Two broken tyres in 2 weeks - what am I doing wrong?

[Mel]

Hi,
I had one tyre that wore out and started bulging in different places, leading to flat inner tubes all the time. So I replaced it with another one (second hand), and a week later that's broken in the same way with a bulge and split outer tyre so you can see the wire hoops, despite the fact it was nearly new and fine when I put it on.
Its definitely the same size as the old one, but the fit seems very loose, how do I measure the wheel to make sure both tyres weren't the wrong size?
Is it possible there's a problem with the wheel, or am I doing something wrong with fitting the tyres?

Any help much appreciated, thanks

[AndrewB]

Wow, are you doing jumps or landings on this bike by chance?

Are the wheels true and straight?

You might be using the wrong tire sizes and/or tube sizes. What do you know about the wheels?

[Joe_W]

Check the brake alignment, might be the brake pads slicing open the tyre. Do you ride with very low pressure, lower than indicated on the side wall of the tyre? It then might slip on the rim and wear.

And definitely check the size of the tyre and the rim: measure diameter and (inner) rim width http://sheldonbrown.com/tire-sizing.html

[Mel]

Hey,
Thanks. I'm not doing any jumps or landings just cycling to work! I'm wondering if the wheel might be warped - how do I tell?
Thanks I'll try measuring the wheels as well.

[DaveM]

If the tires are splitting along the sidewall near the rim, there could be a rough spot on the inside of the rim cutting them. If it's on the road side (tread) I can't think of anything that would cause this other than that they were just old tires that split.