If only replacing two tires should they go on the front or back? [duplicate]

Question

As the titles says I've seen several shops indicate that if you can only replace two tires that they should go on the rear, example Firestone:

So shouldn't tires be placed on the front? I was under the impression that if your older tires were on your front you would loose traction if trying to turn in a rain storm. Another issue I would imagine is braking would be effected since you have greater of percentage power in the front?

Also referenced:

• Replacing new tires on front because rear ones are a different size
• Should one fit the least-worn tires to the rear wheels?

The purpose of this Q&A compares to the above two was to get a better answer on why the rear is preferred to the front. The voted question that is being considered as the duplicate of doesn't mention oversteer.

Answer 1

Officially, the better tires go on the rear to help prevent oversteer. If you front tires loose traction (understeer), you are going to go straight until you catch traction, or hit something. Its safest to hit something with the front of your car. If you oversteer, it is much more difficult to recover. You are more likely to hit things with the side or back of your vehicle.

If you are a bit more experienced, and your tires aren't bald to begin with, having the better tires up front isn't too big a deal. The rear typically has more negative camber to give it better traction. You typically will not have issues as long as you aren't pushing your tires to the limit. However, you will be more likely to loose control in an emergency braking/avoidance situation.

Personally, I run the better tires on the drive wheels. I drove a FWD car for years with sporty 225s up front and all season 195s on the back and never had an issue.

Answer 2

As you may well know: when you're turning, an under-steer condition is when the front tires lose grip and start to slide, and an over-steer condition is when the back tires loose grip and start to slide.

For the inexperienced driver, under-steer conditions are much easier to control, as you can still see where you are heading, and can simply straighten the wheel to regain traction and attempt to control the vehicle.

Over-steer conditions are much more dangerous, because the yaw rate of the car when the back tires lose grip will cause the car to spin. This not only makes the car much more difficult to control (attempting to steer becomes frantic and confusing when you suddenly find yourself traveling backwards), but also makes it hard to see what potential obstacles you are heading toward.

Over-steer conditions will be exacerbated if the front tires have significantly more grip than the rear, as they will allow faster corner entry than the low grip rear tires can't handle: resulting in a spin. Hitting the brakes will also shift the weight of the car onto the front axle, increasing their potential for grip while simultaneously decreasing the load and grip on the rear axle, meaning any movement of the steering wheel will have a higher chance of causing the rear tires to lose grip.

@Moab is probably correct in assuming lawsuits against tire shops for outfitting new tires on the front forced this rule, despite the fault likely being the drivers for traveling too fast for conditions. Either way, if you feel strongly otherwise you are always free to rotate your own tires when you get home.

Answer 3

It really depends. If the car is front wheel drive, then you are expecting your front wheels to do all of the following well:

• Apply power to the road
• Steer
• Do the bulk of the stopping

Sounds like you would want the newest and best tires on the front.

In a rear wheel drive car, if the front lose traction you're going to under steer in a wet corner. (If you're not familiar with it, under steer means the driver turns but the car just goes pretty much straight.) If the rear tires let loose in a corner you will over steer. (The driver turns and the back end comes out making the car steer more than the driver intended). If I had to chose, I would take over steer over under steer any day. With over steer in a rear wheel drive you can control the amount of turn in with the throttle. With under steer, once you are in this state, you can't really slow down because the front wheels are already sliding so you can't expect them to provide good braking.

Honestly, maybe it doesn't matter, I would suggest you put the good tires on the front. Which is exactly what I believe long haul truckers do. They may have retreads on the rear wheels of the tractor, but the fronts are always nice new tires.

Hope that helps!

Answer 4

It turns out that you do want them on the rear.

And one of the reasons is probably not what you would expect.

It turns out that it's important that the front tires lock up first when braking hard, for example, in wet weather.

That sounds backwards, I know. You might think, I want the rear's to lock up so they hold the rear end back and keep me from spinning. Except, that's not how it works.

It turns out that static friction is stronger than sliding friction. Meaning, normal rolling tires can brake harder than skidding tires.

And more braking in the rear keeps you from spinning, unless you just completely blow it and lock up all four tires. But a lockup is a warning. With better tires in front, say, in the rain, it would be easy to brake harder, a little harder, then a bit harder, and then with no warning lock up the rears and start a spin.

And so, the older tires that will skid first should be in front so they don't hold as well in bad weather, where normal drivers are most likely to brake too hard for the conditions.