How to calculate the correct tyre size when upgrading or downgrading your wheel size?

Tyre Size Calculator

I stumbled upon this really nifty utility on the internet. Kouki Tech has this really cool Flash-based utility where you can easily compare different tyre and wheel sizes both through hard numbers (end result of circumference, diameter, sidewall height) as well as visually see how different the tyre sizes will be. It’s very useful if you want to change to a tyre size that’s different from your car’s original size. The utility will also tell you how off your speedometer reading will be. Click the image above to access the Visual Tyre Size Calculator by Kouki Tech.

Looking to sell your car? Sell it with Carro.

10% discount when you renew your car insurance

Compare prices between different insurer providers and use the promo code 'PAULTAN10' when you make your payment to save the most on your car insurance renewal compared to other competing services.

Car Insurance

Paul Tan

After dabbling for years in the IT industry, Paul Tan initially began this site as a general blog covering various topics of personal interest. With an increasing number of readers paying rapt attention to the motoring stories, one thing led to another and the rest, as they say, is history.

 

Comments

  • B33MER on Aug 15, 2009 at 12:09 am

    Nice one paul :)

    Like or Dislike: Thumb up 0 Thumb down 0
  • Simon on Aug 15, 2009 at 12:11 am

    best !!!

    Like or Dislike: Thumb up 0 Thumb down 0
  • Simon on Aug 15, 2009 at 12:11 am

    wonderfull !

    Like or Dislike: Thumb up 0 Thumb down 0
  • 2fast on Aug 15, 2009 at 12:41 am

    I usually go to this site to check tyre sizes

    http://www.miata.net/garage/tirecalc.html

    Instead of Flash it uses Java.

    Like or Dislike: Thumb up 0 Thumb down 0
  • tayamaster on Aug 15, 2009 at 1:34 am

    how to measure the rolling radius? how come diameter is alot smaller than radius? pls clarify

    Like or Dislike: Thumb up 0 Thumb down 0
  • Xoomie on Aug 15, 2009 at 1:44 am

    try this site

    http://www.1010tires.com/tiresizecalculator.asp

    Like or Dislike: Thumb up 0 Thumb down 0
  • damn difficult to explain this to uncles and pa's about the importance of tire sizes…at the tire shops, once the rim size matches, its an all go…little do they take into account the profile, diameters and other relevant measurements…sigh

    Like or Dislike: Thumb up 0 Thumb down 0
  • acerman on Aug 15, 2009 at 2:52 am

    How to use this application, cannot click on anything.

    Like or Dislike: Thumb up 0 Thumb down 0
  • Paul Tan on Aug 15, 2009 at 3:51 am

    rolling radius is circumference, not diameter.

    Like or Dislike: Thumb up 0 Thumb down 0
  • shah333 on Aug 15, 2009 at 6:01 am

    try this..

    http://www.wheelsmaster.com/rt_specs.jsp

    Like or Dislike: Thumb up 0 Thumb down 0
  • http://www.1010tires.com/TireSizeCalculator.asp

    My regular tire size calculator

    Like or Dislike: Thumb up 0 Thumb down 0
  • mikasa on Aug 15, 2009 at 8:23 am

    no need to click .just choose all the number given

    Like or Dislike: Thumb up 0 Thumb down 0
  • http://www.wheelsmaster.com/rt_specs.jsp

    What about this 1.

    Like or Dislike: Thumb up 0 Thumb down 0
  • bugger on Aug 15, 2009 at 9:31 am

    yipeee~~

    for my case:

    from 175/70/13

    to 195/50/15 only 0.1% difference ;)

    Like or Dislike: Thumb up 0 Thumb down 0
  • jonny blaze on Aug 15, 2009 at 4:59 pm

    Rolling radius = radius of wheel + height of sidewall

    eg 205/50/16

    205 is width of tyre in millimeter

    50 is the profile or aspect ratio or height of the sidewall of the tyre and is expressed in percentage of width, 50% of 205 = 102.50mm

    16 is the diameter of the wheel in inches

    radius of wheel is 1/2 of its diameter, 16/2= 8 inches

    1 inch = 25.4mm

    8 inches = 25.4 x 8 = 203.20mm

    Therefore, rolling radius = 203.2 + 102.5 = 305.70mm

    Like or Dislike: Thumb up 0 Thumb down 0
  • jonny blaze on Aug 15, 2009 at 6:24 pm

    Rolling radius = radius of wheel + height of tyre's sidewall

    eg 205/50/16

    205 is the width of the tyre in millimeters

    50 is the profile or aspect ratio or sidewall height, expressed in percentage of width,

    50% of 205 = 102.50mm

    16 is the diameter of the wheel in inches

    radius is 1/2 of diameter, 16/2 = 8 inches

    1 inch = 25.4mm,

    8 inches = 25.4 x 8 = 203.20mm

    Therefore, rolling radius = 203.2 + 102.5 = 305.70mm

    Like or Dislike: Thumb up 0 Thumb down 0
  • jonny blaze on Aug 15, 2009 at 6:30 pm

    sorry for double post.

    my post didn't appear at when I checked at 10.24am, so I resubmitted my comment.

    and that is when the double appeared..

    Like or Dislike: Thumb up 0 Thumb down 0
  • ivan98 on Aug 15, 2009 at 9:50 pm

    http://www.rims-n-tires.com/rt_specs.jsp is the most complete online calculator in this tire size comparison I've seen.

    Like or Dislike: Thumb up 0 Thumb down 0
  • Insomniac on Aug 17, 2009 at 5:28 am

    Hi,

    Just popped in to see where the sudden influx of traffic came from. Glad you like my wee utility, its basic compared to some but I was going for ease of use over masses of numbers. I'm currently developing V2 of the calculator as well as a visual wheel offset calculator.

    If anybody has an idea or suggestion for ways to improve the caculator then please feel free to leave a comment here:
    http://www.kouki.co.uk/tyre-size-calculator-v2-wi…

    PS, for those confused about the term "rolling radius", don't be. Its a daft term I picked up somewhere and probably only makes sense in my head. It is actually the circumference of the wheel & tyre combination.

    Like or Dislike: Thumb up 0 Thumb down 0
  • tyre circumfrace.

    gearbox ratios.

    with calculations, this data enebles you to find speed of the car in relation to rpm.

    Like or Dislike: Thumb up 0 Thumb down 0
  • armandd on Aug 17, 2009 at 10:15 am

    here's another one, complete with tyre width, offset, revs per mile, whether the new rim will hit the fender or not, other size suggestion etc etc…

    http://www.rims-n-tires.com/rt_specs.jsp

    Like or Dislike: Thumb up 0 Thumb down 0
 

Add a comment

required

required