Tire Calculator

**DMAG** · 03-14-2006, 08:15 AM

Thanks to rickcrocetti for supplying this great link for calculating tire sizes and speedmoter changes with different tire sizes.

Car / SUV / Van / Light Truck Tire Calculator

**7thS0N** · 03-14-2006, 02:24 PM

Good link. No fancy picture of tires like the one for the Miata club, but good info (and more detail about speeds).

**bipto** · 03-14-2006, 02:30 PM

Great to have one of these "locally..."

Kudos Anthony & Rick - thanks!

**MAGFX** · 03-15-2006, 01:44 AM

CHECK OUT THIS ONLINE TIRE/WHEEL CALCULATOR: http://www.bigcustomwheels.com/rt_specs.jsp

Just fill out your existing tire/wheel info on the left, and then fill out your dream tire/wheel info on the right. Check out all of the calculated information below the graphics. It gives you a thorough comparison to your existing set-up. Take some of this information and compare it to your measured clearances between your tires and suspension uprights/wheel wells/shocks/outer fenders on your car. Always take into consideration that as the wheel (especially the rear) droops or moves up into the fender, some of those dimensions will change. This calculator sure helps out though. I have spent a lot of time going through many scenarios. The tough part is finding the actual sizes and offsets (et.) of the wheels. Tirerack.com is pretty good at giving the actual (or close to) section widths, etc. of tires from different brands.

I also spent a lot of time measuring the tire clearances with the car in various attitudes to get the tire sucked up in the fender and drooped down. Note: the less the wheel is drooped (including lowering springs), the greater the clearance is on the inside of the rear. Also the closest inside clearance on the rear is the forward-inner part of the wheel well and not the upper-inner of the wheel well. The front suspension upright moves along with the wheel assembly. So what you see is what you get. Also, there is probably some lateral tire movement at the top of a tire as the bottom is pushing in a hard turn. This calculator is theoretical, so double check everything on your car.

HAVE SOME FUN!

Cheers…

**Silver1** · 04-04-2006, 01:19 PM

Just a note on tire size. According to the Continental Tire website, the stock 225/60-18 tire has a diameter of 28.0" - NOT 28.6" as all the tire calculators tell you.

**Scott** · 04-04-2006, 01:37 PM

Originally Posted by Silver1

Just a note on tire size. According to the Continental Tire website, the stock 225/60-18 tire has a diameter of 28.0" - NOT 28.6" as all the tire calculators tell you.

Hey Silver1,

I puzzled about this myself, so I measured the circumference of a fresh set of stock tires and calculated the dia. I don't have the exact results at hand, but the measured size was close to 28.6". Continental's website is in error at this point.

Scott

**Vaderwagon** · 04-04-2006, 02:04 PM

Here is the one I use. Sorry if I posted this before.
http://www.powerdog.com/tiresize.cgi

**ASU_Magnum** · 07-10-2006, 04:05 AM

thats cool. from the stock 17" wheels i only went up .6" in diameter and .3 revolutions per second in going up to my 20"s which offsets my speedo by 1.5mph at 65. anyone know what the true speed would be if the speedo reads 80 then?

**GROUNDED** · 01-01-2007, 11:42 PM

Originally Posted by Scott

Hey Silver1,

I puzzled about this myself, so I measured the circumference of a fresh set of stock tires and calculated the dia. I don't have the exact results at hand, but the measured size was close to 28.6". Continental's website is in error at this point.

Scott

different brand tires measure different heights, just ask the 4x4 guys because they get it the worst in the bigger sizes.

**MattRobertson** · 01-02-2007, 12:38 AM

Originally Posted by Vaderwagon

Here is the one I use. Sorry if I posted this before.
http://www.powerdog.com/tiresize.cgi

Thats my regular bookmark as well. No other calculator can do 2, 3 or 10 different sizes side-by-side like the Powerdog calculator can.

But the bigcustomwheels one gives you offset, which is another unique thing. Not something you need every day, but a useful thing to have in your hip pocket.