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The appropriate bolt will just be the bolt from a Turbo model. For a spacer you need a really beefy one...the calipers are mounted to the steering knuckle along a long, very machined, surface. By introducing a 15mm spacer you're losing all that surface area that I imagine helps keep things from flexing? Not an engineer but I don't think a spacer that doesn't run the length of the caliper is a good idea.
You can test all of this easily on-paper and it should work in real life. the Turbo has 390mm rotors. The S has 360mm rotor. You're adding 15mm to the radius (30mm to the diameter) and thus the 390mm rotor should fit.
If you want to test it in real life, order a 390mm rotor from a local parts store and you can try fitting it. As long as you don't use it they'll take it back.
From what i've found, all cayennes share the same 135mm M14 bolt. The area where the bolt head sits is lower than the caliper top to make up the 15mm extra thickness on the bottom end.
While making a spacer that goes the distance of the caliper is no big deal, if you look at the caliper, the only area that makes contact is about 1.1" squareish around each bolt. See the dark areas here .
None of my local parts stores sell the 390mm rotor, so not so simple to return. The question I have is basically whether the turbo and the S have the same offset, as the ridge between the mounting tabs on the turbo caliper appears thinner than the S model . They do appear to end roughly at where the mounting hole is, so likely not an issue...unless the caliper is just made to different specs, which is hard to verify without both in hand.
worst case, if no one has a used rotor laying around, I'll buy one and if i have to pay to ship it back, then so be it.
From what i've found, all cayennes share the same 135mm M14 bolt. The area where the bolt head sits is lower than the caliper top to make up the 15mm extra thickness on the bottom end.
While making a spacer that goes the distance of the caliper is no big deal, if you look at the caliper, the only area that makes contact is about 1.1" squareish around each bolt. See the dark areas here .
None of my local parts stores sell the 390mm rotor, so not so simple to return. The question I have is basically whether the turbo and the S have the same offset, as the ridge between the mounting tabs on the turbo caliper appears thinner than the S model . They do appear to end roughly at where the mounting hole is, so likely not an issue...unless the caliper is just made to different specs, which is hard to verify without both in hand.
worst case, if no one has a used rotor laying around, I'll buy one and if i have to pay to ship it back, then so be it.
Good call out. Spacer might not work because of offset/thickness. The 390mm rotor is thicker so you may need to use "used" brake pads to get everything to fit inside an "S" caliper.
edit: the 390mm rotors are 1.5in thick. the 360s are 1.42 in. Not a big difference?
Last edited by AnAlbumCover; 02-22-2022 at 06:52 PM.
thats a good figure on the disk thicknesses, thanks for that. It was one of my questions also.
.08 is roughly 2mm, so 1mm a side. I just did brakes on a 2016 base with 360mm rotors and when the pistons are fully compressed, there is some wiggle room with the new pads on new rotors, so I'd imagine that 1mm per side would not be a deal breaker.
The only real question is rotor offset at this point.
thats a good figure on the disk thicknesses, thanks for that. It was one of my questions also.
.08 is roughly 2mm, so 1mm a side. I just did brakes on a 2016 base with 360mm rotors and when the pistons are fully compressed, there is some wiggle room with the new pads on new rotors, so I'd imagine that 1mm per side would not be a deal breaker.
The only real question is rotor offset at this point.
They have to be different because the mounting holes on the knuckle are static. In order for the knuckle to stay static but rotor thickness to be variable the difference in the thickness has to be made up in the bolt holes on the caliper rotor otherwise pads on one side of the rotor will be closer than the other side....but that'll be resolved after you press the brake pedal the first time and everything sets?
edit:i cant type.
Last edited by AnAlbumCover; 02-22-2022 at 07:27 PM.
The width of the caliper could make up this distance, but if its truly that little, I think with the pistons fully compressed, there is room.
I'm not quite sure what you mean by one side vs the other, as a thicker rotor that still sits in the center of the caliper will have equally less distance on each side. What we don't want is a rotor that sits closer or further from the spindle/knuckle so that it would not sit in the middle of the caliper opening. I doubt that porsche would mess with this offset just for turbo models when so much else is the same and there is really no reason for it, but who knows. It could be different so the bigger disk still fits in the 19" wheel. I think a mock up is really the only way to know.
I think we're saying the same thing. You're assigning off-set to the rotor (depth/shallowness of the rotor hat), I'm assigning off-set to the caliper (the holes where the bolts go through). The extra few MM's of thickness between the base rotor and the turbo rotor needs to go somewhere.
I suspect the offset is in the calipers because then you can hold the cross-section centerline of the brake rotor static regardless of which rotor you install and the caliper will "self-center" because the holes on the caliper are a few MM's in or out. Also, then you don't have to worry about rotor mass being off-center, weird weighting on the hub etc etc.
This seems to be a lot of work to add unsprung weight (heavier rotors) and to move the pads out 30 mm. Do you get that much more clamping by doing so? Or are you experiencing significant brake fade due to overheating.
Not sure the juice is worth the squeeze...
Respectfully, what's the problem you're trying to solve?
