we ran on the Cayman in the 24 to a 991 upright?

Would this help?!

orthojoe

Given that the 991 GT3 rotor sizes are 380mm or 420mm (PCCB), I don't think the 996 calipers will fit, no?

0Q991

Agreed.

The steels are 380mm all around. PCCBs are 410mm front and 390mm rear.

BGB Motorsports

Hold on a second here...if the PCCB / 996 GT3 Cup 6-piston calipers were made to accommodate a 350mm disc, with a myriad of different sized caliper bolt spacers from RSS, why can't I achieve clearing a 380mm disc?

I can space it outboard enough to go from a 318m to a 330mm, which is a 5% bump with a 4mm spacer, so in theory, I should be able to space it from fitting a 350mm disc to accommodating a 380mm disc, no?

I have done 3 caliper stud installs for these 981 Caymans with the 991 front calipers.

Petevb

Can you make it fit? Sure. But I've never seen a caliper/ rotor mismatch that large that I felt was engineering good practice.

You'll get point contact between the top and bottom of the caliper and the edge of the rotor, as the caliper was designed for a smaller rotor. You also need to maintain a few mm of clearance here to allow for the rotor's thermal expansion when it gets hot. As a result the caliper gets spaced out more than the straight 15mm radius increase, and with the caliper sitting so far back you're then in danger of the top of the pad falling off the rotor edge, which is very bad. Even if it doesn't you get uneven pad/ rotor wear because the two are different diameters, and the pads likely won't use the rotor as designed. You can grind the inside of the caliper at the top and bottom to modify it for a larger radius, increasing clearance, but this reduces the caliper's stiffness.

Bottom line, I'd feel comfortable playing this game with a small caliper rotor diameter difference, but ~30 mm sounds to large to get a decent solution I'd feel comfortable with, even 18mm (S4 to Big Red) is pretty ugly. $.02