I have a Giant hybrid (with 700x32c 65 PSI tires), stock tires, that I mainly ride on nice roads to and from work ~3.5 km/2.2 miles each way. I weigh 230 lbs/104 kg up from 200 lbs when I bought the bike sadly two years ago.
I check my tire pressure before I start riding again (If it's been more than 2 weeks) or every week. And I've put about 640 miles on the tires, but in that time I've had 3 blowouts.
That seems like a lot.
After doing a bit of reading it feels like my tires might be under inflated (I have a decent floor pump I use and I try to keep it right at 65 PSI) for the weight load (270 lbs/122 kg including bike), but I can't tell. I haven't measured displacement under load (I'll do that when I get a new inner tube) to see if it's above 15% or not, but I don't thing there's any tire or rim damage that would be poking the tube either.
How do I tell what's causing the frequent blow outs? Low tire pressure or too close to the limit? Or are my expectations wrong on how often they occur?
edit: Okay, I removed my back tire and inspected the tube and there's a small hole bigger than a pin prick around the size of a pin head. There also seems to be pitting/cracking on the inner tube (Forte 200x28-32C made in Taiwan 2012 37 03).
This appears to be the puncture.
Do I just have low quality inner tubes? I've just been having the bike shop I bought the bike at replace my tubes.