Purely hypothetical wheel/tire selection scenario
09-09-2009, 02:43 AM
#1
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Purely hypothetical wheel/tire selection scenario
When I bought my (first) 928 I swore that I would not fall victim to obsessing about wheels, and would focus on getting the car running in tip-top shape. Well, I’m now obsessing about wheels. Specifically, I’m trying to come up with the best solution for wheels for the GTS stroker. There are many parameters and constraints to consider, and the combination of all these factors ends up giving me a headache. Dan H. (S4ordie) and I have been going back and forth about possible solutions and all we’ve managed to do is give one another headaches.
SO: throwing this out to the board – what wheels and tires, in what size and what offset, would you install, given the following constraints/options:
1. 93 GTS with (for now) ’87 to ’90 front and rear splash shields in the rear wheelwells (ie- no lateral constraints from the full GTS wheelwell liners.
2. Wheel size should be 17” or 18” – happy medium of tire availability/price/ride quality
3. Prefer stock factory look, but could also go with non-blingy aftermarket rims, see list below
4. I have stock 35 mm GTS spacers and super-long (72 mm) GTS studs in back, and have a set of 15 mm bolt-on hubcentric spacers as well. I’d prefer not to have to replace or shorten studs.
5. Optimal front tire width: 235-245 (?)
6. Optimal rear tire width: At least 275, what’s a sane maximum for a 6.5L stroker with a 2.73 rear end? 295?
7. Keep overall wheel diameter to +/- 2% to minimize speedometer error
8. Simple spoke design is better, don't want to spend an hour/wheel with a toothbrush cleaning bolt heads ('cause I would, given half the chance...)
Possible wheel options (based on my tastes, but open to different suggestions)
A. Stock 7.5” ET65 and 9” ET55 Cup I rims widened to 8.5” and 10.5” . If I understand the simple math, that would make the offsets ET77 in front and ET 74 in back.
B. 18” 997 Carrera III’s – 8x 18 ET57 997.362.136.00 and 10x18 ET 58 997.362.140.01
C. 18” 996 Turbo twist hollow spokes - 996.362.142.03 (8x 18) and 996.362.136.04 (11 x 18)
D. Champion RS184’s
E. Fike FM5’s
F. Anyone ever seen an 18” knockoff of the Ruf RG5’s? I love the look of them but they don’t exactly have any 928 DNA in them…..
G. Wait until the car’s actually running and scare myself silly skating around on 225/255 PS2’s until it’s clear that I need wider rubber and then revisit the subject?
I know sets of takeoff Carrera III's or hollowspoke twists would be the easiest (and probably most cost-effective) thing to do, but I'd just as soon do something a bit different....
H. Say to hell with it and buy up the blingy polished aluminum, custom offset 18 x 8.5 / 18 x 11 HRE545’s that were on the car when I bought it (but passed on the rims)?
[fantasy] What I REALLY want is to feed my 16" CS rims into a computer that spits out a CNC program for an 18" version with the proper offsets. Too much to ask? [/fantasy]
SO: throwing this out to the board – what wheels and tires, in what size and what offset, would you install, given the following constraints/options:
1. 93 GTS with (for now) ’87 to ’90 front and rear splash shields in the rear wheelwells (ie- no lateral constraints from the full GTS wheelwell liners.
2. Wheel size should be 17” or 18” – happy medium of tire availability/price/ride quality
3. Prefer stock factory look, but could also go with non-blingy aftermarket rims, see list below
4. I have stock 35 mm GTS spacers and super-long (72 mm) GTS studs in back, and have a set of 15 mm bolt-on hubcentric spacers as well. I’d prefer not to have to replace or shorten studs.
5. Optimal front tire width: 235-245 (?)
6. Optimal rear tire width: At least 275, what’s a sane maximum for a 6.5L stroker with a 2.73 rear end? 295?
7. Keep overall wheel diameter to +/- 2% to minimize speedometer error
8. Simple spoke design is better, don't want to spend an hour/wheel with a toothbrush cleaning bolt heads ('cause I would, given half the chance...)
