26"-27.5"

[FST4RD]

Hi all, built my ss bike with the intention of having as a mtb/cx hybrid.
Currently running 26" wheels with Larsen 2.1s. Was going to switch to cx wheels (which do for through the frame and fork) however I feel the bb will be too high off the ground.
So I thought 27.5". Can you get a narrow cx style tyre for 27.5"? If so how does the diameter compare to a standard 26" wheel and tyre?

 

[xerxes]

Re:

If you put a narrow, CX type tyre on a 27.5" rim the whole wheel will probably be roughly the same diameter as a 26" wheel with a fatter tyre.

There's less than an inch difference in the diameter of a 650b rim and a 26" rim:

http://www.bikerumor.com/2012/06/06/wha ... down-more/

 

[FST4RD]

Re:

Brilliant thanks for that.

 

[xerxes]

Re:

What do you want to achieve? Why a narrower tyre?

You can get fat, slick, or semi slick 26" tyres. There's no rolling resistance benefit with narrower tyres, the opposite in fact. There is an aerodynamic advantage with narrower tyres, but this only starts to make a difference at higher speeds.

http://www.schwalbe.com/gb/rollwiderstand.html

 

[FST4RD]

Re:

Basically I want a lightweight ss, which I have, but for it to roll fast and keep up momentum easily.
Currently running Maxxis Larsen 2.0 which are quite a big tyre, but I love them. I was thinking about going to the 1.9 as its litterally about half the size.
But I thought running cx style wheels would be even faster?

 

[JamesM]

Re: Re:

What do you want to achieve? Why a narrower tyre?

You can get fat, slick, or semi slick 26" tyres. There's no rolling resistance benefit with narrower tyres, the opposite in fact. There is an aerodynamic advantage with narrower tyres, but this only starts to make a difference at higher speeds.

http://www.schwalbe.com/gb/rollwiderstand.html

I know wider tyres roll better but thats for a given pressure and you can run higher pressures with narrower tyres so they can roll better. If the pressure is too high though then they bounce too much which is wasted energy.

 

[FST4RD]

Re:

I'm running suspension up front.
I tend to run my tyres up towards the max pressures anyway.
Plus the tracks I intend to run are fast and reasonably smooth.

 

[jimo746]

Re: Re:

But I thought running cx style wheels would be even faster?

Pedalling faster or pushing round a bigger gear would make you faster

I'd stick with 26" wheels, for all the faff of finding & fitting bigger wheels & tyres I doubt you'd notice much difference if any.
There are hundreds of 26" tyres to choose from, I use Michelin Wild Run'r 1.1's when I want to go really quick, or Schwalbe Marathon Plus 1.75's for reliability & comfort, and have some Geax Mezcal 2.1 xc tyres which are pretty quick and off-road capable too.
You'll just have to experiment and tyr a different tyre, one which suits the surface you ride on most.