Building a cross bike from a MTB frame?

[A72litespeed]

I am interested in building up a winter training bike/cross bike from my old mountain bike frame. I was wondering how hard this would be with the different sized rims. I know the spacing is different for the rear hub, but other than that what else could cause me problems? Thanks

[jeff williams]

If the fork is drilled, and you have a drilled rear cross strut for mounting U-brakes.
The larger wheels mean the 26 inch wheel canti- bosses will not work.
Do you even have clearence for the larger wheels? 700's?

[SAB]

I would just use 26" wheels. Change the front cranks and rings from a triple to a 'cross-style double, such as 50/36. The rear cassette you can probably leave alone. Next change the bars to road-style drop bars. Then you can run shimano STI's or bar-end shifters. If you want to keep your v-brakes you'll need an adapter pulley to use with the road brake levers. Or you could switch to canti brakes and not need an adapter. Good luck.

[jeff williams]

I would just use 26" wheels. Change the front cranks and rings from a triple to a 'cross-style double, such as 50/36. The rear cassette you can probably leave alone. Next change the bars to road-style drop bars. Then you can run shimano STI's or bar-end shifters. If you want to keep your v-brakes you'll need an adapter pulley to use with the road brake levers. Or you could switch to canti brakes and not need an adapter. Good luck.

How about the same triple cranks\spyder\..running 2 rings\ the outside ring a guard.
And have the bb axle changed to longer and move the chainline (chainrings over).

Possible?

[Phatman]

How about the same triple cranks\spyder\..running 2 rings\ the outside ring a guard.
And have the bb axle changed to longer and move the chainline (chainrings over).

Possible?

that would make a wide MTB q-factor even wider, not a good thing. I'd go with a new cross crank if the chainrings clear the frame.

[jeff williams]

The max ring I can run middle on my mtb frame is 39T. If a double ring is to either side-
I would guess a 36T inside, but I really doubt a 50T would clear the stay? They jutt out pretty far for the wheel clearance compared to a 700 tire bike.

But if use a double, I need to pull\replace the axle..and it will place the rings closer to the frame..hmmm, I really wonder what size of rings I'd get to run.

[SugarHillGMC]

I just put a mountain/'cross bike together for my 17y.o. daughter to ride in some of the Verge series (she had been riding 'cross on a Cannondale mtb). I found a not-too-old Scott rigid mountain bike, pulled it apart and rebuilt it with a mix of the components that came with the Scott and road bike parts. Added 1.5" tires, new chain and a tighter cassette, she tried it on one short test ride and we headed to the Crank Brother's U.S. Gran Prix last weekend. Guess the bike (oh yeah, let's not forget the rider) worked pretty well, since this was her 4th cross race and she placed 7th on Saturday and 5th on Sunday in women's B.
So, the mtb to cross bike can work and pretty well, although if she keeps this up I can see a true cyclocross bike under her next year.