Possible wheel options (based on my tastes, but open to different suggestions)
A. Stock 7.5” ET65 and 9” ET55 Cup I rims widened to 8.5” and 10.5” . If I understand the simple math, that would make the offsets ET77 in front and ET 74 in back.
B. 18” 997 Carrera III’s – 8x 18 ET57 997.362.136.00 and 10x18 ET 58 997.362.140.01
C. 18” 996 Turbo twist hollow spokes - 996.362.142.03 (8x 18) and 996.362.136.04 (11 x 18)
D. Champion RS184’s
E. Fike FM5’s
F. Anyone ever seen an 18” knockoff of the Ruf RG5’s? I love the look of them but they don’t exactly have any 928 DNA in them…..
G. Wait until the car’s actually running and scare myself silly skating around on 225/255 PS2’s until it’s clear that I need wider rubber and then revisit the subject?
I know sets of takeoff Carrera III's or hollowspoke twists would be the easiest (and probably most cost-effective) thing to do, but I'd just as soon do something a bit different....
H. Say to hell with it and buy up the blingy polished aluminum, custom offset 18 x 8.5 / 18 x 11 HRE545’s that were on the car when I bought it (but passed on the rims)?
[fantasy] What I REALLY want is to feed my 16" CS rims into a computer that spits out a CNC program for an 18" version with the proper offsets. Too much to ask? [/fantasy]
Last edited by Rob Edwards; 09-09-2009 at 11:52 PM.
09-09-2009, 02:54 AM
#2
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Yep, what he said.
My desire is to widen the 17" Cup II's already on my car. I am less intersted in aftermarket or later year Porsche designs. I like the concept of stealth.
So please help us here. What do we need to consider when we widen the front and rear wheels. For me, I like a 8.5 width up front and a 10.5 to 11.0 rear.
Sure there are others besides Rob and I who have/are wrestling with this.
My desire is to widen the 17" Cup II's already on my car. I am less intersted in aftermarket or later year Porsche designs. I like the concept of stealth.
So please help us here. What do we need to consider when we widen the front and rear wheels. For me, I like a 8.5 width up front and a 10.5 to 11.0 rear.
Sure there are others besides Rob and I who have/are wrestling with this.
09-09-2009, 02:57 AM
#3
Nordschleife Master
Why would you let $5k or $10k stand between you and the perfection you know your 928 wants?
Do some photoshop or cad or whatever and get exactly what you want.
http://www.trueforgedwheels.com/
*** Several people widen stock wheels, not really a big deal. A local shop we both know had a set for somebody last time I was there.
Do some photoshop or cad or whatever and get exactly what you want.
http://www.trueforgedwheels.com/
*** Several people widen stock wheels, not really a big deal. A local shop we both know had a set for somebody last time I was there.
09-09-2009, 03:03 AM
#4
Nordschleife Master
You can get these in 18" diameter, with whatever width and offset you want.
If you want to go maximum you can get I would go with 11 up front (yes they fit I have them), and 12" in the rear. Then run a 285 front and a 315 rear. This should be no issue on a GTS and you can have them made with or without the need to run the spacers in the rear.
Then I would run the Toyo R888 or something like that. Dont bother to shave them and enjoy the insane street performance!
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09-09-2009, 03:06 AM
#5
Burning Brakes
I believe you exceeding the limit for purely hypothetical questions. 
'89 S4 GP White/Black (17" Cup I)
'912E Silver/Black sunroof
Objects in mirror are losing
'89 S4 GP White/Black (17" Cup I)
'912E Silver/Black sunroof
Objects in mirror are losing
09-09-2009, 03:58 AM
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I wouldn't widen any wheel other than 2 or 3 piece where it can be done by swaping parts. I have seen one 17" factory Cup II pair which were widened to 10.5" by combining pieces from two wheels into one. If I had those I could never use them without thinking what if... Very likely they will work just fine forever but still.
