GeorgeK

Might be stoopid, but...:

I have sourced 4 993 (not big reds) brake calipers, to replace teh heavily oxidised calipers in Shrek, all for a very fair price.

Except I can't make sense of the adapter I need for the front (axial to radial mount). Everyone seems to be selling the adapters for the big reds.

Do I need the same ones, or am I missing something?

Bill Verburg

the normal 993 front and 993RS/tt front calipers will use the same adaptor on a 964, they will use different rotors though.

Start by deciding what rotor you want to use
993 304?
928 S4 304?
964RS 322?
993tt 322?
aftermarket 304? 322?

GeorgeK

Hi Bill,
I plan on using 928 S4 non drilled 304X32 in front and the 964 non drilled rears.

Bill Verburg

VCI will have what you need, I'd suggest changing to the 993 mc and booster too.

You will also want to use the 993 rear calipers on the 964 rear rotors

GeorgeK

Bill,
I have the rear 993 calipers already.

I was under the impression that on the C4 it was not necessary to change the MC?

Bill Verburg

That's correct, C4 already has the 23.8mm mc and hyd booster, that will work fine. But if you swap in a 25.4mm RS version it would be even better

GeorgeK

Bill, others,
I have been inquiring about the correct adapters to fit the 993 celipers/discs to my 964 and I received conflicting info. It seems the adapters that will fit the Big reds over 322 discs are not the same as the adapters to fit 993 calipers over 993/928 302mm discs.
Anyone care to expand?

Bill Verburg

the adapters for 'big red' or 993 are the same for a given combination of chassis, upright and rotor.

the 'big red' caliper is just taller and uses a 322mm rotor to accommodate the extra height. The shorter 993 caliper uses a 304mm rotor.

if the 993 caliper is used on a 322mm rotor it needs extra height which is provided by spacing the caliper outward, the extra spacing is built into 965 and 964RS calipers but would need to be added to the caliper adapter if 993 calipers are used w/ 322s

there is a difference in o/s for 993 rotors or 964/928 rotors

GeorgeK

Bill, As usual you come through with a wealth of info, I thank you for that.

you say:
"there is a difference in o/s for 993 rotors or 964/928 rotors"
I don't understand that part. Does that mean I can not fit in the front 928S4 discs as a straight swap for the 964 discs, with 993 calipers and the correct caliper adpater?

Dave White

I think he means that with the correct parts, which you have, you can use the 928 rotors on the front. You cannot use the 993 rotors as the offset is different. The offset is the same for 964 vs 928. I am doing what you want to do, only I am using the drilled versions.

GeorgeK

Oh good. I can not use drilled rotors, as the car was not homologated with them. that would be noticed right away at tech inspection.

964russ

Just did this conversion on my car, the adapters i purchased didnt fit perfectly.
Had shims made to fit, small 1.7mm spacers. Had to file top edge on adapter to miss leg, ect;
Not a straight forward swop.
My indy said all the adapters hes ever tried have never been a straight swop and have all needed messing!
I used the 28 gt discs (304,s) non drilled solid type.
In hindsight id have probably of bought turbo/rs 964 calipers.

964russ

But, i cant fault the stopping power!

Bill Verburg

993 rear calipers are in all respects except part #s identical.

Bill Verburg

993 rotors have a different lateral o/s from 964 rotors, a caliper adapter designed for one will be wrong for the other even if the rotor OD is the same. A given caliper adapter positions the caliper correctly both radially and axially for either set of 993 rotors or for 928/964 rotors but not both.

Consider the original mounting for 993 calipers. 993 doesn't use a caliper adapter, the original aluminum wheel carriers incorporate the caliper mounts in the same way that the 964t & RS steel wheel carriers incorporate their caliper adapters as part of the wheel carrier structure. The caliper mounting base height from the axle is the same for either 993 or big red caliper. The same wheel carrier can accommodate either the stock 993 caliper or the big red caliper just by using the rotor that matches the caliper height, 993 uses 304, 993RS & tt use 322

there are 2 different 993 wheel carriers, either can use either caliper set w/ the appropriate rotor and tie rod set, the RS wheel carrier is just designed for a lower ride height.