Hi all. Just seen an advert from cycleworld.co.uk advertising bontrager inner tubes at buy 3 or more and get 50% off. Thought I would let u know as sounds good deal to me. I also (as usual) have a question to ask. Most road bikes run 23mm rims, and therefore I assume the best size inner tubes to buy would be 18-23mm? However have seen that you can also buy 18-25mm. Just wondered why? As I guess they'd be (marginally) heavier.