While I was out yesterday, I noticed that the tread on the front (motor) wheel was looking very worn down, so I decided to change the tire. They cost only about £12, and that's for the kind that are Kevlar-reinforced and therefore more puncture resistant.
I also use "thornproof" inner tubes; what that actually means is that they're a lot thicker (and therefore heavier) than normal tubes. But I'm not racing, and I'm going over very rough ground sometimes, and I'm very keen not to get a puncture. Using the thicker inner tubes and Kevlar tires, I've not had a pucture yet.
So I took off the wheel, and removed the old tire. The inner tube looked fine, so I kept that. Also, one of the spokes had lost its nipple, so I replaced that, so that now I have 100% spokes. That wasn't easy - the nipple I tried to use was aluminium, and I couldn't see a way to get it into position so I could screw it into the spoke. So I found a steel nipple, which meant I could hold it magnetically to the screwdriver to get it onto the spoke. I tightened the spoke up, and then tried to put the tire on.
This is a folding tire - that means it doesn't have a steel rim, the rim is nylon, or maybe Kevlar. But that means that the tire is kind of shapeless, and I wrestled with it, trying to get it onto the rim for ages. Eventually, I decided to put the tire on without the inner tube in place, and when I had one of the rims of the tire in place, then I put in the inner tube, then I pushed the other tire rim into place, mostly with my thumbs, but with a little bit of help from tire levers at crucial moments. That worked a lot better.
The tire came from Asda, costing £11.48 (P&P extra). I'm already using one of these, and it's been fine.