Rear brakes?

[Kahuna]

Any thoughts on a good set of rears to match Big Red fronts?

'85 euro Coupe chassis. Mostly track use.

[mr.bch]

Aestetically? Or are you having overheating probs? Seems like the stock 85 rears would be decent. They have 24mm wide rotors and have the larger 2x42mm piston calipers.

If gonzo is what you want, then you would want to fit 309x28mm 930 rotor with 993 calipers modded for the 28mm width. You will need a 930 boosted m/c or a 23mm non-boosted m/c.

NOw.. what should I fit to my SC to match my non-turbo 996 fronts??? Light track use, mostly street, so looks are what I am trying to match.

[Bill Verburg]

Kahuna,
The big Red front will overpower any of the flavors of M rear caliper. The wide M on your car is the closest match of the bunch but will give you horrible front bias.

The rotor to use on the back will clearly be the 309x28 rotor from a '78 - '89 930. It bolts on and will retain the stock parking brake.

There are 2 good choices and 2 increasingly poor choices for the calipers.

Either the 965 30/34 rears or the 993TT 30/28 rears will match up nicely. Unless you've done something very different w/ suspension, wheels and tires remove your p/v and do plan on upgrading to a boosted 23.8mm m/c, which is also a bolt on.

The other 2 choices are probably ok but I wouldn't recommend them because of extra work involved or bias issues w/ the Big Red fronts. You could also use a 993 rear, but this is designed for a 24mm rotor and will need to have the pads ground down to fit on a 28mm rotor. The last and worst choice is a 964 4 piston rear, which will have the same isssues as the 993 rear.

All of these calipers will need the mounts modified to bolt to a 911 trailing arm.

Here is a pic showing the 3 different rear calipers,

Clockwise from the top 993TT, 965, M

Those are my calipers which I am experimenting w/ I have 4 different complete setups and may have 3 for sale at some point.

mr.bch,
What rotor are you using for the front w/ the 996 calipers? Depending on the rotor, you might get away w/ the wide M on 24mm Carrera rears, or a 964 30/28 on either Carrera rear or 930 rear rotors. But it very much depends on the front rotor.

[mr.bch]

Bill, you sound like you are a brake guru.
I have Carrera 282.5x24mm rotors. It is essentially a pieced together Boxster front kit. I am a bit confused as to exactly what the calipers are off of, they are not the flat black Boxter calipers, but gloss black. 996.xxx p/n's, I think I finally determined that they were from an '01. The thickness was definately 24mm with new pads, thus I ordered the rotors I did and made my own spacers. Most of the infor I have been able to locate on rotor/caliper sizing ends around the 964s for some reason.

What I don't inderstand is if most of the power comes from fronts, why do rears frequently have larger diameter rotors? A lot of my choices will put me with larger rear brakes than my fronts!

I am capable of making any adapters or any caliper modifications. Again, this isn't a track car, but rather just a nice looking, fair weather driver. I'd like something that looks nicer than a Carrera caliper back there...

[Bill Verburg]

This pad

Is a 996/Boxster S front, it wants a 28mm rotor

This pad

Is a996?Boxster/Boxster S rear pad, it wants a 24mm rotor

This pad

Is a Boxster front, it wants a 24mm rotor,

All of the fronts are 40/36 all of the rears are 30/28

A wide Carrera M rear caliper and matching rotor w/o p/v is a very good match for thany of those calipers.


The "power' of a caliper /rotor combination comes from 3 areas[list=1][*]hydraulic ratios[*]rotor diameter[*]pad area[/list=1]
A larger rotor can be used to offset pistons which are too small
Bigger pads can be used to offset rotors that are too small etc.

All of these things can be juggled to get the blend that is desired, another tuning aid is a p/v. Though this later is too coarse and intrusive for my taste.

[mr.bch]

Looks like I mounted up the middle pic, so I have rears for my fronts!

Maybe I should move the calipers that I have to the rear, find rotors for them and make new adapters for those, and search for some real fronts. I would like to have 4 calipers that look like they belong somewhate together (this rules out carrera calipers).

Also, PAd area only helps in heat dissapation, but doesn't really add to the stopping force, that would be the pad's Coeff. of friction.

[Kahuna]

Thanks Bill!

Any ideas where the 965 ot 993tt rear can be purchased? Are you going to sell one of your set?

[mr.bch]

Kahuna, I purchased my 996 rears off ebay, of all places. They were 225+15 shipping and came with pads, all in brand new shape.

[Bill Verburg]

I agree, you just need to monitor ebay , the classifieds here and at Rennlist. I was the only bidder on a set of 965 rears last summer.