ok, heads spinning, just need a straight answer...

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Khyron

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Ok, i have read this up and down, most people are using b-body rear, shakle offset and not the full relocation... so i'm just gonna ask...

What size tire can I fit on a 74 Plymouth Duster ralley 360

I have the full spring relocation kit in, no mini tub, and a posi 8 1/4 rear end...

looking for 17 inch to 19 inch rims.

Want in the well as much as i can without a mini tub if possible.

What size and offset am i looking for? been hunting craisglist and i've been reading a lot of u guys using late model mustang rims.
 
At least 10" wide. The gt had 17x9. You will have to measure how much useable space you have since you are using stock wheel wells
 
Every now and then someone will pose similar questions. I always figure that you're best off doing some measurements if you want the correct answer. There are so many variables that it would be easy to give a spec that worked on another car that will not work on yours.

I'm not criticizing you for seeking an answer. I've got several cars that I needed to figure out the same thing on.

When I'm in the situation you're in these are the steps I take using a tape measure and some straight edges (sometimes I'll use a yard stick or a square as a straight edge):

1st I try to determine how much room I have inboard. I remove the wheels and put a straight edge across the surface that the wheels will mount to. Then I use a tape measure to read how much room I have between that line and the inner fenderwell. Record that measurement.

2nd I measure from that same plane outward towards the inner lip of the rear quarter. Record that measurement.

With those 2 measurements you can begin to calculate a rim width (and offset) that will work for you. You will want some clearance on both the inside and outside of your tires so your tires won't rub. Not everyone is comfortable with the same amount of clearance. You will most likely be safe with 1 inch of clearance on each side of the tire.

It would be simple if this was the only factor you needed to consider. The amount that tires bulge out beyond the rim will vary from size to size and between different manufacturers. Once you've determined a rim width that suites your needs you will need to research the type of tire you wish to run. Find a chart that shows a recommended rim width, tread width, and section width. Keep in mind that a chart for one brand/model of tire will be different for another brand/model tire.

View attachment 163_0710_23z+hankook_rf10+size_and_specification_chart.jpg

The overall tire diameter or tire height is in part a matter of personal preference. Some guys want super low profile tires they believe will aid them in handling. Some want a tall tire that fills out the wheel well. A measurement outward from the center of your axle will get you in the ballpark of what will fit.

Choose the tire/wheel sizes based upon how you want the car to perform and look.

Because you had mentioned large diameter wheels you will most likely be running tires with a lower profile. Keep in mind that they usually will give you a rougher ride than tires that are taller.

Good luck.
 
This question gets asked so much it ought to be stickied somewhere. I agree with 'cuda, every car is different and YOU should measure YOUR'S so YOU know what will fit on YOUR car. How pissed off would you be because someone on the internet told you that these wheels would fit on your car and they didn't?!? You think that the guy on Craigslist is gonna give you your money back because some internet expert said they fit on his car?

This is the method that I used to measure for my wheels and tires and they fit like a glove. I didn't have a plumb bob so I used a washer tied to a string. I laid a big piece of cardboard under the tubs and marked on it to get my measurements. I also measured each side about twenty times to make sure that I got the right numbers. Good luck!

How To Measure for Proper Wheel Spacing
 
Also make sure to measure both sides. There can be differences. Tmm
 
1967 'cuda said:
Yes this is a definite MUST. I generally find about a half inch difference between left and right wheel wells.
Click to expand...

Yep... Always measure because no two cars are the same. I was test fitting a wheel on my Dart (I knew it's offset was too much). Anyways, on one side I barely cleared the leaf springs while the other the tire was rubbing.
 
toolmanmike said:
Also make sure to measure both sides. There can be differences. Tmm
Click to expand...

1967 'cuda said:
Yes this is a definite MUST. I generally find about a half inch difference between left and right wheel wells.
Click to expand...

Absolutely this! Not all of these cars are created the same.

As for your question- The 3" relocation means that you don't have to worry about the springs at all, so you're really just looking at the wheel tubs. Without a mini-tub, you're basically in the same boat as folks with a 1/2" offset though, because that is still inboard of the wheel tubs.

