Vintage Mustang Forums banner

1 - 20 of 20 Posts

·
Registered
Joined
·
1,646 Posts
Discussion Starter #1
Guys,
There is a lot of conjecture out there on max tire size for an 8" wide rim.
I have found a pretty good deal on a pair of 255 wide RA1s and Tire Rack's web site says they will "fit" on my 8" wide rims.
My question is, will the tire be supported enough to not feel squishy in turn in?
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #3 (Edited)
First of all, this is for a 69 mustang and I already have 225s and looking for more contact patch. I can certainly run larger tires than 225s on the front.

Thanks for the reply.
 

·
Registered
Joined
·
4,050 Posts
your good 16x8x4.5 225/50/16. @dobrostang has a formula for rim vs tirewidth
I actually run 16x7x4.5 with a 1" adapter with 225/50/16 with fair results

THe story I understand is that you want your side walls to be parallel as possible. This puts a flat contact patch on the ground. 0.9 to 1.1 times the rim width. Yes many will tell you they got a 315s on a 5" rim and it handled great, I have no idea if what I heard is right but my 225s on 8"rims are a delight to drive on the track or autocross so I'm sticking with it, call it a superstition but hey - its an internet forum you didn't expect a scientific answer did you? I did'm\nt do so good in science - was kinda hard.... ;o)
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #7
I have seen a similar formula that says .85 to 1.00 of tread width...
So using that formula, 245 is the widest you can run on an 8 inch without Ill effects.
 

·
Registered
Joined
·
3,065 Posts
I have seen a similar formula that says .85 to 1.00 of tread width...
So using that formula, 245 is the widest you can run on an 8 inch without Ill effects.
I disagree, even the Mfg. has a suggested range of 7-9" for that size tire. I run "oversize" tires, ( 275/35-18 on a 9" wheel ) on my Boxster. I didn't feel any extra "squishiness" or "ill effects". Your 8" is right in the middle of the range, you'll be fine. Those numbers are ideals in theory, but most of use don't have the luxury of changing wheels every time we make a tire change ! IMO section width around 1" wider than the wheel is perfect for most situations, that's where modern Z06's and Porches are at. I think section=rim width is a bit stretched.
 

·
Registered
Joined
·
4,646 Posts
Every tire is different. You'll look at ten different 225s that have different tread widths. 225 may in be in the ball park for an 8" but other sizes can probably fit and not be in a sub-optimal situation.

Personally, I think 255 is pushing it on an 8" rim. Only real way to know is to try it out.
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #10
Well I’m going to try it ....
 

·
Registered
Joined
·
436 Posts
Been doing it for years on the track. no issues what so ever. Have even gone with 275/45/16. 255/50/16 toyo ra1's are the best track tire I have ever run so far.
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #12
I figure that 255s on the front ought to increase grip...
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #13 (Edited)
Ok, they are on the wheels and on the car. The drivers side has less tire clearance. I’ll have to install upper arm shims and then lengthen the strut rod to center the wheel in the arch. Then roll the fender.
One step forward, two steps back....
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #15
We can only lead you to the water...it’s all up to you after that.
I don’t think clearence was ever discussed in this thread,
My cars body is shifted to the drivers side about 3/8” when measured from side to side.
 

·
Registered
Joined
·
436 Posts
I have done so much to the body I have no idea what stock clearances are. Anything is possible with enough hammer work welding and bondo.
 

·
Registered
Joined
·
1,646 Posts
Discussion Starter #17
They fit with no mods on the passenger side. On the drivers side I have to center the wheel in the opening and the roll the lip it looks like.
 

·
Registered
Joined
·
3,231 Posts
Just to add to the confusion, brand of the tire can make a huge difference. I had a Sumitomo 255 tire mounted on an 8 inch rim to do some clearance testing on the front end. I currently have some 245 Nexens on front. Surprise! The supposedly wider Sumitomo's aren't. The Nexen's seem to be closer to manufacturers specs. I wouldn't have been too surprised if they had been about the same width but to be a totally size diff in other direction was something else.
 

Attachments

·
Registered
Joined
·
4,260 Posts
Eastwood makes a nice tool to roll the lips. Bolts on to the wheel flange.
Check ebay for that wheel lip tool, a bunch cheaper and some of the ebay fender lip rollers are identical to the Eastwood tool.
 
1 - 20 of 20 Posts
Top