Okay, so thats the difference. SS/SC's are 215/45r right, and thats what I have on my fronts for my toyo proxes 4...but I cant find that size anymore, and now they only have 215/40r

soooooooo can I slap those on my stockers and not worry? Thanks for the help..

ttt pleaseeeeeeeee

 

yes most ppl do switch to a 40 series because there are more to choose from and slightly cheaper

 

If you switch to a 225/40 the speedo will stay pretty much right on. Plus, you will get the benefit of having a slightly wider tire. Not to mention that 225/40 are typically cheaper as they are a more widely used tire.

 

how about a 235/40/18? will those fit on the stock ss rims?

 

Yes 235/40s do fit on stock rims buttt some people rub if they are lowered and some dont

 

My speedo is already fast and going from 45 to 40 will make it a lil faster so id rather go wit 225/45/18 to even it out.

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

 

I am running 235/40/18 with Sportline springs on my SC/SS. They do rub when I have a lot of stuff in the tunk. However the car handles like it is on rails. The rubbing can get frustrating. I would suggest if you are lowered that you run a 225/40/18.

Oh yeah and here is a little tire size tech. The 215 is the width of your tire from the tip of the sidewall to the tip of the sidewall on the other side. It is 215 mm wide The 45 represents a percentage of the width. Basically it is 45% of 215 and represents the size of the sidewall. And of course the 18 is the rim size.

So if you change the size of your tires from a 215/45/18 to a 225/45/18 you are actually make the tire taller. However if you change from 215/45/18 to a 225/40/18 you are running the same size tire as the 215/45/18 except you have a wider contact patch(Contact patch= the amount of tread in contact with the road).

Hope this helps.

 

Actually this helps a lot. Thats the first time I've ever heard that, or the first time someone's explained it to the point where I understand it! Thanks!!!!

 

I've got 225/40's in the front and 225/45's in the rear, long story short I blew out my front tire one Sunday afternoon and needed tires quick, 225/40's were all they had so I said do it. When checking my speedo mileage I'm ~.1 short every mile according to the handy dandy interstate mileage check areas..

 

That is true to a certain degree but not always.......for example, a 215/45R18 (25.6") is actually 1/2" taller than a 225/40R18 (25.1") which is pretty significant.