Cycling UK Forum

samsbike wrote:Sorry I wasnt getting updates via email.

The bike currently runs discs and hope disc hubs so am assuming its 135. Its a burls ti that someone else had built.

I guess what I was trying to do is to see the whole impact of 26 tires with more air/ suspension.

you keep saying tyres, do you mean wheels and tyres? because i'm fairly sure 26" tyres won't fit on 700c wheels.

edit:

the other thing bear in mind if you have mtb wheels and and tyres that you are swapping over, is rotor size and adaptors. make sure you have the fittings for the brakes and rotors to match.

I was being rubbish in my description. I was swapping 26 wheels and tires onto my current bike which runs 700c currently

Brucey wrote:the steering will be different (less trail) the gearing will be lower if the wheel is appreciably smaller, and whilst the bike may accelerate more quickly (with similar width tyres) you may be fractionally slower overall.

But... the rear wheel may not fit at all. An MTB will most likely be 135mm oln but a road-going machine could be 130mm oln instead.

cheers

Steering will be unchanged in terms of wheel base as it is determined by the location of the centre of the wheel (front fork ends to rear drop outs) - which remains unchanged with any matched wheel sizes, as does the contact point with the road vertically under that. The only impact of steering feel will be due to differing wheel weight (MTB wheels and tyres typically being 'chunkier' and therefore heavier). Depending on tyre and tyre pressure the feel may be sluggish on the MTB tyres that typically are softer, lower pressure and wider than road tyres.

The wheelbase may be unchanged, but the trail will not be, and it is this that affects the steering, as Brucey has pointed out.

Yes, when Brucey first said that it hurt my head for a while. But as always he's right.
Imagine you drew a line straight down the centre of the steerer until it hit the floor. You then measure perpendicularly from the line to the point where the tyre touches the floor. Swap the wheel and do the same. The perpendicular measurement has changed, thus the trail is different.

However, I don't think that it would make that much difference to the feel of the steering - leastways you'd soon get used to it.

Is the lesson from this thread that disc brakes open up the tantalising possibility of switching 700c and 26" wheels across one's fleet of bikes with impunity? (All my touring bikes, MTBs and tandems are 135mm.) And indeed switching on demand to 650B?

So the things holding us back are the brakes (which have to align with the rim), the fact that the frames won't take disc brakes (so our starting point has to be disc fitted frames), and clearance (which on most touring bikes is OK).

As I'm wedded to V brakes this new possibility has no benefit to me at present but let's just say I swapped all my bikes in their present format to discs (my Sardar is half way there). Or even just new forks for front swapping. What would be the advantages and downsides?