brad@tirerack.com

Maybe this link will help:

http://www.tirerack.com/tires/tirete...jsp?techid=136

Don't mix and match on a staggered fitment sports car. There's too many variables that could result in differences to the handling characteristics.

jimbo3

+1. While Mark may know from experience that some tire combos work, most of us don't have the time or finances (or bravery) for experimenting with mixing tires. As with non N-rated tires, there are some that work and some that simply don't. Experience is usually the only teacher.

Naturally, manufacturers aren't going to say anything except "don't mix tires", but it's not a sales/profit motive, rather more of a liability issue.

black ice

All that the posts from Mark and me say is that mixing tires does not create a dichotonomous situations where the care is immediately dangerous to drive. Clearly having tires of the same make and model on each corner of the car is the best alternative. What most posts on this thread have said, however, is that mixing tires is a no-no.

Damon,
I have to disagree with your assessment of the very note to which you refer on TireRack's website. While it states that the best alternative is not to mix, it also says, "The second option is to choose equivalent tires from the same tire performance category that share the same speed rating, handling and traction characteristics of the original tires. While this isn't as desirable as selecting the exact tire currently on the vehicle, it can become necessary when the original tires are no longer available."

Dave

CP

Hi Folks,

Here is a thread I posted some 10 months ago. I have since had the Ruf on track, and Brandon Kraus drove the Ruf at 9/10ths. The mixed tires came through with flying colors.

However, once this set is done, I will NEVER mix tires again. If I find a tire I like, I'll buy 2 fronts and 4 rears just in case I face the SO3s delimma again.

CP

Wilder

+1. I too very much respect Mark's advice and he is a much more experienced driver than I but have to agree with Danny also based on Personal experience.

I killed a rear P-Zero tire on a previous sports car and it was an odd size, 335 or something, so I had to wait for a month before they could get my new set of rears. In the meantime, a found a set of proper sized Michelins and put them on. The car had 400HP and felt twitchy off the line even under mid load, never mind WOT or high speed.

Mixing is a no no for me. Maybe Mark lucked out with the particular brand of tires he mixed where there might've been close similarities in pattern/compound???

Mark in Baltimore

I knew my post was going to be unpopular. Thanks to everyone for the responses that were devoid of extreme castigation, although I slept with Nomex on last night.

I prefer to take measured looks at situations. Due to liability issues, it would only make sense for a car manufacturer, tire supplier or tire company to state that mixing tires is a big no-no. Again, I am not stating that mixing tires will not result in detrimental handling, but I am also saying that mixing tires in some scenarios may not result in detrimental handling. To me, it's just simple logic. I also understand that people new to Porsches, high performance cars and/or track driving may run right out and slap on a set of 22 year old Phoenix Stahlflexes (anyone remember that tire? Yes, I'm that old...it's also how Tire Rack got their start, BTW) with a set of fresh Hoosier R6's, which would surely result in some unusual transient responses and would be inadvisable.

What I am saying is that, if you make the decision to mix tires, use your head. If the car feels squirrelly, pull the tires off. If it feels okay as you slowly ramp up speed and physical forces, then perhaps you understand that your car might not turn and bite you. However...use your head. Listen to the car. If you're not sensitive enough to know what the car is doing, don't mix. If you are, tread cautiously.

There was a recent thread on the racing board (https://rennlist.com/forums/showthre...p=15&highlight) about whether it was okay to run a patched and plugged tire on the track. Many of the respondents recommended against the practice, but, being the doubting Thomas that I am and having run a plugged and patched tire on the track before, I wanted to see if anyone had experienced a tire failure from a PnP'd tire. One guy posted a photo which, on the face of it, would seem to indicate that PnPing a tire is a bad thing. But did anyone verify that the leak occurred from the patch? (Yes, I know the tire was roached so it would not hold air.) Maybe it came from another source? Maybe the owner let the pressures go down? Valid questions, IMHO.

We all make calculated assessments, and we all take risks. Should I run that tire to the cord? Should I push it harder on the next corner of this fun run? Should I change sway bar settings to make the car looser? Should I drive fifteen mph over the speed limit? Should I punch it when the light goes from green to yellow? Should I eat that tasty turkey, spinach and mayo on cheese bread sandwich that has been sitting in the fridge for five days? If one wants to be 100% safe in the aforementioned examples, the answer to each and every one of them is...no. But the truth is that we all take chances to a degree, based on the situation, based on experience, based on our tolerance for risk and based on information, to name but a few. I'm doing my part to distribute information, just as you guys are doing. Intelligent drivers will make their own decisions based on these posts.

