Another No-Mod Tire Fitment Question

[Dodge72]

I've been skimming this forum for a while now trying to figure out the right tire combo for my incoming 15x7 Rallye wheels with 4.25" backspacing. Just want to clarify a few things...

I'm not looking to relocate springs or mini tub or anything. Just want a beefier tire than my skinny-stock 195/70/14's, something that gives it a more muscle-car aggressive stance than grandma's ride. What is the max size for the wheel well? I heard on another post that 235's might be the max without mods, but it might be 225? And would 60 series tires be a good choice? Tires and wheels give a car a lot of it's attitude and I want it to be just right! Thank you!

 

[MuuMuu101]

What rear end are you running? The easiest thing to do is make some cardboard templates and measure measure measure. I was able to fit 255/40/18 tires perfectly in my wheel tubs but that's going to require minor trimming on my part.

 

[Dodge72]

Forgot that one little part. I'll be running a 8 1/4. And the trimming...I keep seeing it but I'm not totally understanding what that means.

 

[72bluNblu]

225/60/15 up front, 245/60/15 out back if it's an A-body 8 1/4. Should give you a decent stance and shouldn't require any significant modifications.

A 255 will fit some cars if the lip on the back of the quarter panel wheel opening is cut back for additional clearance. But based on the measurements I've taken off of my '71 dart, even with trimming the quarter lips the clearance would be minimal, so it might not work on all cars, and the backspace would have to be perfect. Definitely no guarantee they can made made to fit your car, even if they have been made to work on others. Plus not everyone wants to mess with cutting/rolling the quarter lips.

 

[2 Darts]

Many moons ago, I asked Stockton Wheel the "How big?" question regarding my 72 Demon. The fellow I spoke to said 235/60-15. So I went with that. The wheels are stock cop car, 15 x 7, 4¼ backspacing. The car has a 75 sub-frame and a re-purposed Mopar BBP disk brake system. This adds about 1½ inches to the front tread.

In the meantime, I had a pair of 255/60-15 that I tried on the car. The front tires would not clear the fenders. ops: In back, tires were less than ½" off the leaf spring.

The 235s fit in front for static testing fine. In real world driving, they occasionally kissed the top-inside of the wheel opening. Things were little better in back. The top of the wheel well would greet the tire under significant jounce (upstroke in shock-speak, to some). I did not have any contact with the spring. Small wonder. #-o The rear architecture of the car was first built in 1959 for a 6.50-13 wheel/tire package.

These tires are going to age out before they wear out. When they do, I plan to fit 225/60-15s.

 

[72bluNblu]

Many moons ago, I asked Stockton Wheel the "How big?" question regarding my 72 Demon. The fellow I spoke to said 235/60-15. So I went with that. The wheels are stock cop car, 15 x 7, 4¼ backspacing. The car has a 75 sub-frame and a re-purposed Mopar BBP disk brake system. This adds about 1½ inches to the front tread.

In the meantime, I had a pair of 255/60-15 that I tried on the car. The front tires would not clear the fenders. ops: In back, tires were less than ½" off the leaf spring.

The 235s fit in front for static testing fine. In real world driving, they occasionally kissed the top-inside of the wheel opening. Things were little better in back. The top of the wheel well would greet the tire under significant jounce (upstroke in shock-speak, to some). I did not have any contact with the spring. Small wonder. #-o The rear architecture of the car was first built in 1959 for a 6.50-13 wheel/tire package.

These tires are going to age out before they wear out. When they do, I plan to fit 225/60-15s.

Stock 73+ BBP disk brakes add about 5/16"- 3/8" per side compared to SBP drums. As for 235's, I know of one other person on here that runs them. I can say that when I was running 225/60/15's on 15x7's with 4.25" of backspacing on my Duster I had very little "extra" clearance to the fenders. Clearance depends very much on both ride height and alignment when you get that close. The current wheel package on my Demon has the same fender clearance as a 235/60/15 would on a police rim, but my fenders have been trimmed and modified. My car sits pretty low, so that's probably on account of my ride height, but I definitely wouldn't say that a 235/60/15 will fit every car without modifications.

For the rear wheels, Demons/Dusters have significantly more room in the rear wheelhouses than Darts/Valiants/Scamps. As in, more than an inch of additional clearance. I fit a 275/40/17 on a 17x9 with 4.75" of backspace on my Duster when the spring were in the stock location and the quarter lips were untrimmed, they cleared with room to spare. You can fit a 275/60/15 on a Demon/Duster with everything in the stock locations. I know for sure on BOTH of the Dart's I own that the absolute largest I could go without cutting anything is probably a 245/60/15, and those would still require pretty accurate backspacing.

