Mountain bike to cyclocross bike?

leopard trek

Lads,
Is this possible? and if so how...?
thanks,
LPT

Tenzor07

Yup, swap your tyres for 1.125 or 1.5 tyres, swap the cassette for a smaller ratio such as 12-17, get a short cage rear mech, swap the front chainrings for a say 38-44...Remove any bar-ends, water-bottle cages, if you have a frame mounted pump or saddlebag...

Greyspoke

Unlikely - I think one of the rules of cx is that you've to use 700c wheels so unless your mtb is a 29er you'd be stuck there.
I'm not sure if it's also a rule that you've to run drop handlebars which would require a whole new set of shifters/brake levers.
v-brakes would be fine and even discs are now allowed so you'd be okay on the braking front. Might be cheaper just to look out for a second hand cx bike!

blorg

It is not really possible economically. What are you trying to do? Race cross, or something else?

There is a rule that you must use drop bars, and possibly a rigid fork, if it is for racing. Wheel diameter is specified but that is with tyres, it MAY be possible to get the right diameter on 26" wheels with the right tyre.

Lumen

blorg wrote: »

it MAY be possible to get the right diameter on 26" wheels with the right tyre.

Well, most national regs follow the UCI, and UCI rules say:

"Wheels of the bicycle may vary in diameter between 70 cm maximum and 55 cm minimum, including the tyre. For the cyclo-cross bicycle the width of the tyre (measured between the widest parts) shall not exceed 33 mm and it may not incorporate any form of spike or stud."

Traditional 700x35 cross tyres just squeeze into the 70cm maximum. Even 26×1.0 are over 60cm.

So I don't think tyre diameter is a problem, and in any case the UCI is now mandating maximum 33mm tyre diameter which I'd expect is widely ignored except for at the top of the sport.

Theses rule apply to the road too, so there's nothing to stop riders using 26" wheels on a road bike in the TdF, for instance.

I think handlebar shape is implicitly covered by the "it must look like this" diagrams and...

"1.3.001 Each licence holder shall ensure that his equipment (bicycle with accessories and other devices fitted,
headgear, clothing, etc.) does not, by virtue of its quality, materials or design, constitute any danger to himself or to others."

C3PO

Well I know for sure that the Cross organisers here won't let people use mountain bikes in the championship races but where they draw the line I've no idea!

rosscollins88

I'm in the middle of this conversion at the minute. I had an old rigid 26in mtb frame and forks.

I had a 7 speed mtb wheels that i've put 8 of the 9 sprockets from a 9 speed cassette on. Learned from Sheldon Brown.

The frame didn't have a derailleur hanger and I had to use a vintage derailleur that slides into the horizontal drops.

I'm putting on 9 speed tiagra levers that will work with the 9 speed cassette and just set the limit screws so it will only go over the 8 sprockets.

I have a 50-36 compact chainset that I am putting a 46 or 48 outer ring onto.

I bought tektro 720 (i think) cantilever brakes. I only have the front brake set up and it works great, I don't understand why cantis get such abuse.

I am going to put on schwalbe cx pro tyres that are 1.35(?) in diameter which is equivalent to about 34-35mm. 35mm tyres were legal until this year when they reduced this to 33mm. Only time I think there will be any issue is at the national champs. These tyres can be picked up cheap on planet-x.

I just need to get some oversize handlebars, pull off the old seized crankset and do the cabling.

With a bit of research you can get a lot of things that shouldn't work together to work.

I plan on finishing it off this week and it will only have cost me about €150 in total. Hopefully the geometry/handling isn't too bad.

I'll post a review/picture when I'm finished.

Edit: Also my frame didn't have a rear cable mount so I'm using the surly long cable hanger for the rear brake.

leopard trek

thanks lads @Ross That'd be great, thanks

rosscollins88

Just an update on my build. I had severe difficulty removing the fixed cup of the bottom bracket (drive side) from the frame. Wore out the edges on my wrench. Brought it to a couple of bike shops to remove but they were unsuccessful but told me to weld the axle to the cup and use the crank as the lever.

Got that done this morning by a neighbour and the cup came out easily enough then.

Should have the bike built up midweek now.

blorg

@Ross- most people complaining about cantis have low profile ones, which are shït. Tektro 720s are wide profile and very effective (I have them on my own cross bike.)

rosscollins88

Built up the bike tonight. Took more time than I expected. Will do a proper test ride tomorrow and post up a few pictures.

Happy with the geometry and the gears are shifting nicely.

funkyjebus

rosscollins88 wrote: »

The frame didn't have a derailleur hanger and I had to use a vintage derailleur that slides into the horizontal drops.

You can use one of this last week, not for racing, just for winter and running the dog into the ground in the pheonix park - total cost was 150 as had some bits lying around.

rosscollins88

Right so got her out for a proper tough test ride today. Up kilmashogue lane and across the fire road to 3 rock and around the mtb trails and a few fire roads.

Bike was well fit for all of it but wouldn't recommend it (no fun gripping the brakes all the way down). Have 50-36 up front and a 34 on the back so can manage any climb. However when on the road the jumps between gears are massive. The gears shift beautifully - better than my road bike at the minute 105/ultegra mix.

My position on the bike is very similar to my road bike so delighted the geometry worked out as I just used whatever parts I had to hand. A fella told me when I began cycling that when in the drops the handle bars should line up with the front axle in your eyeline. I'm using a 140mm adjustable stem and it places the handlebars in this position.

Found the cantilevers easy to set up. I've got no squeeking and adequate stopping power.

The cable stops for the rear brake where on the underside of the top tube and it made it very difficult to get the cable to go through the surly rear cable hanger. So I ran a full length cable outer over the top of the top tube and zip tied it to the frame. It works perfectly and seals more of the inner cable from dirt.

Pictures show the old school shimano derailleur, 8 cogs from a 9 speed cassette mounted to the 7 speed wheel.

Ross

cyco

Good man. looks great ross. Definitely use that for the epic blast!