mark kibort

The guys from the racing board said you guys might be interested in an easy upgrade to your brake system if you have a 951 with the 928 style S4 brakes.

You can turn your S4 brakes into the Big blacks with a set of radial spacers! S4 calipers and S4 pads are more than enough pad. the difference is the diameter. If you look at the stoptech ST40 13" set up, they use the exact same pads as the 928S4. The only difference is the diameter. If you have the same offset as the 928S4 rotor, you can use the 964T turbo rotors.
You will have more than enough brake to deal with the fade and better stoping power.

A little background on the S4 calipers, is that they are the same size as the Ferrari F50 calipers, that fit on 14" rotors. the pads are almost the same. Its all about diameter with brakes, and our calipers are very capable. This is a way to basically get Big Red brakes, by only buying replacement rotors and these spacers.

We are trying to get a group buy as I can supply the spacers to allow the modification . the difference in buying replacement rotors, pads vs this kit might only be a couple of hundred bucks.

If we can get 5-10 takers, the cost would be around $725 shipped, or $480 without pads. this is the cast hole rotors, 322mm, spacers to move the calipers out, and longer GTS caliper bolts. (and with pads, pagid black or orange racing pads)

Let me know if there is an interest

Mark

ehall

Wow. This is pretty cool. gonna have to think on it.

Olli Snellman

Iam not sure did i get it right. So you are using a S4/951S caliper with bigger rotor than S4/951S normally use. It would be good to put a picture of that caliper adapter here, so we can see how it is done. I suppose this is quite easy to do, you just need longer caliper bolts and a spacer type of adapter between caliper & spindle, which moves caliper outwards to accept a bigger rotor.So if the price is almost 500$ for that, it's IMHO quite expensive. You can have suitable spacer done at local machine shop about 50-100$ depending material to be used. I can understand 500$ price tag if you offer adapters for non S 951 models which use axial attachment calipers.

333pg333

Mark is working off the principle of leverage here. You go up in rotor size to increase the potential for exerting greater leverage and apply the same pad size as our standard Medium Blacks. There's no reason why it shouldn't work better? On face value the Big Reds offer the largest jump in pad area cm2 over the next size down. ie 112.5 cm2 vs 151cm2. This is a big jump up in swept area, but he would contend that this extra area is down towards the hub and not nearly as efficient as on the outside of the rotor. Plus Porsche never repeated this format pad. They went wider rather than higher.
I guess the only possible downside is extra unsprung weight of the rotor plus more inertia to have to turn and stop. Having said that, all modern supercars have bigger rotors than even the large 995 drilled 332mm discs.
So you're saying that for $725 shipped Cont US you get the 2 drilled Porsche rotors and the adapters? That sounds pretty good for you US guys?

azmi951

I will take a bolt and spacer kit since I dont need rotos for a little while but would liek to get in on this.

The larger rotors will have a much greater heat capacity due to more mass thus prolonging fade as well as greater heat dissapation due to the longer vanes and larger diameter. The larger diameter increases the velocity of the air at the exit to the vanes causing lower pressure and a tiny bit more airflow too. Remeber the area increase is the square of the radius and the area is what will determine brake cooling.

There is a lot of little details in the physics of why this is a good system. They all combine to make a very good cheap big brake kit.

mikeroz

Mark,
This seems like an excellent idea, especially for me as I've recently had my M030 calipers fully rebuilt and powder coated (they look great) but didn't replace my rotors because they looked OK.
Because the cost of shipping heavy rotors across the water to UK would be quite expensive, would you be prepared to supply just the adaptor kit plus part number for the rotors?
If so, how much would these cost excluding shipping? If you give me the weigths I can work out shipping costs from USPS website; i've had enough things shipped from the US to know my way around their website.
Cheers
Mike

edh

Looks interesting - Do you need to go to 17"s with this mod?

Diver944

A guy in the UK with S4 brakes on his 993 did this a few years ago and wrote a nice website with his findings. As well as using an 11mm spacer so the S4 calliper fitted over the 322mm disks he then went a step further and modified the calliper so that Big Black pads would fit inside the S4 calliper

http://www.sandher.com/Mark_Cole_BrakesMod.htm

Here's what they looked like

Chris White

A little info here –
Big Reds and Big Black (S4 caliper and 951S caliper) are the same casting, the only difference is that the big reds are set up for use on the trailing edge of the rotor and the black on the leading edge – all you have to do is swap the bleeders and the crossover pipe (5 minutes) and they are the same.
The cost of Marks kit is really the rotors – not cheap parts and the shipping is not cheap either!
Most likely you will have to run 17” wheels – it all depends on the casting of the wheel.

Olli Snellman

If you need only adapters, they are basically a block of aluminium/iron with holes drilled to them. I suppose most of us can even fabricate them ourselves, so the cost is few $/€ per side. Also longer bolts can be found very easily locally.I bought longer (high grade)bolts for 4€.

Here's picture of spacers which can be found from the URL Paul sent.

I suppose no rocket science with these


I suppose these are the spacers Mark use

PorscheDoc

One other difference, the big reds/blacks use a deeper pad holder. If you try and shove big red brake pads in a 951S caliper, they stick out the top and you can't shut the gate.

FWIW, I ran S4 calipers, and 3.6L rotors, and had horrible brake squeal (like ear shattering brake squeal). Tried numerous sets of different pads to no avail. I attributed it to the s4 pad not covering the entire width of the 965 rotor, but that was a guess. I finally pulled them and went back to stock calipers.

milani

Very interesting, but I assume this kit wouldn't fit under the Turbo's stock 16 inch wheels (i.e. the Club Sports on the Turbo S).

Also very interesting that the S4 calipers are the same size as the calipers on the F50. That's a quite the fun fact!

Techno Duck

If you could perhaps come up with an integral adapter to go from axial to radial mount i would be interested in that, but either way am interested in just the adapters also. Alot of us 951 guys are just using adapters to go with larger front calipers as the Turbo S / 968 M030 front radial mount spindles go for 2x-3x the cost of normal axial mount spindles. I have S4 calipers waiting to go on my car but have not bough the adapters for them yet. If i would get a one piece adapter i would much rather do that then deal with having two different adapters stacked on each other (not a big deal, but if i can simplify the mounting that would be nice). I am interested in doing this because i would like the extra thermal capacity aswell as increase the swept radius as mentioned. I actually thought about buying the big blacks, but figure not really worth it cost wise..but this makes for a viable cost / performance option.

Kool

I thought Big Reds(993TT) and Big Blacks(928 GTS) were the same. And 928 S4/951S(Medium Blacks) were the same?

Techno Duck

That is right. What is being done here with the adapters is allowing you to use the S4 / 951S caliper with the larger diameter rotor of the Big Red / Big Blacks. The rotor diameter difference is 304mm vs 322mm, thickness is the same. I guess the point with the F50is that it used the same sized S4 / 951S caliper with a 14'' rotor (355mm) diameter rotor.