jackal2513

does anyone know if these are different from 993 turbo calipers ?

I gather they are slightly larger pistons ? And what is on the rear of an RS ... is it a front stock 993 caliper ?


regards

Rich

Bill Verburg

The rear 993RS and 993tt are the same caliper, EXCEPTtt has 28/28 while RS has 30/36 mm pistons., You will want an effective lsd
to use the RS calipers.


993 n/a front , rear 993RS and rear 993tt all use the same pads. front calipers all have radial mounts and rear calipers all have axial mounts. fronts also want 32mm rotors rears 28mm rotors(993 n/a rear rotors are 24mm)

jackal2513

ok thanks Bill

your link is very good as well


so basically big reds at the front as per 993tt (RS discs have 40mm top hat instead of 45mm though)

rears are 928S4 rear calipers ? with 30/36 pistons

Geoffrey

I have run the RS rears on my race car and with the stock proportioning of the master cylinder it puts way too much bias on the rear for track usage. Now, my race car is quite a bit lighter than the RS they originally came on, but even Porsche used the TT rear caliper on all of their race cars - 993RSR, GT2, GT2 Evo. I even tried a less agressive compound on the rear and it was not sufficient to balance the brake bias. So, I have a nice set sitting on a shelf and am using the TT on the rear instead and I don't recommend the RS unless you have an adjustable bias (not pressure limiting valve) control with dual master cylinders. In that case, I would definately run them. If you install them on a street car with the pressure limiting valve, they might work 'Ok', but I would question why when you can remove the pressure limiting valve and run the stock TT caliper.

Bill Verburg

in front the oem RS rotors were 1 piece 322x32mm, tt used 2 piece 322x32mm. These rotors are completly interchangeable, most use the tt because they are cheaper.

the 928S4 front and 993na front are 2 versions of the same caliper, early S4s used different pistons and seals but latter use the same 36/44 as the 993 n/a fronts. The difference is that the S4s are trailing mount and 993 leeading mount, they can be converted by swapping the bleeds and feeds.

here is a pic showing from the left, 993RS rear(axial mounting ears), 993RS rear modified for use on a 911 rear(the axial mounting ears are machined off and it has been converted to radial mount) and a 993RS/tt front(radial mount)


Here's a comparison of the pads

from the back 993RS/tt front(aka Big Red), 993RS/tt rear(also used on 993n/a front), 993n/a rear(also used on 930 f/r, 964f/r)

Bill Verburg

Despite Geoffreys well considered opinion, I like the 993RS rears(I also used and sold a set of tt rears), you offload a lot of stress from the fronts w/ them. They are much more rear biased than tts and you do want the effective lsd. Geoffrey doesn't like to use any p/v(for good reasons) but for most of us they are a non issue and are a part of the stock package

jackal2513

sure, i know about the S4's being the same caliper body as the 993tt as i have these on my 968 (M030)


but is the RS rear the same as 928S4 rear ?

bobesser

993s with ABD/LSD come with an automatic proportioning valve that should take care of this, right?

Bob

Bill Verburg

The 928S4 front is NOT the same as the 993RS/tt front, the legth and width are the same but the caliper & pads of the RS/tt are ~10mm taller. See the pic of the pads above.

the 928S4 front is basicly the same as the 993 n/a front(again leading vs trailing mount config being the diff)

928GTS did use the Big Red(in different colors and in trailing mount config) 993RS/tt front

no, the 993RS rear and the 993 n/a rear and the 928S4 rear are 3 different calipers

again refer to the pad pics above the small(orange above) pads are for 928S4 rear, 930 f/r, 964 f/r, 993r, 964RS r, 964t(all) r

the middle pads are for 993 f, 993RS rear, 993tt r, 964RS f, 964 3.3t f, 928 S4 f

the tallest pads at the rear in the pic are 993RS/tt f, 964 3.6 t f, 928 GTS f

Bill Verburg

all 993 n/a including RS come w/ either 1 or 2x 40bar p/v(Geoffrey dosn't like that name because he is an engineer and is well aware that it is really just a pressure limiting valve, but.....)

all M220 option 993 cars and RS(it wasn't an option but rather standard)come w/ 2 p/v because they also have 4 channel abs. All the other n/a 993 come w/ 1 40 bar valve and 3 channel abs, 1 channel for each front wheel and 1 for the rear circuit which is both rear wheels.

JoeMag

Kind of late on this one, but there is really a BIG difference in clamping power between the 993 rear tt's and rs's. comparing 28/28 with 30/36 you have ~40% more clamping (or stopping power) with the RS vs the tt. Even if you have abs, since they both have same fronts, one of the setups is obviously not balanced very well.

jackal2513

amazing

and to think i know people who run 968's with standard 968 rears and 993tt calipers up front and no uptade bias valve !

viperbob

I posted some pics in a long time ago in a Forum far far away pics of TT rear brake pistons. Not all of them were 28/28. No way to tell unless you look. But the RS is a MUCH better solution for most applications...

Bill Verburg

not necessarily, they are very different chassis
2wd vs awd
RS has a much more effective lsd
weight distribution
ride height
springs
design usage
etc

jungleboy