To be perfectly objective, yes, absolutely, perhaps I got lucky with the Dunlops I had on my car (tread patterns were very different). Also, I'm not sure if it's a good thing or a bad thing, but, after reading Danny's post, I tallied up my track hours and it's nowhere even close to the thousands. I have approximately 75 track days under my belt and, at roughly 25 minutes per session and an average of four sessions per day, only have roughly 125 hours of track time, so definitely take what I say with a grain of salt. I moved up the DE ranks at a perhaps typical(?) pace (spent five days in green, two days in blue in my region (plus an additional seven days of blue group driving in two other regions) before being moved to white), did about 28 total DE days before I moved to club racing and am working my way up the CR ranks in a similarly modest pace (PCA club racing results are public knowledge, so one can see how well or poorly any racer has done. I finished my first race and first time ever visit to Watkins Glen nearly DFL.) I continue to make significant improvements based on the right tools, the right coaching and the right thinking, especially in light of the relatively few days that I am actually on the track. Perhaps after my 500th track hour I will be ready for...C class.

However, I don't think it's necessarily the number of hours (quantity) but the intact skills that one brings into the sport and how much learning and improvement is being done per track hour (quality). I have seen guys start club racing, after the requisite DE days, of course, and win or podium right off of the bat...and keep on winning, despite having had the bare minimum of track days. And these are not loose cannons who can hardly keep it on the track. I've also seen guys who have started doing DE's since the beginning of such things in PCA with, most likely, a thousand hours of track time, in essence tons of experience, and they are not quite ready for prime-time.

Anyway. I suppose what I am saying is that I may not be that experienced, if you define experience by sheer number of track hours (and those of you who have read my posts before know that I am a big proponent of people agreeing upon defined parameters), but I am lucky and/or somewhat sensitive to my car. If you're not experienced, lucky and/or sensitive and desire to mix your tires...well, YMMV.

Perhaps some may see this as a sweeping generalization but...I abhor sweeping generalizations.

Greg Fishman

My suggestion for you guys that think mixing tires is no big deal:

1) don't let any loved ones ride in your car.
2) make sure your liability coverage is at its max
3) buy lots of life and disability coverage.

Mark in Baltimore

Dave's right. Tire Rack, despite Damon's post, actually recommends, in writing, mixing tires as a viable possibility, albeit it is not the first choice.

From the link that Damon posted:
The second option is to choose equivalent tires from the same tire performance category that share the same speed rating, handling and traction characteristics of the original tires. While this isn't as desirable as selecting the exact tire currently on the vehicle, it can become necessary when the original tires are no longer available.

My interpretation? Use your head.

95 C4 993

I wouldnt even consider it unless I got a flat tire out in the middle of Tim Buck Two and I had no choice.

I just dont see the rational unless your a tight ***, broke, it was a Porsche recommendation, your others just say its ok.

Martin S.

If someone is dumb enough to go against all recommendations from Tire Mfg and Porsche factory, and experienced 993 Rennlisters such as yourself, ...they are just going to do it anyway, regardless of all the invaluable input you and others provide. It probably comes down to them being stretched for every dollar they put into their Porsche car...they should probably be in a Camero or Mustang, possibly a Taurus. The ironic part, you can get a good set of tires fort a Porsche for about $500 if you shop around...the BF Goodrich 205s and 255s I am thinking about.

I won't respond to this thread any further...let them mix and match tires...you see it all the time where the low life's congregate! Take that 150,000 mile 993 with a salvage title out on the road, push it hard with some crazy mix of tires...you get what you deserve when something unpredictable happens.

Gott en Himmel, why do I even respond to these idiotic threads.

Bruce SEA 993

Stepping back from this a little and looking at the variables...how much will:

Tire pressure affect the characteristics?

Suspension wear (shocks, bushings, etc) effect the handling?

Options and aftermarket stereos adding weight in the front.

Changing from 205 to 225 width or 225 to 235 width in front?

Alignment...front and Kinematic

Weight balance

Drivers skill...can we all tell when we need to get a little weight on the front?

How good are we at catching an oversteer situation (I have never had to react that fast with anything else!)?

Again, the car is unbalanced from the git go. There are lots of factors that go into the feel and balance of the car.

