Still trying to find out a cheap way to give 13" rotors to the '84's
12-20-2010, 07:20 PM
#16
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Thread Starter
12-21-2010, 01:18 AM
#17
What are the front spindle caliper bolt center to centers? I haven't heard back from a few weeks ago from an Aussie guy wanting to put the Lexus calps on. I would say that the 330mm dia. rotors would be the max for those calps.
12-21-2010, 01:22 AM
#18
Nordschleife Master
Mark, I think this needs to be your winter off season project man. You need to figure out how to put 330mm rotors on a 928 with S calipers! Then sell a little kit for the stand-offs we will need and the bolts and maybe even a favorite rotor! It would be perfect for EURO85!!!
12-21-2010, 12:26 PM
#20
Those 330mm rotors were installed under 17's and the 350mm rotors under 18's. That is alot of rotational weight. Even the 928GTS rotors are too heavy IMO, that's why I didn't run them (even though they fit over the hub) and went with the lighter BoxsterS rotors.
12-21-2010, 12:47 PM
#21
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So looking at the specs from centric it specifies he Hub Reg which I assume to be the diameter of the hole at the canter of the disk the hub passes through, is the correct? If so as long as it's bigger than the hub centric diameter for the wheel it should be acceptable. This diameter IIRC is not the centering diameter for the rotor. Doesn't the rotor actually centers off the ID of the hat section onto the OD of the hub. Unfortunately this diameter isn't speced on the centric drawings. So this may need to be an additional area of research.
12-21-2010, 12:56 PM
#22
Bingo....Unless it's been mic'd and documented, you can't assume it fits the O.D. of the hub where the factory rotors are centered on.... I found that the 87-up 944 hubs are the same bearings as some years of 928 (more than likely later as well but want to confirm) If the Porsche calipers are the same 130mm C2C eyebolts then you can adjust the axial/radial dims of this drawing to fit them on the 928 spindles with 89mm spindle C2C's....
12-21-2010, 01:18 PM
#23
Administrator - "Tyson"
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12-21-2010, 01:43 PM
#24
Hats is where it's at. At least they made theirs hubcentric. I will only upgrade when a manufacturer Brembo/Audi comes out with an inexpensive Carbon-Ceramic disc that I will make hats for. Right now I have all the dims to make a hat and rotor combo at 13 LBS, I would like to shave another 5 lbs from each side.
12-21-2010, 02:25 PM
#25
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Thread Starter
THATS IT! Thanks!
OK,
so, it looks like the big VW/porsche rotors are 70mm,
S4 are 80mm and the '84 S rotors are 60mm. this might work out.
What this means is that the rotors I want to use are 10mm offset to the inside. PERFECT. Im sure that .5" of steel is enough to thread and hold calipers to the hub mounting points.
the only question now, is how close is the lower tie rod to the rotor. if we got 10mm gap , this will work. remember, at 80mm for the 928 S4 rotors, it wouldnt work, but that is a full inch further in to the tie rod than the the stock 84 rotor.
This means
OK,
so, it looks like the big VW/porsche rotors are 70mm,
S4 are 80mm and the '84 S rotors are 60mm. this might work out.
What this means is that the rotors I want to use are 10mm offset to the inside. PERFECT. Im sure that .5" of steel is enough to thread and hold calipers to the hub mounting points.
the only question now, is how close is the lower tie rod to the rotor. if we got 10mm gap , this will work. remember, at 80mm for the 928 S4 rotors, it wouldnt work, but that is a full inch further in to the tie rod than the the stock 84 rotor.
This means
12-21-2010, 02:29 PM
#26
Rennlist Member
Thread Starter
im confused? what is the logic here??
Boxster S rotors are what diameter? why are they lighter?
why do you care about 1 lb more weight on the rotors?
Do you understand that the weight is on a very small (relatively )diameter?
(we are talking 13" vs 26" of the entire rolling mass)
Plus, what do you think the effects are on handling or acceleration?
