Frequently Asked Questions

Buying tires online is a daunting business, but we are here to answer all your questions:


How accurate are the calculated tire results of your tire calculators?

Tire calculators help in measuring tire size dimensions and rpm (revolutions per mile). The results are mathematical calculations based on specific data. However, in practice, the tires from different manufacturers have minor variations. These variations can be in diameter or width. 

In most cases, the calculations are very close, and you can also find a list of tires manufactured in each size.


What is the measured rim, and how accurate is that?

You will find measured rim specs for most tires on 

To measure tire specs, tires are mounted on a rim, and ‘Measured Rim’ is the width of the rim on which the tire was mounted. If you mount the tire on a rim with different width, there will be a slight difference in specifications. But the difference is very minimal and doesn’t exceed half an inch in most cases.


How accurate are the ‘revs per mile’ specs?

Revs per mile’ is measured when the tires are under vehicle load, so it spins more than an unloaded tire. Therefore, it is hard to calculate the rev per mile value. Normally, for a loaded tire the rpm value is 3% more than that for an unloaded tire.


What are alternate tire sizes? Do you recommend choosing an alternate tire size?

When you calculate results for a tire, the system generates a list of alternate sizes. The list shows the alternate tire size diameter, width, and wheel diameter as well as the difference from the calculated tire size.

You can choose an alternate tire that doesn’t exceed 3% in difference. In most cases, the alternate tire sizes that match work well. However, there is no guarantee that an alternate size will definitely work.

How do I read tire size?

Manufacturers display tire size specs in two ways:

  1. Inches

It is very easy to read tire size in inches. Just follow the following example.

For example: 37.4×12.4R30


37.4🡪 Tire diameter or Height

12.4🡪 Tire width

30🡪 Wheel size (Diameter of the wheel that the tire will fit on).


  1. Metric

Compared to inches, reading tire size in metrics is a little tricky. You may need to keep a calculator handy.

For example: 315/30R17

315🡪 Tire width in mm (millimeters) 

[25.4 mm= 1 in. Therefore, 315 mm= {315/25.4} = 12.4 in.

30🡪 Percentage of width that is the sidewall measurement of the tire.

[70% of 12.4 = {70/100 x 12.4} = 8.68

17🡪 Wheel size

Height of the tire🡪 2 x Sidewall measurement + Wheel size

[(2×8.68) + 17 = 34.86]


It is important to learn the conversion method for inches and metrics. Most manufacturers share tire specs in one way only. In such cases, this can be valuable.

If you have any questions, feel free to contact us. We will be happy to help you find the best tire for your vehicle at the most reasonable price.