ptcolombo

I need to buy a new set of tires because Falken doesn't make my rears anymore. Have a 2004 996 C4S. So I'm looking new tires on Tire Rack and start comparing tires. I was looking at the Sumitomo's and noticed that front diameter/rev's per mile are different for fronts and back (25.1/826 v 24.9/834). So I'm thinking maybe because they're cheap. I then look at the Bridgestone Potenza's and they're worse at 25.3/823 fronts and 24.9/837 rears! And they are Porsche N3 approved. With the car being AWD, am I asking for trouble down the line? Thanks

Macster

The AWD depends on different front and rear tire diameters.

The "trick" is to stay within the wheel/tire sizes and the resulting different revolutions per mile numbers sanctioned by Porsche.

5CHN3LL

I think OP was wondering if there is an acceptable range for variance in revolutions per mile...

OKB

I dont think there will be any difference in any tire mfg for a specific size tire. if one mfg makes a 295/30 /18 the next mfg will be in the same spec
you go by the size that porsche recommends , do you think the front and rear are equal?

Sneaky Pete

If I remember correctly you can have as much as a 5% diff in diameter from the front to rear and be good.

Cuda911

Yes. I went through this tire exercise recently with the Boxste', and had to try many combos before I could find one that was within Porsche "sanctioned" size and within 5% F/R.

Macster

There is but Porsche AFAIK doesn't publish the ranges. One can infer these indirectly by running the sanctioned wheel/tire numbers and obtaining the differences in revs per distance traveled or some other number and then taking the numbers of the setup one wants to use and seeing if its numbers fall inside that range of numbers obtained from the sanctioned wheel/tire sets.

If they do fine. If they do not I would be leery of using the non-sanctioned set of wheels/tires. That front diff and its viscous coupling is an expensive piece of hardware.

OKB

almost every tire mfg has charts of tire specs just look them up and compare

ptcolombo

Macster, that's my thought also. I figure if they're within the range Porsche specs, then I'm fine. Thanks!

5CHN3LL

True...it's also easy to remove from the car and hang from a rafter. Now I can run 16's up front and 22's in the back...

DBJoe996

Like this?

5CHN3LL

Awwww yeah. That would look SWEET on a 911.

Macster

PSM might still be an issue along with ABS.

And the car would have the steering of a decades old shopping cart.

DBJoe996

New uses for shopping carts:


Grab one now for a whole new grilling experience!

5CHN3LL

That's exactly what I'm going for! Good to know that there are two of us who appreciate this look!