Still trying to find out a cheap way to give 13" rotors to the '84's
12-20-2010, 04:25 PM
#1
Rennlist Member
Thread Starter
Still trying to find out a cheap way to give 13" rotors to the '84's
I did a break job on a VW touareg. they have MASSIVE calipers (6 piston) and the bolt pattern, i would say is porsche. dont know about inner hub diameter, but the offset looks similar to the early cars. anyone know what the early offset is? rotor surface to ground, if the rotor is sitting on its outer face.
im thinking we can make a flat steel bar with it bolted to the axial mouints of the '84s and then have two holes drilled and tapped for mounting the calipers to. obviously, we would need to have some safety level of thickness to drill and tap to have enough threads for brake mounting. what , 5 threads, or .3" or so?? then, the question is will the rotor hit the lower tierod end?
if possible, this would give the '84 some GTS brakes with single piston calipers with decent size pads for racing. rotors are real cheap, so this would be a great solution.
im thinking we can make a flat steel bar with it bolted to the axial mouints of the '84s and then have two holes drilled and tapped for mounting the calipers to. obviously, we would need to have some safety level of thickness to drill and tap to have enough threads for brake mounting. what , 5 threads, or .3" or so?? then, the question is will the rotor hit the lower tierod end?
if possible, this would give the '84 some GTS brakes with single piston calipers with decent size pads for racing. rotors are real cheap, so this would be a great solution.
12-20-2010, 05:37 PM
#3
Rennlist Member
Hmmm - there used to be a site that had all sorts of brake hardware specs listed (diameter, offset, bolt pattersn, etc.). I found it when it started becoming popular to bolt on Infiniti Q45 brakes to 240SXs. I'll start scanning my "Favorites."
12-20-2010, 06:09 PM
#5
Rennlist Member
I'm guessing it would need some sort of hubcentric adapter? I think our hubs are 71.6mm. I've heard of vibration issues when trying to use rotors that were riding solely on the lugs rather than centered on the hub.
12-20-2010, 06:19 PM
#7
Rennlist Member
Thread Starter
those are the ones I have off the VW. the smallest option. (13s vs 14" rotors)
330mm (13") rotors are the ones Im thinking migth be adapted to the early 928s
330mm (13") rotors are the ones Im thinking migth be adapted to the early 928s
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12-20-2010, 06:22 PM
#8
Rennlist Member
Thread Starter
thats the 2nd issue. I think there are some here that have done it without a fit to the inner hub. (i.e. a little larger rotor ID at the hub mounting) im trying to picture how it might move after crank down of the lug nuts. Its possible that a tap of the hub for a positioning set screw might do it. (the beefie one found on these 13" rotors )
12-20-2010, 06:28 PM
#9
Race Director
I also have thought about getting larger rotors with the S caliper....since I am very happy with the brakes on the Estate....a larger rotor would just make it that much better!!!
12-20-2010, 06:43 PM
#10
Rennlist Member
I've thought about larger rotors too, but haven't given it a lot of time since there allways seem to be other more pressing issues I'm trying to sort on my 85.
I don't think the issue is movement once the wheel is installed but keeping the rotor centered while the wheel is being installed. I think a positioning screw would suffice.
I don't think the issue is movement once the wheel is installed but keeping the rotor centered while the wheel is being installed. I think a positioning screw would suffice.
thats the 2nd issue. I think there are some here that have done it without a fit to the inner hub. (i.e. a little larger rotor ID at the hub mounting) im trying to picture how it might move after crank down of the lug nuts. Its possible that a tap of the hub for a positioning set screw might do it. (the beefie one found on these 13" rotors )
12-20-2010, 06:49 PM
#11
Rennlist Member
Thread Starter
that would be pretty simple to do.
Its all for not unless we can get the right dimensions.
I need:
distance from the rotor surface to the lower tie rod end.
and over all thickness of the early rotors ('80-84ish)
Its all for not unless we can get the right dimensions.
I need:
distance from the rotor surface to the lower tie rod end.
and over all thickness of the early rotors ('80-84ish)
I've thought about larger rotors too, but haven't given it a lot of time since there allways seem to be other more pressing issues I'm trying to sort on my 85.
I don't think the issue is movement once the wheel is installed but keeping the rotor centered while the wheel is being installed. I think a positioning screw would suffice.
I don't think the issue is movement once the wheel is installed but keeping the rotor centered while the wheel is being installed. I think a positioning screw would suffice.
12-20-2010, 06:57 PM
#12
Nordschleife Master
I am not sure if I am understanding what I am reading quite right here, but it sounds like some guys are not talking about having a hubcentric design of the rotor to the hub and that would NOT be a good idea. If you don't have it set up in a hubcentric fashion then you are actually supporting the car on your wheel studs and they were NOT designed to support the car. The HUB is designed to support the car and that is why it is important to use wheels, brake rotors and spacers that are ALL hubcentric.
12-20-2010, 07:05 PM
#13
Rennlist Member
Thread Starter
so this is the VW rotor. 70mm about.
so i just measured the S4 rotor (same as GTS) and it is 80mm
what is the stock '84ish rotor thickness?
how thick does a caliper mounting plate adapter need to be for thickness to be strong enough. how deep do the threads need to be. .25" enough?
mk
so i just measured the S4 rotor (same as GTS) and it is 80mm
what is the stock '84ish rotor thickness?
how thick does a caliper mounting plate adapter need to be for thickness to be strong enough. how deep do the threads need to be. .25" enough?
mk
12-20-2010, 07:11 PM
#14
Rennlist Member
Thread Starter
actually, yes, our cars use a "hubcentric design", but thats not the reason for the rotors to fit that way. there is no "weight" on the rotors, only alignment.
as far as hubs, we all use spacers in the racing world, on hub centric cars. I remember using a non hubsentric spacer in the front (1/8" ) and you cold see the spacing of the hub (not the same part of the hub that we are talking about here with the rotors) and the wheel . it wasnt touching. without it, it barely touched, and there really wasnt any real support contact. I do have "stock, hubcentric " wheel spacers on the rear and most all of the weight is still on the wheel studs. most aftermarket wheels dont machine that part of the wheel correctly anyway to be truely hubcentric. stock wheels, maybe yes, but the wheels Ive used and use now, no.
I have used 1/2" non hubcentric spacers for years up front with no issues. I dont now, due to running the 1/2" wider 305 tire up front, but for years I didnt. actually, I still do run a 1/8" spacer up front with my 275s. There is nothing to worrry about.
as far as hubs, we all use spacers in the racing world, on hub centric cars. I remember using a non hubsentric spacer in the front (1/8" ) and you cold see the spacing of the hub (not the same part of the hub that we are talking about here with the rotors) and the wheel . it wasnt touching. without it, it barely touched, and there really wasnt any real support contact. I do have "stock, hubcentric " wheel spacers on the rear and most all of the weight is still on the wheel studs. most aftermarket wheels dont machine that part of the wheel correctly anyway to be truely hubcentric. stock wheels, maybe yes, but the wheels Ive used and use now, no.
I have used 1/2" non hubcentric spacers for years up front with no issues. I dont now, due to running the 1/2" wider 305 tire up front, but for years I didnt. actually, I still do run a 1/8" spacer up front with my 275s. There is nothing to worrry about.
I am not sure if I am understanding what I am reading quite right here, but it sounds like some guys are not talking about having a hubcentric design of the rotor to the hub and that would NOT be a good idea. If you don't have it set up in a hubcentric fashion then you are actually supporting the car on your wheel studs and they were NOT designed to support the car. The HUB is designed to support the car and that is why it is important to use wheels, brake rotors and spacers that are ALL hubcentric.