How important is it for all 4 tires to match?

[Son_of_a_Rich]

@Muffin

Also, you can get the tread on new tires shaved down so that they match the remaining tires.

Joking, right?

[Kimballkid]

@Anaamika

Wow, people actually replace all four tires at once? And it’s illegal not to do so somewhere?

Front wheel drive, and I never change all of my tires at once. Never.

I always change all four at once. Always.

[LouisB]

@Son_of_a_Rich

Joking, right?

We used to call the process “shaving”; it’s not a joke but it was expensive and it was terrifying to watch it done as the new tread you just bought is cut away. It was done to ensure that none of the tires on a car were not out of round. (My experience goes back to the 1950s so take it with large amounts of salt. Tires have come a long way since then.)

[pulykamell]

@LouisB

We used to call the process “shaving”; it’s not a joke but it was expensive and it was terrifying to watch it done as the new tread you just bought is cut away. It was done to ensure that none of the tires on a car were not out of round. (My experience goes back to the 1950s so take it with large amounts of salt. Tires have come a long way since then.)

Good story about it here, with reference to why you still might want to do it.

But shaving still has its uses. Say you have an all-wheel-drive car that started with a full set of fresh rubber ten thousand miles or so ago and suddenly you find yourself needing a new tire as a result of a failure. A mismatched set of tires could force a modern four- or all-wheel-drive system to be constantly working to manage torque, causing undue stress and wear on the components. In order to prevent that type of problem, you could replace all four tires, or replace just the one and have it shaved down to the diameter of the three worn treads. Obviously, the second option would save you a lot of money.

[Rick]

@Zep_Tepi

That is then the time to put the new tyres on the front and the older ones on the rear. You definitely need better traction on the front than the rear of a car.

Glad you know more about it than some of these guys
The Michelin mans says:

Michelin recommends replacing all four tires at the same time, however if replacing only two new tires, be sure that the new tires are the same size & tire type as the current tires and that the dealer always installs the new tires on the rear axle of the vehicle.

The tire Rack:

However due to a front-wheel drive vehicle’s front tires’ responsibility for transmitting acceleration, steering and most of the braking forces, it’s normal for them to wear faster than rear tires. Therefore if the tires aren’t rotated on a regular basis, tires will typically wear out in pairs rather than in sets. And if the tires aren’t rotated at all, it’s likely that the rear tires will still have about 1/2 of their original tread depth remaining when the front tires are completely worn out.

Intuition suggests that since the front tires wore out first and because there is still about half of the tread remaining on the rear tires, the new tires should be installed on the front axle. This will provide more wet and wintry traction; and by the time the front tires have worn out for the second time, the rear tires will be worn out, too. However in this case, intuition isn’t right…and following it can be downright dangerous.

When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the partially worn tires moved to the front. New tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.

Or maybe the Tire Industry Association:

Q: Why should I install two new tires on the rear axle of my front-wheel-drive vehicle?

A: Because a vehicle with brand-new tires on the front axle and worn tires on the rear has a greater tendency to lose control when turning in wet or slippery conditions. While the new tires on the front may “hug the turn,” the worn tires on the rear may slide out and “fishtail.” This condition is known as oversteer, and it has been known to cause serious and fatal accidents on front-wheel-drive vehicles with two new tires on the front axle and two worn tires on the rear.

[LouisB]

Thanks for the link. It’s nice to know that I’m not yet completely insane but I am closing in on it. Shaving tires was more of art than a science, probably due to less than optimum equipment for the job.

[FoieGrasIsEvil]

@Nars_Glinley

It’s a fairly common problem with the 2 door model. I’ve read (with a large grain of salt) that the back end isn’t heavy enough and that the rear tires don’t have the best contact with the road. My awful Oklahoma roads can’t be helping the situation either.

That seems really counterintuitive to me. Less weight in the rear end of a FWD vehicle should make the rear tires wear even less, not more. Or so you’d think.

[andyleonard]

Shaving tires is standard procedure for sedan race classes that have to use a spec tire. About 1/2 original tread depth is where the serious guys start with a new set. Unless I’m out of date, Tire Rack will shave and ship.

Odd sized or mismatched tires, whether on an axle or in a fancy all-wheel-drive setup like BMW’s XDrive, will chew the hell out of the transfer case and front and rear diff clutches. A BMW X3 - for example - has a transfer case that holds 1 liter of $80 fluid that only comes from the BMW dealer and said case has no dipstick. Originally the fluid was “lifetime fluid” but BMW changed their mind and now it is to be changed. Point being, this is a fairly delicate unit with a “rebuilt” cost of around $5K. To protect it, the ABS, DSC and tire pressure systems will not accept a tire diameter above or below a certain range without setting off all sorts of alarms. BMW really, really wants all tires to be the same size…a pretty good argument for keeping matched sets on the car.

With 2wd, obviously you are only concerned with one axle at a time being matched, and as stated above, some cars come with staggered sizes anyway. Personally, Tire Rack notwithstanding, I will not be driving in any kind of weather in a FWD car with bad tires on the front and new ones on the rear. I’m guessing way more people have understeered off a wet road than have looped it.

