I bought new wheels for my roadbike (shimano wh-rs80 which have c24 alu/carbon rims). I was mounting tires on them yesterday and inflated them to 8 bar (~116 psi). After a few moments (30 seconds or so), the tire started to slide off of the rim at a certain place, resulting in the inner tube to expand more than it could handle, and blow out.
I tried again with a new inner tube, checked that no part of the inner tube was stuck between the rim and the tire, inflated to 4 bar or so, checked again, inflated to 8 bar, BOOM. Same problem.
The tires are almost new continental GP4000s 23mm (a few 100 kms on a fulcrum 7 wheelset this summer) which were stored for a few months without using them. The inner tubes are also continental.
I checked the inside of the rim and can not see any damage or anything that looks odd. There is a factory installed rim tape in place, all brand new.
I had this twice with the front wheel and the same tire. I could try the rear wheel and/or the other tire to see if there is any difference, but I am a bit reluctant to potentially destroy yet another inner tube at this point.
Am I doing something wrong? Did I miss something given that these are new wheels?