Blew up rear tube supposedly at 20 psi below max
Hi folks.
I was pumping my tires today with a pump that has an integrated digital pressure-o-meter (terminology?). These are 90 PSI tires. At 70 PSI the tires were feeling very stiff and did not want to be inflated any more. I hopped on and road to campus. While walking the bike from the road to the rack, the rear wheel suddenly "stuck". I leaned my face real close to it (maybe it was bulging near the brake? I only had about 5 seconds to look at it.) when the tube went off like a gunshot - I jumped 3 feet in the air!
I bought the bike (1969 Raleigh Super Course) with new tires (and presumably tubes) on it a few weeks ago and had noticed the "firm before full" issue, but had no problem riding it. I'm confident that I didn't puncture the tube; the road was clear the whole way and the 20 feet I walked it to the rack was clear pavement.
Do you think the pump is innacurate, or is it possible that I had "bad" tubes that didn't match the spec on the side of the tire?
I'll take the wheel to the shop to get the replacement tube and get a feel for what 90 PSI feels like on the fingers. I can pick up an analog pressure-o-meter-thingy while I'm there too if the pump seems to be the culprit. Is there a way I could quickly test the pump? It's just a cheap Bell gadget, nothing fancy.
Any advice is appreciated!