Polyglas

[70Tom]

Not sure I've ever heard of the Goodyear Custom Power Cushion Polyglas. They really went all out with the RWL sizing.

I am still considering going with some G70-15 RWL Polyglas when my 70 SF is done. I just like the period correct look. Drift be damned. I'm driving a 1970 car like it's 1970. Only problem is price. Oof. Definitely not 1970.

 

[commando1]

Not sure I've ever heard of the Goodyear Custom Power Cushion Polyglas

How old are you.

 

[70Tom]

Well, I mean I've heard of Goodyear Polyglas. Was Custom Power Cushion part of the official name?

 

[70Tom]

I think Custom Wide Tread GT were the usual name for the RWL tires. At least the ones on the 70.

 

[fc7_plumcrazy]

the tires used on 1970 Mopars are the Goodyear Polyglas

Kelsey Tires

There is Polyglas and Polyglas GT tires
The regular Polyglas could be had with redline&whiteline, too

If you order the RWL version check your SPD on the fender tag because the cosmetics changed during the 1970 model year

Carsten

 

[SIPLOWGUY]

Well, I mean I've heard of Goodyear Polyglas. Was Custom Power Cushion part of the official name?

I think the Custom Power Cushion was the "non-belted" tire. My Dad's 77 Aspen came with those.

 

[70Tom]

If you order the RWL version check your SPD on the fender tag because the cosmetics changed during the 1970 model year

Carsten

What are the differences?

 

[fc7_plumcrazy]

early version only read "Goodyear" and "Polyglas" while the later edition also had the tire szie printed in letters

 

[Big_John]

I've never seen that size RWL. I think that's just for the ad. Your car would not have come with RWL or a 70 series tire.

"Power Cushion" was a pretty generic Goodyear term that they used on their passenger car tires.

But... are you really sure you want to run belted tires?? I've driven a lot of miles on belted tires and they pretty much suck in comparison to the cheapest modern radial. If you were doing a 100 point resto, I would understand, but since you are talking about putting a G70-15 on it, you aren't going for a restoration.

BTW, I think that G70 would also be too small in diameter.

 

[saylor]

can confirm texas proving grounds. I know in the 70s, i remember seeing bright yellow cars and they would just be driving all over out there testing tires - van horn / alpine / Marfa / pecos / ft Stockton / el paso I'm pretty sure they did a big huge loop of several hundred miles around that end of texas.

just adding random content for provenance

- saylor

 

[70Tom]

I've never seen that size RWL. I think that's just for the ad. Your car would not have come with RWL or a 70 series tire.

"Power Cushion" was a pretty generic Goodyear term that they used on their passenger car tires.

But... are you really sure you want to run belted tires?? I've driven a lot of miles on belted tires and they pretty much suck in comparison to the cheapest modern radial. If you were doing a 100 point resto, I would understand, but since you are talking about putting a G70-15 on it, you aren't going for a restoration.

BTW, I think that G70 would also be too small in diameter.

a) I had belted redlines on my '68 442 and I had no problem driving it.

b) If I'm not mistaken the car could have been ordered with the RWL H70-15. I have no idea what my car came with as the build sheet under my rear seat wasn't for my car (thanks Plymouth). I believe it originally came with wheel covers, so if I had to guess, it came with whitewalls, which I hate.

c) I wasn't implying that the tires in the ad would have ever been on my car or any other Mopar for that matter. I just had never heard them called that and had never seen lettering that large.

d) I did some comparison measurements today between 225 70-15, 235 75-15, the H70-15 and G70-15, and they're really not all that far apart. I think the G70-15 was something like 0.4" in diameter smaller than the 235's which I'm otherwise considering, and was bigger than the 225's which I have on the car now. My numbers are at work. I can post them up tomorrow.

Sorry for the confusion. I was really just showing that ad, which I had never seen before. And, it'll be a tough sell on the Polyglas, as much as I like the looks of them, mainly due to how expensive they are.

 

[Big_John]

a) I had belted redlines on my '68 442 and I had no problem driving it.

b) If I'm not mistaken the car could have been ordered with the RWL H70-15. I have no idea what my car came with as the build sheet under my rear seat wasn't for my car (thanks Plymouth). I believe it originally came with wheel covers, so if I had to guess, it came with whitewalls, which I hate.

c) I wasn't implying that the tires in the ad would have ever been on my car or any other Mopar for that matter. I just had never heard them called that and had never seen lettering that large.

d) I did some comparison measurements today between 225 70-15, 235 75-15, the H70-15 and G70-15, and they're really not all that far apart. I think the G70-15 was something like 0.4" in diameter smaller than the 235's which I'm otherwise considering, and was bigger than the 225's which I have on the car now. My numbers are at work. I can post them up tomorrow.

