Tire question -- 17" wheels...HELP!!
 

After a lot of research (and I posted my findings here) I decided and ordered a set of Fikse (Fuchs) for my 1987 930: 17 X 9 and 17 X 11. And I plan on keeping the 28mm rear spacers, the fenders are not rolled or trimmed, stock steering ratio, and street alignment.

I am thinking of the following which gives me a 1" rake, and need advice please:):
Front: 245/40X17 (24.7")
Rear: 315/35X17 (25.7")

Any idea on tires, since it seems impossible to find a matched set for the street! :(

TIA!

Yep - they will work - but, a couple of notes....

Fronts - if your 930 is lowered, you *might* have a bit of rubbing of the right front wheel against the support bracket when the wheel is turned to the left about one rotation short of lock.. It is easily remedied by taking about 1/4" off the support... Other than that, the 245/40x17s should work fine (AGAIN, however - every tire has a slightly different profile - and I'm running the Kumho Ecsta XS' on 17x8.5" Fiske rims in the front)...

The 315s will fit at stock ride height - BUT - given the 1 to 1.5 degree rake of the normal suspension with the addition of an extra inch of tire height - you may have to lower the rear suspension 2.5 to 3 degrees to maintain the "stock" rake. Otherwise, the rear will appear unusually high... Again - I was running them on Fiske 17x11" rims using the factory offset.

Anyway - yes - the combination will fit without rubbing - or did in my case...

I've got 17" Fuchs (modified) 3 piece wheels with Sumitomos.
Mine are: CMW Racing Fuchs 3 Piece wheels-Tires 315/35ZR17 and 245/45ZR17
I am very happy with the grip and handling. I'm not a "ragged edge" type driver but enjoy a little spirited driving occasionally. In that role the Sumitomos fit the bill well.

^Thank you!
245/45/17 fit OK? I was a bit worried about fit and so I was opting for the 245/40s...Your choice makes both the front and rear heights exactly the same which is nice! Any possibility of posting a side view of the car please?

TIA!

The 45s fit well even with the fact my car is lowered.

If you guys go back to the original 165 or 185/70 tire that Porsche used on the early 911s you get a tire height and what is interesting is all we have done is basically move from 14 to 15 to 16, 17 to 18 to 19 and the height has remained almost the same. 225/40 /18 the Porsche used on the 965 cars was usually 25" or 25.1 -- so I usually work off that range. jim

+++Thanks folks! +++

Rear I am going with 315/35X17...

I am probably over thinking this, but on the front I am now leaning towards either the 235/45X17 or the 245/45X17...not sure, just worried about clearance at full lock and jounce. (I definitely decided against the 245/40X17 since the 1" rake is too much.)

The only match set brand out there are Sumitomos (HTR Z) which will be a first for me. But the reviews appear to be OK.

Pix will follow in a few weeks...it takes 4 weeks for the wheels.

Try the Vredstien brand tires. I'm running 245/35/17 & 315/40/17 on my 87. They are replacing Summitotos, and they are much superior in the traction dept. Philip

Ugh - I hate mobile app...where's the darn delete post button?

To those that are running with 245/315 combination - I'd like to know your thoughts as to why this choice .


Perhaps I'm more an exception than the norm, but being in 400 hp range & 2700 lbs I found them overkill for the street. For my setup 285 on 10" provides best response & balance (w/ 245 on 8-9" in front). For me it proved quicker, no wheel spin - acceleration traction is xlnt & no excessive understeer to dial out. Theoretically they should provide more braking traction but I didn't notice any difference at all with stock brake bias & lateral traction was not balanced as well as I've found with 245 fronts (note: I have adj sways & Elephant Racing plates). IMHO 275 fronts are better match but that's a track setup not particularly street use friendly.

BTW - I'm using Goodyear Eagle F1 GS-D3 rubber.

Don't mean to hijack thread, thinking this furthers discussion as I'm thankful for all the tech sharing here!

^ good information IMO!
My intention is pure looks on a mostly stock car, just slightly lowered. I am just looking to go as wide as I can go without rolling fenders/trimming fenders, etc.

And it seems like a 315/35 ZR17 is the "right" size for that -- 25.7" height
On the front, I am worried more about rubbing at full wheel cut and jounce, and so I am thinking 235/45 ZR17 -- 25.3" height (or maybe 245/45 for a 25.7" height)

I have a feeling that my setup with stock alignment will be a setup for mostly understeer? TBD. Once I get it up and running I will report back.

Yes although adjustable sway bars will help tremendously.
Also add front cross bracing/bar with upper shock bearing type mounts.
Then it's upgrade spring rates & shock valving.
=
Dramatic handling improvement.

Also remember, if go any more than "slightly lowered" on the setup be sure to get the bump steer correct.

Great information and will do...As soon as I get her back on the road soon!

I just ordered tires and continue to (un)patiently wait for the Fikse (Fuchs) to arrive...one or two more weeks of waiting as this is a 4-5 weeks lead time.
The fellow at TireRack highly recommended Kumho Ecsta XS, and since I drive this beast sparingly and in dry weather only I agreed...
I ordered 315X35/17 and 235X45/17.

Tires are here! :)
 

315/35X17 and 235/45X17...now we wait (some more) for the Fikse (Fuchs)...

Nice!