Hi I'm spending a few weeks doing a Calais to Nice run in June/July, about 900 miles ish. It's going to be a credit-card lightweight style tour, so using hotels and just a rear rack, on my 07 Allez Triple. At the moment the bike has the stock 23c Specialized Mondo tyres. Is it worth going for a bigger tyre for comfort / ability to take a heavier load, say 25c? Would the average speed get affected much by going up to 25? Thanks!