mark kibort

we need a little more room on the thin part side. more room for the "ear" to fit into it. 2mm more than half will do the trick for the thinner section vs the thicker section.

I think the 63.5mm (2.5") should only really be 2.25" (57.5mm)

xschop

Hey MK, how far is that Cayenne rear rotor surface away from the ball joint edge(mm)? Your last pic helps too as I was wondering what the 928 Tie rod lock-nut looked like past the knuckle. The Wilwood Superlite calipers will fit even if rotated down to get an offset bracket/adapter.

Edit: just posted right as you were posting. I just threw the 2.5" dim up there for simplicity/non machining. The problem is the ear to ear interface. The simple solution is to throw on 350mm rotors and make the 24mm dim = 34mm and grind the bridge some more LOL.

The step dimension can be milled very close to the caliper thru bolt, it will not affect strength.

mark kibort

I didnt get that mesurement because i was rushed, but I will get it, along with the set screw dimension that will hold the rotor in place, PLUS the seemingly larger ID of the older rotor. I think we are stilll verifying that the ID of the old rotors. (or hubs) is 155mm, vs the 157.1mm of the newer stuff.
However, it wont matter much if we simply drill a set screw hole in the proper place or places. (i.e. two will be easy to do.) Its just a drilled and chamfered hole.

the ear to ear interface?? that cant be helped with a taller dimension, as that is a fixed issue, however, if the thin part of the adapter is greater than the thicker part, it will be a non issue (at least for the spindle ear to the adpater surface . now the ear and the caliper ear, thats a function of the outer positioning. nothing we can do about that,but go for a larger rotor. thats a function of us moving the radius out 24mm and having room for the two ears to co-exist. Looks like that is a grinding /cut off wheel away from a solution. 2mm grind, that problem is gone. Sure, we go to 350mm rotors and its a non issue. (not a bad idea ! the only thing we have to do now is grind the edges off the caliper bridge edges . that looks very easy too.

xschop

Good work.
Yes the Early 928 Hub is 155mm O.D. confirmed by CMM and the Cayenne rotor is 157mm I.D

The 928 hub set screws are M6 x 1.0 at 136mm PCD positioned 36* and 108* out from any wheel stud (just like 944/968 hubs/rotors)

I have another question... What is the MC bore of the Early 928's?

mark kibort

so, we are not going to get a hub centric hub to the rotor, but it is only 1mm off at the radius. that can and will be easily solved by drilling the proper aligment screws. another way is to weld on the hub, 3 1mm centering tabs and file them down so you have a nice close fit, but the centering screws should be enough, along with proper lug nut torque. I guess a nice layer of dirt or rust might do the same thing.
anyway, the centering screws can be seen from my picture, lining up to a little offset on the cayanne centering screw (much larger and only one). rotate the rotor off a stud by one and start drilling a couple of holes. piece of cake.

xschop

Can you mic the I.D. of the hub bore on the rotor?
The spec sheet states 85mm with 7.5mm thickness at the face, it could be generic measurement and this is a critical dim for centering rings. I would make centering rings so you wouldn't have to keep setting up and drilling rotors down the road.

pcar928fan

Being Hub-centric all the way through the chain is EXTREMELY IMPORTANT! Do you REALLY want the weight of your car being carried by one lug stud 5 different times through each revolution of the tire? Remember the reason for hub centricity is to carry the weight on something designed to bear (bare?) that weight. The lugs were NEVER intended to carry the weight of our cars. They are there to hold the wheel TO THE HUB.

mark kibort

yes, the cayanne rotor has the 85mm hole in the face, and the thickness is 7.5mm. just mic'ed it. but what do you do with this to use it for centering. it doesnt touch anything.

I think a quick template that you could drill 2 holes through would be very easy and quick. once you have the correct holes drilled, just make a metal template using the studs for alignment and drill 2 holes. pretty quick it seems.

I guess I dont understand how to make a centering plate.

xschop

Pcar, you talking at me?

I'm talking about lathing out centering rings 71.6mm I.D x 85mm O.D. x 7.45mm just like the Boxster S rotor needed.

Just so we're on the same page, you are technically pushing the wheel out 1.5mm on each side, the wheel is still hub-centric on the 71.6mm hub flange, just missing 1.5mm depth.

mark kibort

I understand, but the wheels, expecially aftermarket, are not that hubcentric anyway. some are , some arent. the kinesis are about 1mm off, the stock stuff is pretty close. the 5 lugs center the wheel very very tightly and all the weight is on all 5 studs, equally. the entire chain is NOT important. the rotor has no bearing on the weight of the car. its all studs, with tappered fittingn lugs to center the wheel perfectly. again, the hub outer diameter, is use for the brake rotor and the bearing outer area is for the wheel, that barely touches anyway. Ive used spacers that negate its effect and had absolutely no issues at all. again, the wheels have some slop in this hubcentric area, unless you are talking stock wheels.

the rotor is a different story, as there is no weight on it, just the stopping force and the clamping force of the lugs to keep it moving around, or the centeriing screws will take this force, if it exceeds the clamping force, which it wont.
Im not too worried about it, and will do some testing first when its all together. the pros outweigh the cons in this case. $90 330mm rotors for the pre S4 brakes, is pretty cool and will work fantastic,

xschop

I asked the question previously about the later 928 hub O.D being 157mm as compared to the Early 928 hub being 155mm O.D.
My point is 2mm oscillation of this heavy rotor will show up in vibes at high speed. The even lighter 318x28mm BoxsterS rotor did this when we installed them on the Early 944 hubs. The centering rings cleared the vibes.

mark kibort

I think I understand. you are using a ring to center the rotor and its fitting in the space now occupied by this spacer. why would you loose any hubcentric contact? the wheel is flush and meets the same area it would normallly, so you wouldnt be pushing anything out. as another side note to reality, the kinesis rims I have, have a pretty deep chamfer, so the likeyhood that the hub centric portion ever touches or guides/supports the wheel, is very very slim, at best.

xschop

Factory 928 rotor flange is 6.0mm thick...Cayenne is 7.5mm so you get a free
+3mm wheelbase out the deal and some big *** brakes!

mark kibort

interesting. I dont think that is so on the S4,but maybe the new thickness came along with the 157.1mm ID on the hub mount.

if you have seen the camfer of most wheels, you can appriciate my comment back to Pcar about the fact that the hubcentric issues are really mute. It barely touches. there are a ton of folks using non hubcentric spacers and ive never heard of a vibration, and certainly, not a safety issue. the wheel certainly is centered by the tapered mount of the wheels and tappered lugs. that is solid!
the rotor, is a little more risky but the worst that can happen is 1mm off on the radius. not a big deal, and certainly unlikely if you use the two centering screws or the centric ring you proposed. cool idea. dont think we will need it.

xschop

Yes, the wheel lug profile that matches the wheel lug channels are what truly center any wheel if they are precision machined. I was referring to the +1.5mm offset per side that is gained due to the fact that the top hat portion/thickness of the Cayenne rotor (between hub face and wheel face) is 1.5mm thicker than the 928 rotor.