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Dynaflash8

Is there a market for near new radial tires?

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Posted (edited)

The 820s are much, much too big. They are trying to make radials that look like bias-ply tires, and that's commendable and I think in many cases they've been successful. My initial recommendation for Earl's car was the 700R15 that Diamondback sold based on a Yokohama carcass, but if I recall correctly those were not available at the time Earl was shopping for tires. Diamondback was also still in limbo on their "Auburn" radial, which is apparently now available in limited release. 

 

Shortly before Earl, I was going though this exact same situation with my 1941 Cadillac 60S which wears exactly the same size tires as his Roadmaster on exactly the same size wheels. I ultimately chose the 760R15 Coker radials which were just about ideal. They were larger than the recommended 700R15 but in comparison to the original 7.00-15 bias-ply, they were much closer overall. Whatever the numbers were that led to the 820R15, they weren't right. Looking at just the height or just the tread width or whatever wasn't enough. Here's the Cadillac after it was fitted with the Coker 760R15 radials:

 

001.jpg006.jpg

 

IMG_20170418_190316712a.thumb.jpg.6b83f8e2ad5c17555248a5847480ca1b.jpg IMG_20170418_190237559a.thumb.jpg.e55e3a98f385b9e17bb8ce02a02acf1d.jpg

 

I thought they looked pretty correct and they did ride and handle beautifully with reasonable steering effort. I hate to admit that I loved those Coker tires, but they looked great and worked well. I sold the car shortly thereafter so I can't comment on longevity, noise, or resistance to whitewall staining.


Everyone knows I prefer Diamondback, but since they couldn't sell me anything to fit this car, I went with Coker and was satisfied. Now that Diamondback offers their Auburn radial in sizes that should fit, I would probably start there and see which one looked right. If I was unsure of sizing I might buy one and try it out before buying a set or I would trust them--they seem to know sizes a bit better. 


Comparing the numbers doesn't always tell you the whole story. I looked at these Cokers for a long time before deciding on the 760R15 even though it seemed wrong on paper. I'm glad I chose that size because the 700R15 would have been too small. I suspect that Coker is cheating a bit with the sizing (undersized) to make them applicable to more cars and the 760s were closer to the right size than the 700s that were "supposed" to be correct.


Does this help?

Edited by Matt Harwood (see edit history)
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17 hours ago, Bloo said:

Well, I was going for something they might have actually shot for at design. Yeah, in reality it is closer to 100.....

Sure I realize that. I was just throwing out some calculations, not testing your accuracy.

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15 hours ago, Lebowski said:

 

That doesn't sound like the size of any radial tire that I've ever heard of. Usually it's 225-70R15 or 215-75R16 or something similar to that. What country were they made in? :(

The sizes you quote are for modern car tires.  They are made by Coker and are 820R-15

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Posted (edited)
15 hours ago, MCHinson said:

 

Here is the information on that tire size: https://www.cokertire.com/american-classic-820r15-3-1-4-inch-whitewall.html They are Radials designed to replace a 820x15 Bias Ply tire. 

I don't know about what they were designed for, but the height, width, etc. measurements match a 7.00x15 bias tire.  I went over it with the Coker salesman.  In addition, in 1947 Buick changed the factory size for the Roadmaster (Model 70) from 7.00x15 to 8.20x15.  I would have guessed I should use 7.60R15 but they didn't match the measurements of the original 7.00x15 tire.  They were smaller.  In any case, they would have still squatted.  I just wish I'd gone bias tire, but I didn't.

Edited by Dynaflash8 (see edit history)

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On 8/17/2019 at 8:43 AM, Dynaflash8 said:

In addition, in 1947 Buick changed the factory size for the Roadmaster (Model 70) from 7.00x15 to 8.20x15.

The change was actually in 1948.  When getting my '47 Series 70 ready for the road, I followed the BCA Judging Guidelines and ordered 8.20x15 tires.  They wouldn't fit under the rear finders or in the spare tire well in the trunk.  I researched It further and found the change was in 1948.  Documentation was sent to BCA and the Judges Guidelines were corrected.  I used the 8.20x15's on my '48 Cadillac 60S.  I just wasn't planning on buying 10 tires that month.

