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Tires Size

Posted by rabwabsab (My Page) on
Mon, Jun 13, 05 at 7:56


I have a Mazda 323 Model 94. The recommended tyre size for the car is 155/80 R13. However, I bought used ones and latter realized that they are 155/70 R13. I have now put on the new ones and apparently it did not make any difference. Do you know if it can cause a problem in some way?



Follow-Up Postings:

RE: Tires Size

They are somewhat undersized. Your speedometer now will be inaccurate (you'll actually be going about 5% slower than the speedometer says you are).

And you should check the load range of the tires (it's a number stamped on the side of the tire, like 89H or 75S or somesuch, most likely listed after the size) against the load range that Mazda recommends (it's in your owner's manual or a tire store can tell you). The number on the tire should be the same or larger than Mazda's recommendation. If it is not, you will not be able to carry as much in the car as you may have before.

RE: Tires Size

From your post I'm not exactly clear which way you're recent change just went, however 70's series tires are a lower profile (i.e. shorter that 80's series); the 155 is the width (in mm) and its the same for both sizes; as is the rim diameter (13 in.).

If the original tire specs are 80's series it means that the speedometer was calibrated at the larger diameter and will read high, as Steve_o pointed out, with 70's series on the car.

IMHO, it shouldn't matter worth a darn.

Here is a link that might be useful: tire calculator

RE: Tires Size

Thanks for the replies. I had a clue that my car will go slow now, keeping in view the small circumference of new tyres, at the same acceleration. I think its good to have higher reading on the speedometer then actual as it will save me from tickets :)

Thanks for the info, I feel more relaxed now.

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