Quote Originally Posted by mr brightside View Post
So how does the diligent cyclist know when to change a rear tyre? My rear on the winter Dolan has a definite flat surface to it now. I don't care about 'performance' and will happily ride it until the belting shows through; it's a kevlar lined Gatorskin and may have lost as much as 3mm of rubber off the centre area.
I’d be tempted to change it now.

Having said that you could always wait until you get a puncture but having a severely worn tyre will heighten the chances of it tearing. I’d suggest carrying, in addition to your spare tube, a length of plastic cut from an empty fairy liquid bottle in order to line your potentially damaged tyre.