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 Chances are that your tires are 2 or 3 years old now and that will effect the price. Maybe 50%, then add shipping, and you may be lucky to receive 20% of your cost.

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Posted (edited)

Yeah, that's my problem if I switch back to 7.00x15.  It seems to me I looked up the tire size in 1946 and it was still 7.00x15, but they quoted 8.20x15 for the 1947.  That was a brochure. But, they didn't always do what they said they would do in those brochures.  The 8.20R15 fit my 41 Buick Roadmaster all around.  I used to sell Buick parts and the 1947-48 rear fenders and the skirts were all the same part number, so I don't quite understand.

Edited by Dynaflash8 (see edit history)

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2 minutes ago, Roger Walling said:

 Chances are that your tires are 2 or 3 years old now and that will effect the price. Maybe 50%, then add shipping, and you may be lucky to receive 20% of your cost.

Yeah, they are 2 years old with no miles on two of them, and about 150 on the other three.  I backed into a curb on the tour with one and Coker replaced it under the warranty I purchased.  I might just put up with them when I can drive the car again.  One of the therapists said 6 months, but I haven't talked to the Cardiologist about that yet.

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Something is telling me there was more of a difference between an .00, .20, or .25 than it sounds like but I forget exactly what it was. Recall Corvettes using 7.75x15 and my Jags 6.00x16. Boy Howdy they even looked skinny then.

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On 8/16/2019 at 5:57 PM, Matt Harwood said:

The 820s are much, much too big. They are trying to make radials that look like bias-ply tires, and that's commendable and I think in many cases they've been successful. My initial recommendation for Earl's car was the 700R15 that Diamondback sold based on a Yokohama carcass, but if I recall correctly those were not available at the time Earl was shopping for tires. Diamondback was also still in limbo on their "Auburn" radial, which is apparently now available in limited release. 

 

Shortly before Earl, I was going though this exact same situation with my 1941 Cadillac 60S which wears exactly the same size tires as his Roadmaster on exactly the same size wheels. I ultimately chose the 760R15 Coker radials which were just about ideal. They were larger than the recommended 700R15 but in comparison to the original 7.00-15 bias-ply, they were much closer overall. Whatever the numbers were that led to the 820R15, they weren't right. Looking at just the height or just the tread width or whatever wasn't enough. Here's the Cadillac after it was fitted with the Coker 760R15 radials:

 

001.jpg006.jpg

 

IMG_20170418_190316712a.thumb.jpg.6b83f8e2ad5c17555248a5847480ca1b.jpg IMG_20170418_190237559a.thumb.jpg.e55e3a98f385b9e17bb8ce02a02acf1d.jpg

 

I thought they looked pretty correct and they did ride and handle beautifully with reasonable steering effort. I hate to admit that I loved those Coker tires, but they looked great and worked well. I sold the car shortly thereafter so I can't comment on longevity, noise, or resistance to whitewall staining.


Everyone knows I prefer Diamondback, but since they couldn't sell me anything to fit this car, I went with Coker and was satisfied. Now that Diamondback offers their Auburn radial in sizes that should fit, I would probably start there and see which one looked right. If I was unsure of sizing I might buy one and try it out before buying a set or I would trust them--they seem to know sizes a bit better. 


Comparing the numbers doesn't always tell you the whole story. I looked at these Cokers for a long time before deciding on the 760R15 even though it seemed wrong on paper. I'm glad I chose that size because the 700R15 would have been too small. I suspect that Coker is cheating a bit with the sizing (undersized) to make them applicable to more cars and the 760s were closer to the right size than the 700s that were "supposed" to be correct.


Does this help?

Thanks, I appreciate the response.  Yes it helps.  I haven't seen any ads from Diamondback in a number of months in Hemmings.  As I recall Diamondback offered the rub ring like used on many of the old bias tires, which would have made them look nicer too.  As to the numbers, those quoting the height, width, etc. of the 7.00x15 matched the 820R15 and the 760R15 was much shorter that the 7.00x15.  It's hard to argue with numbers, but then again they were numbers quoted bu Coker, so there you have it.

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