Tyres 25,28,32mm

Hondated

I know that I am only talking of a few millimetres in tyre sizes but as they say every little helps. So could I ask given I want to spend as little energy that I can what size tyre is the minimum size I should use to go on a tour with. When I eventually get around to it I want to load the bike with a tent, Sleeping bag etc. I do have good touring wheels already.

andymiller

You can tour fine on 25mm tyres, but equally if you can fit wider tyres then why not.

If your question is motivated by concerns about rolling resistance, Chris Juden (the CTC's technical guru) has argued that while narrower tyres may have lower rolling resistance, equally they are more fatiguing to ride. Seems quite a sensible argument to me.

In any event, frankly I'd doubt whether you'd notice mush difference between 25mm, 28mm or 32mm so I doubt it would be worth buying a new set of tyres - use what you've got.

vernonlevy

Hondated wrote:

I know that I am only talking of a few millimetres in tyre sizes but as they say every little helps. So could I ask given I want to spend as little energy that I can what size tyre is the minimum size I should use to go on a tour with. When I eventually get around to it I want to load the bike with a tent, Sleeping bag etc. I do have good touring wheels already.

Ive used 25, 28 and 35 and to be honest I've not really noticed that much difference other than the 35mm tyres gave a more comfortable ride - they certainly weren't any slower.

alfablue

Schwalbe argue that for a given pressure, a larger diameter tyre will roll better, see page 17 of their technical Information download.

If you are doing a heavily loaded tour I reckon it is worth having more volume, I am using Schwalbe Marathon Supremes 700x32 and it does seem to be an improvement over the 700x25 tyres I was using previously. That said, I only spent the £50 because the others wore out.

andymiller

alfablue wrote:

Schwalbe argue that for a given pressure, a larger diameter tyre will roll better, see page 17 of their technical Information download.

Yep - you caught me out being economical with the truth out of laziness. In my defence larger tyres would tend to run at lower pressures and lower pressure would mean greater rolling resistance. I suspect there's not a lot of difference between the working pressures for 35mm, 28 and 32mm tyres, and it all becomes a bit academic if they aren't fully pumped up.

alfablue

Ah, not trying to catch you out, it is complicated though, and as I understand it the advantage of larger volumes is that you can run lower pressures - I think I read that a narrow, very hard tyre (23) theoretically may roll well, but on real world tarmac it deflects on the rough stuff and rolls less well, a larger lower pressure tyre can deform over the rough stuff, and roll better.

I run 23's at about 115, 25's at about 110, and my 32's at about 90 - using a vaguely scientific calculation, that I have since forgotten.

Anyway, I really am on the fence because I went for 32's, if I had more faith I might have gone for 37's :?

andrew_s

1) At the same pressure, a larger tyre has a lower rolling resistance than a narrow one.
2) If the road surface is smooth, the rolling resistance is lower the higher the pressure (for the same tyre).
3) If the road surface is rough, the rolling resistance is lower the lower the pressure.

1 & 2 are because the tyre deforms less
3 is because the bike and rider bounce about less

A narrower tyre can be run at a higher pressure than a wide one (and has to be, if you want to avoid pinch punctures).
A narrower tyre is more aerodynamic than a wider one.

All comparisons assume the same tyre construction - eg various sizes of Panaracer Pasela.

If you get off road, the advantages given by wider softer tyres can be quite dramatic. On rough tracks you may descend twice as fast on 26x2 as you can on 700x25.

I have been using 700x28 (the largest that I could fit), but I've recently got a new bike and traded up to 700x35.