Re: Re: 28" recommendation…
The extra clearance on a Nimbus 2 will NOT create extra Q factor compared to a Nimbus 1.
The frames are the same width, and the unis use the same hub. The Q factor will be identical.
The extra clearance comes from the Nimbus 1 having a traditional inverted Y shaped crown, whereas the Nimbus 2 has more of an H shape. This means that in the Nimbus 2, the tyre is moving through a square channel, and on the Nimbus 1 it is moving through a channel which is like an inverted V.
So on a Nimbus 1, you put a fat tyre in, and the tyre has a ‘taller’ as well as wider profile, and catches against the sloping bits of the fork. It gets ‘choked’.
So no problem with Q factor. Go for the Nimbus 2 as preferable to the Nimbus 1, if either (a) you want to put a fatter tyre in, or (b) you want to do ‘foot on crown’ tricks like one footed riding.
And rolling resistance? This will be influenced by three things:
- The actual width of the tyre’s footprint. Crudely speaking, a wider tyre will have a wider footprint.
- The tread pattern. Generally speaking, a fatter tyre will have a knobblier tread.
- Tyre pressure. Generally speaking, you are likely to run a fatter tyre at lower pressure.
I think the order of importance is pressure, tread, width. So if you put a wide smooth tyre on and run it at high pressure, there will be little difference. Of the three variables, lowering the pressure will make the most difference, because you are increasing the amount of work you have to perform in flexing the tyre walls and tread.
But (rhetorical question!) why put a fat tyre on and run it at high pressure? This would make no sense on the road. It would help in mud, although you’d be even better off lowering the pressure a bit.
On a hard surface (tarmac, concrete, compacted fine ballast, baked mud, etc.) you have a straight forward choice, then:
Hard tyre = speed and discomfort. Narrow tyre OK.
Soft tyre = slower, but a bit more comfort. Wider tyre to compensate for lower pressure, to protect rim.
Racing bicyclists run narrow tyres at ‘3 figure’ psi. That’s why they seldom sing the bass parts. ;0)
The Nimbus comes with a narrow 700 c road tyre suitable for a road touring/commuting bicycle. (It is sold as a ‘commuter’.)
I’ve found this good for 20 mile rides, and it will cope with slime and shallow mud, but not deep mud.
You can’t go wrong with a Nimbus, but if I had the choice I would go for the Nimbus 2 frame because
a) It offers more versatility for tyres.
b) It offers some scope for tricks. (Difficult on a 28 to do too much, though.)
c) Simply, it looks more businesslike.
I have a Nimbus 2 20inch. My 24 and 28 are both Nimbus 1. They’re all decent rides - and the 28 is sooooo light.