New tyres needed but what size?

D13exile

My trusty and ultra reliable Conti GP4000’s have reached the end of their life. Truth be told, I’m on borrowed time with them. I’ve never had a puncture in the two years and 10,000kms I’ve put on them. Great tyres but now they’re showing some nicks and a few bald patches. So it’s time to replace.

My current tyres are 700x25 and I was going to replace with the same size in the newer GP5,000’s but after reading a lot of reviews, I can’t decide whether to stick with the 25 or go up to 28? I know the wider tyres are supposed to be more comfortable but I’m a stopwatch man and I’d hate to see my times decrease because of fatter tyres. There’s the school of thought that the wider tyres can be as fast as the narrower ones but I just don’t know. My bike is a Trek Domane with Mavic Aksum rims and I’m sure it could take the wider tyres but I don’t want to spend the guts of a hundred quid on wider tyres to regret it.

Any thoughts?

Type 17

Discs or rim brakes? Some 28's may not fit under some rim brakes.

You won't notice the difference between 25's and 28's on a stopwatch (but you may even be a bit faster, as they'll be more comfortable).

For the last while, I've used 25's in winter and 28's in summer (no reason, just the lighter tyres were 28's and the winter ones were 25's) and although it feels faster in summer, that's because I've no mudguards on in summer, and may go out further/more often, so I'm a bit fitter in Summer. Either way, I can't really see a difference in the week or two before/after I change the tyres in Spring/Autumn.

Assuming no brake-fit issues, try 28's - there's a reason they're more popular in the last few years, and they'll be at least the same or probably better - unlikely to be worse.

MrSkinny

D13exile wrote: »

Any thoughts?

Three days ago I replaced a set of GP4000 25c with GP5000 28c. The GP5000 are a lot more true to size than the GP4000, which are nearly a size up. If you stay with 25c I think in practice you'll end up with slightly narrower tyres, so go with the 28c to keep tyre size more or less unchanged.

In fact, I would say the brand new GP5000 28c actually measure slightly smaller than the four year old GP4000 25c they have replaced. I also tried a set of GP4000 28c (which measure more like a 30c) but the height was a problem and my rear calliper didn't have enough clearance. The GP5000 28c is about 3mm 'shorter' so not a problem.

I don't race so I'm not particularly worried about speed or rolling resistance or any of that but this site (which you have probably come across already) has plenty of detailed reviews of both models, size comparisons, etc: https://www.bicyclerollingresistance.com/

MojoMaker

28mm GP5Ks will be a noticeable improvement OP. The only question lingering is around durability, the newer tyre doesn't seem to be as 'tough' as the outgoing 4Ks.

D13exile

Thanks guys. Yes I read the reviews that said the GP 4000s were already a “size up” and that my current 25’s would be more akin to the GP5000’s 28. So I’ll guess I’ll go with the 28’s and see how I go.

For anyone interested, Merlin cycles appear to be the cheapest at the moment for the GP5,000 where they doing two tyres and two inner tubes for €86.96.