On my '74 Duster I have 295/35/18's in the stock wheel tubs. I have the 1/2" offset, and I also trimmed the inner quarter lip back by about a 1/2" as well. That's as wide as you can go if you want your wheels to actually fit inside the wheel tubs and quarters (ie, stock ride height or lower).

So, I would say that a 10" wide rim should fit your set up. As far as the backspacing, that's where it gets tricky. I found out myself that the A-body 7.25" BBP rear axles and the A body 8 3/4 housings are NOT the same width. The A-body 8 3/4 housing is over an inch wider!!! I found that the 8 3/4" A-body housings do in fact measure the 52-5/8" flange to flange like most of the specs say, but the stock '74 BBP 7.25" in my car measured 51.5".

I personally run a 68-70 B body 8 3/4, which is 54-15/16" wide. I measured it, it really does match the spec to a 1/16". What I don't know is how wide the 8.25" A-body rear housings are. Given that the A-body 7.25" rears do not match the specs out there for the 8 3/4's, you can't assume that the 8.25's are the same width as the 8 3/4's. If your goal is to max out the wheel well with a 295, you will absolutely have to measure the width of the 8.25, because a 1/2" per side will absolutely mean those wheels won't fit. On my car, even a 1/4" in the wrong direction would mean they wouldn't fit.

If the 8.25" in your car matches the A-body 8 3/4 spec, I would tell you that you need a 5.75" backspace to fit 10" rims and 295's, based on the measurements from my rims and adjusting for the narrower rear. But that assumes the 8.25" is the same width as the 8 3/4, and it probably isn't.
 
all great information, I will use the math as stated above and double check with what stated sizes have been used, as for the rear being off centered, We just finished the rear today, she is dead on center now with new perches :) pinion angle and everything set and all spring mounts burned in :) Rim and tire time :)
 
Great thread. I am in the same boat. I just rebuilt the entire front end and am finishing my floor pans this week. I will be starting my rear end rebuild within the next two weeks. I have SS springs and 1/2 in offsets and a Dana 60 to replace the 7 3/4 rear end and stock springs. I am trying to fit 10 in rims under it if possible without mini tubing.
 
NodakDuster said:
Great thread. I am in the same boat. I just rebuilt the entire front end and am finishing my floor pans this week. I will be starting my rear end rebuild within the next two weeks. I have SS springs and 1/2 in offsets and a Dana 60 to replace the 7 3/4 rear end and stock springs. I am trying to fit 10 in rims under it if possible without mini tubing.
Click to expand...

10" rims are definitely possible with the 1/2" offset on a Duster. It's just a matter of setting up the backspace to match with the width of the rear axle so everything is centered in the wheel wells. But without a mini-tub the widest tire you're going to get under there is a 295. With a mini tub the sky's the limit, 335's aren't a problem.
 
Khyron said:
found a set of 18 x 10 inch rims but the back spacing is 6.38 :-(

damnit...
Click to expand...

That could work. Have you done any measuring? If you don't measure your car up, it's very hard to get a feel of what wheel offset could fit.
 
Khyron said:
found a set of 18 x 10 inch rims but the back spacing is 6.38 :-(

damnit...
Click to expand...

MuuMuu101 said:
That could work. Have you done any measuring? If you don't measure your car up, it's very hard to get a feel of what wheel offset could fit.
Click to expand...

I would measure that 8.25" rear. It's probably not wide enough for those rims to work without a spacer, but it may be close enouch to use a set of spacers. My 18x10's have a 7" backspace and work fine with my B-body 8 3/4. It's all about the width of the rear axle.
 
