Good day to all.
Not sure if this belongs here, but I need to ask this question.

My Lexus (RX300) needs one new tire to replace the one that went flat and cannot be repaired.
The other three tires are evenly used, about half worn out.
I contacted Tirerack and they have a tire BUT warned me against placing a new tire on a vehicle where the other tires are not the same age. They say it will cause harm to the drive train. They mention that I must get the new tire "scrubbed down" where the groove depth is the same as the other tires on the vehicle.

Have you heard of this ?
Right now I am using the spare tire which is brand new but not the same type and I want four of the same tires.

Will there be drive train problems running one new tire with three used tires that probable still have 40,000 miles left on them ?

Thanks, have a great day.

R. May

Its not a good idea. Tires need to be replaced in pairs on the same axle, and the new ones moved to the rear. Its not so much an issue of drivetrain problems, its a safety issue. Tire's traction, rolling resistance, and tread height change as the tire wears, and if you have two tires on the same axle that are not similar you may experience issues with emergency maneuvers etc.

Your tires are the only part of the vehicle that make contact with the road, and they are just about the most important aspect of your vehicle's safety for you and your family. Don't cheap out...replace both tires like you should.

I Definetly agree with Sw

I agree too. It sucks, but that is the way to go. Just had to do this on another car a few months ago.

Please delete- double post.

My understanding is that it WILL damage the drivetrain in an AWD because the odd tire either more worn or less worn causes different input speed to the transfer case. I am not telling you this IS FACT, simply saying I have read it a number of times before. Most knowledgeable tire companies will tell you the same thing, quite a few of them even refusing to sell you the tire. You should never put a worn tire with a new one on a vehicle with LSA (limited slip axle) as it will wear the clutches in the LSA out from constantly trying to compensate for the different speed of the wheels, be it ever so slight.

I think if you have both front or both rear tires worn, it's ok (as long as they're both worn the same amount). If the right is worn and left isn't, you will have problems.

Theoretically the worn wheel (smaller wheel) will be rotating more than the new wheel (larger wheel) at the same time. If the left and right are rotating at different speeds, that will definitely mess with the drivetrain- unless it's a rear wheel drive car and we're talking about the front wheels, in this case it wouldn't matter (you might just feel pulling).

Especially if it`s AWD.

I know this isn't an Audi forum, but Audi recommends no more than 4/32 difference in tread on AWD cars. Also, in my experience, Discount Tire follows that rule and won't install a single tire with 3 worn ones on an AWD vehicle.

Interesting discussion; I once asked my Lexus stealer why they didn't include the spare in tire rotation and he just said they don't (no explanation). Perhaps this is why?

Begs the question of what to do when you get a flat (especially when tires are near end of life). Presumably it's a good idea to get the flat fixed quickly and don't do too many miles with the full diameter spare on one wheel.

Definitely why

That would be no different than cars that have space saver spares; they are only meant for 50 miles or less, basically just enough to get you to a service station.

Also, in recent years the age of a tire has become an issue, particularly in context of classic cars that may have plenty of tread left but are driven infrequently so the tires may be 10 or 15 years older. I used to just let spare tires go forever and ocassionally check the pressure on them, but now whenever I change a complete set of tires, I pick the best of the 4 old ones and make that the new spare so the spare doesn't have too much age on it. It would be extremely inconvenient to have a flat, put on the spare, and then have the spare blow out shortly afterwards because the rubber no longer has any strength to it.

For the OP, since your RX is now 7 years old, and since you really should be buying two new tires, you may want to consider having the relatively good existing tire rotated to the spare, and discard the old spare due to age. If you haven't looked at your spare lately, I would bet it is holding less than 10 psi or may be even entirely flat (0 psi).