mark kibort

that would be a nice upgrade, but i would wonder about ease of brake line transfer. yes, some wheels are snug to the hub boss. mine, in the rear were like that too, but the fronts were loose. kinesis, should have made it tighter if it mattered


yep, that is the advantage, being able to bolt on without any bridge grinding, although, that will be a 2 min process to fix. making the adapter to fit this set up will be easy. in fact, the adapter Im making might be able to be made with two sets of holes in it.

It doesnt put anything to shame, but it is larger in size overall and does have two pistons, but thats not a huge difference in reality. still pressing from one side. actually, more heat can be transfered to the caliper this way. yes, it would be a drop in almost too. your rigtht

NOW, the pad size. cool, thats a huge pad. BUT, you were measuring from mounting flange, end to end. (big difference.) if we do this with the stock 928S pad, its not that much bigger. 170mm vs 160mm plus the 928 pad is a little wider radius wise. (50mm vs 57mm)
BTW, the S4 pad is 132mm and the GTS big red pad is also 132mm too ! did you know that?? Ferarri F50 same pad as S4, and even the other brembo calipers, like big reds are no more than 140mm. the S pads are not much smaller than the S4 pads if I remember correctly. The GTS pad is no different than the S4 pad, but it is thicker to the inside, which is not really all that great. (lots of heat generated, and no stopping force on the inner diameter area. that is why cup cars and all the racing brake systems dont use a pad width like the GTS , big red type pad and caliper. they go for longer spread, thiner width pads.

mark kibort

remember, BMW, VW, Audi, etc, all use bolts rather than studs, so they NEED to have the hubcentric ring to put the darn wheel on the car.

it cant be critical , because most all the guys at the track dont have rims that are truely hubcentric.

VT928

Mark,

"yep, that is the advantage, being able to bolt on without any bridge grinding, although, that will be a 2 min process to fix. making the adapter to fit this set up will be easy. in fact, the adapter Im making might be able to be made with two sets of holes in it."


I'm unsure about how much you will be able to grind the "S" caliper to match the 330 mm rotor, the "S" rotor is only 282 mm in diameter. The structure may not have enough meat in the casting to maintain its structural strength. The 48 mm increase in rotor diameter makes a huge difference rotor circumfrence.

Because the caliper fits multiple diameters of rotors and the abutment is all that needs to be changed you could do a adaptor that would allow for differing rotor sizes to match both 17 and 18 inch wheels. The biggest difference between the "S" caliper and the Vette caliper is 30 years of development.

Paul

1980 Euro S Red/Blk Lea

mark kibort

Well, i assume you understand how much material will have to be grind off to match the 330mm rotor. If so, then you might not remember or have seen how the bridge is oriented its kind of angled and very thick.

The good news is that i have the caliper resting on the rotor. if you see the picture of the caliper pads, you can see that there's not much pad showing over the edge of the rotor, so, to get the caliper to squat down on the rotor, its only going to take a few mm of grinding. It might seem like there should be more to grind off, but there is a reallly nice solid beam to cut into and not as much material as you might think needs to be removed. you dont need to cut out the full 24mm difference to make it fit. thats at the center, and that room is made by the fact that the caliper is moved out. the arc is wrong on the S calipers and anyone with some old trig, can calculate out the the amount of cutting needed 3-4" off the center of the arc. at 90 degrees, it would be the full 24mm, at 45degrees, 12mm, and at 23 degrees, its more like 7mm about 1/4" . PLus there is a wide clearance stock, and we will end up with a only a couple of mm of clearance when through. just enough to clear the rotor and its expansion.

VT928

Mark,

I went back and looked at the photo of the caliper you posted, I had forgotten how beefy the bridge was. Guess it was because the "S" caliper looked so small compared to the S4 caliper when I did my upgrade. Definitely looks doable.

RFJ

Mark, just want to say thank you to you and others for the work you are doing, i know it will pay off in the end and many of us will benefit. again thanks, Ray



QUOTE=mark kibort;8207915]Well, i assume you understand how much material will have to be grind off to match the 330mm rotor. If so, then you might not remember or have seen how the bridge is oriented its kind of angled and very thick.

The good news is that i have the caliper resting on the rotor. if you see the picture of the caliper pads, you can see that there's not much pad showing over the edge of the rotor, so, to get the caliper to squat down on the rotor, its only going to take a few mm of grinding. It might seem like there should be more to grind off, but there is a reallly nice solid beam to cut into and not as much material as you might think needs to be removed. you dont need to cut out the full 24mm difference to make it fit. thats at the center, and that room is made by the fact that the caliper is moved out. the arc is wrong on the S calipers and anyone with some old trig, can calculate out the the amount of cutting needed 3-4" off the center of the arc. at 90 degrees, it would be the full 24mm, at 45degrees, 12mm, and at 23 degrees, its more like 7mm about 1/4" . PLus there is a wide clearance stock, and we will end up with a only a couple of mm of clearance when through. just enough to clear the rotor and its expansion.[/QUOTE]

xschop

I've mic'd the '85 928 pad and it pales to the C5 pad....That 50mm dim may be a little wider on the 928 pad by maybe an mm or two on different manufacturer's pads, but same goes for the C5 pad.

