This is a nice calculator you can use to determine percentage error of your speedometer/odometer if you replace your OEM tires with others which are a different diameter:

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

David.

__________________

That's pretty neat...I'm only a little off going from the stock 285's to the 315's. I can't read the percentage cuz the tire graphic goes over that part of the sentence?

__________________
2004 White SE, CC, BT, Off Road 4x4
• Banks Monster Exhaust • Pro Comp 6" Stage II • PRG Radflo External Reservoir Coilovers w/King Springs • EBC Slotted Rotor • Yellow Stuff Pads
• PRG OR Traction Bars • American Racing Chamber w/Teflon 17" • BFG T/A KO 315/70 17 • Active Tuning Grounding Kit
• FramBoost Air Intake • XM Satellite Radio • Hoppy Assist Tailgate • Grillcraft Black Mesh Grille • TruTrac

Wahoo

PB...try this one...it is considered the "new" version but looks the same.

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

Hopefully you will be able to read the results on it. Sorry the tire extends over the % error - what a dumb oversight!!

David

__________________

Here is another one that squid found:

http://cat.cc/tiresize.htm

Check it out!!!

David

__________________

Oh well...same result, can't see the percentage? It's ?.1%, I think it's 5.1% since 5% of 60 is close to 63?

Thanks

__________________
2004 White SE, CC, BT, Off Road 4x4
• Banks Monster Exhaust • Pro Comp 6" Stage II • PRG Radflo External Reservoir Coilovers w/King Springs • EBC Slotted Rotor • Yellow Stuff Pads
• PRG OR Traction Bars • American Racing Chamber w/Teflon 17" • BFG T/A KO 315/70 17 • Active Tuning Grounding Kit
• FramBoost Air Intake • XM Satellite Radio • Hoppy Assist Tailgate • Grillcraft Black Mesh Grille • TruTrac

Wahoo

PB, did you try the 3rd calculator I posted (the one that squid found)??

See if it will work better for you.

I think you are right about the missing number being 5. That sounds viable.

David

__________________

Those are pretty cool but I just do it the old school way.
Wait for the flashing lights in the rearview mirror, the nice man in the hat is always willing to tell you your speed. Even gives it to you in writing so you can tape it to your dash.

If you scroll down on the newer Miata one, of post #3, there is a text based version that allows multiple tire sizes to be compared to an original.
http://www.miata.net/garage/tirecalc.html
Thanks Tex!

Ah...that's the trick...wow my Revs/Mile went from 617 down to 587.

I thought the stock 17" tires were 33's not 32's, huh?

Where's those 3.73 gears set from PRG so I can get back to/or close to stock? LOL

__________________
2004 White SE, CC, BT, Off Road 4x4
• Banks Monster Exhaust • Pro Comp 6" Stage II • PRG Radflo External Reservoir Coilovers w/King Springs • EBC Slotted Rotor • Yellow Stuff Pads
• PRG OR Traction Bars • American Racing Chamber w/Teflon 17" • BFG T/A KO 315/70 17 • Active Tuning Grounding Kit
• FramBoost Air Intake • XM Satellite Radio • Hoppy Assist Tailgate • Grillcraft Black Mesh Grille • TruTrac

Wahoo

Good find, I was at Discount Tire last week getting new tires, the guy there have a program on his PC that does the same thing. He punch in the stock size, than the new size and it tell you the difference.