Mazda 6 Forums banner
1 - 11 of 11 Posts

·
Registered
Joined
·
451 Posts
Discussion Starter · #1 ·
Hey guys, so the story is this:

I'm looking to replace the rubbers on my speed6 with some falken azenis rt-615's. I want to get 225's, but the question then is 225/40/18? or 225/45/18? Falken says that the minimum wheel width on the 40 profile is 7.5" when the min wheel width on the 45 profile is 7".

I would prefer to run the 40 profile b/c it's almost $30 cheaper per corner, has a slightly higher load rating, and i'm a tiny bit worried about rubbing (i'm also lowered on the autoexe springs)... BUT are there any dangers to running 40 profile vs the 45 profile?? I've emailed Falken with no response yet. I ask about dangers because I'm going to be taking the car to a track day at streets of willow springs, and I don't want anything bad to happen while running the 40 profile.

anyone have any input? i kind of need to get tires quick.

thanks in advance!
 

·
Registered
Joined
·
1,004 Posts
I've got 225/40/18 on and I like the look. Depending on where you live, it might be a problem. This winter has been brutal in Colorado and I blame it for having 2 tires go out on me in the span of 10 days.

I think next time I will go for the 45. The 40s look good but the drop with my Mazdaspeed springs still leaves some gap so I could fill it in a little more.

It's up to you, man. If you live in Cali or someplace sunny, I would go 40.
 

·
Registered
Joined
·
676 Posts

·
Registered
Joined
·
451 Posts
Discussion Starter · #4 ·
I've got 225/40/18 on and I like the look. Depending on where you live, it might be a problem. This winter has been brutal in Colorado and I blame it for having 2 tires go out on me in the span of 10 days.

I think next time I will go for the 45. The 40s look good but the drop with my Mazdaspeed springs still leaves some gap so I could fill it in a little more.

It's up to you, man. If you live in Cali or someplace sunny, I would go 40.[/b]
it's not that i wouldn't want to run a 225/40, it's that for some reason, the manufacturer says that it's meant for a 7.5" rim (and i only have a 7")... whereas the 45 profile can go on a 7" rim. I'm wondering why that's the case and if there's any inherent danger for doing that.
 

·
Registered
Joined
·
676 Posts
it's not that i wouldn't want to run a 225/40, it's that for some reason, the manufacturer says that it's meant for a 7.5" rim (and i only have a 7")... whereas the 45 profile can go on a 7" rim. I'm wondering why that's the case and if there's any inherent danger for doing that.[/b]
Yes, there is! You're stressin' the sidewalls of the tire. You will have sidewall failure over time.
 

·
Registered
Joined
·
940 Posts
This has been gone over soooo many times. 7 inch rim is too narrow - there is too much angle on the sidewall. Manufacturers give specs for a reason, they are not just trying to annoy you. If you want 225/40, get a 7.5" or 8" rim. If you want to keep the stock rim, go with 215/45 or 225/45.
 

·
Registered
Joined
·
451 Posts
Discussion Starter · #7 ·
yeah, i've pretty much come to that conclusion myself... and i've resigned to the fate of getting 225/45's instead of 225/40's... thanks!
 

·
Registered
Joined
·
451 Posts
Discussion Starter · #8 ·
do i need to worry about the oem load rating being a 93 and the load rating of the tires i'm getting being a 91?
 

·
Registered
Joined
·
1,495 Posts
i've resigned to the fate of getting 225/45's instead of 225/40's... thanks![/b]
Even at 225/45, you're pushing it. It is not a good idea to mount on the very narrowest rim the tire manufacturer approves. For every size of tire, the manufacturer specifies a "measuring rim," and that is the ideal rim width for safety and best handling. It is safer to put a "narrow" tire on a rim that is wider than the measuring rim than it is to put a "wide" tire on a rim narrower than the measuring rim. See the discussion here: Scroll down (or use your browser's "find in page" function to "Aspect Ratio and Rim / Pan Width."
 

·
Registered
Joined
·
451 Posts
Discussion Starter · #11 ·
i don't have the 400lb weight reduction mod, but i have the common sense and research mod... :D

with a load index of 91, it would support up to 1356lbs per corner...

assuming the speed6 weighs 3600lbs and a grossly inaccurate 70/30 distribution, that would put the load that the tire needs to carry at 1260lbs per front corner... that leaves me about 100lbs/corner of added load that i could put on (if we were using a 70/30 number which is wrong, i just didn't feel like looking up the actual distribution)...

as it stands straight up w/o taking weight distribution into account, at 1356/corner, that's 5424lbs that these 4 tires can handle... i don't think i need a 400lb weight reduction mod to get to that weight :)
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top