Old Tire Size Conversion?

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KOZ45

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I just got two new aluminum slot wheels, so I have a matching set at all four corners

14" wheels

Here is what came with the car (1970 Duster):

Rear: G50-14

Front: GR70-14 / 205SR-14

GR70-14 were on two tires in the trunk, I assume a matching size for the rear

What do these convert to, in modern sizes?

I did a quick Google search for the G50-14 and they are like $310 each!

What is a modern tire size equivalent?

Does this make sense:

G70-14:
235/60-14
205/70-14
205/80-14

What about the G50-14?
 
For the rear, is there a one step smaller , width, size?

I think the G50 is 10 inches wide

I know the car will need a wide tire with the 440, but maybe looking an inch in width will be much cheaper and easily found
 
KOZ45 said:
For the rear, is there a one step smaller , width, size?

I think the G50 is 10 inches wide

I know the car will need a wide tire with the 440, but maybe looking an inch in width will be much cheaper and easily found
Click to expand...
Probably a 245/60
 
Every tire manufacturer offers data on their tires. You can compare dimensions. Or you can check at places like Tire Rack, but they do not carry everything. Only stuff that they can sell in large volumes, so you won't find many of the old sizes. Coker Tire is another good resource. For some of those oddballs like N50-14, there is no modern equivalent.
 
chryslerfat said:
Probably a 245/60
Click to expand...


245/60 Just "sortof" fit on a 3" raised 6 leaf spring. 3/8" clearance on the top outer wheel well. it's tight on the dart, valiants might be too tight.
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245/60s are more narrow, but also taller

I have 2.5" leafs springs
 
The front tire is a G70-14, that is also marked 205SR-14

So, from the link I assume I should look more towards a 205?

235/60R14.......$110-$150 each
205/70R14.......$50-$110 each
205/80R14.......not widely available

Now for the size difference:
235/60R14: 25.1" (tall) x 9.25" (wide)
205/70R14: 25.3" (tall) x 8.07" (wide)

Sidewall height is pretty close to each other

Remember, the G70 is the front tire
 
I found a guy who is running 225/70R14 on the front of his Duster

225/70R14: 26.4" x 8.86"

Seems much taller than the other two sizes

This size runs around $95 each
 
Talked with two more Duster owners who are running these sized front tires:

185/75R14: 24.93" x 7.28"
$35-$65 each

215/70R14: 25.85" x 8.46"
$50-$95 each
 
KOZ45 said:
The front tire is a G70-14, that is also marked 205SR-14

So, from the link I assume I should look more towards a 205?
Click to expand...
It depends on what you're trying to do.
KOZ45 said:
I found a guy who is running 225/70R14 on the front of his Duster

225/70R14: 26.4" x 8.86"

Seems much taller than the other two sizes
Click to expand...
yes! A 'G' tire is a big tire. Factory A-bodies got 'D' or 'E' in some optional packages.

G was a load rating.
We can get a rough idea of the load from a 'reproduction' GR70-14
GR70-14 Firestone Wide Oval Redline Tire
1620 lbs.
And we can also get a rough idea of the original diameter. 27"

205 and 225 are roughly the tire widths in milimeters.
The 78, 75, 70 that follows is the sidewall as percentage of the width.

So to have the same height (rolling radius) on the rear as on the front using the Euro-metric or P metric, it works like this.
Standard everyday type tires: 205R-14, P215/75-R14 should have similar height and load carrying capacity
A wider tire of similar diameter and load carrying capacity will be: 225/70-R14

If you want tire diameters closer to factory, then something in the range of 205/75-r14, 215/70-r14 will be closer.
Those sizes are ballparks. Most manufactures publish the specifics for each tire, at least for when they are mounted on a test rim.
Do check the recomended rim size (width) for the tire before you buy.
 
Thanks for all the great info

I found this:

Standard tire size for 1970 Plymouth Duster 340:

Standard tire size: E70 - 14

Tire width (mm):
205

Tire sidewall factor:
70

Rim size (in):
14

Since my Duster was a 340 factory car, I assume the 440 weight likely caused the front end to sag alittle

I don't need or want any larger of a tire on the front end

I will look around for a 215/70-r14 or 205s if I can find a good deal
 
Last edited:
The 440 wasn't a factory Duster motor either, so it's a runner and not a show car

My aluminum slots for the front are 14x6
I will not being changing over to a 15" rim, as I like these 14" slots

Thanks for the info on the 215s, I'll look in to them
 
Front wheels and tires filled the fender pretty good

Could be the weight of the 440

IMG_0582_zps332gcwcz.jpg
 
G70-14 is 26.8 tall

I just measured the ones I have and they are 27" tall and have a 7" wide tread width
 
That actually looks a bit tight up front. The places I had big tires clip the edge of the fender was the top but watch th efront and rear corners of the opening as well. Probably when compressing (going over bumps) and the steering turned left or right. Not sure how similar Barracuda front fenders are to the Dusters. In any any event, the risk will go away with the 215/70 tires.

440s were an option for the Barracuda in '69. There's a reprint of the Car Life road test in the Brookland Books Plymouth Barracuda 1966-1974
It says the torsion bars were 110 lbs / in - which could be the .89" dia bars. I vaguely recall seeing a listing for slightly larger factory t-bars but don't recall where. I could be wrong. In any event, once you get the new tires all around, just crank the t-bars up or down to get the factory settings.

Same article lists rear leafs as 150 lb/in - which might be a unique spring pack for those cars - maybe based on the 383 leafs which had a different main leaf than the others according the parts books.
Tires were E70-14 Goodyear "wide ovals" on 14 x 5.5 rims

You may have to change speedometer pinion to get the odo and speedo calibrated for the tires you end up with. Pretty easy.
 
KOZ45 said:
G70-14 is 26.8 tall

I just measured the ones I have and they are 27" tall and have a 7" wide tread width
Click to expand...

It all depends on what BRAND you choose. Brand A for example might measure your 26.8" at G70-14. Brand B might be up to an inch taller or shorter. It's still that way today with the metric sizing. You simply have to look at the brands and sizes individually and decide what height you want to run.
 
I don´t know if this helps or not but this is a compilation of charts with a lot of info.
 
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