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WARNING - Coker Radial Tires

  • Josh Malks
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13 Aug 2010 22:24 #17621 by Josh Malks
Replied by Josh Malks on topic WARNING - Coker Radial Tires
When I was working on my book "How To Keep Your Collector Car Alive" (Yeah, yeah, plug) I spent some time researching radial tires (again). I spoke with tech people (not sales people) at Michelin and Goodrich. They told me to NEVER put a tube in a radial tire. That's because the sidewall on the radial "works". Since the tread is held flat by the belts (steel or nylon) the rolling energy is dissipated by the sidewall movement. (In a bias-ply tire the tread squirms, which is why they wander.) The relative movement between the radial tire and a tube, they told me, will eventually cause failure. I asked the Michelin man (pun) howcum I had seen inner tubes saying "Michelin Radial". He said those were intended for agricultural equipment which never goes very fast.

The salesperson at Coker could not answer why their tires need tubes. I finally got to a tech guy who said "Confidentially, it's because without tubes they leak". (!!!)

The attraction of the Coker radial is that it looks like a bias-ply 6.50-16. Goodyear and Hankook 215/R75-16 do not. But I'm not sure I want to trust my life to a company that sells a product that contradicts hard technical data. And a 4-year life expectation for a tube in their own tires, in cars that may be driven 1,000 to 5,000 miles in that time sounds like an excuse for an engineering issue.

Jim's experience is sobering.

Here's the link to which Dennis refers.
[url:ihx017bj]http://forums.aaca.org/f143/warning-defective-inner-tubes-286287.html[/url:ihx017bj]

Josh B. Malks
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  • Chris Summers
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13 Aug 2010 22:38 #17622 by Chris Summers
Replied by Chris Summers on topic WARNING - Coker Radial Tires
Josh, what tires do you use for Moonshadow?

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  • Josh Malks
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14 Aug 2010 00:47 #17624 by Josh Malks
Replied by Josh Malks on topic WARNING - Coker Radial Tires
Hankook, with whitewalls added by Diamond Back. (Hankook is Michelin's Korean subsidiary.)

Josh B. Malks
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15 Aug 2010 14:13 #17635 by Josh Malks
Replied by Josh Malks on topic WARNING - Coker Radial Tires
Had a very interesting discussion with Stan Lucas at Pebble Beach yesterday. Stan is a major distributor of tires and tubes for collector cars. I brought up the subject of splitting inner tubes in members' radial tires, and without my even telling him he asked "Were they stamped 'Denmark' or 'EEC'"?

Seems there are two issues. First, these tubes are all made in Poland. The manufacturer stamps on the tube whatever country name the customer wants. When the company started making them they had no previous experience making tubes and delivered a bad batch. These are the ones that are splitting. Current production has no problem, says Stan. Still, this does not explain Jim's pinhole, or instill a great deal of confidence.

Stan also says that a tube may be used in a radial tire if the tire sidewall says "tube-type". (Jim, could you tell us what the Coker sidewall says?) Those tires do not have the sealing bead that tubeless tires have, so they will indeed leak without a tube. Even more important for users of Coker radials, Stan says that a radial tube is different from a bias-ply tube. The bias-ply tube has a butt joint around the circumference of the tube. Radial tubes must have an overlapping joint. (Jim, could you tell us what joint your tubes have? And are the splits or the pinhole at a joint?)

This is serious, potentially life-threatening issue. Anyone else have any experience with this?

Josh B. Malks
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15 Aug 2010 18:06 #17639 by West Peterson
Replied by West Peterson on topic WARNING - Coker Radial Tires
Perhaps they leak because the vintage rims were not designed for radial tires? Just a thought.

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  • Josh Malks
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15 Aug 2010 18:31 #17640 by Josh Malks
Replied by Josh Malks on topic WARNING - Coker Radial Tires
Nope. I have at least 20,000 miles on Goodyear and Hankook radials mounted on stock 1936 Cord rims with no leakage. (I am running out to knock on my wooden stairway railing.)

When Allstate-labeled Michelin tubeless radial tires were first offered for sale in the US by Sears in 1966 they were often mounted on rims designed for tube-type bias-ply tires. No significant problems.

Josh B. Malks
810 2087A
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Past president
www.automaven.com

Check out CORD COMPLETE at www.cordcomplete.com

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