Tire overheat versus atmospheric oxidation

[JHZR2]

Tires are old Dunlop sport A2, which is a type that I have had very good luck with. These are in the size 195/70HR14, on my 1981 Mercedes 240 D; don't have a date code with me but I think the tires are roughly 2002-04 vintage.

In early September I caught shrapnel in one tire on the interstate. It slowly lost air because we did not feel any real change or noise right away. But when we coasted down to a stop and saw the tire it was very warm to the touch.


Fast-forward to today when I'm actually trying to get the tire repaired. The car has sent since that event in my garage, because it is just a pleasure vehicle that we used to go to the beach and other pleasure trips. It has a full size spare and metal hubcaps so it looks exactly the same and the tire that was on the spare was an exact match. But I just haven't driven it until last night.

Imagine my surprise when I pulled the tire from the trunk and saw that the tread the surface was very discolored. Keep in mind we had driven on the tire with low or no hair for a little bit at interstate speeds, and as mentioned was a bit warm to the touch. The car maybe sees 1000 miles a year if that, and it is mostly trips between 30 and 50 miles away on the local highways and generally not outside of 150 mile radius. I'm not sure if that makes a difference regarding the antiozonant and UV chemicals inside of the rubber.

The sidewalls of the tire look just fine, it is evident that there was someway on the sidewalls when the car was rolling, but they are a healthy normal black color. It is only the actual tread surface where it meets the road. The tire was stored inside the trunk of the car inside of an unheated garage.

So what do you make of the discoloration of the tire? Is this a sign of heat damage? Heat induced oxidation? Or is this just normal oxidation of a used tire which I would never otherwise see because the tires never sit unused for that long?

Thoughts? Thanks!

 

[gfh77665]

I think you are over thinking it. It would not get hot in just one or two spots. Just air it up and roll with it. I have had MUCH worse looking tires that lasted for years and years. In fact the discoloration might be due to whatever it may have come in contact with sitting in the trunk. Rusty jackstand? Etc.?

I think you are good to go.

 

[Quattro Pete]

So how deep does this discoloration go? Is it just on the surface? Would it go away if you drove on this tire for a few miles?

 

[JHZR2]

Originally Posted By: gfh77665
I think you are over thinking it. It would not get hot in just one or two spots. Just air it up and roll with it. I have had MUCH worse looking tires that lasted for years and years. In fact the discoloration might be due to whatever it may have come in contact with sitting in the trunk. Rusty jackstand? Etc.?

I think you are good to go.


It is not in one or two spots, there is a discoloration (reminds me of the metal on a nice shotgun) all over the entire tread surface. The tire was sitting without contacting anything in the trunk. No jack stands or anything else.

Originally Posted By: Quattro Pete
So how deep does this discoloration go? Is it just on the surface? Would it go away if you drove on this tire for a few miles?



No idea. I should have scrateched it but was rushing to drop it off for repair.

For all I know, most tires do this when sitting exposed to the elements for many months... and we turn the car on, drive away and it scratches off in no time. I just dont know, Ive never noticed, that's why Im asking the collective.

If this was on a spare tire, I wouldnt be worried, and chalk it up to sitting. Since it was on a tire that was flat and got hot, my other fears come to surface.

 

[SwampSurvivor]

Was it exposed to oil or something?

 

[gfh77665]

I know this is anecdotal, but my Mom-in-Law drove 15 miles at Interstate speed with a lock up brake on the right rear. She got home and the TIRE was smoking and so hot scorched the grass it rested on. Brake was repaired, and we still roll on that same tire today.

 

[JHZR2]

Originally Posted By: Miller88
Was it exposed to oil or something?


No, never.

 

[JHZR2]

Originally Posted By: gfh77665
I know this is anecdotal, but my Mom-in-Law drove 15 miles at Interstate speed with a lock up brake on the right rear. She got home and the TIRE was smoking and so hot scorched the grass it rested on. Brake was repaired, and we still roll on that same tire today.

makes me feel real safe, glad I dont drive in TX much!

