All 4 of my tires have cracks where the sidewall and tread come together. It goes all the way around the tire, but only in the grooves of the tread. Its hard to see in the pic so I have an arrow point to it. They say Kuhmo 732 Touring Plus and they are 205/60/R15 This is on the outside of the tire, I haven't looked to see if its like this on the inside.

 

Um, that's cut into the tire in production I think

 

The arrows are pointing to the location of the cracks, but the cracks cannot be seen in the pictures. I can see them with my eyes, but my camera has a hard time getting a good picture of it. There are cracks in the rubber down inside that groove.

 

Age. Tires get hard and crack after a few years. Get new tires if you are planning to do some high speed / high performance driving.

-Max

 

As Maxcooper mentioned, it has to do w/ age. Where did you purchase the tires from?

I experienced the same problem on my former daily driver. I purchased the tires from a "tire speciality store" (Discount Tire retail store)...and the tires had sat on a shelf for awhile.

I learned my lesson, as it freaked me out that my tires were cracking and I was daily driving on them.

So I now purchase tires from Tire Rack, as they are a HUGE volume seller. Large volume means more inventory that moves. More moving inventory means constantly "fresh" tires.

 

These tires were on the car when I bought it about 3 years ago. Its not a daily driver, but I do drive it on the weekends and I autocross it. I wanted new tires for autocross anyway as these aren't really that wide and they are a touring tire. I'll look into tire-rack and see what they have.

 

The location that you're pointing out is one of three high stress locations that typically see terminal failure when a tire isn’t properly maintained. The other two would be the bead belt that attaches to the rim and the flex point within the sidewall. What you’re most likely looking at is a tire that was driven on under inflated.

When you ride on under inflated tires for excessive periods of time, the steel belts within the tires start twisting causing the steel to heat up. Think back to a time when you may have taken a wire hanger and bent it back and forth to the point where you broke the wire in half but couldn’t touch the ends where it broke because it was too hot. That is in essence what you’re doing to an under inflated tire.

This particular tire heated up and then sat in a somewhat damp place causing it to start dry-rotting.

On another note, most people do not realize that tires are assembled in sections with the carcass (steel belts and the multiple plys) encased in synthetic rubber to keep the design together. The next ingredient includes “rubber” that is fused to the sidewall and a strip that constitutes the contact patch. All of that is either encased in another strip of “rubber” fusing the two parts together or there may be a flap of rubber on either the sidewall or contact patch that integrates the two sections. Depending on how cheap this tire is, you could simply have the separation of the two synthetic rubbers (the contact patch and the sidewall).

~Mike