Sorry for the confusion. I was really just showing that ad, which I had never seen before. And, it'll be a tough sell on the Polyglas, as much as I like the looks of them, mainly due to how expensive they are.

I stand corrected on the tire availability. I forgot you had a Sport Fury.

 

[70Tom]

I stand corrected on the tire availability. I forgot you had a Sport Fury.

No problem!

 

[commando1]

A million years ago when the universe was switching over from bias to radial, I don't remember the handling improving any. But we're talking about suspensions designed for bias.
Id love to throw a set of bias tires onto my NYB to feel the difference, if any.

 

[polara71]

I drove my convertible home two hours on Bias ....The car was all over the road and hanging up in every little divot .
The radials put a stop to that

 

[Beep Beep Dave]

I drove my convertible home two hours on Bias ....The car was all over the road and hanging up in every little divot .
The radials put a stop to that

That is a characteristic of bias ply tires...especially on highways with lots of truck traffic. What makes that effect worse is that people inflate those tires to 35 lbs, which doesn't make for much of a contact patch on the road.

Dave

 

[MrMoparCHP]

A million years ago when the universe was switching over from bias to radial, I don't remember the handling improving any. But we're talking about suspensions designed for bias.
Id love to throw a set of bias tires onto my NYB to feel the difference, if any.

When I first met my friend with his restored CHP 69 Polara he had Coker bias tires on it. The first time I drove it I went into a turn at 70 and went halfway into the next lane, from then on I had to lead the turns a little more. A little while ago he swapped them out for some current (non reproduction) light truck bias 8 ply tires, what a difference. The most annoying thing about bias ply is the tires going square after sitting even just hours, take about 5 miles to heat them up for the patter to go away.

Long as you know you have bias ply tires and drive accordingly I don't see the issue. Just think about Bullitt, those were probably bias ply tires. Some where I have a video of the CHP testing cars in the 60's and 70's, bias ply.

Are radials better, probably, are bias death traps like some people say, no.


Alan

 

[70Tom]

OK, I'm at work and I promised the specs of the various tires I was looking at/people often use. Here we go. (I believe the radials were Hankook & Kumho.)

235 75-15
Diameter: 28.9
Section Width: 9.3
Tread Width: 5.9

225 70-15
Diameter: 27.4
Section Width: 9.0
Tread Width: 6.6

Kelsey Goodyear Polyglas G70-15
Diameter: 27.85
Section Width: 9.0
Tread Width: 6.625

H70-15
Diameter: 28.1
Section Width: 8.95
Design Rim Width: 6.0
(From Fred Puhn's "How to Make Your Car Handle." Not Polyglas specific. Couldn't find that info.)

 

[Big_John]

It's interesting to me that the guys that are saying bias and belted tires drive OK live in the western states where there is no snow and cold to heave the roads and no snow plows to tear up the roads. Are these concrete surfaces?

The ones that are saying that the radials are better live in areas of snow, cold and plows. The surfaces are asphalt and there will be wear from trucks and the road will have a high crown in the center for drainage.

 

[70Tom]

It's interesting to me that the guys that are saying bias and belted tires drive OK live in the western states where there is no snow and cold to heave the roads and no snow plows to tear up the roads. Are these concrete surfaces?

The ones that are saying that the radials are better live in areas of snow, cold and plows. The surfaces are asphalt and there will be wear from trucks and the road will have a high crown in the center for drainage.

John, there's a mix of concrete and asphalt here out west. There's also some roadways that have been paved with an asphalt that contains rubber in it, resulting in a super-quiet ride in your car. It's quite nice.

I think one of the reasons why the bias-ply/belted tires don't bother me that much is because my daily driver hits ruts and grooves and takes it in a particular direction. It's a 2013 Camaro 1LE, so it's really a track car and handles like it's on rails. Because of the precision, ruts and grooves throw steering in that direction. And as you can imagine, the tires are super wide. I just deal with it. I guess I actually call it 'driving' vs. what most new cars allow people to do (not pay attention at all).