255/50/16 RA1s on a 8" wide rim - Vintage Mustang Forums
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post #1 of 20 (permalink) Old 04-20-2019, 06:01 PM Thread Starter
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255/50/16 RA1s on a 8" wide rim

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?

1969 coupe
372 Cleveland, 4 speed, 9" T.50 Trac Lock axle, Toploader, Global west suspension, Big Lincoln Trans Am Brakes front, Eldorado caliper/ MK VII disk rear.
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post #2 of 20 (permalink) Old 04-20-2019, 06:17 PM
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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


Brad

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post #3 of 20 (permalink) Old 04-20-2019, 06:59 PM Thread Starter
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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.

1969 coupe
372 Cleveland, 4 speed, 9" T.50 Trac Lock axle, Toploader, Global west suspension, Big Lincoln Trans Am Brakes front, Eldorado caliper/ MK VII disk rear.

Last edited by Jsams; 04-20-2019 at 07:03 PM.
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post #4 of 20 (permalink) Old 04-20-2019, 07:01 PM
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Quote:
Originally Posted by Jsams View Post
First of all, this is for a 69 mustang and I already have 225s and looking for more contact patch.
Thanks for the reply.
Sorry read it wrong, I thought I read 225. I see now it says 255 ,long day


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post #5 of 20 (permalink) Old 04-20-2019, 08:56 PM
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Ideally, 225 is the perfect tire for for a 8” rim. RA1’s are pretty sticky. They’re probably going to roll over a bit on you.
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post #6 of 20 (permalink) Old 04-20-2019, 09:30 PM
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Quote:
Originally Posted by 2nd 66 View Post
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)
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post #7 of 20 (permalink) Old 04-20-2019, 10:27 PM Thread Starter
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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.
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1969 coupe
372 Cleveland, 4 speed, 9" T.50 Trac Lock axle, Toploader, Global west suspension, Big Lincoln Trans Am Brakes front, Eldorado caliper/ MK VII disk rear.
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post #8 of 20 (permalink) Old 04-22-2019, 08:46 AM
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Originally Posted by Jsams View Post
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.
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post #9 of 20 (permalink) Old 04-22-2019, 12:27 PM
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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.

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post #10 of 20 (permalink) Old 04-23-2019, 07:55 AM Thread Starter
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Well Iím going to try it ....
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post #11 of 20 (permalink) Old 04-23-2019, 06:12 PM
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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.
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post #12 of 20 (permalink) Old 04-23-2019, 08:52 PM Thread Starter
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I figure that 255s on the front ought to increase grip...

1969 coupe
372 Cleveland, 4 speed, 9" T.50 Trac Lock axle, Toploader, Global west suspension, Big Lincoln Trans Am Brakes front, Eldorado caliper/ MK VII disk rear.
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post #13 of 20 (permalink) Old 05-04-2019, 03:24 PM Thread Starter
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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....

1969 coupe
372 Cleveland, 4 speed, 9" T.50 Trac Lock axle, Toploader, Global west suspension, Big Lincoln Trans Am Brakes front, Eldorado caliper/ MK VII disk rear.

Last edited by Jsams; 05-04-2019 at 03:27 PM.
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post #14 of 20 (permalink) Old 05-04-2019, 09:44 PM
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We can only lead you to the water...itís all up to you after that.

Regards,
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post #15 of 20 (permalink) Old 05-04-2019, 10:39 PM Thread Starter
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Quote:
Originally Posted by patrickstapler View Post
We can only lead you to the water...itís all up to you after that.
I donít think clearence was ever discussed in this thread,
My cars body is shifted to the drivers side about 3/8Ē when measured from side to side.
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