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mikefocke · 03-03-2009, 06:01 AM

by putting A/S tires on the back...are you trying to transition to all A/S? Or imitating the old "put snows on the driven axle only"? What weather do you drive in that you are considering A/Ss?

Can you get away with it legally in the US? Yes. If the car is just an around town car and you don't track the car will it screw things up? No. But if you ever have to call on the car for all the handling it is capable of giving you (on the track or in an emergency situation), will the axle mismatch be troublesome? Could be. You are putting tires on with differing water dispersion characteristics, different sidewall flexs, different tread grip and depths. So in a situation where Porsche has designed the car and its suspension and how the suspension works with the tires to do A, your axle differences may cause the car to do B. Might help you, might hurt you bad.

My first Boxster had Pirelli tires which were of different designs for the front and rear but they were specifically designed to work together and their handling characteristics were safety matched even though the tread patterns were different.

I totaled my car because I was driving it one day when the temperatures were too cold and I needed to stop fast and the tires wouldn't grip. Didn't have anything to do with the mismatch, just using the summer tires on too cold a day. Which brings up the point that you'll have, in 40 degree and below temps, if you A/S in back and Ribs or PS2s in front, a situation where you have more grip in the cold in back than in the front. Can you handle the mismatch as a driver? Go into a corner and try to turn and the front end doesn't but the rears grip. Or can you avoid this situation by never driving in those conditions (I was only going to the store, not on any high speed excursion? You just never know when you are just gonna have to do it NOW)

03-03-2009, 06:01 AM	#8
mikefocke Registered User Join Date: Aug 2005 Location: Sanford NC Posts: 2,537	What are you trying to achieve by putting A/S tires on the back...are you trying to transition to all A/S? Or imitating the old "put snows on the driven axle only"? What weather do you drive in that you are considering A/Ss? Can you get away with it legally in the US? Yes. If the car is just an around town car and you don't track the car will it screw things up? No. But if you ever have to call on the car for all the handling it is capable of giving you (on the track or in an emergency situation), will the axle mismatch be troublesome? Could be. You are putting tires on with differing water dispersion characteristics, different sidewall flexs, different tread grip and depths. So in a situation where Porsche has designed the car and its suspension and how the suspension works with the tires to do A, your axle differences may cause the car to do B. Might help you, might hurt you bad. My first Boxster had Pirelli tires which were of different designs for the front and rear but they were specifically designed to work together and their handling characteristics were safety matched even though the tread patterns were different. I totaled my car because I was driving it one day when the temperatures were too cold and I needed to stop fast and the tires wouldn't grip. Didn't have anything to do with the mismatch, just using the summer tires on too cold a day. Which brings up the point that you'll have, in 40 degree and below temps, if you A/S in back and Ribs or PS2s in front, a situation where you have more grip in the cold in back than in the front. Can you handle the mismatch as a driver? Go into a corner and try to turn and the front end doesn't but the rears grip. Or can you avoid this situation by never driving in those conditions (I was only going to the store, not on any high speed excursion? You just never know when you are just gonna have to do it NOW)