245/40 too sloppy for 8 inch rim?

Miata Parts, Intakes, Superchargers, Headers, Exhausts, Shocks, Springs, Sway Bars, Brake Kits, Autocross and track mods.

245/40 too sloppy for 8 inch rim?

Postby ctompkins5 » Fri Feb 11, 2011 6:14 pm

Brian,

Just wondering if 245/40 will be too sloppy on an 8 inch rim? The PF01 17x8 et50 rims I just bought from you by the way.

Thanks
ctompkins5
 
Posts: 90
Joined: Sun Dec 03, 2006 9:44 am
Location: Fairfax, Virginia

Re: 245/40 too sloppy for 8 inch rim?

Postby Brian » Fri Feb 11, 2011 7:08 pm

Well....my preference would be no more than 235/40/17 on that wheel. The 245/40/17 will fit but feel a little sloppy.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 10189
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: 245/40 too sloppy for 8 inch rim?

Postby grey_NC » Fri Feb 11, 2011 7:54 pm

brian,

How about 265/40 on a 17x9 wheel?
grey_NC
 
Posts: 147
Joined: Mon May 26, 2008 1:27 am

Re: 245/40 too sloppy for 8 inch rim?

Postby Brian » Fri Feb 11, 2011 8:22 pm

About the same... a little sloppy. For 17x9 I would not push beyond 255 wide.


Below is a picture of a 235/40/17 R888 on a 17x9 RPF1. Notice nicely supported vertical sidewalls. When sidewalls are straight up and down you get fast response, stable contact patch, more grip from the tire, etc. The car is easier to drive at the limit when the tires are not sloshing all over the rim. For autocross we often shove more tire on the rim than is ideal because we have a limit on rim width for many classes. We compensate for the mess this makes with higher tire pressures. The result MAY be faster around the autocross course...but it can feel numb, sloppy, and if not for the rules on wheel width we would not be doing it!

Thus, you could do the 265 on the 17x9 if you are running CSP but I suggest no more than 255 for that rim. And if you really want to lay down 265 size tires, get a 10 inch rim. For example, our NC Light track project MX5 started with 9.5 inch wide wheels....with just a 255 wide tire. Recently picked up some 17x10 for NC LIGHT....to run 265 tires.

Image
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 10189
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: 245/40 too sloppy for 8 inch rim?

Postby morrisg » Mon Feb 14, 2011 1:35 am

STR class is limited to 255 width tires on the RWD cars.
morrisg
 
Posts: 128
Joined: Mon Nov 15, 2010 12:02 am


Return to Mazda Miata and Fiat 124

Who is online

Users browsing this forum: No registered users and 4 guests