im just wondering whats the widest rim and tire you can fit on the 928 and thats not a GTS. Im planning on selling my rivas after having them for a couple of months. I didnt realize when i bought them that everyone and there mother has them. I also dont plan on rolling or cutting fender lip.

Lou
83 928 5speed

 

295 on a 10 x18 fits the rear.......... but tires vary from manufacturer to manufacturer

 

i was wondering the same thing! i do plan to purchase a set of 18" rims for my 88se and would be happy with 9" front and 10-11" rear.

lagavulin has a nice set of 18" HRE wheels 9"front and 10"rear all made to his specs. i think ive read that 11" is max that can be fitted to the rear depending on offset and fender lip rolled vs non rolled. not sure what the max front size would be, where i think offset is more critical.

 

I've answered this question many times. Given the implications of the most accurate answer...there is often "resistance." Why? Mostly it means that all the "cheap" Porsche wheels don't meet this criteria. So what's the widest wheel and tire that fits? I'll use the S4 and newer cars as an example...they have more clearance with the front suspension, because the upper a-arm is different. I published...way back in the '91 Porsche Panorama. the widest front wheel being a 9.5" with a 68 mm offset. It's that big offset that's the challenge. There was lots of whining about it, which can happen when you tell somebody something they don't want to hear. And? Shortly after this, the Porsche factory came out with their data for the (German Porsche Club) 928 GT CUP. Guess what front wheel they recommended? 9.5" by 68 mm offset. The same, right down to the mm. You would think that having them "agree" would settle all this! But it doesn't seem to. Why? Mostly it means three piece wheels are what you "gotta step up to the bar" for...not cheap. Later I did a wheels and tires story, I recommended that 9.5 width/68 offset front, in an 18" and a 10 x 18 rear, 60 offset. You'd use a 255/35 or 265/35 front tire...both will be near the original 25" Porsche height (check those 225/50/16 and 245/45/16's...you'll see) and a 285/30 rear tire. You can squeeze on an 11" and a 295/30 tire on the rear, if you really want to push the envelope. That Porsche tire height is lots shorter than average, so you really gotta watch it. Oh, if you put on a taller tire, you get the tread area closer to the (outer) front fender lip...which you certainly don't want...plus there are the classic gearing and center-of-gravity (cornering) issues. I wish there were less expensive WIDE wheels, with the proper offsets, for installing maximum width tires on the 928...but, so far, I haven't seen any cheap wheels with these specs. Please let me know if you do! I often get this kind of inquiry: "hey I just got a good deal on a set of used "xxx" Porsche wheels for my 928, what kind of spacers do I need?" I have to ask: "How good are you at spacing IN?" Because the 928 uses a superior double a-arm suspension design, we have more clearance on the inside than the "strut" suspension Porsches....which are all the rest...911/914/944/968, etc. This is why when we want to go wider...we go IN (more offset) and they go OUT (less offset.) Leaving us with mostly "null set" in using wheels from other Porsche models, when you're trying maximize width...certainly an understandable goal! Warning: many manufacturers just copy the fitment charts of others...I often find they haven't actually done a full 928 evaluation. This little detail may not stop them from trying to sell you a set of wheels? I won't go thru the agony it took me to "learn" all this. The school of hard knocks is an effective teacher though. I hope that answers your question....and spares you the agony of some of the misinformation out there, and (maybe expensively) repeating some previous mistakes... Kim

 

Good info!

 

Ive got them but cant convince my mom to get them yet.

I know of MAYBE 5 cars that have them? Bill here in Vegas, whose car I saw at SITM 3yrs ago with the "I gotta have those" wheels. ME, I got the wheels the following summer. . I saw another car at the Frenzy 2 yrs ago that had them....then Chris Lockhart.... then you.
IMHO they look great, throw the Porsche center caps on them and it completes them. but my next set will probably....make that DEFINITELY be a set of custom FIKSEs or perhaps KINESIS in 17" or 18". I want a lighter wheel.

 

Tony;

I have 'em. They're sitting in boxes in the corner.

Does that count??

Scott
18" Rivas
18" SSR GT3
18" Moda R6's
some 17" stuff also...

 

Cool!

Could you do a favor and weigh them ? AS well as the SSR GT3's..i love those as well

Just curious. Mine came mounted with rubber.

 

I think the specs state that the Fikse's weigh in at 19 lbs unshodded.

I didn't weigh mine before mounting....but are they light!

 

right now im running 18x9.5 on the rear with a 285/30 tire. With a simple measurement on the rear from inside of tire to inner well it seems i have about 1.75 inches.So im possible thinking a 10.5 to 11 inch rim might fit with worst case scenerio fender lip and to fit a 305/30/18.What do you think?

Lou
83 928 5speed

 

kim,

i know that 9.5" on the front would be adequate for my needs and 10" on the rear probably. if i went to 10.5 or 11" on the rear would you recommend a different offset?

 

@ all,
See this link: http://www.landsharkoz.com/forms/928wheels.pdf

 

EriK
Lots of good info there, but some duff also Re. scrub radius ?
see below from UK list.

Looking at the Workshop Manual, page 44-01 1986 gives the offset of 7" front
wheels as 65mm (except for Club Sport at 60mm).
But, page 40-04 shows the scrub radius as -10.2 not -18 as quoted below.

This means that the CS will have SR of -5.2.

The CS could well be set up for easier turning/less straight line stability,
so the comment that a small SR reduces self-centring still makes sense.

But, I have searched a few web-sites, and they all say that positive SR is
good for stability.

I have never tried changing my front offsets, so have no experience of the
change in feel, but I am reluctant to believe Mr. Cumming when his standard
figure differs from the WM.

I'm confused.

Smiffy

 

right now this is my wheel set up:
Front---225/40/18 Tire 18x8 Rim 47mm offset
Rear---285/30/18 tire 18x9.5 Rim 53mm offset

Lou
83 928 5speed

 

smiffy,

i have an se with the forged wheels and 60mm front offsets and straightline stability is fine. i read kims post where he recommends an offset of 68mm to fit 9.5 " rims and because i dont fully understand these things the question naturaly springs to mind of what effect a 60mm offset will have on maximum rim size, does it increase or decrease?