 

[CapriRacer]

The multicolor is the oil migrating to the surface of the tire - and yes, that was the result of the over heating.

The brownish color is the antioxidants (AO's) also migrating to the surface - and being captured by the wax coating that forms as the waxes also migrate to the surface. Flexing the tire flakes the wax off, along with the AO's - so the color gradually disappears - unless the rate of flaking off is matched by the rate of migration.

 

[JHZR2]

Thanks. FYI The tanish brownish color on the tire was actually mud from where we had parked the car one time. But it makes sense what you are saying. What is your take on the oils migrating and tire life/safety/flexibility/etc?

The car has 67hp and so we dont go anywhere fast. I usually dont cruise above 65-70MPH. We dont take it far and dont rely upon the car. Would you drive on that tire?

On another note, given the shrapnel in the tire, is there a pracical limit to how big the repair can be?

 

[Kuato]

Nice chemistry, CapriRacer.

Yes there's a limit to how large a hole can be repaired. Your tire repair shop will tell you if they can repair it, or not. I'm not sure of the size but that's a big chunk.

I wouldn't use that tire except as a spare; and at 10 years+ old, I'd be looking for a new set.

 

[JHZR2]

Im looking for a new set sooner or later. Good 195/70r14 US made tires are rare, no US made tires are stocked locally (!). Probably wont have the car out again until solidly in the spring, and given the use profile, Im not worried much.

Ill actually keep my nice spare as a spare.

 

[Quattro Pete]

Originally Posted By: JHZR2
Good 195/70r14 US made tires are rare, no US made tires are stocked locally (!).

Yokohama Avid Touring-S. It's a rather popular tire, so you should be able to find it locally.

 

[JHZR2]

I checked the local places as that is on my list... No dice!!!

 

[djb]

Ideally the waxes/oils migrate to the surface just quickly enough to prevent oxidation. Too little flexing will allow the surface rubber to degrade. Overheating such as this will speed the migration and thus shorten the storage life of the tire, although perhaps not the service life. (Most people wear out the tread or get a puncture before the rubber cracks. )

 

[CapriRacer]

Originally Posted By: JHZR2
Thanks. FYI The tanish brownish color on the tire was actually mud from where we had parked the car one time. But it makes sense what you are saying. What is your take on the oils migrating and tire life/safety/flexibility/etc? .....


The tire's longevity has been hurt. I would plan on replacing the tires earlier than you originally planned.

Originally Posted By: JHZR2
......The car has 67hp and so we dont go anywhere fast. I usually dont cruise above 65-70MPH. We dont take it far and dont rely upon the car. Would you drive on that tire?....


Yes, but not forever.

Originally Posted By: JHZR2
.....On another note, given the shrapnel in the tire, is there a pracical limit to how big the repair can be?


And while I wanted to comment on the damage separately, it has become the elephant in the room. The repair limit is 3/16" - and that looks to be larger than that. So I think the tire is toast.

 

[JHZR2]

They were going to be replaced in the next year or so anyway. If they get 500 miles on them I'll be surprised.

 

[eljefino]

Two anecdotes. You all are going to cringe.

I get junkyard tires that are that color brown. It doesn't go away right away either (on the tread). I haven't thought about it much, really. They are universally that color so it's not like they were sitting in nasty gasoline or anything at the yard on one sidewall etc.

I was fixing up a cavalier earlier this winter for my brother in law. My manual tire changer is tough in the best of times, and this 205/55/16 was fairly stiff. I brought it inside by the woodstove and warmed it up enough for the rubber to get gooey. When I drove it the goo immediately picked up some sand. After a couple days driving it was back to normal, except inside the tread, and this tire hasn't popped yet.

 

[gfh77665]

If you want to see how tough tires really are, google "redneck tire mounting". Some are totally engulfed in flames during the mounting explosion, and then just roll on...