Originally Posted by
FBinNY
Do you by any chance have a narrow rim? 17mm or less? if so I suspect you're seeing the effects of hyper-stretching of the belly of the tube.
I had a serious case of hyper-stretching several tire tubes when I switched from a pair of thin casing 25c tires to a nearly bomb proof thick casing 37c's. The 37c's were almost destine to hang in the rafters indefinitely after several blowouts without even making a single run, that was until I wore out that set of wheels and purchased a set of wider wheels with a smaller width shoulder. Though my tubes didn't have dimples per se, but a row of small bulges all the way around the tube, and with one being the weak link in causing the tire to go flat.
Happily to say that the 37c's now have many miles on them without incident.