[ira968]

I have seen a couple mentions on various forums of running 9" x 17" ET55 OEM wheels with 255 40s on all four corners. First question, does this wheel tire size work on the front of a std. ride height car? Is more camber needed? or other mods? Do you have a recommended Alignment spec? And any feedback on handling characteristics is appreciated. Thanks!

Partial Post: Please Login or Register to read the full post.

[Georges]

I've got the 16" wheels all the way around 245/45/16. This is for autox. The handling is much better and I'm cutting 2-3 seconds off my time. The car is completely neutral now. No understeer and I can initiate oversteer when I want. I did not change any of the camber settings etc and am very happy with the setup.

Partial Post: Please Login or Register to read the full post.

[rxter]

Do the diff tire sizes fit on the same rims (are the stock rims on my car the same size front and rear)?



If the car handles better with the same size on all 4 then why would anyone in their right mind use a staggered set up? Can't rotate the tires and your forced into buying sets out of sync and likely just generally more often. Makes no sense. Marketing?

Partial Post: Please Login or Register to read the full post.

[Anchorman]

From what I understand (but I'm sure there are others with more Porsche knowledge that may have better insights), the staggered tire sizes were derived from this necessary setup on the 911 - and was carried to the 968 (and, I assume, the 924/944) as "tradition".

Partial Post: Please Login or Register to read the full post.

[968crazy]

I've run 245/45/16's all the way around, also 275/40/17's all around, and 275/40/17 front and 295/35/17 rear. On my car the 17's are way faster than the 16's and the staggered setup is slightly better than the 275's all around. The biggest advantage too the same size tires is obviously less money and able to rotate tires. All this was BS SCCA autocrossing when I tested all these setups, but I have never tried the rear wheels on the front I think something would probably rub.

Partial Post: Please Login or Register to read the full post.

[Ryan]

I saw a picture of a 968 for sale that had the rims backwards. Some non P-car dealer that didn't know the difference and rotated the tires. It looked weird, but looked like it would work.



The 911 started with wheels the same size front and rear and changed in order to tame the snap oversteer that the cars were famous for. That did not solve the problem, but it helped. I think they may have carried it through the lineup as a safety thing as it does induce understeer.

Partial Post: Please Login or Register to read the full post.

[flash]

not sure if a 55mm offset will work up front - i have a 9" rim up front with a 57mm offset - this is pushed as far to the outside as possible, and as it is, hits the bra when turning at my ride height - another 2mm out and it would be a mess



at stock ride height, especially if you choose a brand of tire that tends to run narrow in that size, might work - but if you choose one like the bridgestone that is wide in that size, and lower your car, i think you will run into problems



i'll let you know though - i am thinking about doing a set of 17s for a set of track wheels, and they would probably be 9 all around at about that offset

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

I have had 17x7 et55 up front no problem, as shown in the pic. There was enough clearance for at least an 8" wide front with an et of 55.



[quote name='flash' post='57594' date='Aug 8 2008, 01:45 PM']not sure if a 55mm offset will work up front - i have a 9" rim up front with a 57mm offset - this is pushed as far to the outside as possible, and as it is, hits the bra when turning at my ride height - another 2mm out and it would be a mess



at stock ride height, especially if you choose a brand of tire that tends to run narrow in that size, might work - but if you choose one like the bridgestone that is wide in that size, and lower your car, i think you will run into problems



i'll let you know though - i am thinking about doing a set of 17s for a set of track wheels, and they would probably be 9 all around at about that offset[/quote]

I have a pair of 17x9's with 255 et55 I could throw and see what kind of clearance there is.

Partial Post: Please Login or Register to read the full post.

[flash]

go for it - it's gonna be close, but like said, at the right height, with the right tire, it could be ok



tough on the spindles, suspension, and all that, but maybe ok on fitment



lol - i know from experience that 52mm offset does not work on a 9 with a 255/40 S0-3

Partial Post: Please Login or Register to read the full post.

