Pics of my Genuine Porsche 9" Front Wheel with 69 mm offset
04-21-2010, 08:02 AM
#31
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Hi Ragnar, I think you have a good understanding of where I am at and agree that you have a valid point in theory at least. I was operating within a set of parameters which meant only rolled front guards and not like some racers which add big flared guards.
I plugged into the calculator 7.5" and 9" fronts, with 65 mm offset and compared this with a 69 mm for the 9" and found (as you would expect) that they were only off centred by 4 mm i.e if the 9" was 65 mm the 9" wheel would have an extra inch each side of the 7" wheel which I believe is where you are coming from.
Now the 8" club sport wheels have even a lower offset than these 7.5" so all of these 928s are set up a bit differently, Also to my knowledge which is a bit light on this subject the change in the camber setting can also effect the scrub radius and as I am using the early suspension I have an 6 mm grace in that regard. As Gary said earlier, the proof of the pudding is in the eating and his car appears to be doing good things so I will stay with this until I find to the contrary.
Wheel alignment settings I believe are also going to have an influence and I hope to get an expert to sort mine.
Regards
Greg
I plugged into the calculator 7.5" and 9" fronts, with 65 mm offset and compared this with a 69 mm for the 9" and found (as you would expect) that they were only off centred by 4 mm i.e if the 9" was 65 mm the 9" wheel would have an extra inch each side of the 7" wheel which I believe is where you are coming from.
Now the 8" club sport wheels have even a lower offset than these 7.5" so all of these 928s are set up a bit differently, Also to my knowledge which is a bit light on this subject the change in the camber setting can also effect the scrub radius and as I am using the early suspension I have an 6 mm grace in that regard. As Gary said earlier, the proof of the pudding is in the eating and his car appears to be doing good things so I will stay with this until I find to the contrary.
Wheel alignment settings I believe are also going to have an influence and I hope to get an expert to sort mine.
Regards
Greg
04-21-2010, 10:33 AM
#32
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Ragnar,
I also now understand how you are aproaching this. And - it does seem there were a lot of different approaches from the factory! I'm going with what seems to work on the GTS, and I'm trying to keep the scrub angles as close as possible to the OE 7.5" wheels. The ~et70 on the 9" wheels seems to do that farily well.
Dan,
I guess I'd stay with the 18" wheel - but be sure it is sturdy. They do bend more frequently than the 16 and 17's. The BBS barrels I'm using on the Sport Design seem pretty rugged. With respect to offsets, I'd probably try for something in the range of et 70-77 for a 9" wheel. I'm not sure you can get along with anything much wider than 9" on the front, as I think you'd get rubbing on the inner fender area during sharp turns. IF I recall correctly, Kim Crumb - the legendary 928 racing enthusiast in Minneapolis concluded back in the late 90's that 9" fronts were the widest tire he could use. Offsets have always been the problem up front!!
And - yes, I'm using 295/30's on the rear. That is about the widest profile I can use on the GTS with the OE spacers witihout pushing the fender out a bit. Tire Rack gives a wheel width of 10-11" for the 295/30 PS2 on their web site, so I think it's OK. Their spec measurements for the tire were made with a 10.5" rim width.
Cheers,
Gary
I also now understand how you are aproaching this. And - it does seem there were a lot of different approaches from the factory! I'm going with what seems to work on the GTS, and I'm trying to keep the scrub angles as close as possible to the OE 7.5" wheels. The ~et70 on the 9" wheels seems to do that farily well.
Dan,
I guess I'd stay with the 18" wheel - but be sure it is sturdy. They do bend more frequently than the 16 and 17's. The BBS barrels I'm using on the Sport Design seem pretty rugged. With respect to offsets, I'd probably try for something in the range of et 70-77 for a 9" wheel. I'm not sure you can get along with anything much wider than 9" on the front, as I think you'd get rubbing on the inner fender area during sharp turns. IF I recall correctly, Kim Crumb - the legendary 928 racing enthusiast in Minneapolis concluded back in the late 90's that 9" fronts were the widest tire he could use. Offsets have always been the problem up front!!
And - yes, I'm using 295/30's on the rear. That is about the widest profile I can use on the GTS with the OE spacers witihout pushing the fender out a bit. Tire Rack gives a wheel width of 10-11" for the 295/30 PS2 on their web site, so I think it's OK. Their spec measurements for the tire were made with a 10.5" rim width.
Cheers,
Gary
04-21-2010, 03:24 PM
#33
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The Panamera front brakes are nothing like the F50 setup. The F50 setup is a lightweight system compared to the Panamera. I would not use them on a 928. The front disc diameter is 394 mm from memory if not it is within a couple of mm and that means 19" wheels. Also the front discs are 36 or 38 mm wide, a real heavy duty system for a 2 ton car.
Greg
Greg
