rj777

Hey guys, I'm still loving my '88 S4.

My rear tires are getting pretty shot up and I just noticed that I picked up a nail in the left rear (although the loyal tire still takes and holds 44 lbs of air ), but I don't want to mess around any longer, and I'm ready to order new tires.

I have 17 x 7.5 Cup II wheels, (supplied with the car by the previous owner), and pictured below, and the front wheels were fitted with 235/45/17 Yokohama Avid H4S all season tires. (The rears with 255/40/17).

I want to stay with all season tires because I drive my car all year round (made possible with the generally cool rainy weather we get in the winters here in the mid-south). But, I am noticing on Tirerack that 235-width tires aren't offered at all in the 'all season' tire types.

In your experience, are the 225-width tires sufficiently wide enough to fit over 7.5 inch wheels? I'm thinking 'yes', but just wanted to get your feedback.



Many thanks,

Rick

Rob Edwards

225's were what was on those wheels from the factory, so Porsche thought so.

In the Landshark.oz 928 wheel writeup (http://www.landsharkoz.com/forms/928wheels.pdf), they mention Marc Thomas' rule of thumb that for tires of X width, you want wheels that measure 0.85 to 1.15X. So for 225's (8.85"), you can use 7.5 to 10" wheels safely. (Not that anyone's going to put such a relatively narrow tire on 10" rim...)

rj777

Good stuff, Rob. Thanks for confirming.

Regards, -rick.

Randy V

While 225s will work, they will look very whimpy.

That gap between the outer tire and the fender will be even more pronounced - take a look at that pic and you can see that it's pretty gappy already.

If you are set on using such a skinny rear tire you should consider adding wheel spacers.

rj777

Lol, the 225s will be going on the front wheels, Randy. I have 255s currently on the 9inch rear wheels. Maybe I can go with 265s to fill out the space a bit.

Regards, -rick

Randy V

Ah, my mistake - that makes sense.

But - going with a 265 rear and 225 front will only increase understeer.

AdaptecSpeedware

as it sits the rear looks like it needs spacers in a bad way.

Alan

You shoud be able to go the 275's (but no wider) on a 9" with the right spacer.

Alan

Randy V

I'm guessing he searches the forums for 'wheel spacers'.

928man

I have 225/50/16 tires on 9.5 inch BBS Wheels, and they look good on the rear, but what is a larger width tire that would fit on the BBS Rims?

Rob Edwards

I have 295's on 10" wheels on my GTS (just barely violating the rule of thumb I posted above) but you could certainly get 275's on a 9.5" wheel, as long as the offset is in the ballpark for use on the rear of a 928. Offsets are a whole 'nuther subject, tho.

rj777

Guys, the photo I posted is slightly misleading because the zoom lens tends to compress the image a bit. Honestly, in person, the rear wheels are not 'set in' that far. On the older cars (including mine) there is a fender overhang that covers up the top of the tire. I placed my finger in there, and there is barely a half-inch (if that much) of space between the fender overhang and the sidewall.

The offset on my rear Cup II wheels is 55. I don't know if the wheels are 928-specific Cup wheels, or if they were sourced from another car, but I'm just not realistically seeing any additional usable space here. I don't see how spacers are possible on cars with these fender overhangs.

I just took a quick look at Wilhoit's site, and I note on three GTS models currently listed for sale, that this overhang is removed on the later cars.

All kidding aside, , unless it's going to result in substantially improved handling, I'll probably keep things the way they are and go with 225/45 & 255/40 sizes for my next set of tires.

Constructive follow-up responses are welcomed.

Jerry Feather

My rule of thumb is to add "about" one inch to the width of the rim and then convert to MM. In this case that results in tires about 215 wide, so I would go with the 225's. On all of my S4's I use these wheels, or ones of the same size and offset and put 225 45 17 on the front and 255 40 17 on the rear. I too have just about the same limited clearance between the tires and fenders, front and rear. I don't have any room for spacers.

Jerry Feather

Jerry Feather

By the way, when I was running 40 pounds of pressure I tended to wear the middle of the tread out. Without noticeing it once I wore a rear tire down to the air and had to limp home 65 miles on the spare. Now I run about 34 psi all around. JF

mark kibort

I was REAL happy when my 84 was a street DE car, with 245-45-17s on the 7.5s and 275s in the rear on 9s it handled much better, and certainly was safe. 225 was WAY too small for the look i wanted and handling was worse . 235s were an improvment, but the 245s seemed to work well.