Porsche Enthusiasts Club Forum

hi there i have a turbo with the mo30 928s4 brake upgade fitted, the braking is good but could be improved.

i am interested to know what larger discs and calipers can be fitted to my hubs ?

will the 993 twin turbo calipers work ?

also anyone tried putting the six piston calipers on a 944 ?

Here is my take on this:

More grip is a consideration as much as bigger discs, ultimately the braking force you can apply to the car comes from how much grip your tyres have during breaking. Are you struggling to get the ABS to come on? If not then you need more grip not bigger brakes which means wider/softer tyres.

If you are struggling to get the ABS to come on, meaning you are not maximising the available grip, then you need more braking force. Bigger calipers/discs/pads means more contact area between disc/pad but it also means you are spreading out the force on the pads so you get less pressure per unit area. So you need more brake fluid pressure so push harder or add more assist to the brake servo. That or you need pads that produce more friction for the same force applied.

The main advantage of bigger calipers/pads/discs is that they can dissipate more heat. This means you can pull more kinetic energy from the car, but you need to generate the fluid pressure in order to apply the braking force and extract the kinetic energy. If you apply enough force you can generate big brake force from small brakes but they will get very hot and eventually overheat.

In short if you aren't changing how much fluid pressure your generating then the benefit of bigger callipers etc is negligible assuming the brakes aren't overheating.

thanks for the reply , that is some interesting info.

to produce more braking force would you require a more powerful brake servo ?
if so is this an area that can be modified ?

Yes it would do, I've not heard of it being done though. Sure it can be done though. A longer pedal would have the same effect as well as it would create more leverage, the downside being that you would have to push it further. What pads are you running out of interest, I have the same brakes as you and I recently changed from EBC yellows to OEM pads. The OEM pads are much nicer on the road as they work better when cold and tbh just as well when hot. Not like the brakes get that hot anyway they are pretty massive!

i am running oem pads and have no complaints , but was wondering about trying uprated pads.

i see you have the promax level 2 kit listed as fitted, can you give me your opinion on it ?

did you fit it ?

No I didn't fit it and its pretty good. I'm on a k26/6 making about 275bhp. Car certainly goes well. I get boost drop at high rpm's not sure if its the turbo or the wastegate. I suspect the turbo as its only small . Personally though I want to go to either a MAF or MAP based setup although this is more ££.

i am running the promax exhaust (which sounds brilliant) and their induction kit and was looking at their stage 2 kit,
but i can not make my mind up between just adding a bit more power from this or going all out and getting a bigger turbo, maf kit and custom mapping as well as the other bits i would need.

it can quite easily get expensive but they are a lot of fun.

Is that the Wortex exhaust. Got to admit I've been tempted by that! A modern turbo will make your car seriously quick. They can make full boost by 2.5k while making 370+ bhp. You've done the exhaust which is essential so sort out the injection system and add a good turbo and you will be flying. You might also want to look at the clutch as well! If you don't want massive BHP then you can use the standard intake and head. My preference is towards massive mid range torque as that is what the 8v head is good for. A MAF kit and turbo might cost you 3k or so in parts. I got my intercooler modified for about 80 quid. There's some pics in the link in my sig. If you go into the turbo hose install you can see pics of the intercooler. Basically the design is good for low boost as it ensures even flow through the cooler, but at high flow it is quite restrictive. The end tank design on the intake side is what I had modified. Basically its what most companies offer as stage 1 upgrade for the intercooler although I'm not sure quite how it would compare .

I have the larger disks and callipers from the 928GTS (same as the 993 Big Reds except they are black). They will not make you stop any quicker or brake any harder as the existing brakes were already able to lockup the tyres. To stop quicker you will need more grip which means wider or stickier rubber.

What the Big Blacks do give you is a much larger heat soak so they are almost impossible to promote brake fade through overheating during repeated track use

Paul, are they a direct replacement for the radial mount 928 S4 ones? Can they be used with the existing 304mm M030 disks?
Alasdair

barks944

i checked out the hose kit photos you have,

who supplied the hose kit ?

how good was the fit ?

My dad made the kit, they are all prototypes but it all fits well. Its been on my car for about 4 months now with no issues. We aren't making them atm but hopefully will be in the near future.

Yes the Big Black/Red callipers bolt straight on to a 250bhp Turbo as they are radially mounted with the bolts in the same position. You will need the larger 322mm disks from a 928GTS as the calliper is 9mm wider and so would stick out from the standard 304mm disk and cause very odd pad wear.

I have seen a way where you can use the larger 322mm disk with the standard 250bhp calliper by the use of spacers http://www.sandher.com/Mark_Cole_BrakesMod.htm

If youve got S4 calipers and you cant stop properly, then somethings very wrong somewhere, surely.