Porsche Brakes

[ZZZZDAVE]

After Advice

I have a 1988 Carrerra 3.2 , just had it over a year. The car has Standard Calipers on the rear, but has 4 POT Turbo Calipers on the front with drilled and vented floating Discs . According to the History with the car , they where added just before I bought the car.

The History shows a NEW Master Cylinder Fitted ( not sure which Master cylinder was fitted Standard Versus Turbo ) as receipt does not quote part number.
I.ve changed the fluid, I,ve changed all the hoses ( Braided type), and I,ve renewed all pads , and ALL Pistons free.

So whats the issue!!!
The Car just scraped through MOT on Brake efficiency on front brakes ( plus Brakes Sqeal really loud), Rear were fine. driving the Car the Brakes Lack Bite . Theres no signicant Pedal travel . quite a hard pedal in fact (( which suggest to me a Turbo Master Cylinder has been fitted). My thoughts at the moment is an imbalance in the braking , i.e should the rears Calipers have been changed to Turbo Brakes? i.e 4 pots as well , my thinking for this is the Turbo Master Cylinder Shifts more fluid.( for the 4 pots) , but with standard rear brakes don,t really need this extra fluid so is thus making the hard pedal hard before the fronts have time to BITE. Can I change rear Calipers to 964 type and keep same Discs? or do I change front Calipers Back to Standard and change Master Cylinder to standard. Further thoughts on the Brake Squeal do front turbo calipers require damping pad between Pad and Piston??? Any advice thoughts would be appreciated
Thanks

 

[Big_nige]

I don't know the answer, but is there an inline pressure reducer front to rear. Have they ever been good at braking whilst you have owned the car?

I'd post or search for questions and answers on here.
http://www.impactbumpers.com/forum/

There is alot about brake mod's on there.

 

[ZZZZDAVE]

thanks for the reply, yes there is a restictor in the feed to the rear brakes, they have never been good brakes since i have had the car

cheers

 

[alex.powell]

i've been looking at brakes for my car recently. Several people have said that i should upgrade the servo also as they will feel squidgy otherwise...

cheers
Alex

 

[nathan 1981 930 G50]

If you don't have a lot of pedal travel then you may well have a larger diameter master cylinder. This does not mean you will have better brakes, quite the opposite (fluid dynamics). If you have a larger master cylinder diameter then you will have to push your pedal even harder than with the stock part. The advantage of a larger master cylinder is that you will have less pedal travel as you have more fluid to fill your pistons when you brake.
If we were to fit smaller diamater master cylinders to our cars then we would have more pedal travel, but once the fluid has moved we would need less pressure on the pedal for the same amount to the pads.

I'm not actually sure if the calipers you have need more fluid than the stock calipers. You would have to take measurements and do some calculations. I am a plumber and have done these calculations for hot water storage etc etc. It is surprising how much volume you get by increasing diameter as opposed to doubling up with a smaller diameter which is what's probably happened with your calipers.

Are you sure the vacuum is working?