Gary Knox

All you hot shoe racers - I have a question about the use of these tires/wheels on the front of my 928 S4 for DE track driving. I'm an "old" (73) driver who enjoys driving in the white group at Porsche DE events.

I've been driving on street tires ever since I started doing this about 6 years ago. I have been using Michelin PS2 tires on front and rear (R was 10" X 18 Sport design 2 pc wheel with 295/30 tires, F was 7.5" X 18" Sport Design 2 pc with 255/35 tires).

I recently acquired a set of 18" hollow spoke wheels (8" and 10") and am currently using Michelin Pilot Sport Cup tires (295 R, 225/40 F) on them. They are about worn out, and I plan to convert to Hoosiers. A friend has a set of 295/35 and 255/35 Hoosiers with about 3/32nds tread depth. I know Hoosier recommends a minimum of 8.5" for this tire, but am wondering what "you'all" think of using them on an 8" for moderate track driving in a stock 928. (e.g. Watkins Glen lap of ~2 min, 25 sec plus or minus).

Assuming the fronts aren't right, I'd try to find a set of 245/35 fronts. But - the 928 is a bit heavy in the front (compared to the various models of the 911), and I like a larger tire up there.

Thanks for any suggestions comments.

Gary Knox

SG_M3

The 255/35 R6 is way too big for a 8" wheel. I had them on a 9" wheel and it would be the minimum width I would use. They still felt sloppy. The tire actually measures a 270/30, keep that in mind.

Brian A.

I wouldn't go more than 245s on 8"

mark kibort

255 on an 8 is pushing it. actually, i ran 245x45s on a 7.5, and didnt go the 40 series, because we needed the sidewall to help with the fit. with an 8, it would have been perfect, as the car COMES with 245s on an 8 (225s front/245 rears if I rememeber correctly. Ill check). so, its not bad, but its not great. 275s on a 9.5" is a perfect fit and you can run up to 285s very easily, so I would think 255s on an 8 is in that same fit range, but pushing it just a bit.

(just as 305s on an 11 is perfect and a 335s on an 11 is pushing the envelope)

U4EEAH

8" in wheels really don't like more than 225's. 245's 8.5". 255's 9". The wider tire does no good if the edges are not planted on the ground

roberga

^ what he said.

mikew968

i had 255's on 8.5" wheels and the sides were "rounded" not flat like they should have been. You can probably do it but it will not perform as well as with wider wheels.

mark kibort

I did it and it was much better, even though the sides were a little rounded. even did the 275 on the 9" for rears with the 245x45s on the front 7.5s which were a stretch. It was still better than the 225 , and 235 i had before up front and much better in the rear than the 255s.

To your point, i did the 335 on the rear on a 11, which really should only be a 305, 325, and it didnt make any difference, because the sides were rounded and the tires were near the same size anyway.
Porsche STOCK rear rim sizing on a 8" rim was a 245 from the factory, so I would say that would be just fine.

Gary Knox

Many Thanks to all you who replied to my question. I found them helpful - now I've just got to make the right decision!!

Cheers,

Gary Knox

Glen

Mount em up and go drive. Cheap rubber is cheap rubber. Been racing on dumpster slicks a long time. Been flipping slicks a long time that you aren't supposed to flip, we run them forwards, backward, sideways, upside down, etc...
warning, don't take my advice, I'm an idiot...!

IcemanG17

Gary
One consideration is if you drive to and from the track..IF you do then I would stay away from Hoosiers, BFG R1 or Kumho V710...since those are just about true slicks....

I run 245/45-16 BFG R1's on S4 rear 8" rims all around on the estate and it works GREAT...sure bigger tires should be faster..but I am very happy with the grip of the little tires & their cost is far less too!!

Using the standard .86 wheel-tire ratio a 255 tire on a 8" (203.2mm) rim puts you at .796...so a bit under

Gary R.

+1, especially the last part...
We run 275's on 9" wheels, 245's on 8" wheels all the time..

Z-man

+1 - I've been running 245-45/16's on my 8Jx16 wheels for quite some time now, and never had any issues.

-Z-man.

mark kibort

again,since that was stock from the factory from porsche, it cant be all that bad. So, going one size larger wont be a big deal.

(i.e. 225 fronts on 7s and 245s on rears on 8s for the 928 S4 in 1987)
1987 Porsche 928 S4 Specifications - Specs

price $58 900 usd
engine V8
valvetrain DOHC 4 valves / cyl
displacement 4957 cc / 302.5 cu in
bore 100.0 mm / 3.94 in
stroke 78.9 mm / 3.11 in
compression 10.0:1
power 235.6 kw / 315.9 bhp @ 6000 rpm
hp per litre 63.73 bhp per litre
bhp/weight
torque 429.8 nm / 317.0 ft lbs @ 3000 rpm
drive wheels Front Engine / RWD
body / frame Unit Steel
front brakes Vented Discs w/ Vacuum Assist
f brake size 305 mm / 12.0 in
r brake size 300 mm / 11.8 in
front wheels F 40.6 x 17.8 cm / 16.0 x 7.0 in
rear wheels R 40.6 x 20.3 cm / 16.0 x 8.0 in
front tire size 225/50VR-16
rear tire size 245/45VR-16




mk

Glen

Worst case is the 255's mounted on 8's looks alot like Brian A's avatar above....bound to increase performance...