I have been running Specialized Mondo Pros (700x23) with a Kevlar Belt for the past 2 years. I have approximately 3500 miles on them. First flat I had on Friday I attributed to something poking through the belt of the tire. After I removed it, I still noticed a "burr" in the area. Is it possible that the Kevlar belt was cut by the obtrusion and is sticking out in the inside of the tire? I put a boot in the tire and seemed to have no more problems in that area.
Next two flats were near the valve stem. One was a longer presta valve and the other the standard presta. Both were Specialized tubes. My question is this: is this a manufacturer problem, or is it possible that the valve hole caused the abrasion? In both instances I was not using the locking washer.
I have a 1-year old turbo pro on the front that has gone 6500 miles with no flats. I periodically pick out small stone chips and glass shards from these tires and I am impressed with how well the belt stops them from penetrating. I am on my third rear tire having gone through the original turbo and one mondo pro. My currrent mondo on the rear has had one flat from a staple (30 miles into its inaugural ride).
I have been impressed with the durability of these tires since the staple and an earlier rock chip are the only puncture flats I have had on them. The original turbo failed early because I rode for a while with the wheel out of true after an incident with an errant cager (nearly endoed, partially ejected the rear whel, and then slammed down on it). This scrubbed the tread down quickly and the tire developed a bulge in an area that was likely damaged in the cager incident. The first mondo pro on the rear lasted a while (>3500 miles, one flat) until I hit some metal object and lost a chunk of rubber that made it unsafe to ride on. I didn't notice the chunk until a few days later since there was no noticable change in the feel of the tire. The exposed cords were still holding together well although there was some fraying. While I haven't noticed any burr on the two puncture flats I've experienced, the exposed fibers under the missing chunk of rubber were noticably stiff and rough. I doubt any fibers poking through would be a problem for a normal butyl tube though.
The valve stem failure problem can be caused by a bad tube but it is often a result of installation error. You have to be careful to keep the stem centered in the holes when the tube is installed. Otherwise you will eventually wear a hole at the stem junction from abrasion. I too have found that the presta nuts tend to tighten up on the stem and lead to premature failure. I keep them locked against the valve cap to they are there when I need them but can't cause any trouble while riding. I have had one stem failure on the original Specailized tube that was clearly an installation problem from the factory or LBS since I had never dismounted the front tire previously. It blew out in my apartment shortly after I inflated it before a ride so there was no abnormal stress on the stem.
