Help .. Biggest tires on 7 + 8 x 15 " fuch

[POVI]

Hello all ,

Just a quick question to the experts here ..

Im planning on buying a set of 7 + 8 x 15 " fuch rims
Offset for the front is 23.3mm and the rear is 10.6mm.

Whats s the largest tire combo i can run on the above in a 1970 911 rs clone with 9" rear carrera flares ??????

Please post , as im planning on purchasing these rims, and need tire options

Thanks to all in advance

- Joe -

[Chuck Moreland]

Well, you could run up to 225 / 245. But Those tires will pucker a bit on your rims. You will need to roll the front fender lips.

A better choice would be 205 / 225.

[RallyJon]

I have 225s/245s Euro T/As on 7s and 8s. They look cool, but are not particularly sticky. With such unsupported sidewalls, they bounce a bit, too. There are no good "ultra" street tires in 245/50-15. Next spring I'm going to switch to a sticky, modern tire in 205/225 sizes to try to get the car to handle.

[Bill Verburg]

You are running into a problem all hardcore Porsche fanatics will eventually have to deal with. There are only 2 245 series tires available in 15s and unfortunately they are both 245/50x15 which makes for an awfully tall tire, negating the benefits of the 15" rim size. These 2 are

• Dunlop Sp-8000 @ 24.7" OD
• Hoosier R3SO3 @24.5" OD (also not street legal)

This is why the 245/45x16 on a 9x16" rim @ ~24.6"OD is such an attractive choice you get the width, the short sidewalls and lighter weight just by spending some $ on rims/tires. There is no downside to this setup on the back except monetarily

That leaves any of a fair # of 225/50 series tires which have an OD of ~23.9". Hoosier does have an interesting tire in the 225/45x15 size at 22.8"OD(again not street legal) but a perfect match for their front 205/50x15 also at 22.8"OD. This 205/50 & 245/45x15 combo is particularly intriguing because of the R nature of the tread compound and the low rolling radius. Unfortunately most of us need a street legal tire.

I used 205/50x15 on 7x15(+23.3mm o/s) front and 225/50x15 on 8" (+10.6mm o/s) rear on my C3 for many years. Modern tread compounds have only improved on the tires good points. I would recommend one of the newer silica based compounds offered by Bridgestone, Dunlop and Michelin among others. The Michelin Sport Cup offering by far the best performance.

Unfortunately as the drivers skillls improve and or stronger engines are installed the 15" tires ability to cope is reached. Necessitating a move to 16, 17 and possibly 18" wheel sizes to get more flexibility in tire sizes and profiles.

[RallyJon]

Unfortunately as the drivers skillls improve and or stronger engines are installed the 15" tires ability to cope is reached.

By "ability to cope" are you referring to tire width, sidewall height, something else? A 225/50 ultra high performance tire on a 2200lb car seems pretty good sized to me. Maybe as you get below 10lbs/hp it becomes a problem?

[Bill Verburg]

What happens w/ the 225/50x15 rears is that as your cornering speeds go up(for what ever reason) the ability of the tire to stick is exceeded(the friction circle of 15" 50 series tires is smaller than the friction circle for equivalent 16" 45 series tires, with the sequence carrying on to the 17 "40 series and 18" 35 series), this leads to lots of steering wheel/throttle correction(oversteer). It can be lots of fun but it is not the quickest way around a course(unless of course you are limited by class rules). If you hang out at a PCA club race (where rim widths 1" larger than stock are allowed and tires are free) you will find virtually everyone making the gearing sacrifice inherent in 17" and 18' tires for the extra sidewall stability in 40 and 35 series tires and the extra width that is possible with them. Michelin Sport Cups are becoming the standard in the street radial classes.

Love your car!

[Fishcop]

I'm running 225/205 combo on Falkens. Can't complain, but then again I'm not tracking the car.

I too love your car... very sweet.