Different tire sizes on front and rear?

tires

#1

Hi guys,



This is Christy, aka weecamlass from the old forum (they said I couldn’t use my old name because it contained “inappropriate words” - would that be the first part of the name or the last?)



Anyway, after teasing my boyfriend about his failure to buy new tires until it was (almost) too late, I decided I’d better take a good look at the ones on my own 2000 mazda protege LS (188,000 miles, driven about 15,000 a year). When I did, I discovered the tires on the front and back are different sizes!



I bought 2 new tires when I got the car 2 years ago (I know you’re supposed to buy 4 at a time, but I’m on a budget here). The newer ones are on the front, and they’re the correct size according to the owners manual: 185/65. The ones on the back are 175/65. No one, including the guys who installed the new tires, ever pointed this out to me.



Is this bad? I check tire pressure regularly and the car doesn’t seem to have a problem, but I want to make sure I’m not hurting anything.



The other question is: I guess I’ve been lame about rotating tires. I was about to have that done, but now I’m guessing that’s not a good idea given the different sizes. How important is it to rotate the tires?


#2

d’oh…I meant the car has 88,000 total miles, not 188,000


#3

It should not be too much of a problem if you make sure to keep the like pairs on the same axle, that is both on the front matching and both on the back matching. You also want to keep the best tyres on the back.

If you were to mix them so both of one size were on the left and a different size on the right then in an emergency stop you would not stop straight. The reason to keep the best tyres on the back is likewise safety in an emergency because if your back tyres are not as good or better than the front, you may end up looking where you have been and not where you are going.


#4

In this case the tires are the same diameter, so it’s not a real big deal. They are a different width, but the ones that are the wrong width are (presumably) the next ones you’ll replace. If you don’t drive like a maniac you should be fine until it’s time to replace them.

Russ


#5

Actually, the 185 tires are about 2% larger diameter than the 175 tires, but it should be OK if they are are kept on the same axle. As others have said, put the new tires on the back and replace the front tires with the matching size when they wear out.

When you have good tires on all four wheels, you can have them rotated every 5000 miles or so. Most tire shops will rotate them for free when you buy their tires.


#6

The smaller tire is about 2.3% smaller in diameter so your speedo will have a 2.3% error; will read high as will your odo when you have the smaller tires on the drive wheels. Verify this by Googling Tire Size Calculator.

I ran 155s and 165s on a car until the wrong size wore out; I couldn’t notice the difference.

As was said, rotate but make sure that you keep the same size on the front and the same size on the rear.


#7

When you buy tires a store that advertises based on low prices, and you go in saying you want inexpensive tires, they sometimes will sell you a tire a size smaller to keep the price low. That happened to me, but I caught it the same day and returned them for the proper size tire- they didn’t charge more, but you have to pay attenion these days…as the other posters have said, no real problem, just keep the same size tires on the same axle.


#8

so it sounds like it wouldn’t do any good to move the drivers side tires to passenger and vice versa?

I wonder if the people who owned it before me got ripped off by the tire place, as you suggest. I honestly don’t remember the size of the tires I replaced two years ago, but the old ones are cheapo tires, so I wouldn’t be surprised if that’s what happened to them.

Another question: do front tires wear out faster on a front-wheel-drive car? The new tires are on the front wheels, but the (cheapo) back tires seem to have as much tread as the front ones.

Thanks for your help!


#9

Another question: do front tires wear out faster on a front-wheel-drive car? The new tires are on the front wheels, but the (cheapo) back tires seem to have as much tread as the front ones.

Yes the front tires will wear faster, I would put the new tires on the back and replace the front tires with the proper size when they wear out.


#10

i have a question about tires also i need to replace my 2 tires on the back which are 235 70 15 and i found some tires but they are 235 75 15 if i replace those and keep 235 70 15 on the front would that cause any damage to my xterra?


#11

On a 4 wheel drive mismatched tire sizes front to rear are a problem but on 2 wheel drive there is rarely a problem and then not in mechanical wear of the drive train but possibly in handling and braking but there is so little difference in the circumference of the 2 tire sizes you mentioned that on a rear wheel drive vehicle I feel pretty sure you’r OK. I have driven many miles with significantly greater size differences on front to rear on many different vehicles.


#12

Hello from 2007 I guess. I can’t remember what year the car was, I think 2007 or 8 but on my son’s old Infinity, the rear tires were wider than the front tires by design. I really don’t know why and didn’t seem to affect handling at all, but made tire rotation impossible except for side to side.


#13

Same with my brothers BMW. 245/35-20 on the front and 275/30-20 on the rear. Staggered sizes are fairly common on “performance/sport” cars.


#14

Didn’t a mid 80’s Corvette do that? different size tire front to rear, plus directional.

If you had a problem with the left front tire, you had to buy a left front tire.


#15

I have heard of some ABS systems having issues with tires of different sizes front to rear. Please note that vehicles with staggered fitments from the factory usually have similar diameters front to rear - and in any case, the vehicle manufacturer designs the ABS system around that particular issue.


#16

Let’s not sweat the details @Bing. We don’t need no calendar, just let the idle chatter flow. But really, I don’t see a problem with the uninitiated DIYers dropping in and tagging their questions onto a well worn similar thread.


#17

And then you get directional tires and have to actually have the tires dismounted from the wheels to rotate them.