RKD in OKC

Okay so I found these 2 pc wheels I really really like, BUT... They are 18x9et50 and 18x10.5et44 and would stick out way more than I want to try to deal with fender wise.

Getting a great deal on these rims and since they are 2pc I can have them re-barrelled. The best re-barrel deal is on 18x8 and 18x10 what are the optimum offsets of 8s and 10s. My Carrera IIIs are 18x8et57 and 18x10et58.

Photoshopped fitmet...



After I get these wheels on I will have a set of Carrera IIIs available for sale.

Ladybug83

Those look really nice

jcorenman

Richard, you are correct that ET50 in the front will stick out too far. If you are happy with the ET57 of the Cararra-III then I would stick close to that, in the 55-60 mm range. The "magic number" is 55mm, that is the offset for a neutral steering axis (assuming a 25" diameter tire). A larger wheel offset e.g. ET57 is a positive steering-axis offset which is good.

What size tires? What is the OD?

Cheers, Jim

RKD in OKC

Stock 225/45/17 is 25"
225/40/18 gets me 25.1"
235/40/18 gets me 25.4"

Vilhuer

It can be difficult to find 8" wide rims which have large enough ET. You might have to accept 50ish instead of 55+.

77tony

For the GTS, Fikse recommended, fronts: 18 x 8.5 57mm, rears: 18 x 11 64mm. T

Gary Knox

Three 'wider than GTS' rims (17 X 7.5 et 65) produced by Porsche are good for the front of a 928. They are:

17 X 8 et 70 Cup II wheels (original equipment rear winter wheels on SOME 911's) These are excellent, as they keep the centerline of the tire in exactly the same place as the OE GTS fronts - scrub radius unchanged.

17 X 9 et 70 Cup II wheels (Very rare, only 3 sets in the US that I know of, all imported from Germany within the past 3 years or so).

AND for 18" rims, you can combine a set of Boxster 2 piece wheels - either Sport Design or Classic Design. Use the front spider from the 7.5" fronts and the barrel from 9" rear wheels and you have an 18 X 9 et 69 wheel. You can use 255/35 X 18 tires nicely with no rubbing (well, at complete full lock in a slow turn on the driveway, you might have a little bit of touching on the inner edge of the outside tire). There are about 3-4 of us in the world who have these 'custom built' OE Porsche wheels, combined with 10" et55 rears from a 911 (295/30 X 18 works great there).

Anyone interested in a set of Sport Design (10 spokes) can contact me, as I have a set that can be made up for the front of a 928. I also have one pair of the 8" et 70 Cup II that are available (one refinished, the other one can be refinished for a concours set - now tentatively sold.).

Gary Knox

Vilhuer

They probably can't make larger ET 8.5" wide wheels using stock stuff they normally put their wheels together. For 8.5" ideal would be closer to 67mm.

Rob Edwards

FWIW, the Kinesis wheels on the Zombie are 18x11 ET 63.5 in front, 18x11 ET70 in back. It uses the stock GTS spacer on the back. I have 295-30R18s on them right now.

I also have 295-30-18's on 18x10 ET58 Cup 4's on my street GTS with GTS rear spacers, they fit fine. 235-40-18's on 18 x 8 ET 54's in front. The fronts rub a tiny bit on the inside at full lock when traversing the gutter, but otherwise are fine wrt to the (rolled) fender lips.

Here are the measurements on fhe Kinesis wheels:

Offset = ((Rim width /2) - backspacing)

RKD in OKC

The bottom half of the pictures above are Carrera IIIs, 18x8et57 with 235-40s in front and 18x10et58 with GTS spacers and 295-30s on the rear. with no rubbing Sounds like those are the offsets I should shoot for with 8 and 10 inch rims.

Pretty sure trying to go with something wider than 8s and 10s is going to cost a LOT more as the company that does the re-barrelling gave me the quote based on having 8 and 10 2pc shells in stock. And the centers were not compatible with going to a 3 piece wheel which would open up the width and offset possibilities.

Courtshark

Can GTS's use wide-body wheels, ala 911 Turbo wheels? The rear spacer is 38mm on each side, taking that 58mm offset down to 20mm. Lots of room with which to work minus the spacer, or using a smaller one.

Hilton

Yes, there's a widebody version of the Carrerra III's, with an 18x11 ET51 rear, which fits GTS's nicely.

Malcolm had a thread about them a few months back on his GTS.

RKD in OKC

The wheels made it to the shop that's going to re-barrel them...

Have a DEVEK front Sway bar, that kinda limits how wide of a tire I can put up there before I get rubbing on turns. a 235 on the 18x8et57 are at the limit. So still leaning towards the 18x8et57 and 18x10et58 like the Csrrera IIIs on the car now. Think that will make the wheels very re-sellable also since those offsets will fit almost any Porsche that is not a wide body.

Wheel guy says he needs to make a 2 piece barrel by welding together 3 piece, and they will be lighter than 2 piece. Says he will contact me when he figures out what the offset range and widths he can make for me from the centers.

RKD in OKC

Turned out re-barreling the wheels was a good thing. On two of the wheels whomever refinished them messed them up. About half the bolts were cracked where the thread starts and way to many of those left had been replaced by just gluing in screws that looked the same as the bolts. Would hate to think what would have happened at speed if one of those wheels had come apart!

the flyin' scotsman

The widebody Carrera III rear wheels do fit nicely but the stock 38mm spacer has to be changed.

The thread Hilton mentions concluded 17mm would be ideal but that size is not readily available so I took Chucks advice and sourced 15mm spacers that fit with the long stock studs.