[ira968]

I got the front 9" 55 offset 17" OEM twist wheel "cup 3" wiith Falken ST 615 Azenis 255 40 17 tire on the front and there are no clearance issues with fenders and inner fenders. My ride height is factory with -2 camber. The only issue may be with the inside wheel rim to spring clearance -- it is very close like 2-3 mm. This may never rub but I don't know if I want to risk the damage if it does. I can change the camber or use a wheel spacer to add another 3-5mm. If I go with a small spacer do I need to do longer lugs? I plan to go to steel nuts.

By the way this wheel tire combo is 1.5 Lbs. lighter than the front factory 7.5" inch cup 1 wheel if it had a Brigestone 225 45 on it. Its 5 Lbs lighter than the rear 9" cup 1 with the same tire -- just 45 Lbs.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Interesting discussion. So, is there a verdict? Does anybody know why Porsche decided to put wider wheels/tires on the back of a modestly powered car with 50/50 weight distribution? Running the same size all around seems to make a lot of sense for several reasons. But then again, it seems that a lot of manufacturers (Corvette, RX7 twin turbo, and many others, I'm sure) do the same thing as Porsche did with the 968.

Partial Post: Please Login or Register to read the full post.

[flash]

cosmetics - the 911 was that way for a long time, and porsche did not want to depart from their position - some will say it was to induce oversteer, but that is a hard way to go about it - the real problem is the load on the hub and spindle - a rim much larger than oem will overload that under hard use, and ultimately cause it to fail - that is why the M030 setup is beefier

Partial Post: Please Login or Register to read the full post.

[rxter]

So If I don't mind looking like I'm afraid to drive a manly car with fat tires in the back I would use fronts for both then, right?



   



Frankly I'm not sure that I am all that comfortable with my feminine side. I'm already running stock 16s, so going skinny is just asking for abuse.

Partial Post: Please Login or Register to read the full post.

[flash]

there are guys successfully running the same size 16s all around

Partial Post: Please Login or Register to read the full post.

[ira968]

Got my wheel project finished with the 17x9" turbo twists and 255-40 Azenis 615s on all four corners. Have front at -1 camber and rear at -1.5. What a DIFFERENCE. Car is finally neutral. Went autocrossing and found it nearly impossible to make the car understeer (no squealing tires). It really turns in great now. And it brakes extremely better. It was easy to induce oversteer and in the S's it behaved great. Porsche must have put those skinny tires on the front simply to induce oversteer which makes the car safer but its way more than anyone who has decent driving skills needs. AND you can rotate all four wheels!

Partial Post: Please Login or Register to read the full post.

[flash]

i think you meant to say they put the skinny ones up front to induce understeer, which would indeed be the "safer" choice



anyway, glad it worked out - i am probably not far behind doing this myself

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

Keep an eye on your castor blocks, with the added traction and leverage.

If they have never been replaced, this my accelerate wear in the bushing.

Partial Post: Please Login or Register to read the full post.

[wjk_glynn]

[quote name='rxter' post='57546' date='Aug 7 2008, 04:52 PM']...If the car handles better with the same size on all 4 then why would anyone in their right mind use a staggered set up?[/quote]



[quote name='Cloud9...68' post='58149' date='Aug 20 2008, 06:23 PM']...Does anybody know why Porsche decided to put wider wheels/tires on the back of a modestly powered car with 50/50 weight distribution? ...it seems that a lot of manufacturers (Corvette, RX7 twin turbo, and many others, I'm sure) do the same thing as Porsche did with the 968.[/quote]



Because:



[quote name='ira968' post='62763' date='Nov 6 2008, 10:08 AM']...Porsche must have put those skinny tires on the front simply to induce oversteer which makes the car safer...[/quote]



Though I'm guessing ira968 meant to say "induce understeer"...



While enthuasists like Georges, 968crazy and ira968 want and like a neutral handling car, no car maker (Porsche included) can take the liability risk of being accused of making an unsafe car. So they build in a decent amount of margin by making a car that understeers. If I were in their position, I'd do the same thing.



Now with the arrival of quite sophisticated stability handling systems, manufacturers can build (if they so chose) cars that are inherently more square and use software to keep customers out of trouble.



Karl.

Partial Post: Please Login or Register to read the full post.