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S03 Rear Mixing with SP800 in Fronts. Is it OK?

 
Old 04-21-2002, 11:48 PM
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kadeer
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Post S03 Rear Mixing with SP800 in Fronts. Is it OK?

I have to replace my rear tires and wanted to go with S03, but Front are kind of Ok with SP800.

I can mix the tires on car without a problem?

I have a 95 Porsche 993.
Thanks
-Kadeer
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Old 04-22-2002, 12:55 AM
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ked
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No you can't. You can't mix tires on a 911 w/o problems. Especially if you do more than drive the car to the corner for grocieries & gas. So don't do it thinking that your car will be able to achieve a high level of ride, handling & braking performance.
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Old 04-22-2002, 04:00 AM
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kadeer
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Instead of the S03, I opted for the Sumitomo II, I understand these are made by Dunplop factory and maybe they will behave better with SP800.

My Rears go too fast and can not justifying replacing the good fronts.

Any idea, why mixing is bad with different F/R.

-Kadeer
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Old 04-22-2002, 05:38 AM
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Kadeer

Different tyres have different characteristics - wet grip, dry grip, wet traction, dry traction, temperatures and compounds. A 911 (and most other high performance cars) is supposed to have the same type of tyre on front and rear to make the handling safe. Not even tyres from the same brand should be used if different type - for example P7000 and PZero <img src="graemlins/nono.gif" border="0" alt="[nono]" />

It depends though, if you just cruise around town in it then it won't make any difference. Why not fir Dunlops at the rear to match your fronts or don't they make them anymore. If they don't then the other thing to consider is that a tyre will start to become stale after 2 years or so. So if your fronts have a good tread but are 4 years old, then these should also be replaced.

If cost is an issue then I would recommend Kumho Ecsta 712's all round - have a look at <a href="http://www.tirerack.com" target="_blank">www.tirerack.com</a> - these tyres scored 8.2 out of 10 and are half the price of SO2's...!

Hope thsi helps

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Old 04-22-2002, 08:08 PM
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kadeer
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I tried the order the Sumitomos then the 712, but delivery date from tire track was later than my next week planned trip.

So ended up getting the S03 for the rear.
I just got the SP800 last year, but rear lasted only 7-8K miles. (4 Autocross and one day at track).

Now wanted to upgrade to S03, but it gets expensive to waste the SP800 fronts.

Would this make the car unstable at high speeds or cornering. I am not clear why this would be, say in ry roads.

Anyone out there noticed problems mixing?

-Kadeer
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Old 04-22-2002, 09:05 PM
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Different tire compounds + tread patterns have distinct coefficients-of-friction (grip). Different compounds also have different degrees of water absorption and water rejection (more formally, "hydrophilic or hydrophobic" chemistry). Different tread patterns have different water-flow management (how much rain they can "pump" before hydroplaning). Different compounds + tread patterns have different thermal dissipation characteristics (critical in braking). & on & on.

The factory engineered these cars to operate in emergency, bad weather, &/or "sporting" conditions w/ predictability, at very high limits, and delivering performance (in the broadest sense) that might just save your life, or at least your car's body. They insist that you match all 4 tires.

I have run what some may think of as a "mild mismatch" (BS RE71 front, RE730 rear) and I was expecting a little sub-optimal behavior. Wrong - it was so noticeable I was shocked. The whole "of-a-piece" stability that I demand in a 911 was gone, even in "normal" driving. I lost confidence in the car's handling and thereby lost alot of the satisfaction in driving a 911. IMO, 911's may be particularly susceptable to these issues because of the rearward weight balance, different frt / rear tire sizes (fine-tuning to address the weight bias), the fantastic brakes & the all around performance envelop. It IS a sports car, not a fwd econobox.

OK, do whatever you want, but I would ask myself, "did I buy this thing to ignore the Porsche designer-engineer intent & screw w/ the machine - physical environment interface? Am I that smart & skilled?".
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Old 04-22-2002, 09:26 PM
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Kevin,
Thanks that was detailed and enriching. I did not realize the importance of matching. I figured it was not written in stone like 'change oil at 3k' by dealer, while some say 5k and porsche says 15K.

If it effects the performance drastically, I will consider changing the fronts to S03 too.

-Kadeer
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Old 04-23-2002, 05:24 AM
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Patrik S
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I can only aggre on what most people has written, do not mix your tires. When I bought my 964 Turbo it had P7000 in the front and PZero in the back.
The car did not drive and brake well at all. Even though I still had 80% in the front I replaced all four tires. I got CONTINENTAL SPORTCONTACT 2 (N2) and I think they work fine. We will see how they do on the track on May 5
/Patrik
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