Which tire sizes work for stock rims

[golfer339]

I have a 2007 MazdaSpeed 6 and it's about time for new tires. I was wondering which sizes work well on stock rims. Can I get 225/40 or would it be better to get 225/45?

 

[Blendercloud]

Your answer can be found in the sticky below.

http://www.mazdas247.com/forum/showthread.php?t=123666992

 

[golfer339]

I appreciate that but I am a novice and don't really have much knowledge about offset etc. and the sticky was kind of confusing to me. It sounds like offset mainly applies to changing wheels not tires but I may be completely wrong. I was just wondering if someone could give a quick response about which works best. I would prefer 225/40 but if it would cause problems I would just get 225/45.
Thank you

 

[Blendercloud]

If you are on stock suspension you can use 225/40's on stock wheels with no problem.

If you go with a 225/45 you will alter your speedometer more than what I would recommend. With the 40-series tire you will be pretty close to stock height.

 

[golfer339]

Thank you very much. This is just a curious question, but if stock tires are 45 series how come the 225/40's would be closer to stock height? Is it just because they are wider and it balances off the lower aspect ratio?

 

[bova80]

actually 225/45/18 are closer to stock size.

diameter
215/45/18 - 25.61"
225/45/18 - 25.97"
225/40/18 - 25.08"

with 225/45/18 your speedometer will read 1.398%
slower diameter differences is 1.39%

with 225/40/18 your speedometer will read 2.117%
faster diameter differences is 2.07%

with that said, i have run 225/45/18's since i ditched the stock tires and have never had any problems.

 

[golfer339]

Sorry for so many questions but I remember reading somewhere in the owners manual that if you change the tires from stock size that it will affect the the AWD system or stability control. I can't remember which it said, it was one of them, but is there any validity to it?

 

[bova80]

if the tires aren't even.

 

[Blendercloud]

The "series" is the tire height itself. It is determined as a percentage of the tire width. I know that's a little bit confusing, but here's an example.

On a 45-series tire that is 225mm wide, your sidewall height will be 45% of 225mm. Which is 101.25mm.

On a 40-series tire that is 225mm wide, your sidewall height will be 40% of 225mm. Which is 90mm.

The stock tires are 215/45 which makes the sidewall height 96.75mm. The reason it is encouraged to go with a 225/40 instead of a 225/45 is with a shorter sidewall on the 40-series you will be going slower than your speedometer says. Whereas with the 225/45 you will be going faster than what your speedometer says. Does that make sense?

 

[Blendercloud]

Nice post, Bova. That's a neat tool you have. A lot easier than hand-jamming those calcs.

 

[bova80]

its just a calculator on 1010tires.com

 

[golfer339]

Yes that does make a lot of sense. Thank you very much to both of you. I guess I will go with 225/40 now. That is what I was hoping to be able to get in the first place. So I guess it is okay that the diameter difference (around 2%) will be greater with these as opposed to the 45's? I think I saw that less than 1% was desirable but less than 3% is acceptable.

 

[Blendercloud]

You're quite welcome. Good luck!

 

[amilliems6]

i just got 225/40/18 and they fit on stock wheels

 

[golfer339]

i just got 225/40/18 and they fit on stock wheels

I read somewhere that no tire expert would recommend a 40 series tire on a 7 inch wide wheel- that it would have to be at least 7.5 and the MS6 stock wheel is 7". Have you noticed any problem with yours?

 

[amilliems6]

nop. actually i think the 225/40 is much better then my stock 215/40.. i feel like the drive is more comfortable

 

[Mistersix]

is there any reason-other than have more tires to choose from-to go with a different tire size? why not just stick with the 215/45's!

 

[amilliems6]

is there any reason-other than have more tires to choose from-to go with a different tire size? why not just stick with the 215/45's!

well idk why ppl keep sayin that our cars came with 215/45 but mine came with 215/40 factory tires. And idk about you but i prefer wider tires on a car then little thin looking ones. Plus i feel like my drive is more comfortable with the 225/40

 

[ballesteros_91]

go 225/45's

 

[Mistersix]

well idk why ppl keep sayin that our cars came with 215/45 but mine came with 215/40 factory tires. And idk about you but i prefer wider tires on a car then little thin looking ones. Plus i feel like my drive is more comfortable with the 225/40

well thats understandable. but i wouldnt even think there'd be a visible difference between the two as far as width is concerned so certainly its not an appearence thing.
really though, 225's are still skinny little tires. but there is a hell of lot more tires to choose from in that size.
215 seems more popular for 17 inchers.