(and as point of reference, my indie mechanic asked me exactly the same question when I put 17z calipers and RacingBrake roters on my '04 Audi allroad)...
This seems to be a lot of work to add unsprung weight (heavier rotors) and to move the pads out 30 mm. Do you get that much more clamping by doing so? Or are you experiencing significant brake fade due to overheating.
Not sure the juice is worth the squeeze...
Respectfully, what's the problem you're trying to solve?
(and as point of reference, my indie mechanic asked me exactly the same question when I put 17z calipers and RacingBrake roters on my '04 Audi allroad)...
Each rotor weighs about 1.5 pounds more. Getting an extra 1.2 inchs of rotor is pretty significant considering the minimal weight
Getting an extra 1.2 inchs of rotor is pretty significant considering the minimal weight
In terms of looks or stopping power?
If the latter, then you need to think about adding some additional braking capacity to the rear so that it remains balanced.
When I did brake upgrades on my A4 and allroad, I added S4 rear brakes, and A8 rear brakes, ending up with balanced systems. The A4 was particularly good...no fade, well balanced, felt great on the track, even though JD referred to it as a "momentum" car when he was instructing me at Lime Rock. Thanks John! Of course he would know...he started in a 914...
I'm not terribly concerned with the brake balance. Its not as though I'm threshold braking this thing into turn one. I tow with my car and any additional heat capacity and quite frankly, some nicer looks would be great. Considering the small price differential, and maybe an hour of my time making the spacers, I don't mind doing it.
I'm not terribly concerned with the brake balance. Its not as though I'm threshold braking this thing into turn one. I tow with my car and any additional heat capacity and quite frankly, some nicer looks would be great. Considering the small price differential, and maybe an hour of my time making the spacers, I don't mind doing it.
If you can make spacers, I'm willing to test it out. I need to do brakes seen enough and I'll order 390mm rotors for the test and deal with returns if it doesn't work.
I'm not terribly concerned with the brake balance. Its not as though I'm threshold braking this thing into turn one. I tow with my car and any additional heat capacity and quite frankly, some nicer looks would be great. Considering the small price differential, and maybe an hour of my time making the spacers, I don't mind doing it.
(emphasis added)
My opinion is worth what's been paid for it but reading through this thread, if it were me looking to change the aesthetics of the brake calipers, I'd be looking at powder coating them. Color choices are seemingly endless so you can get what you want. Personally, I've seen blue and burnt orange metallic that I thought looked nice. Another guy had his wife's done in pink, etc.
Will freely admit I don't tow and don't know details of your situation but have you had issues with the brakes on your Cayenne when you're towing? I wouldn't modify a crucial safety system on my vehicle based on something I *think* would work, especially on a vehicle that's for use on public roads (a track toy is another matter). Will also admit that I have no legal expertise but were the modified brakes to fail and there was property damage and/or personal injury, I can imagine thorny liability issues.
My opinion is worth what's been paid for it but reading through this thread, if it were me looking to change the aesthetics of the brake calipers, I'd be looking at powder coating them. Color choices are seemingly endless so you can get what you want. Personally, I've seen blue and burnt orange metallic that I thought looked nice. Another guy had his wife's done in pink, etc.
Will freely admit I don't tow and don't know details of your situation but have you had issues with the brakes on your Cayenne when you're towing? I wouldn't modify a crucial safety system on my vehicle based on something I *think* would work, especially on a vehicle that's for use on public roads (a track toy is another matter). Will also admit that I have no legal expertise but were the modified brakes to fail and there was property damage and/or personal injury, I can imagine thorny liability issues.
I'm generally not all that impressed with the brakes on my cayenne, but I don't think this mod will change that. Really the nicer looks of the larger disk along with very slight brake improvement, and more heat capacity headroom in the case of quick stops on long downhills would be my primary motivator. Considering the only extra cost would be $140 extra for the rotors and $25 for the spacer material, if it works, seems like a no brainer. I don't necessarily want the calipers in another color, as I'm fine with the plain silver.
As to modifying the brakes, its not really a question of thinking. If the rotor offset is the same as on the S, there is no "thinking" involved as the brakes will operate exactly as stock. The pad swept area is the same as the pads used are the same. The only difference is moving the caliper outwards. There is no change to how the caliper bolts on or is supported. Furthermore, a solid block of 6061 aluminum in compression is plenty strong and has similar properties to the aluminums used to make the calipers (354 or 357 alloy). The bolt used would be oem. There is really nothing to fail, but lets say for whatever reason the spacer crumbles and falls off, the brake caliper may rub the rotor (although would likely bind up on the bolt), but you would still be able to stop.
I am not concerned whatsoever about this causing or even making slightly more likely a brake failure.
Most cost effective way to improve performance is to switch to more aggressive pads, front and rear. I've stuck with stock pads as they stop well, don't squeal and are relatively low dust.
...but if I needed more stopping, I'd go with a Hawk HPS pad.
02-22-2022, 06:38 PM
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. They do appear to end roughly at where the mounting hole is, so likely not an issue...unless the caliper is just made to different specs, which is hard to verify without both in hand. 
