jet911

Was wondering if anyone could shed some light on how to determine what size my wheels are with the tires on the wheels.

Currently on my '86 911 coupe (bought two years ago), I'm running Fuchs on all four. The front tire size is 205/55/16 and the rear are 245/45/16. The fronts appear to be the 6" Factory original wheels. The rear wheels are the question. In order to run the 245's would they need to be 8" wheels? Is the size stamped on the wheel somewhere?

I'm looking to purchase new rear tires and have not quite decided if I want to stay with the 245s or drop back to the 225/55s that were standard. The 245s make the car look more aggresive with the whale tail, but would I get nearly as good of grip, handling and a better ride with the 225s? I don't autocross anymore and use my 911 for weekend trips and fun only. Once in a while I drive her to work.

Suggestions?

Regards,
Jim
'86 911

Jim Michaels

With Fuch I think you'll have to look on the back side of the rim to find the width and offset numbers. Rim size will be shown after a "J." Offset will be shown after an "ET." With some of the newer alum alloy rims the width and offset numbers are "stamped" (molded) right next to the valve stem.

The usual combo tire sizes for that era seem to be either 205s with 225s, or 225s with 245s. The narrower setup is usually on 6 and 7" rims, and the wider setup on 7 or 8" (front) and 8 or 9" (rear) rims. Without any notion of tracking or autocrossing, I think I would retire with tire widths considered optimal for whatever rim widths you have. If your Fuchs are 6 and 7" wide, then I think 205s and 225s would be a proper fit. If you had 7s and 8s, then you could consider 225s and 245s. I still use the OE rims and tire sizes for the street (where they seem quite sufficient), but wider rims and tires for track.

jet911

Thanks Jim,
I'll take a look a the back side of the wheels to determine size. Appreciate your input.

Regards,
Jim
'86 911

Richard Bernau

Small point, if you run a 225, then it should be a 50 profile not a 55 profile. The OE sizes for 16 inch rims are 205/55 and 225/50 - right thru to 1989 even when the rear rim width increased from 7 inches to 8. It is however, perfectly possible and acceptable to run a 245/45 on an 8 inch rim should you prefer. IMHO this is too much rear tyre and not enough front (certainly for DEs) but it seems to work for some people.

Richard

jet911

Thanks Richard,
The point you brought up is exactly what I was considering. After checking this weekend to see what size wheels I have on the back (currently running 245/45s) and if it is an 8" wheel, I believe I will drop back to the 225/50s. Since I'm running 205/55s on the front (OE), I believe it will be a better balance. It should also give a bit more power and speed as the car is not turning as much rubber. If the wheels are wider than 8", I guess I'll have to stick with 245/45s until I can pick up some 7 or 8" wheels.

Regards,
Jim
'86 911

Christian K

Q: Wouldn't 205's with 245's alter the understeer/oversteer balance of the car? I'm not an expert, but I know that if you put too much rubber in the back your 911 will under steer more when driven hard. Not very desirable ...

Ed Bighi

Of course, by looking behind the rim, you will find the exact size. But it is quite easy to know if you have 8's or 9's in the back as they have a very deep dish or a very wide lip as in the 930 turbos. If they are 8's or 9's, the easiest way to differentiate between the two is by countersunk lug nut holes. The 9's have countersunk lug nut holes, which when viewed on the car, place the lug nuts somewhat inside the holes. The 9's should be run with 245/45, the 8's with 225/50, though 245/45 works as well. As far as the 7's, if in the back of the car, should be run with 225/50 and no larger. If in the front, then with 205/55. Front tires were always 205/55, regardless of wheel used. If those 7's are run in the front, then obviously there is either a 8 or 9 in the rear. I prefer to run a 205/55 in the front with my 7's, but there are people out there running 225's. That is fine too.