Tires are a crucial part of any vehicle, and they’re often overlooked. If you take a moment to really consider it, you’ll realize they are involved in everything from accelerating, to steering, to braking. Any time the car is moving (and even when it’s not; it’s gotta stay put somehow, right?) the tires are playing a key role. Naturally, you’ll want each tire to be the best it can be, as they can only be as good as their weakest link.
What about mixing and matching tires? Brands? Models? SIZES? There are a lot of things to think about here. Usually this is a bad idea, but in a pinch or certain situations it can be OK. Let’s take a look at what it can really mean to mix your tires around and how it affects the way your car performs.
Table of Contents
Mixing Brands or Models
Different brands of tires, and even different models from the same brand, will all behave a little differently on the road. Each were designed with a specific goal in mind. The goal could be to prioritize tread life, dry grip, safety, comfort and even fuel economy. Many tires combine different aspects to achieve two or more goals at once.
Let’s say your ho-hum, “gets me from A to B” daily driver has a flat. You don’t want to spend hundreds of dollars on a set of four tires (I mean, who would?) so you opt to replace just the one. Unfortunately the tires on your car have been discontinued, so you get the first off the shelf model that will get the job done. 98% of the time, this is totally fine, but you should remember a few things are going to change.
Your car’s ABS and traction control (if it has them) read the speed of each wheel individually to determine if you’re losing traction. When it sees a large enough difference in speed, it determines what’s happening (brakes locking up, spinning out, etc) and acts accordingly. The issue is that with a different or brand new tire, the overall diameter will be ever so slightly different from your other three tires. This means the new one has to spin either faster or slower to cover the same distance, causing a discrepancy between the individual wheel speeds.
Again, most of the time there won’t be enough of a difference to really cause a problem. As long as you’re using the same size and in normal driving it should work fine. For performance oriented cars, or cars driven “spiritedly”, it would really be best to at least replace tires in pairs. This would be both fronts or both rears. Mixing from side to side is a bad idea no matter what.
Tire Size Differences
What about sizes? Can they be mixed? The short answer would be no, but it’s never that easy. We know that some cars come with a larger size on the rear, and some (more rarely) have a larger size on the front. Obviously these are fine, since they were designed that way. It’s extremely important to STICK to those overall diameters, however, as changing things is a lot more likely to affect the traction and ABS logic.
Maybe you’re interested in a staggered setup like this but your car is “square” (has the same size tire on the front and back). It’s possible in certain situations to put a larger size on the rear, provided you keep the overall diameter as close as possible to the original size. It also hinges somewhat on how sophisticated your traction and ABS systems are. Most newer vehicles are going to be too sensitive to accommodate using different sizes.
Finally, if you’re in a pinch and are thinking about putting ONE differently sized tire on your car, just don’t. You’ll have a horrible pull to one side that will get worse with braking, and it’s almost guaranteed to screw with your traction control. It could also cause driveline damage in extreme cases. It’s worth it to do the extra leg work to find a tire in the same size as your other three.
Special AWD Considerations
All wheel drive can be a finicky thing. The whole point is extra traction, be it for inclement weather or performance. As such, most AWD cars have a slightly heavier emphasis on how their traction control operates. They’ll be even more sensitive to mixed up tire sizes and grip levels, but that’s the least of your worries.
When I mentioned driveline damage earlier, you may have thought “No way. How’s that even possible?”. You wouldn’t be alone, but rest assured that it can happen. ESPECIALLY on AWD.
The driveline of an open differential and two wheel drive car can, in theory, have its drive wheels spinning at totally different rates and be completely fine with it. AWD however has 4 wheels working together, and two of them can steer. When you bring limited slip differentials (LSDs) into the mix, things can really get hazardous when tires are mixed.
Take a Subaru STI for example. It has three limited slip differentials in its driveline. All the computers are assuming you’ve got the same size tires with the same level of grip at each corner of the car. Based on this and the info from the wheel speed sensors (among other things) it determines how much power to send to which axle at any given moment.
Now let’s put one smaller tire on the right rear. The rear LSD is now binding against itself constantly, trying to get the rear wheel speeds more in sync. LSDs are designed to bind; it’s how they work, but when it happens constantly it will overheat. Heat causes the gear oil to break down and could eventually burn up the differential.
Hang on, it gets worse. The STI has a center differential, too, that controls the front and rear balance. Since the rear overall is now spinning faster, the center diff is binding as well.
Different Types of Tires and Performance Driving
So, you can see now why tossing the wrong size on a car can be bad. But what about different styles of tire, and are there any performance benefits to having two different compounds front and rear?
Usually, you’ll want the same level of grip at each corner. For performance driving it’s almost a no brainer. Some have experimented with less grip on the front or rear, but proceed at your own risk. Mixing compounds can make it more difficult to predict how a car will behave and react to road situations. Especially for spirited driving, it’s best to keep grip levels equalized. It will be safer, and you’ll also likely have better lap times.
The Finish Line
There you have it. Simply put, a different tire is usually fine on your everyday car, provided you use the same size. For performance driving, AWD and sports cars, try to stick to the same size and type of tire on each wheel and you’ll have much better results.
If you’re after a staggered setup, proceed with caution and do your homework. See if others have had success with the sizes you’re thinking of and look into the traction control systems for your vehicle. If you don’t, you could find yourself having issues due to the tires you just spent a decent chunk of change on.
As always, happy motoring, friends.
Hi there. I have a 2017 ram 4×4 with rear LSD. I realize the standard rule – best if all tires are the same brand and tread depth; and OF COURSE, the same size tire. I’m not asking about different size; I would never mix size of tire. However, let’s say indeed a person has to replace a tire (or two) with a tire with similar tread depth, similar tread design, but different brand (same size of course). I am wondering how the LSD system can be that sensitive to be messed up by this. I mean, most roads aren’t that perfectly straight or flat. If that were the case, I’d have to believe LSD systems would be burning out all the time. Thank you!
Interesting comment/question, thanks for taking the time to write.
It’s hard to say really as everybody seems to have a slightly different opinion on this matter. What I do know is that you want to keep the tires the same type (or at the least tread depth and pattern) on each axle, and I believe it is better to have all four the same if possible.
I think where issues tend to arise is somebody has an 4×4/AWD car and they have say 50% worn tires. One tire gets an non-repairable puncture, and so they get just that tire replaced. This puts undue wear on the differential system.
I’d just consult the owner’s manual and see what it says and go from there.