Bill Verburg

There are 3 reasons why tire height, both absolute and differential are important
1) ABS function, the factory ABS is designed around an equal f/r tire height, it works best w/ no differential. There is some wiggle room but the further from nil the differential is, the more issues

2) fitment, the taller the tire the more restrictions are placed on chassis set up, things like alignment and ride height can be compromised

3) gearing effects, everyone has different needs here but a taller tires will have a lesser ability to accelerate the car at any given speed or rpm.

sundog

I use the Nitto NT-01 on my 964. Great tire for DE.

TheOtherEric

The NT01 is by far my favorite DE tire. Have been running it for a few years now. Very economical too.

Nader Fotouhi

Bill, Thanks for chiming in, as usual useful.

Is there any problem with using a taller (bigger diameter) front? Based on spec I see:

Michelin 235/40-18 are 25.4", 285/30-18 is 25.2" and 295/30-18 are 25.2"

Nitto 235/40-18 and 275/35-18 are 25.6"

Hankook 245/35-18 is 24.7" and 245/40-18 is 25.6", 275/35-18 is 25.5"

888 255/35-18 and 295/30-18 are 25.1". Not sure I can get 255 on the front.

Comparing Hankook 275/35 and Hoosiers 295/30, diameters are 25.5" and 25.3"

I may give Hankkok 245/35 and 275/ 35 a try as they seem most similar to Hoosiers that I likely use for racing.

Bill Verburg

The further from 0 difference f/r the worse as far as ABS goes, up to ~5%max, whether the front is taller than the rear or vice versa makes no difference per se but once the springs are set up to give you the f/r ride heights that you want and the stance you want and then aligned to that spec it's not helpful to just change tire heights

So far I've made the decision to stay w/ 225/40 & 265/35 MPSC, w/ 8.5" fronts(vs 8's) to help initial turn in. Tire heights difference is close to zero, Some cornering performance is being left on the table but to me the abs performance and durability are worth the compromise.

Friends use the 235/40 & 280/30 MPSC and and are very happy, If MPSC or some other brand were available in a durable tire ideally you would use 245/35 and 280/30 on 8.5 & 10, that is the setup that the 993Cups were optimized w/

All non stock size choices besides Hoosier 245/35 & 280/30 will involve some compromise
Hancook 245/40 & 275/35 are very close to equal height, so if they can be fitted in the wheel well and the gearing penalty is acceptable then that is a fair choice, 245/35 & 275/35 has a ~3% height difference and as long as the abs issue at that difference is acceptable then the gearing penalty and possible fitment issue in back are all that need tneed to be considered

James Achard

Bill, Have Michelin improved the 225/40 MSPC? I know when I was first using them on my '87 Carrera the 225's were quite a narrow 225. The 235's on my 964 are much better and give me great turn in and braking, then again, Dan Jacobs sets my car up for these tires only so I'm really running a great setup.

Cheers, James

Bill Verburg

No, they are the same as ever
here's a comparison, to get decent turn in I need to have Cup tie rods and the wider wheels, plus a decent alignment. But now they do work fine


Not mentioned previously is weight, just something else to muddy the water w/

Bill Lehman

I was looking at Hankook Z214 for my Cayman S. There were no 275/35 x 18 available and none are expected until June. I went with BFG R1.