Conti GP5k tyre and inner tube size advice

[Peter Salt]

I've always been using Conti GP5k 700x25c tyres with the Conti 'Race 28' inner tubes. All my wheelsets are around 26mm wide (external) so the tyre to rim transition is quite nice, and I'm not a particularly heavy chap so they're giving me enough comfort - even on long rides, so I never really felt like going up in tyre width - seemed pointless.

Thing is, I'm doing a new bike build and getting new wheels. Pretty much all manufacturers make wider sets nowadays - 27, 28mm wide (external) so I might as well jump onto the 700x28c tyre to get a nicer tyre-rim transition.

Long way round to ask a simple question: Should I just stick the 'Race 28' tubes in them (recommended for 700x20c - 700x25c tyres) or is it really necessary to go 'Race 28 Wide' (recommended for 700x25c - 700x32c tyres).

I suppose the wide version would provide a bit more puncture protection, can't think of any other benefits.

 

[13 rider]

I'd go tubeless 👍
The way a tyre sits on the rim is really dictated by the internal rim width ,having run a 28mm tyre on the rear during the winter I've now gone back to 26mm as it just sits on the rim better as that's the width my wheel was designed around probable a bit more aero if that matters to you .What width tyres do your new wheels recommend ? . As for the tubes I'd go for the wide as if I've read your recommendations charts you would be above that and stretching the tube to its max

 

[T4tomo]

certainly not necessary, might be marginally better. i'd still probably use up the race 28s though, either as a spare in the saddlebag or just phase them out when or if they puncture. I got new tubes when I did similar, but that was because my new wheels needed longer valve stems.

 

[Peter Salt]

I'd go tubeless 👍
The way a tyre sits on the rim is really dictated by the internal rim width ,having run a 28mm tyre on the rear during the winter I've now gone back to 26mm as it just sits on the rim better as that's the width my wheel was designed around probable a bit more aero if that matters to you .What width tyres do your new wheels recommend ? . As for the tubes I'd go for the wide as if I've read your recommendations charts you would be above that and stretching the tube to its max

The new wheels are 21 [mm] internal and 27.6 [mm] external, so aerodynamically I suppose they're optimised for a 28c tyre. Not all that bothered with it, but as you say - the wider tyre should sit on the rim better and just look nicer overall. You're right - with the smaller inner tubes I would be taking them to the absolute limit, whereas the wide tube is recommended for up to 32c so wouldn't be nearly as stressed. That may have some safety implications, so probably best to go wide.

certainly not necessary, might be marginally better. i'd still probably use up the race 28s though, either as a spare in the saddlebag or just phase them out when or if they puncture. I got new tubes when I did similar, but that was because my new wheels needed longer valve stems.

My narrower tubes will still get used on other bikes (with narrower wheels and tyres), so no concerns on that front. That said, it is a bit annoying that I will now have to stock another type of tubes. Hey ho.