[andyleonard]

@Nars_Glinley

It’s a fairly common problem with the 2 door model. I’ve read (with a large grain of salt) that the back end isn’t heavy enough and that the rear tires don’t have the best contact with the road. My awful Oklahoma roads can’t be helping the situation either.

I ran into a version of this on a 2WD Suburban which had a habit of using up rear brake pads at a rate about 3 times as fast as the front…exactly opposite of what you might expect. Research showed GM had diddled the front-to-rear brake balance to prevent “nosediving” at stoplights and had the back brakes going on first. Is it possible something like this is going on with your car? Either on purpose or by accident?

It seems implausible that the rear tires - aligned and inflated properly - on a FWD car would experience much wear at all compared to the front drive and steering wheels. Maybe you need your proportional valve redone/replaced to have more braking in front and less skidding of unweighted rear tires.

[Muffin]

@Son_of_a_Rich

Joking, right?

No joke.

Tire Rack has offered a tire shaving service that has been primarily used for preparing competition tires for racetrack use. This same service can also be used to remove tread rubber from new pairs or individual street tires used on four-wheel drive and all-wheel drive vehicles to allow them to match the remaining tread depth of the other partially worn tires that will remain on the vehicle. In addition to providing equivalent tread depth to eliminate driveline stress, shaved tires will also better match the traction and handling qualities of the remaining worn tires.

[Zep_Tepi]

Not convinced that I have been doing things wrong for the last 50 plus years, I posted the question on a British Classic Car web page asking where would you place the two new tyres and the consensus who replied said definitely on the front.

I feel that I regulate my speed for road conditions and over the last 50 years have never lost control of the rear of a car, but should I have to take avoiding action of say a child running out in front of the car, I would prefer to have the new tyres on the front where the braking pressure is greater and also to be able to take avoiding action.

[Rick]

So you don’t believe the professionals who tell you the facts, but you do agree with other equally misinformed people.
I to have owned LBCs and I participate on a couple of online mailing lists for LBC owners. The lack of technical knowledge on those lists is amazing.
I would not hold up the collective (lack of) wisdom of a bunch of LBC* owners as a reason to do anything.
But hey what do I know, I’ve only been doing this shit for over 40 years professionally.

• for those playing along at home LBC= Little British Car, think MG Trimuph, Austin Healey etc.

[california_jobcase]

I used to run tires until the cords showed. Yes, I know that’s bad, but I was broke back then. I always kept the better tires on the front because getting a blowout on the rear 's a lot less dangerous than on the front. This was generally on RWD no power steering cars, but also on one FWD car. Have a blowout on the front of a manual steering car, and it gets hard to steer real quick. Power steering helps some, but it still pulls hard to the blowout side.

Maybe that’s why people stick to the better tires on the front concept.

[andyleonard]

@Rick

So you don’t believe the professionals who tell you the facts, but you do agree with other equally misinformed people.
I to have owned LBCs and I participate on a couple of online mailing lists for LBC owners. The lack of technical knowledge on those lists is amazing.
I would not hold up the collective (lack of) wisdom of a bunch of LBC* owners as a reason to do anything.
But hey what do I know, I’ve only been doing this shit for over 40 years professionally.

• for those playing along at home LBC= Little British Car, think MG Trimuph, Austin Healey etc.

My suggestion, Rick, is that you professionally put your new tires on the back and the rest of us who own repair shops, drive race cars and live in the mountains will put them on the front, O.K.?

[Zep_Tepi]

I think I now know why American Cars don’t go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.

[Gary_T]

@Zep_Tepi

I think I now know why American Cars don’t go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.

Yeah, that must be it, the factory puts half-worn tires on the front. :rolleyes:

[Rick]

@Zep_Tepi

I think I now know why American Cars don’t go round corners as well as the European cars do.

Must be something to do with the best tyres on the back.

:rolleyes:
Yes unlike those great handling British cars.
Second best selling car with a plastic body after the Corvette.

[TurboNuke]

I currently have a car with four different tires on it. Doesn’t seem to affect the handling at all in normal conditions. Maybe in extreme circumstances it might make a difference. As far as I know the whole matching tires thing started with bias ply and radials. Since almost all tires are radials these days I don’t think it makes as much difference as the old days.

[Zep_Tepi]

1963 Corvette. 5358 cc - Top speed 142 mph

1964 Shelby Mustang 4735 cc - Top Speed 119 mph

1962 Jaguar E Type 3781 cc - Top Speed 150 mph.

1962 Aston Martin DB-4 3670 cc - Top Speed 140 mph

1962 Ferrari 250 GTO 2953 cc - Top Speed 185 mph

And the European cars go round corners.

[Aestivalis]

Here’s two times we’ve discussed it before:

Does Rotating Your Tires Make Sense?

Grippiest tires on the front or back of a front-wheel drive car?

But people remain unconvinced. How about video evidence?

New tires Front or Rear

You can tell that under the same conditions, the car with the poor rear tires loses control well ahead of the car with the good tires on the rear. How can you argue with that?