mark kibort

certainly is a bigger pad, no question, but it is thinner to start out with and that is not great for racing, unless they come in a thicker version, i would never buy a pad, even larger that started out at only 10mm or so. (4-5mm backing plate). If there is a pad that is thicker, that would be good. the S pad is smaller, but certainly will work compared to the S4 pad, used by the Ferrari F50, as well as the famous StopTech ST40s as well, its not much of a drawback. as you can see below, the ST40 vs the Ferrari F50 (same brakes as Anderson uses with 14" rotors) and the 928S4, that they are all identical pads. notice that these pads almost the exact same height as the "S" pads and are only about 1/2" (13mm) narrower in width.

dont get me wrong, the corvette upgrade would be ineresting. get a wider pad, and dual piston calipers, but i dont know how much gain that would really be. certainly if they are aluminum, the weight savings would be good. but for $200 even more, i think I would wait and do S4 calipers down the road.

we are talking an upgrade that costs nothing more than the spacer ONLY. same pads and rotors are actually slightly cheaper than the originals.

VT928

xschop,

When I suggested using the Corvette caliper my primary thought was the low cost of it. Looking at the pad drawings shows what thirty years of technology development looks like when it comes to automotive brakes. Given the benefits of the Corvette caliper and its enhanced pad size it looks to me that while the "S" caliper and Corvette caliper will both work. However, the Corvette caliper would be a significant upgrade in braking capability over the "S" caliper. In my mind when it comes to brakes it is all about performance. Looking at how easy it would beo use the Corvette caliper if I had to do an brake upgrade again I would not use the S4 components I would adapt the Corvette Caliper

xschop

Thanks for the Apples2Apples. One thing that should be noted is the larger surface pads will wear down at a slower rate than the smaller pads even though they are thinner.Thicker is better in any case for sure, but Chevrolet or any MFR, wants you to change pads hopefully as often as you change your undies LOL. Also Dual piston sliding calp pistons have way less propensity to "****" on their bores and stick than single pistons.

VT928

Interesting excersise here, two solutions that will both work to improve the braking significantly on Cars with "S" Brakes. My guess is the solution with the lowest cost would win out in the marketplace, Lets face it most 928 owners will opt for the low cost solution, esp for a car that rarely if ever sees a racetrack.

Paul

mark kibort

they wont wear down that much slower, but you are right . you just dont want that thin of a pad. at 10mm, they transfer more heat too. However, i do agree, at first glance the calipers are much more capable. i dont think there is any worry that the calipers and single piston set up is not a good one. guys in the BMW ranks raced them FAST for years and years! Im not convinced that the US made corvette caliper is an equal, but for sure its bigger. Im trusting your reserch that they have been used in racing sucessfully. most all vet racers i know all have changed out the brakes as a first step. the vipers also had a lot of trouble with their calipers and pad set ups and change it out first. I think its similar to the vet, but dont remember. dont know enough about it, but what I do know is the 928 system is a good one and the pad is not much smaller than the S4. on a 330mm rotor, the system gets very capable!

dont confuse big pad size with brake system performance for the only metrix.
i would NEVER use this corvette caliper in place of a 4 pot brembo stock S4 928 caliper! no way. ask anderson or any other racer if they would change their S4 caliper, or stoptech, ST40, or Ferarri F50 caliper (all near the same as the S4) for a corvette dual piston caliper, just to get a half of an inch or even an inch of pad width. I dont think you made a bad choice by any means.

xschop

If someone wants to send me a C5 caliper and "abutment" as you call it along with a new Cayenne 330mm rotor, I would mock them and design the adapters. I think I'm going to hold onto these spindles and hubs for awhile anyways.

I've just started making adapters for the Wilwood Superlites that have substantial pad surfaces and different compounds available with various piston sizes. I figure the 41mm 4-pots would be a great match for the stock 928 MC.

Re: 928 MC size......

The front circuit is a 23.81mm piston and the rear is 20.64mm

VT928

Mark,

Don't get me wrong the S4 upgrade I did on my 80 Euro S is clearly the best way to go. That said I will never use them to thier performance limits. Those limits exceed my skills and courage. For a street application and ease of installation using Corvette calipers and not having to replace the front spindles and all that it entails to remove them, a caliper swap with the advantages we have talked about here would be very cost effective and an serious upgrade in performance. I still would never use the to thier full capability, and I would have more money left in my wallet.

Paul

mark kibort

I get it! I totally agree. much easier (than what you did with spindles, etc) and a much bigger brake system for CHEAP! trust me, you got me thinking, but we are doing this for the total cheapness of not having to buy anything but a couple of bolts and this spacer.

by the way, as a side note, why do you have to change spindles to do the S4 brake upgrade? cant you just bolt on a spacer adapter and bolt the S4 calipers on? or do the 80mm offset rotors get too close to the lower ball joint. sure looks lke there is about 1" even now, with the cayanne rotors, which were about 1/2" closer than the stock 60mm rotor offset S rotors.

now, just waiting for the parts. hopefully, they will arrive this weekend.

any takers on a run of these things on a CnC machine? probably be something like $100 each set. Just curious. otherwise, he is just going to cut and drill with traditional low budget machine shop techniques.