Should be OK as long as you keep it off the track

 

If you mix tires the car will feel VERY unstable at high speed. I experienced this with mixing Yokohama's S1 Z in the front and Yokohama AVS N1 sport in the back. Bought a set for the front and all is good now.

Regards

 

I had an awful mix of tires for awhile, and even though the car was not at its best, for street use I got away with it.

Of course, I'm driving the car close to 10K miles a year, so tires are not the long term commitment as they are on other vehicles.

 

Hopefully today I'll get some relief, off the pain pills and then back to dull ole me with nary a touch of humor

 

what you guys have to think is that in a normal situation where everyone is driving at 5/10ths calling it fast, you may not notice an issue. Come an emergency situation though like an avoidance and mixed tires will have a detrimental effect. It happened to me with a rented Boxster a few years ago with mixed tires. I can tell you it was not pretty and it scared the living daylights out of me. You have to think that different compounds and tread have different characteristics on the limit. The 911 is already an oddball in weight distribution. Different compounds will have a detrimental effect on the limit and how the car responds.
Never play with different compounds on a 911.

 

Good post.

 

Yet another good post. It would pay others to listen to these two guys.

 

No way dude!

I read on the al gore web that its cool, and ok to mix tires plus it save lots of money.. oh, and I also read that the stock shocks on a 993 will last forever......

 

OK, if we're buying all four, what do we think of the Bridgestone RE-01R?

On Tire Rack, it gets better reviews than the PS2 (even tradwear!) for about 10% less...

 

I refused to mix tires on a '65 Volkswagen Bug. I wouldn't even think of doing
such a thing on my 1996 C4.

 

Bias plys are cheap if you can find 'em in 17inch

 

PUH LEEEEZE.

You've got to be smoking your socks if you think "mixing tires" with matching pairs on each axle in and of itself creates a magically dangerous situation. Now if you're leaving a pair of tires on the car that are dry rotting from age or are crappy tires to begin with, I understand. But when you've got good tires like P-zeros on the front and good tires like PS-2s on the rear - I'm trying to figure out what physics makes this so dangerous.

On the track, the car is going to behave differently. Is it that different from changing sway bars or brake pads? Running different tire pressures?

Help me out here!

 

I could not agree more.

Like the threads where people ask about whether it's okay to patch a tire for the track, you'll find lots of different responses. Part of the issue in mixing tires is making sure that grip and response levels are the same between two different types of tires. Mix an old pair of Goodyear F-1 tires on the front with a set of fresh Hoosiers and you will definitely experience some unusual handling characteristics...if you push it hard enough. Part of being a good driver (and I know we're all phenomenal drivers, right?) is knowing to to adapt to changing handling situations. On the track, your car may be understeering for an hour and then suddenly become tail happy. As a driver, on the street or on the track, it is up to you to be aware of this and compensate for it. Now, factor in a situation where the handling characteristic may have changed from the past five years to different handling after changing tires; I maintain that, as a driver, one should be able to adapt to this relatively untaxing dynamic scenario.

On this board, it is highly unpopular to make this statement, but I have mixed two different types of tires and, gasp, driven them on the track, yes, the track(!) with zero histrionics or catastrophic situations. Just like saying that it is always okay to mix different types of tires, it is just as incorrect to state that mixing tires will result in disaster and/or is always inadvisable. One must assess the individual case and make an assessment based on the facts, not sweeping generalizations.

Flame on. Don't care.

 

Hey Mark, you know how much I respect you and your opinion. I feel that this particular situation is a very sensitive area to give an otherwise advise on a public forum contrary to what the manufacturer states, as at the end of the day it is a safety matter.
My self I'm driven by my own personal experience on the matter. The fact is that noone can say for sure that mixing tires is safe. It may work, it may backfire. Just think in slippery conditions the effect of the different compounds, tread and character of a tire. It effects braking, balance and adhesion.
Granted a good driver will drive around most of the issues, but you have logged thousands of hours probably on your 911, not many people can say that even on this very board...
Respectfully then, I believe that the correct advise is not to mix tires, playing it on the safe side always...

 

An excellent post Danny. I'm sure that Mark and many, many other Rennlisters have far more experience than I do when it comes to mixing tires and driving at the limit, but your post really sums it up. Why take a chance and go against the tire experts (see Tire Rack's web site) and Porsche (see your owner's manual) and mix tires? I don't think a lot of people realize just how complex a tire is. A year or so ago I attended a seminar by a faculty candidate in my department who was doing research sponsored by Michelin on tire dynamics. There are umpteen variables including things like sidewall stiffness, compound, tread pattern, track surface, rotation speed, etc. and most of these don't remain constant, but vary with speed, temperature, time, etc. For around-town driving, or at 5/10 as someone put it, you can run on anything with no danger I'm sure, but I'll listen to the experts and not mix tires myself.

Pete