5~10mm rupture (crack) on my tire - should I replace it? This is on my rear tire. I ride about 100 miles a week and the tire has been fine. Will this lead to a blow out?
The tyre wall appears to be splitting or the layers are coming away from each other. Yes, that's bad because it will lead to failure of the tyre. Failure probably isn't imminent but you should replace it as soon as is practical; new tyres aren't very expensive.