I'm having a tremendously bad day. I rode the bike to work, hoping to get the rear tyre repaired at lunchtime. The tyre fitters (I went to two) said they couldn't repair it as it was too close to the shoulder of the tyre. One suggested putting in that gunk to seal it so it won't continue to leak, but not bother about repairing it, just change the tyre in a month or so. I think the nail must have been in there a while, but I just hadn't noticed, as it's been going down about 2-3 psi per week (there's not enough tread left to warrant a repair really). I put the gunk in, and found that I just picked up *another* nail - this time going at 45 degrees in through the tread and out of the tyre wall. So I need a new tyre after all, which I can't get until monday. No biking this weekend then.