Next month I'm embarking on a 250 mile ride over one day - I've done plenty of training and I'm ready. Currently my bike has 25mm tyres and some of the 100 - 175mile training rides I've done have proved by the end fairly uncomfortable.
I'm wondering what real world difference in terms of watts having 28's on instead of 25's would make? Obviously over 250 miles we won't be going very fast, perhaps averaging 16mph or so.
The route is fairly flat (St. Ives Cambridgeshire -> Newcastle (in the UK)). So I guess weight isn't a huge issue.
Is there a calculator or something out there that can help me decide?