MuuMuu101 said:
That could work. Have you done any measuring? If you don't measure your car up, it's very hard to get a feel of what wheel offset could fit.
Click to expand...

i have to get to the garage my cars at.... i'm gonna take some measurments tomorrow night, they ar fr500 series, would look great on the car! 18 x 10 and 18 x 9
 
ok, took my measuremends, it seems from outside hub to rear wheel well is 6 inches, rear end from back plate to back plate is 49 inches, from outside hub to outside hub is 56 inches? sound about right..


rims im looking at have a 6.38 inch offset and 10 inch rim. 275/35R18 ... fronts are 245/40R18
 

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Khyron said:
ok, took my measuremends, it seems from outside hub to rear wheel well is 6 inches, rear end from back plate to back plate is 49 inches, from outside hub to outside hub is 56 inches? sound about right..


rims im looking at have a 6.38 inch offset and 10 inch rim. 275/35R18 ... fronts are 245/40R18
Click to expand...

I'm not sure I understand what you mean by a 6.38" offset. I assume that is different than a 6.38" backspace. I would look for rims that have a 5" backspace if you've got 6" from the mounting surface to your inner wheel well. That will give you less than 1" of clearance when you take into account how much tire bulge you will have.
 
1967 'cuda said:
I'm not sure I understand what you mean by a 6.38" offset. I assume that is different than a 6.38" backspace. I would look for rims that have a 5" backspace if you've got 6" from the mounting surface to your inner wheel well. That will give you less than 1" of clearance when you take into account how much tire bulge you will have.
Click to expand...

That's what i mean, heheh 6.38 inch backspacing :)
 
do you think i can get away with a 1 inch spacer? or should I stay away from a spacer that big, I could hunt for a B body rear in my area, but would rather not.

The wheels are 275/35R18's, so i'm not worried about tire bulge.. it's a 10 inch rim
 
Khyron said:
do you think i can get away with a 1 inch spacer? or should I stay away from a spacer that big, I could hunt for a B body rear in my area, but would rather not.

The wheels are 275/35R18's, so i'm not worried about tire bulge.. it's a 10 inch rim
Click to expand...

If you've got a backspace of 6.38" it would only leave you .62" of tire clearance to the inner wheel well even if the tires had no bulge and you were using 1" spacers. That's cutting it pretty close. I'd say it's 'iffy' whether or not you'd experience tire rub when cornering.

As far as using wheel spacers go, I'd prefer not. Some folks see nothing wrong with them while others consider them unsafe.
 
The condition of your leaf springs, leaf spring bushings, whether or not you've got a rear sway bar, and how hard you corner will affect whether or not your tires would rub. The rear end is not fixed solid under the car and there will be movement.
 
gotcha, springs, bushings, everything is all brand new, but i see your point, i will continue to look for another set of rims, thank you got your input.

but she will be getting a rear sway bar :)
 
ok, one more thing, i'm trying to understand offset vrs backspacing, so you subtract the offset from the backspacing? i don't get it... for example, the rims im looking at is

Manufacturer: AmericanMuscle Wheels
Style: FR500
Size: 18x10
Finish: Black
Placement: Rear Only
Centercap Size: Large (2-1/2")
Back Spacing: 6.3" (161mm)
Offset: +22mm (0.9")
Bolt Pattern: 5x4.5" (5x114.3mm)
Weight: 26.5 lbs
Material: Aluminum
Lip Size : 1.75"


don't understand...read it on a few sites, anyone explain it in plane english to me?
 
khyron said:
ok, one more thing, i'm trying to understand offset vrs backspacing, so you subtract the offset from the backspacing? I don't get it... For example, the rims im looking at is

manufacturer: Americanmuscle wheels
style: Fr500
size: 18x10
finish: Black
placement: Rear only
centercap size: Large (2-1/2")
back spacing: 6.3" (161mm)
offset: +22mm (0.9")
bolt pattern: 5x4.5" (5x114.3mm)
weight: 26.5 lbs
material: Aluminum
lip size : 1.75"


don't understand...read it on a few sites, anyone explain it in plane english to me?
Click to expand...

to measure backspace:

View attachment +measuring_backspacing.jpg

the more the offset/backspace, the more the wheel will tuck inwards towards the suspension or away from the fender.

View attachment backspace_offset.jpg

I find the backspace measurement to be the most useful when determining fit. The offset is measured from the center of the rim and rims do not always have the same thickness centers.
 
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