MX-3.com

ive been looking into getting wheels w/ a thicker sidewall to fill in my wheelwell better (thanks jesse...lol) right now i run motegi mr7s with 205/40/17 series tires. i guess my question is what wheel/tire combos are you guys with thicker sidewalls running? ive been thinking of lowering the car too, but i figured the wheels were do for an upgrade so would start there. also open to trade my motegis

its the middle number... so you could move up to 45 and still be pretty accurate on the speedo. in truth, complete accuracy is right between 40 and 45

Heres tire size calculator, you can play around and figure out whats the best option for you.

http://www.miata.net/garage/tirecalc.html" onclick="window.open(this.href);return false;


Also, tirerack.com has alot of specifics about tires. You can compare performance in different conditions, weight of tires (varies alot between manufacturers). Also what I found kinda interesting is that even tires of the same size are different in size. What I mean by that is a 205/40R17 tire is not exact same size from different manufactures.

http://www.tirerack.com/indexA.jsp" onclick="window.open(this.href);return false;

The overall diameter of the wheel is part of the calibration of the speedometer. Changing wheel diameter to fill the wheel well will alter the indicated speed on your speedo. For example, in exchanging your 205/40/17 tires for 205/45/17 you are actually changing from a tire with a wall height of 82mm to 92.5mm. It will increase the reading on your speedometer by about 3 - 4%.

Not bad, but not ideal either. I suggest sticking with the stock overall tire dimension and lowering the car to center the wheels in the wheel well. Getting a bigger tire is not the solution.

wytbishop wrote:The overall diameter of the wheel is part of the calibration of the speedometer. Changing wheel diameter to fill the wheel well will alter the indicated speed on your speedo. For example, in exchanging your 205/40/17 tires for 205/45/17 you are actually changing from a tire with a wall height of 82mm to 92.5mm. It will increase the reading on your speedometer by about 3 - 4%.

Not bad, but not ideal either. I suggest sticking with the stock overall tire dimension and lowering the car to center the wheels in the wheel well. Getting a bigger tire is not the solution.

that calls for a bud light mr. tire diameter guy!

Ima math nerd...I can't help myself.

you're right there's a ~3% difference, but youre going on the assumption that 205/40/17 is the equivelent of stock 15's. it's not. it's actually 1.7% too fast. 205/45/17 is 1.7% too slow. so there's not much of a trade off either way, and its ok to do. either way you won't have a 100% accurate speedo and it will be
+ or - the same percentage either way

yeah your 205/40/17 is smaller then the 205/55/15 so going with 205/45/17 woudn't make much of a difference at all

Now I get it, size really does matter

the whole speedometer being off by a few percent is non-issue. right now im just trying to address wheel well space. ive been looking into lowering the car too, but my erebuni bumper already hangs low so i dont know if id be able to close the wheel well space without putting my kit at risk.

the point being is yes you could get bigger sidewalls and still be within the same range of accuracy you are now. i don't think you'll find anyone saying they use sizes other than whats been listed in this thread because typically people want their speedometers to show the speed they're actually going at...

but if all you care about is wheel well gap, then what are you asking the question for? go to the store and put a tire next to your car and see what fills the gap up. get 55's get 65's get whatever

^^^Anarchist.

wytbishop wrote:^^^Anarchist.

free country lol...

More sidewall = worse handling

True for most applications. Don't just get a bigger sidewall, it will look stupid and will make the car handle odd.

thats a good point... i dont want to sacrifice handling. some guy wants to trade me 16 inch slipstreams w/ 205/45/16 tires i might just do that and lower it a bit