jzaruby

Merry Christmas Everyone!

I have searched/read the many discussions about wheel spacers and there seems to be some conflicting posts, so I thought I would solicit input for my situation:
1998 C2S with OEM 17" Sport Classic
Front: 7.5 Jx 17 ET 55
Rear: 9J x 17 ET55 with a factory 31 mm spacer

I have a set of OEM 18" Sport Classic II's that I want to put on:
front: 7.5J x 18 ET50 (#993 362 134 55)
rear: 10J x 18 ET65 (#993 362 140 50)

Most posts agree that the fronts should simply swap out without any issues (inspite of the 5mm offset difference).

In terms of the rears, some suggest that I can simply swap them out (ET55 in a 9" rim to ET 65 with the 10" rim) with no need to change the 31mm OEM spacer. Other rennlist threads state that the 31mm spacer needs to be downsized to a 25mm spacer for proper fitment.

Any/all clarification on this would be greatly appreciated. Many Thanks!!

JimPA

I have a '98 C2S and have been using 18" Sport Classic II wheels with Michelin PS2 tires since I bought the car eight years ago. Fronts are 8J/ET 52 and rears are 10J/ET 65. I expect your fronts will be fine. I run a factory spacer on the rear to fill out the wheel well. I thought it measured 30mm but perhaps it is 31mm. There's no rubbing in the rear with 265/35 tires. If you want to email me, I can send a few pics.

jzaruby

Thanks! Out of interest, I thought the rear tire size was a 285/30/18? Why do you run 265/25's ?

JimPA

When I got the car, it had 265/35/18s on it. I've replaced them with the same size as needed because that size meets my needs and performs fine. Reasons for not moving to a 285/30/18 rear tire are:

1. The 265s are plenty wide for the way I use the car. The approx 0.75" extra section width of a 285 tire would be of marginal benefit to me.
2. The sidewall height of a 265/35 is already pretty low. I've killed two of them due to "road hazards" (running over small rocks on the road). A 285/30 sidewall is about 0.3" shorter, meaning ride quality will be poorer and tire or wheel damage more likely.
3. Pilot Sports are costly and the rears need more frequent replacement. The wider 285 is, of course, more expensive than the 265 tire.

YMMV.

vaujot

I think the answer to your initial question will depend on the wheel and tire combination you wish to use. I think the stock wheels for the turbo/4s where 10x18 ET 40 with 285/30 rear wheels. Your wheels are ET 65. Add a 31mm spacer and you end up at ET 34. Chances are that these extra 6mm of offset may cause clearance issues. I understand that there is a significant variance in tire widths between different manufacturers so it may even end up depending on the tire brand you chose. And you'll likely have less problems if you go for a 265/35 rear tire size, since those should be 2cm (one cm on each side) narrower.

Bill Verburg

w/
Front: 7.5 Jx 17 ET 55
Rear: 9J x 17 ET55 with a factory 31 mm spacer
the factory says that you may use a 5mm spacer(996 361 605 90) in front and that you must use a 31mm spacer(996 361 631 00) in back. The 5mm spacer changes the front ET from 55 to 50, the 31mm spacer changes the rear ET from 55 to 24.

w/
front: 7.5J x 18 ET50 (#993 362 134 55)
rear: 10J x 18 ET65 (#993 362 140 50)
to get a factory fit you do not use spacers in front, in back the 10ET65 needs a 25mm spacer(996 361 625 00)

the more usual front fitment is 8" ET50 or 52, in back 10"ET40 is the fitment w/o spacers

factory tire fitments on the 8/10 setup was 225/40 ZR 18 & 285/35 ZR 18 Continental SportContact 2 N2 and Michelin Pilot Sport N0

Bill Verburg

for those of you that asked about this, It came from,
'Service Technical Bulletins, This bulletins replaces bulletin Group 4,# 4/97, dated 8-21-98.'

I am sure that it is a typo, but I just copied it w/o reading.

I believe that it should be 285/30 not 285/35

also 'bulletins' should probably be singular.

Oh those factory eds.

jzaruby

Bill - when I saw your original post I did a search and came across a Porsche technical Bulletin( 4-4440 2-1998) that outlines approved winter tires for 993's and they list 265/35/18's as an approved winter tire size. So it woudl seem that perhaps a 35 ratio tire for a C2S is not out of the realm of acceptable.

Bill Verburg

yes 265/35 and 280/30 can both be fitted to n/b and w/b.

I just posted the TSB specs for oem normal fitment aka summer tires.

winter tires are generally a little narrower and a little taller and the factory specs additional room for chains.

JimPA

In line with Bill's post about narrower and taller for winter, I run Dunlop SP Winter Sport 3D tires on 17" aftermarket turbo twists (no spacers on the rear for this setup):

Front 7.5J x 17 ET52 wheel with 205/50 x 17 tire
Rear 9J x 17 ET15 wheel with 245/40 x 17 tire

These just replaced a nine year old set of Michelin Alpin tires. The Alpin fronts were the same size but Michelin no longer makes the worn out 255/40 that was on the rear.