When I change the tube on my bike (it's s Dawes Super Galaxy). When. I pump up the tube it pushes the tyre out of the rim. Happened 4-5 times yesterday. Lost a brand new tube.
Does this mean the tyre is knackered?
Thanks in advance.
Could be the tire, could be the rim. Does the bulging occur in the same spot all the time? Check the bead on the tire and check the rim to make sure there are not any damaged spots where the tire seats to the rim.
If there was not a problem with a blowout previous to removing the tire and tube the problem is most likely due to poor installation technique. You need to make sure that none of the tube is sitting underneath the tire bead after you install the tire, especially near the valve, which is reinforced. Push the valve up into the tire and then pull it back out again to prevent that occurrence at the valve.
It was the tyre, got a new one today. Tried again with the old one and it pushed out 2-3 times in different places on rim.
New one, no problems whatsoever. With two tyres to compare, the old one had stretched somewhat.