Did you know, rotating weight at that diameter, is only about 20%more of the effect, than if it was sittign in the car. I dont know the weight differences, but the S4 vs GTS rotor was only a pound or two different.
Boxster S rotors are what diameter? why are they lighter?
why do you care about 1 lb more weight on the rotors?
Do you understand that the weight is on a very small (relatively )diameter?
(we are talking 13" vs 26" of the entire rolling mass)
Plus, what do you think the effects are on handling or acceleration?
Did you know, rotating weight at that diameter, is only about 20%more of the effect, than if it was sittign in the car. I dont know the weight differences, but the S4 vs GTS rotor was only a pound or two different.
12-21-2010, 02:32 PM
#27
Rennlist Member
Thread Starter
EXACTLY correct! that was my point as well.
the problem will be if the rotor ID that fits to the hub OD, is too small. that was my problem with the mercedes rotors that made me think of this idea in the first place. however, i measured the ID of the rotors from the VW and they look large, so i think it will be ok. it may not fit perfect, but the centering setscrew will do the trick. thats one hole to drill
the problem will be if the rotor ID that fits to the hub OD, is too small. that was my problem with the mercedes rotors that made me think of this idea in the first place. however, i measured the ID of the rotors from the VW and they look large, so i think it will be ok. it may not fit perfect, but the centering setscrew will do the trick. thats one hole to drill
So looking at the specs from centric it specifies he Hub Reg which I assume to be the diameter of the hole at the canter of the disk the hub passes through, is the correct? If so as long as it's bigger than the hub centric diameter for the wheel it should be acceptable. This diameter IIRC is not the centering diameter for the rotor. Doesn't the rotor actually centers off the ID of the hat section onto the OD of the hub. Unfortunately this diameter isn't speced on the centric drawings. So this may need to be an additional area of research.
12-21-2010, 02:39 PM
#28
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Thread Starter
Hats certainly are where it is at, but at a cost. weight is not that big of a deal in this case. cheap carbon ceramic??? good luck with that 
13lbs for a hat and rotor combo? thats nice.
heat disipation is another factor. the rotor being disconnected from the hubs saves the hub, but heats the rotors more. trade offs!
13lbs for a hat and rotor combo? thats nice.
heat disipation is another factor. the rotor being disconnected from the hubs saves the hub, but heats the rotors more. trade offs!
Hats is where it's at. At least they made theirs hubcentric. I will only upgrade when a manufacturer Brembo/Audi comes out with an inexpensive Carbon-Ceramic disc that I will make hats for. Right now I have all the dims to make a hat and rotor combo at 13 LBS, I would like to shave another 5 lbs from each side.
12-21-2010, 02:43 PM
#29
Nordschleife Master
Man, you guys have really geeked out on me... I lost interest about 8 posts or more back. Just make a little kit with a stand off piece of steel and the proper bolts and the rotors Mark and I'll take a set!
12-21-2010, 02:46 PM
#30
Rennlist Member
Thread Starter
quick facts:
this new rotor (VW porsche 4x4, 13" rotor weighs near 17lbs)
the ID of the rotor is about 6 3/16", so it will fit over our hubs.
Last question is remaining, how close is the lower tie rod to the rotor on the OBs, and '84 928 setups?
since we have 10mm to play with , it sure seems like this will work.
I can have this made from aluminum or steel. which would be better?
Its a simple part to make. it has to be exactly the difference in the rotor offset, which is 9mm.
I think we have found a solution for big brakes for the 84s !
mk
this new rotor (VW porsche 4x4, 13" rotor weighs near 17lbs)
the ID of the rotor is about 6 3/16", so it will fit over our hubs.
Last question is remaining, how close is the lower tie rod to the rotor on the OBs, and '84 928 setups?
since we have 10mm to play with , it sure seems like this will work.
I can have this made from aluminum or steel. which would be better?
Its a simple part to make. it has to be exactly the difference in the rotor offset, which is 9mm.
I think we have found a solution for big brakes for the 84s !
mk