Goodyear Marathon Sidewall Depressions

[bfezel]

Like many of you I have had tire problems, including an interstate blowout last month in South Dakota. Before my most recent outing I bought new Marathons. Not because I was thrilled with them, but because the choices for trailer tires are so limited. We returned Tuesday from a 1700 mile trip and I cleaned the TM today. Noted that the street side tire has two significant sidewall depressions extending from near the outer edge of the sidewall (just below where the tread stops) to the rim of the wheel. These depressions are about the width and depth of a man's little finger and are almost 180 degrees across from each other. The curb side tire has one less pronounced depression.

Anyone else noted anything like this? Does anyone know if this should be a cause of concern?

Thanks in advance.

Bill in Tennessee

[rickst29]

The tubing on which the spare tire sits, combined with the very tight fit against the bottom of the TM, will often create two parallel "impressions" of the type which you seem to be describing.

If that was the cause, then you might look at two fixes. Fix #1 rests the spare tire on two plates, instead of the two thin bars. Here: http://www.trailmanorowners.com/forum/showthread.php?t=5672

And Fix #2, lowering the spare tire carrier down by a bit less than 1" (so that it isn't squeezed so hard between the hanger and the bottom of the TM body), is discussed at the end of that thread in my version, but also has two other variations (by Eric and Bill) shown WITH PICTURES in this Thread:
http://www.trailmanorowners.com/forum/showthread.php?t=5828

If you do fix #1, then fix #2 is mandatory-- the added thickness of the plates makes lengthening of the carrier "hanger" distance even more necessary.

[Bill]

I may be reading bfezel's post incorrectly, but it doesn't sound like the depressions in the sidewall were caused by the spare tire carrier. The depressions were on BOTH tires, and I gather that these were the new Marathons he purchased before the last trip. Neither one sounds like it was ever in the spare tire rack. Bill, can you elaborate on this?

Bill

[bfezel]

Bill,

You are correct, the tires are brand new and mounted on the wheels on the ground, not the spare. Since making this inquiry I have discovered some information on the Toyo Tire website that makes a lot of sense. According to their technical information indentations are caused by the extra stiffness where the carcass plys overlap in the sidewall. This area is more stiff than the rest of the sidewall, hence it refects the identation when inflated. This is cosmetic only and is more common in tires with high pressure.

They go on to say that bulges in a sidewall are an entirely different matter and tires wiht these should be taken out of service.

Bill

[wmtire]

Ah yes, I probably get at least one customer a week with the same question. The technical term for this is called undulation. We keep a poster in our waiting area, showing this condition, to help explain it to people. I always recommend that if you can't tell if it is an indention or a bulge, to feel with your hand on the backside of the tire. Undulation will be present on both sidewalls of the tire in the same place. As Bfezel posted previously, undulation is purely cosmetic, and will not hurt the performance of the tire at all.

http://www.firestoneuae.com/images/faq/images/sidewall_radial.jpg

A tire with broke cord (bulge) will just be on one sidewall, where the cord is broke.

Some tires will have several undulation places on them. I have seen 4-5 on many tires.

Here is a pdf file from the Rubber Manufacturers Association about undulation.

https://www.rma.org/getfile.cfm?ID=376&type=publication