Tire size question

-

cawley

383 Bcuda
Joined
Sep 10, 2013
Messages
2,340
Reaction score
673
Location
milton
Does anyone know if a 275/60/15 tire will fit on a 9.5 or 10 inch rim ?
 
yes it will but fits better on an 8.5" rim looks good, and give full sidewall, going @10.0" fits, but will stretch side wall some and wont' be 28" anymore, goes to 26.5-27" and stiffer ride. I have 275/60/15 Mickey Thompson sport radials on 8.5" rim and work well.
 
I run nitto 275/50/15 on 8 inch cragars and they fit very nice
 
They wear very well on 8.5s . Nice flat wear-pattern at the right air pressure. I suspect on 10s they will not wear the centers as fast as the outer bands, and that means they won't be giving you optimum traction either.
 
All you need to do is look them up on a tire manufacturers site:
BF Goodrich P275/60R15
Diameter 28"
Section width 11"
Section width is measured on an 8" wheel
Recommended wheel is 7.5"-9.5"
 
Are you to going put wheels that wide on your Barracuda, Wayne?
Yea, I would like to go wider but I don't want to fully mini tub it. I want to keep my fold down rear seat. I did move the inner wheel well in 1.5 inches
 
275/60-15s calculate out to 27.99. Installed on 8.5s they might be a little under that.
295/50-15s calc out to 26.61. Installed on 10s, they are closer to 27
That is a 5% difference., with a ride height drop of about .7 inch
28s are about the max you can fit,if you can keep the tire in the tub. As soon as it moves out a bit, it is in danger of rubbing on the outer fender,bottom front corner. I moved my rear-end back a half inch for clearance, to fit those.
The -5% is about one gear size, making 3.55s a blast.
3.25/50 15s fit in my stock 68 Barracuda tubs.They calc out to27.8 tall. With your bigger tubs, these should slide right in there. Mine are on 10s, but it wouldn't hurt for the rims to be wider. I cannot run more than 24psi, to get even treadwear.Ima thinking 12s. I cannot run more than 10s cuz the section width would grow,right into, everything.
 
Last edited:
What I did- moved springs in, mini tubed it 1.5 inches, moved rear back .5 inch. If I remember right with out looking again I have 10 inches from the inner quarter lip to the inner wheel well.
 
I wonder if that 10.0 is correct
325/50-15s are a tic over 13 inch section width, and the fit into my stock 68Barracuda tubs. Now the tread is only about 10. so the 3 inch difference has to be made up for; half to the inside and half to the outside. so that would make it 10 + 1.5 = 11.5 from the outside edge of the tread to the zero point of the inner fender. My sidewalls are flush to the outer body line. And the tire is about 1 inch below the bottom edge of the fender lip. I bent that lip up and out of the way.The rear suspension is stiff enough to not let the lip kiss the sidewall. So I am estimating 10 + 1.5 +.75 + 12.25 from the bent-up lip to the inner fender, and 13 from the painted surface of the body to the inner fender. With 1.5 mini-tubs, you should have 14.5 from paint to inner, and about 1.25 less if your lip is virgin. So That would be 13.25. If your springs are moved inboard, to the same plane, then you should have plenty of room for 325s, without bending that lip. The backspace will have to be very carefully worked out tho.....
 
Yea I was wrong. It is 13 inches from the inner wheel well ( moved in 1.5 ) to the inner quarter lip. I really don't want to cut the quarter lip. It has new quarters & it gets the wheel well moldings. Here is my measurements- wheel mounting surface to leaf springs is 8in. Wheel mounting surface to inside of quarter is 6 3/4
 
I have a friend who has 325/50/15 tires. Now if he measured right, he said they are 13.0 inches wide. I only have 13 inches of space in my wheel well. Inner wheel well to quarter lip is 13 inches.
 
Mine are 13.2 on 10s.
If I had to guess,These would be around 14.5 or a little more on 12s. This is the SECTION width, which your outer fender lips will never see on account of this width is around 3 inches down from the tread. What your lip will see is tread width plus the section bulge on one side plus about 1/2 inch clearance to the inner tub or 1/4 inch to the spring. So Ima guessing 13.75. Since the available room is 8 plus 6.75 equals 14.75, you have a full inch to the lip.
Unless you are lowering the body to below the tread surface. Then you will be lip-limited. But most guys run the ride height up about 1 to 1.5 inches HIGHER than the tread surface.
So the way I see it, is borrow that friends 325 and stick it in there!
 
Mine are 13.2 on 10s.
If I had to guess,These would be around 14.5 or a little more on 12s. This is the SECTION width, which your outer fender lips will never see on account of this width is around 3 inches down from the tread. What your lip will see is tread width plus the section bulge on one side plus about 1/2 inch clearance to the inner tub or 1/4 inch to the spring. So Ima guessing 13.75. Since the available room is 8 plus 6.75 equals 14.75, you have a full inch to the lip.
Unless you are lowering the body to below the tread surface. Then you will be lip-limited. But most guys run the ride height up about 1 to 1.5 inches HIGHER than the tread surface.
So the way I see it, is borrow that friends 325 and stick it in there!
Do you have any pictures of your Barracuda with that size tire ? Do you know your back spacing ?
 
