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Bulge in sidewall

2000 Blazer 4wd with 235/70R15 Uniroyal Cross Country tires. The tires have about 35k and 7/32" to 8/32" of tread left.

I noticed a slight bulge (1/16 to 1/8" high and ~1.5" round) next to an indentation across the sidewall. There are two indentions on each tire 180 degrees apart so I’m assuming this is normal. The other three tires do not have any noticeable bulges.

There has been no change to the ride or handling of the truck. No noticeable vibration either. Tire pressure is maintained between 32 and 35 psi. The tires were rotated and balanced a month ago.

The bulge does not give when pressure is applied. At what point should I be concerned with the size of the bulge? Are there any circumstances where a bulge would be a cosmetic defect only? I would prefer to err on the side of caution.


Ed B.

All of the cords in a radial tire run at 90 degrees to the bead and tread. During the manufacturing process, sometimes a “tight wrap” occurs as the machine whips the cords around the carcass. This shows up later as little hills and valleys in the sidewall, some wraps a little tighter or looser than others. As long as the rippling is not extreme, 1/16"-1/8" is acceptable, there is nothing to worry about as this is considered normal.

Having said that, most tire companies have improved their quality control so this sidewall lumpiness is seldom seen anymore…

Have the tire guys look at it. You can check it yourself. If you can push it in and feel it start out soft and then hit somthing solid, your tire has to go.

Back in the early 1980s, sidewall cord separation was common on some brands of tires. The manufacturers would not replace the tires unless it was so bad that you could hear or feel vibration from it. I have not seen that problem in a while.

Thanks for the replies. I’ll keep an eye on it and have my mechanic check it.

Ed B