09-09-2009, 04:06 AM
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Yep, what he said.
My desire is to widen the 17" Cup II's already on my car. I am less intersted in aftermarket or later year Porsche designs. I like the concept of stealth.
So please help us here. What do we need to consider when we widen the front and rear wheels. For me, I like a 8.5 width up front and a 10.5 to 11.0 rear.
Sure there are others besides Rob and I who have/are wrestling with this.
My desire is to widen the 17" Cup II's already on my car. I am less intersted in aftermarket or later year Porsche designs. I like the concept of stealth.
So please help us here. What do we need to consider when we widen the front and rear wheels. For me, I like a 8.5 width up front and a 10.5 to 11.0 rear.
Sure there are others besides Rob and I who have/are wrestling with this.
Did you know that there was a Porsche Exclusive option for widened front fenders (steel) and 8" front wheels on the GTS models?
Unfortunately, we know few details about this option - none of us has ever seen it, nor do we have any technical specs like ET.
We only know that it can be done.
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09-09-2009, 11:48 AM
#9
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Here are my thoughts.
Becasue you're talking about possibly going up to a 295 tire, I think that pretty much eliminates 17" wheels. The 17"'s seem to max out at 265 with a few going up to 275 and very few going to 285. I don't recall ever seeing a 17" tire in a 295. 18's will give you a wider selection to choose from.
That said, yes the Carrera III's are probably the most cost-effective solution. I personally feel the hollow spoke twists give the car a dated look. If you want a Fikse look, I'd strongly suggest you look at Carl's solution. You will get an absolute custom wheel with proper offsets, etc. for about the same price... maybe a bit less.
In the end, it's your car and your wallet. Good luck.
Becasue you're talking about possibly going up to a 295 tire, I think that pretty much eliminates 17" wheels. The 17"'s seem to max out at 265 with a few going up to 275 and very few going to 285. I don't recall ever seeing a 17" tire in a 295. 18's will give you a wider selection to choose from.
That said, yes the Carrera III's are probably the most cost-effective solution. I personally feel the hollow spoke twists give the car a dated look. If you want a Fikse look, I'd strongly suggest you look at Carl's solution. You will get an absolute custom wheel with proper offsets, etc. for about the same price... maybe a bit less.
In the end, it's your car and your wallet. Good luck.
09-09-2009, 11:51 AM
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Wheels and Tires
Rob,
For 17" wheels Kumho makes a 255/40 and a 295/35 that I run for a front rear combo. The tire name is ESCTA XS. They are very close to the stock diameter and fit with no rolling of the fenders. I mount them on 60mm offset rims. the XS tires are asymetical in design and are very sticky, but they will wear quickly. My wheels are made by ROH, but are no longer available.These tires combined with the larger diameter sway bars and upgraded springs and shocks make for a car that really handles the turn in is quick and grip is very good. Braking is much better than stock due in part to the tires and in part to the upgraded brakes, S4 spec.
Paul Mammorella 1980 Euro S Red/Blk Lea
For 17" wheels Kumho makes a 255/40 and a 295/35 that I run for a front rear combo. The tire name is ESCTA XS. They are very close to the stock diameter and fit with no rolling of the fenders. I mount them on 60mm offset rims. the XS tires are asymetical in design and are very sticky, but they will wear quickly. My wheels are made by ROH, but are no longer available.These tires combined with the larger diameter sway bars and upgraded springs and shocks make for a car that really handles the turn in is quick and grip is very good. Braking is much better than stock due in part to the tires and in part to the upgraded brakes, S4 spec.
