If you are thinking of changing your car tire size or are planning on buying a new wheel/tire combination then you can use the flash tool below for a visual tire size comparison of your stock wheel and tire size versus your new wheel and tire combination.

Click here to leave a comment or ask a question

## Why is this important?

Matching the combined wheel and tire diameter is important as it will ensure your ride height and speedometer readings don’t change drastically. An example of this would be fitting 17″ wheels to a car that has 14″ wheels as standard, there are three main consequences:

- the ride height will change, the car will be further from the ground.
- the top speed will increase slightly and the speedometer will under read.
- the car will acceleration slower.

Read on to see the reason for this in detail.

# Tire Size Guide

## Ride Height

Take the default example in the flash tire size calculator above, here we have a stock tire size of 165/55R14 and a new tire size of 215/45R17. There is a total difference of 8.82cm in the two wheel and tire diameters, if we divide this by two we get a difference in radius of 4.41cm. If we ignore tire pressures and the effects of adding larger, wider wheels to suspension geometry; then this is roughly how much higher the car will be from the ground.

## Speedometer

Then there’s the speedometer, a cars speed reading is usually taken from the transmission and is set based on a number of predefined constants. When you change your wheel and tire combination you are taking one of these constants and making it variable. The speedometer does not know the new value and so continues to read based on the original wheel & tire size. If you look at the above default example again you will see that with a 215/45R17 wheel and tire combination there is a difference of 16.4% in the speedometer reading over the stock setup. As you can see, at 60mph your speedometer should actually be reading 69.9mph!

## Acceleration

If we fall back to the default example again, the 215/45R17 wheel and tire combination has a larger overall diameter by 8.82cm. A larger diameter has a greater rotational inertia which requires more energy to accelerate. Or in other words: the bigger the wheel, the slower the acceleration.

It should be noted that putting a bigger wheel and tire combination on your car *does not* reduce your cars power. Your cars power remains the same; however it takes more force to turn your car’s wheels resulting in slower acceleration.

## Tire Width Equivalency Table

You may also find the following table of recommended tire widths for given rim widths useful when changing your tire width.

Rim width | Min tyre width | Ideal tyre width | Max tyre width |
---|---|---|---|

5 .0 inches | 155 mm | 165 ou 175 mm | 185 mm |

5.5 inches | 165 mm | 175 ou 185 mm | 195 mm |

6.0 inches | 175 mm | 185 ou 195 mm | 205 mm |

6.5 inches | 185 mm | 195 ou 205 mm | 215 mm |

7.0 inches | 195 mm | 205 ou 215 mm | 225 mm |

7.5 inches | 205 mm | 215 ou 225 mm | 235 mm |

8.0 inches | 215 mm | 225 ou 235 mm | 245 mm |

8.5 inches | 225 mm | 235 ou 245 mm | 255 mm |

9,0 inches | 235 mm | 245 ou 255 mm | 265 mm |

9.5 inches | 245 mm | 255 ou 265 mm | 275 mm |

10.0 inches | 255 mm | 265 or 275 mm | 285 mm |

10.5 inches | 265 mm | 275 or 285 mm | 295 mm |

11.0 inches | 275 mm | 285 or 295 mm | 305 mm |

11.5 inches | 285 mm | 295 or 305 mm | 315 mm |

12.0 inches | 295 mm | 305 or 315 mm | 325 mm |

12.5 inches | 305 mm | 315 or 325 mm | 335 mm |

Just a comment that the correspondence between rim width and recommended tire tread width applies to cars. Trucks will likely have higher widths for a give rim. For example, a 16×7 rim is often spplied on SUVs with tire tread widths from 235 mm through 265 mm.

great site really usefull ,

a point worth mentioning that the use of bigger diameter wheels puts more strain on the brakes and drive shafts due to leverage

oppss! fat fingered the numbers. Sorry. But the old is:BL 215/60R15; new recommended is: BL P205/65R15. Which one is better and safer? Thanks.

dr.jim

I drive a 2001 Camry. The old installed tire size is BL 215/60R15 @ 200.75cm. I went to a different Firestone tire stoe and was told that BL P205/65R15 92H is better which measures 196.98cm. I searched on this great website you have and i found out the new recommendation is a bit smaller than the old ones I still have, for the same price w/50k miles warranty. basing on your info of acceleration, speedometer readings, etc, which will be a better choice and safer? Also, is it safe with the same reems? Pls advice. Thanks much and stay safe.

hi,

these speedo readings, is this taking into account that all speedos are three miles per hour fast,

when my speedo says 30mph would i by law doing 27 mph.

thanks,

its a good site,

rick.

Thanks in advance for your advice ,,

I am intending to change the radius of my VW Golf MK4 Rims to be 17 inch instead of the 15 inch so what is the best tire size ?

Thanks

It would really depend on the width of the new 17″ rim as the width of the rim determines the section width of the tyre. Once you know the width of the rim add 1 inch, convert it to millimeters and you’ll have a rough idea of the tyre section you’ll need.