So I don't know the answer but I just wanted to throw out some of the items I saw the contributed to the balance of the car.

On another note, I would be surprised if Tire Rack said anything other than “do not mix”. It is not from wanting us to buy more tires; it is a liability thing from the corporate lawyers.

Oh even more on another note; Damon, I love your tag line " Please put me on your order" ****, you have to call back in order to have me put your name on an order. Believe me you are no Scott Collins. I will take the first yuck who answers the phone than wait for you. I guess after about 15 sets of wheels and tires I know what good communications is about from Tirerack.

Back to our regular scheduled programming. I am going to replace a rear set of SO3s and am not sure what to go with.


I am very interested in the info in this thread…It all adds to our knowledge base.

Cheers!

richardew

My front and rear tires, although they are the same tires, are always different. I replace my rear tires more frequently that my front tires. I go through 2-3 sets of rear tires per set of front tires.
1.new set, 100% tread front, 100% rear
2.rears worn out, ~67% tread front, less than 33% rear
3.new rears, ~ 67% tread front, 100% rear
4.rears worn out ~ 33% tread front, less than 33% rear
5.new rears, ~ 33% tread front, 100% rear
The same is true for lots of other parts of the car, suspension, alignment, steering, etc. as they wear out. The driver has to "feel" what is going on with the car and adjust to those conditions. The same is true when driving on a dry hot, dry cold, wet,
or snowy road. You adjust to the conditions. Nobody here would drive the same way on a warm dry road as on a snowy one. You adjust to the conditions. I have never tried different front and rear sets. I don't think that this would produce anything other than subtle changes in the handling characteristics of the car. What I have found to affect the handling of the car the most is whether or not there are passengers in the car.

Martin S.

"Again, the car is unbalanced from the git go. There are lots of factors that go into the feel and balance of the car."

I would modify that statement a wee bit and say that getting the suspension to perform optimally is a bit of a balancing act. All the items he mentioned have to be optimized...and when they are, the 993 is one of the most dead on, forgiving cars in the world, in my opinion. When I take mine around the track, I almost think for a fleeting moment, I really know how to drive......it's not me, it's mostly the car I will confess.

I have had my alignment done...and often rechecked, re-set when needed,
The kinematic toe set by Jae Lee at Mirage International, San Diego
PSS9s and TRG bars installed with 993RS rear drop links,
Camber Plates with -3 degrees front, - 2.5 rear (More of less...I am not giving any secrets away here!)
Always use tires in really good shape properly heat cycled
Have had the LSD rebuilt to factory 60/40 lock up specs...40% lock on acceleration....a Paul Guard rebuild

As a result of the above, my car's track performance (street too) is fantastic....minimal compromises and maximum performance....but getting all of this right is "a balancing act". The last thing I would do is start juggling tires brands on the front and rear of the car....that is of course, up to the point where I found out where this approach yielded better performance...at that point, I'll consider it...I kind of like to see what the Porsche race guys are doing, and so far, I have yet to see mismatched tires on a race car...but never say never!

NP993

I have mixed and matched tires both on the street and on the track (RA-1's in back, MPSC's in front) and when the T1-S's on the back of my 993 are shot, I'm going to replace them with a pair of tires that aren't T1-S's and I'm not going to change the fronts.

You guys are too much. Are any of you actually driving your 993's hard enough on the street to notice, everything else being equal, whether you have a pair of Yoko's on the front and Bridgestone's on the back? If you are, you're endangering yourself and everyone else on the road far more than anyone is "endangered" (if such a word is even relevant) by putting one type of tire on the front and another on the back, assuming that all four tires are high-performance, or all four are snow tires, etc.

And anyone on this thread bemoaning the dangers of mixing tires for street use who has little or no track time under his belt -- that is, someone who has never learned to drive a 911 up to and over its limits -- also probably doesn't know much of what he's talking about...sorry, but I'm calling BS on a lot of this thread. Flame away.

jimbo3

Probably 99.8% or more of the folks on this forum have never driven a 911 "up to and over its limits", so that leaves at least 99.8% here who don't know anything. Some non-N rated tires will work well, too, but there are plenty of high quality, high performance non-N rated tires that don't. Go with what you know, but as Noah points out, 99+% of us don't know anything, so 99+% of us are better off not mixing tires.

I'm largely stupid and have modest means, but at least smart enough to know I'm stupid with modest means, so I don't take unnecessary risks. Call me crazy!