 

[69_340_GTS]

If we are talking about the blue '72 Dart, the 4.25" backspacing 7" wheel will not allow anything bigger than 225/60R15 front or rear. It MAY be possible to squeeze a 235/60 on the back, but do you want to have potential rubbing issues? Plus, IMHO a 235 tire really needs an 8" wheel to look right and not be pinched in.

 

[Dodge72]

Thanks for all the useful info guys. I'm converting over to BBP discs and rear axle soon, so with all that going on I don't think modifying wheel wells and spring location is on my agenda. Definitely wouldn't want anything to be rubbing either. And yes, I did hear that the Demons/Dusters had more wheel clearance.

225/60/15 up front, 245/60/15 out back if it's an A-body 8 1/4. Should give you a decent stance and shouldn't require any significant modifications.

I looked around for images on that and cars that had that combo looked awesome. However, this will be my daily driver so for practicality reasons I think I'm going to have to stick with the one tire size all around, and in a Dodge Dart, 225s shouldn't have a problem as far as rubbing or clearing?

 

[69_340_GTS]

Big bolt pattern in the rear, you'll need around 3/8" more backspace on the wheels.
4 3/4" would be best.

 

[Dodge72]

What would happen if I were to keep the 4 1/4" backspacing?

 

[jtkaaa07]

Biggest I could get on mine is 225/70/15 out back, and there damn close! Going to mini tub and relocate in the coming month before the F up my quarters! These car's suck for clearance, and should have been built with mini tub's and spring located inboard from the factory in my opinion anyway lol.

 

[jtkaaa07]

I am running a 15x8 torque thrust D with 4 1/2" backspacing, and like I stated above 225/70/15 there tight!
View attachment IMG_0660.jpg

View attachment IMG_0661.jpg

 

[72bluNblu]

I am running a 15x8 torque thrust D with 4 1/2" backspacing, and like I stated above 225/70/15

That's because you're set up with a 0 offset rim but you have an A-body 8 3/4 with BBP axles. You probably have about an inch to the springs with that rim and tire, maybe more. Even a 15x7 with a 4.25" backspace is a better choice than that, it's a +6 offset.

Perfectly centered with BBP axles for an A body 8 3/4 is about a +13 offset, and really you can be closer to the springs than the quarters. With an 8" wide rim you'd want at least a 5" backspace (+13 offset). In a perfect world you'd get a 15x8 with 5.125" of backspace so you could adjust for body tolerances if necessary.

It's also worth keeping in mind that BBP 7.25 and 8.25 A-body axles are narrower that the 8 3/4, by more than a little. I measured my BBP 7.25 at 51.5" flange to flange, so over a 1/2" per side shorter. Zero offset is actually where you want to be with a BBP 8.25 or 7.25. With the BBP 7.25 and stock springs in my Duster I actually needed to be at an offset of -6 (or a backspace of 4.75" for my 17x9's). It seems like a small difference, but being a 1/4" off with the offset costs you a 1/2" of tire width. Being 13mm off is a 1/2", which means that you're running 225's instead of 245's.

On my '71 I have almost exactly 11" from the outside of the spring to the uncut quarter lip, and that's with the wheel opening trim installed. That means a 245 will fit with just over a 1/2" of clearance on each side. 6" from the wheel mounting face to the springs, 5" to the quarter for an offset of 13mm to center the rim. But that's on an A-body 8 3/4 with BBP axles. With SBP axles in an 8 3/4 the offset needed is pretty close to +6 (hey, that's why the 15x7" stock rims have a +6 offset!), and with a BBP 7.25 or 8.25 it's more like 0 offset.

So, like I said before, for the OP running a BBP 8.25" I don't think 225/60/15's on 15x7's with a 4.25" backspace will be a problem at all. In fact, I'd bet he could run at least 235's out back with no issues at all. But since he wants to run one size on all 4 corners the 225/60/15 will be a piece of cake.

 

[69_340_GTS]

What would happen if I were to keep the 4 1/4" backspacing?

Rubbing on outer fender, at the lip. Depending on the ride height, this could make the car impossible to drive if low, or just a nuisance if high. The rear disc kit plus the big axles push the wheels out 3/8" to 1/2" so your making a less than ideal 4 1/4" backspacing even worse. 7" wheel with 4 1/2" backspacing works nicely with 225/235 tires (235, not on all cars) if everything is stock.

