Mix Front and Rear Tire Brands??

[911boost]

I have Bridgestone S-02's on my 1992 911 Turbo. The fronts have about 15,000 miles on them, and they are in great shape. The problem is the rears. I go through a set every 8,000 to 9,000 miles (285/30 18's), especially the right rear one. I plan on getting the alignment looked at, since the right one wears faster.

I know I shouldn't expect a ton of miles from these tires, since they are a soft compound, but most of my driving is highway. Yep, I drive the car, I put the rears that are on it, in April of 2007, and they need to be replaced again.

Since the fronts are in good shape, can I try a different brand tire for the rears, or should I stick with the S-02's for another 9,000 miles, and replace all four of them with a different type at one time?

Thanks!

Bill

[Flieger]

Front to rear differences are fine. Most 911s have staggered sizes anyway, which give more grip in the rear than the front. I would only do it for a few miles and get all the same pretty soon, but that is me. I had a flat rear and got 2 new Yokohama Advan A048 R compounds but kept the much harder fronts on until I had the money and opportunity to change them to A048s. Both old tires were Yokos but the models were different. I thought they were fine.

You can sell the good fronts and get new matching ones. That is what I did through Pelican.

[javadog]

Originally Posted by BSiple

Since the fronts are in good shape, can I try a different brand tire for the rears, or should I stick with the S-02's for another 9,000 miles, and replace all four of them with a different type at one time?

The general rule of thumb has always been to use the same tires on both ends of the car. Aside from the differences in ultimate grip between different brands, constructions and compounds, there is also the problem that they can come up to temperature at different rates, have different behaviors between wet and dry conditions on the road, etc. You can screw up the handling balance of the car as well as it's braking performance, although on cars with ABS that is less of a problem.

JR

[Paulporsche]

I don't like the idea of mixing tire brands. Way too many variables.

MAYBE different compounds of the same tire. Like flieger, you MAY find 2 that match up OK for daily driving.

[ChkbookMechanic]

You can mix brands front and back as others have stated and there are the issues with it, but if you are only DDing it and not pushing the car hard; it shouldn't be an issue in my experience. Of course, I'd try and get to the same tire type all around as soon as possible.

[CharlesJones]

I've heard it said many times that you shouldn't mix different tyres front and back, but I can never really understand the reasons why. I can see why you need the same tyre on the same axil, but any car behaves so different between front and back that I can't really see how the subtle performance differences between different brands of tyre are going to make any difference. I mean, the rear tyres are a different width and profile to the fonts anyway, so even if you get exact same brand they are still going to have different adhension levels and side wall flex. However, I can see how if you had really grippy tyres on the front and crappy slippy tyres on the rear if would cause you car to oversteer more, but if you use good quality tyres for both ends that isn't going to be a problem.

Having said the above, I am not saying there is no danger in mixing tyres front and back, but just that I can't really see why there should be a danger. I'm wondering if it's just one of those myths that people stick to because everybody else does - a bit like "only use Brad Penn oil" etc. Then again maybe there is truth in it? I would love to hear some genuine evidence either way.

I currently run different makes of tyres front and back although only because I find it very difficult to get good performance tyres of the same make and of the correct size for both ends (I run 15 inch tyres). I guess if I could get the same brand of tyre all round I probably would just to be on the safe side, but as it happens I feel safer with high quality mixed brands than lesser quality matching brands. I would never mix on the same axil though.

[javadog]

Originally Posted by CharlesJones

I've heard it said many times that you shouldn't mix different tyres front and back, but I can never really understand the reasons why.

Let's take one example. Suppose you have a car that has had it's brake balance optimised for a particular set of tires. It just barely locks the front wheels before the rears. Now, let's say you change the rear tires for a pair that give 10% less grip than the original pair. The next time you hit the brakes hard, the rears will lock first and you'll possibly spin the car.

Here's another example. I have a bunch of cars and they use 8 or 10 different types of tires. I have gotten to know their characteristics well and some of them have very little grip when they are cold. The set I have on my 928 will spin easily when I turn and leave my housing addition. I have to be extremely careful with the throttle and, god forbid the road should be wet. It's so touchy, even my wife has noticed it and as a result, she doesn't drive the car much. The tires perform fine when warmed up. All of our other cars (on other tires) perform fine when the tires are cold. Suppose you put a pair of these tires on the rear of your car. What do you think the result might be? The front grips, the rear does not....