Paul Mammorella 1980 Euro S Red/Blk Lea
09-09-2009, 08:58 PM
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search for the "who's got the coolest wheels" thread, tons of pics to give you an idea of how they look on the car, etc. - also, here's a link to Wheel Enhancement, lots of factory and aftermarket wheels to choose from, hope it helps -
http://www.wheelenhancement.com/index.php?t=Wheels
http://www.wheelenhancement.com/index.php?t=Wheels
09-09-2009, 09:13 PM
#13
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Rob
I 2nd what 9281ndRC51 said.....the CCW wheels are truely custom....any width, diameter, offset you want.....It would be VERY easy to run 18x11 or 12's in the rear of a GTS by removing the 35mm spacer....I'm sure 315's would fit with ease....maybe as wide as a 335 with some fender rolling
Which brings us to how big of a tire do you need....since you are getting Doc Brown torque monster...get the biggest tires you can FIND.....with a 5 speed 2.73 1st gear will be nearly useless even with 335's....I can spin my 335's quite easily in 1st gear (2.64) with only 300whp....
My wheels are 18x10 9inch backspacking front (using double rack stops)....so anything between 255-295 fronts will work....the 18x12x8.25 backspacing rears will work with any rears from 305-345 wide...
I 2nd what 9281ndRC51 said.....the CCW wheels are truely custom....any width, diameter, offset you want.....It would be VERY easy to run 18x11 or 12's in the rear of a GTS by removing the 35mm spacer....I'm sure 315's would fit with ease....maybe as wide as a 335 with some fender rolling
Which brings us to how big of a tire do you need....since you are getting Doc Brown torque monster...get the biggest tires you can FIND.....with a 5 speed 2.73 1st gear will be nearly useless even with 335's....I can spin my 335's quite easily in 1st gear (2.64) with only 300whp....
My wheels are 18x10 9inch backspacking front (using double rack stops)....so anything between 255-295 fronts will work....the 18x12x8.25 backspacing rears will work with any rears from 305-345 wide...
09-09-2009, 09:21 PM
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Why spend any money on a compromised setup built for 997's or 996's when you can get something built that fits our cars perfectly? I vote you get a custom wheel. I like the CCW SP550's for a street car.
Simple 5-spoke, easy to clean, symmetrical, look similar to Cup I's, no 3-pc wheel bolts around the perimeter, cleaner than Fikses. I intensely dislike the full polish, so get them finished for painting and paint them German wheel silver. Plus the offset is completely custom so you don't have to run spacers. I'd run 9.5" fronts and 11" or 11.5" rears w/ 265's & 315's.
CCW SP550 wheels
Simple 5-spoke, easy to clean, symmetrical, look similar to Cup I's, no 3-pc wheel bolts around the perimeter, cleaner than Fikses. I intensely dislike the full polish, so get them finished for painting and paint them German wheel silver. Plus the offset is completely custom so you don't have to run spacers. I'd run 9.5" fronts and 11" or 11.5" rears w/ 265's & 315's.
CCW SP550 wheels
09-09-2009, 11:18 PM
#15
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Dennis-
Funny, I was poking around websites over lunch and came across the CCW site- of all the models I was drawn to the SP550's. That clean style is like the RS184's and the Ruf wheels. I wonder what they'd look like if silver anodized......
I'm still fantasizing (just fantasizing) about truly one-off 18" CS rims. Quite apart from being screwed when you bend your unobtainium rims, and given that I can't ever recall reading about someone having a single quartet of their own deign wheels being fed into a CNC machine, I assume this is absurdly $$$$$. Is it a $5K proposition? A $10K proposition? Mas? What is the economy of scale for 10 sets of custom rims? Anyone know aluminum wheel Econ 101?
Funny, I was poking around websites over lunch and came across the CCW site- of all the models I was drawn to the SP550's. That clean style is like the RS184's and the Ruf wheels. I wonder what they'd look like if silver anodized......
I'm still fantasizing (just fantasizing) about truly one-off 18" CS rims. Quite apart from being screwed when you bend your unobtainium rims, and given that I can't ever recall reading about someone having a single quartet of their own deign wheels being fed into a CNC machine, I assume this is absurdly $$$$$. Is it a $5K proposition? A $10K proposition? Mas? What is the economy of scale for 10 sets of custom rims? Anyone know aluminum wheel Econ 101?