 

[roccodart440]

I've been skimming this forum for a while now trying to figure out the right tire combo for my incoming 15x7 Rallye wheels with 4.25" backspacing. Just want to clarify a few things...

I'm not looking to relocate springs or mini tub or anything. Just want a beefier tire than my skinny-stock 195/70/14's, something that gives it a more muscle-car aggressive stance than grandma's ride. What is the max size for the wheel well? I heard on another post that 235's might be the max without mods, but it might be 225? And would 60 series tires be a good choice? Tires and wheels give a car a lot of it's attitude and I want it to be just right! Thank you!

The wheel well isn't the restriction. The leaf spring is.

You can fit a 9.5" section width with no mods. 9.65" to be exact.

The 225/60 will fit. It's a little short. Not even 26". I guess though it depends on what you plan to do with it and the look you want.

SOME of the 235'/60's will fit. NOT ALL. Pay close attention to the section width.


If I were you this is the tire I'd run. IT will fit.
http://www.summitracing.com/parts/mnh-rod-36/overview/

 

[Dodge72]

69 340 GTS, I'll just be having the drums in the back. The only thing non-stock I have is air shocks, so I think I'll be fine with the 225's.

I hear it's relatively easy to lower a Dart small amounts, like up to 1" with adjusting torsion bars. I also have air shocks in the back....but I'll play around with it to make sure I still have clearance for tires. Yes, the 60 series tires are shorter than my old tires, but I might be able to correct it by adjusting these. At least it will look more correct. And I'll be going with the 225/60's all around, for now. I wanted an improvement but I also need daily driver convenience if something went wrong. It will certainly be better than the stock tires and in the future, I can always go all out with modification and much more precise measurements and adjustments as time rolls on...and as more money is saved, haha. Thanks for all of the help and suggestions, and once I get everything in I'll be looking at it carefully to see if I can make any minor height adjustments to get the stance I want.

 

[69_340_GTS]

225/60-15 is 25.6" diameter. That's almost exactly the diameter of the tall/skinny tires that came on these cars. E70-14 was a popular size with a V8 from the factory. They are 25.7" according to Coker Tire.

 

[abodyjoe]

What would happen if I were to keep the 4 1/4" backspacing?

i don't remember what the width difference between a abody 8 1/4 and a abody 8 3/4 with large bolt pattern axles is but maybe these pics will give ya an idea and help some..

this is with an abody 8 3/4 with large bolt pattern axles...

wheels are 15x7 with 4.5" backspace. if i had to do it over again i'd use 15x7 wheels with a 4.75 backspace at all four corners..

tires are 225/60-15

BELOW: with the car fully loaded and hitting a turn hard like an off ramp type of turn the tires will slightly rub up in the wheel wells some.. didn't mark up the tire or anything. but the 5 leaf espo springs do sag pretty easy. the new eatons if i ever get around to installing them should take care of that issue..

 

[72bluNblu]

Rubbing on outer fender, at the lip. Depending on the ride height, this could make the car impossible to drive if low, or just a nuisance if high. The rear disc kit plus the big axles push the wheels out 3/8" to 1/2" so your making a less than ideal 4 1/4" backspacing even worse. 7" wheel with 4 1/2" backspacing works nicely with 225/235 tires (235, not on all cars) if everything is stock.

Not with an 8.25" rear end. Your information is accurate for an A-body 8 3/4 with BBP axles, but it is completely wrong for a BBP 8.25.

i don't remember what the width difference between a abody 8 1/4 and a abody 8 3/4 with large bolt pattern axles is but maybe these pics will give ya an idea and help some..

An A-body 8 3/4 is 57 1/8" wide drum-to-drum with SBP axles, and just under 57 1/2" wide with BBP axles.

An A-body BBP 8.25 is ~56 5/8" wide

So that's a difference of 7/8". Based on my own experience with the BBP 7.25 (which has the same dimensions as the 8.25") it's more like 1" difference between an A-body 8 3/4 with BBP axles and a BBP 8.25.

So, like I already said above, an A-body 8 3/4 with BBP axles and the stock spring locations should have about a +13mm offset on a Dart/Scamp/Valiant. For an 7.25 or 8.25, that offset should be 0, or even slightly negative, up to -6mm, for the same body style.

 

[oi81b4uu812b4]

I ran through this with 72bluNblu a few months back. The difference added buy a 8 3/4 when swapping out a 7 1/4...
I measured +12.7mm (.5") per side.
13mm is correct. If he's telling you a 7 1/4 is the same dims drum to drum as a 8 1/4. (I don't have one).