SamGrant951

When installing one of the "Big Red" 993tt brake upgrade kits is it common to just leave the back alone, or do most move the front set-up to the rear and lose the original rear brakes altogether...just curious as I know people do it both ways. Also what does it entail to install the front brakes on the rear of a 951?
Thanks!

marksportcts

I've heard from most 944 shops not to move the front to the rear, rather get a 928 5/33 proportioning valve instead.

Turby

With the "Brake bias valve", or "brake booster" you will be better off......and some blue fluid. And most important, make SURE you paint those suckers in the rear RED!!!!!

Danno

The piston-bores of the Big Reds are roughly the same size as the 951's pistons. So you're not throwing off front/rear balance too much.

Tom Pultz

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Danno:
<strong>The piston-bores of the Big Reds are roughly the same size as the 951's pistons.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">The '86 turbo has 36/38 mm pistons, the '87 and on normal turbo 36/40, the 951S 36/44 and the big reds are also 36/44. Changing the proportioning valve to the 5/33 seems to work fine, but it's probably not mandatory either.

As an aside, doesn't the '86 use a smaller brake master cylinder? This might be marginal with the larger pistons.

Moving the front brakes to the rear is not recommended since they are made to function with 28 mm thick rotors, not the 24 mm rear rotors.

Alan C.

I've got Big Reds up front and stock in the rear on my 86 turbo. I have NO proportioning valve and it works just fine.
Alan

Mark G

Alan, Is that for a race car setup, or street? Thanks

krickmann

Tom,
The ratio for the brake piston size you mentioned above is rear/front? What is the stock ratio for the proportioning valve for an 86?

Tom Pultz

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by krickmann:
<strong>Tom,
The ratio for the brake piston size you mentioned above is rear/front? What is the stock ratio for the proportioning valve for an 86?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Oops. Sorry, I wasn't specific enough. The numbers are the piston sizes for the FRONT calipers. For instance, the '86 turbo has two 36 and two 38 mm pistons per caliper, the 951S two 36 and two 44, etc.

Each rear caliper has two 28 and two 30 mm pistons.

Stock proportioning valve is the 5/18. The 18 indicates the pressure in bars where the slope of the pressure curve flattens out a bit... like a kink in a curve. There are 5/33, 5/45, and 5/55 valves available.

krickmann

What are the different rotor diameters? How does the swept area compare between the different size calipers?

Alan C.

Mark G.

Yes, mine is a track only car. But it was seen once on I275 very early one morning on the way to my mechanics. Trailer issue.

Alan

Russ Murphy

With that "low-key" paint job, I can see how it would be easy to slip in under the radar on the way to your mechanic's. <img border="0" title="" alt="[Wink]" src="wink.gif" />

Mark G

Alan C.

Been there, done that. Thanks for the clarification.

Mark

mumzer

i was very unhappy with the pedal feel on my 86 with the stock brake m/c. Too low and too soft. I wasnt happy until i upgraded to the 89 version master.

That was marginally acceptable. If you want a hard pedal, id reccomend this strongly. more primary diameter would be even better.

M Danger

are you saying the 89's feel much harder? I like as much modulation as possible. Not a rock hard pedal after a half inch of stroke.

MD