My rear-end was narrowed to accept common 15 x 10s with 4.5 bs.
The rear-end was removed, and then the wheel and tire assys were installed into the tubs at intended ride height. Then the body was dropped 1.5 inches to simulate a bump or corner. Then the assys were pushed inboard until the sidewalls hit the inner side of the tubs. Finally a tape-measure was stretched from mounting flange to flange.To this measurement I added 1/4 inch per side, for sidewall clearance.Then the rear end was narrowed to provide that measurement.
1/4 inch per side was not enough for aggressive cornering. 3/8 per side is mostly ok.I highly recommend 1/2 inch per side from sidewall to inner tub. To the spring can be less. But it is hard to corner aggressively with 325s. That is a whole new learning curve.
On the street,from a stop, I think 325s are more show than go. I did not notice any significant increase in traction on the streets that I drive. Remember I am a streeter and I usually pull the plug at the top of first gear which is 55 mph. Top of first-over is 68 mph.Top of second is about 85. And top of second-over is 110.Sometimes I might hit 68. They are a little harder to break loose at speed.
But they sure look nice in there.
 
I had a 68 dart that I put 325s on. The rear was narrowed 3 in. from each side, fully mini tubbed, springs moved in & there was plenty of room on both sides. The rear in the barracuda I have now was narrowed 1.5 in. from each side. When I had that dart I got better traction on the street than I did on the track. My barracuda is a 383 4spd car. I am going to run 3:55 gears. It will be a street / strip car mostly street. I figured out the tire / wheel size on that dart the same way you did. I think A bodies look awesome with 325s
 
I just barrowed a pair of wheels & tires from my dad. They are M/T tires 295/50/15s They are 27 in. tall, 11 in. wide ( not the tread ) If I measured the rims right, they are 15x9s with a 5in. back spacing. I have 1 3/4 space between the tire & the inner quarter lip. Also I have 3/4 space between the tire & the inner wheel well.

Cuda tire clearence 001.JPG


Cuda tire clearence 002.JPG


Cuda tire clearence 003.JPG


Cuda tire clearence 004.JPG
 
Something does not compute;
In a previous post, the total tub room was computed to be 14.75.
This last post the total tub room adds up to; 11 + 1.75 +.75 = 13.5 inches
Where is the missing 1.25 inch?
I think it is in the section width.

A 295/50-15 should have a 275mm section on a checking rim of 70% of that 275mm. Converting to Imp we get 295 =11.6, on an 8 inch rim. On a 9 it will be a solid 1/2 inch wider so; 11.6 + .5 =12 . So are you sure the rim is 9? and How accurately was the section measured?

In any case, you have 1.75 + .75 = 2.5 inches clearance.Then 325 less 295 is 30 mm or 1.18 inches. If you add .5 for expansion on a 10 inch rim, that totals; 2.5 less (1.18 + .5 ) = .82 for sidewall clearance.
Once again; a 325 is measured on a 70% rim so; 325 is 12.8" section on a 9" rim. Adding .5 for a 10 inch rim we get 13.2 section. This into a 14.75 tub, leaves 14.75 - 13.2 =1.5 extra,meaning the 325 should fit.
And I already know that a 325 on a 10 fit into my STOCK tubs(just); so you should have up to 1.5 more (your mini-tub dimension),clearance than do I. Since I have about 1/2" total clearance, you should have 2.0
Almost all section widths tend to vary somewhat from the math, so here we have three separate witnesses that speak to 325s on 10s fitting. The clearance could be in the neighborhood of .82 to 1.7, perhaps as much as 2 inches.
Ima thinking you might be able to put those on 12 inch rims and have a considerably more stable platform. The 2 inch wider rims might add an inch or slightly less to the section. So now it is getting tight again. Since I know how those babys corner on 10s at 20 to 24 psi (terrible. That's why they are not under my car full-time) , I highly recommend to at least try 12s in 325s.
Unless you are not into hard charging through corners; then the 10s might be ok. But here is the thing;to get 325s flat to the ground for long treadlife, the pressure has to be dropped way down. Under 20. Cornering with fat tires on 20psi, if you have never done it, is a real wake-up experience the first time, and a surprise every time following. Slow down for the first merge;way down.Please!
 
Last edited:
Yea im not 100% sure on the rim size. I think I am going with a 9 in. rim & 275/60/15s. Only because the rims I want run don't come in 10 in. I am 100% sure of the body measurements.
 
The biggest tire to run on a 9, on the street, would probably be a 275/60-15.
Do NOT put 325s on 9s, and do Not put 295s on 9s either. They will not run flat to the road, and will only burn the treads off prematurely.

I wonder if you are thinking straight. You paid to get those bigger tubs in there. You might as well fill them up now. Your engine needs more than 275s. And you could have put 275s in the factory tubs.
 
-
Back
Top