Here's another example. Some of the tires I have work fine in winter and are not particularly bothered with cold temperatures. Others are essentially useless below freezing temperatures (dry roads, just cold.) I wouldn't want to mix and match these on different ends of the car.

Lastly, when it rains, some tires I have maintain probably 90% of their dry weather performance. You can really push them hard on a wet road and have fun. Others lose more like 30% of their performance and they feel like you are driving on ice at times. Mix and match these and you would be in a world of hurt. You'd drastically change the oversteer/understeer balance of the car.

If you never exceeded the posted limits, drove mainly in straight lines, in good weather and never used the brakes hard or took a turn fast, you could probably mix and match and be fine. That just doesn't describe my driving.

JR

[gerrygug]

There is a lot of information on this subject at TireRack.com but the general consensus is it is best to have same make/model at both ends with good tread on the rears at all times.

[CharlesJones]

Interesting stuff, but basically what this seems to boil down to is the importance of using grippier tyres in the rear than in the front. It sounds to me like the danger of mixing tyres is the rear losing adhesion before the front ones, whether thats because they are just less grippy tyres, not so grippy as the fronts in the wet, or have different warm up characteristics. So in theory as long as you ensure you get better performing tyres for the rear, everything should be okay, although you have to be sure they have greater traction in all conditions. Hmm... I see your point - the only certain way of doing that is to get matching tyres front and rear. Or buy Nangyangs for the front!

[javadog]

Originally Posted by CharlesJones

Interesting stuff, but basically what this seems to boil down to is the importance of using grippier tyres in the rear than in the front.

Nope. You can screw it up by having tires with more grip on either end of the car, although having more grip on the front is usually worse than the other scenario.

The car manufacturers work hard to ensure that the choices they make will provide a generally safe and predictable car under all of the conditions it will likely be used in, or that it will be safe in a worst case scenario. As an example, in an old 911, hard braking in the wet, downhill, can be pretty tricky.

This may mean different tire sizes, wheel sizes and presures front and rear. The pressures may change with vehicle load and the sizes may change, if you fit winter tires. The bottom line is someone has done a fair bit of test driving to determine this. There isn't enough information available to the general public on tire performance to make more than an educated guess before buying a mixed set and most people don't have the skill, facilities and inclination to do any testing after they buy a set of tires. It's better to be safe than sorry.

Of course, it is a free country...

JR

[911boost]

Thanks for the help guys.

I decided to just go ahead and get one more set of S02's, and then I will reaplce all four tires.

Bill

[tcar]

Originally Posted by BSiple

or should I stick with the S-02's for another 9,000 miles, and replace all four of them with a different type at one time?

Thanks!

Bill

Yes, but get a GOOD alignment and corner balance - it can do wonders for tire wear.

Won't totally cancel out the 'turbo foot' effect, though.

[burgermeister]

What javadog said ...

Also, it's not just grip ... the tires' cornering compliance will affect straight line stability, as well as understeer / oversteer balance. Cornering compliance is a function of tread block design, tire compund, and the arrangement of all of the plies of stuff that make up the tire. It is not generally available to the public - OEM's have a tire & wheel group that does testing for this stuff. You want more compliance on the front, less on the rear ...

On a somewhat tail happy performance car, I think it's crazy to mix & match ...

[burgermeister]

What javadog said ...

Also, it's not just grip ... the tires' cornering compliance will affect straight line stability, as well as understeer / oversteer balance. Cornering compliance is a function of tread block design, tire compund, and the arrangement of all of the plies of stuff that make up the tire. It is not generally available to the public - OEM's have a tire & wheel group that does testing for this stuff. You want more compliance on the front, less on the rear ...

On a somewhat tail happy performance car, I think it's crazy to mix & match ...

[Miguel Antonett]

I would consider using different set of tires up front or/and rear. They are different size to start with, and consequently act differently on the road - regardless. However, would never mix different tires on the same axle.