Can I turn this pile of stuff into a cross bike?

[Ypsylon]

I did a little cleaning up and realized I collected quite a bunch of stuff over time. I guess I could try to sell it off, but maybe trying to make a cross bike out of it might be more fun.

I have a couple of stems in the 90-110mm range, a bar I thought was too wide to use on the road, seatposts in 27,2 and 31,6mm width, an old saddle and it's my understanding that all that stuff is the same for cross bikes.

The trickier part is the drivetrain. I have Ultegra 3/10 STIs, an Ultegra double FD, and a Tiagra triple crank which has a 50-39-30t gearing.

My plan is to just ditch the 50 for a bash guard and use the 39/30. Might be a little short but with an 11 in the back should be ok up to 40 km/h. A triple STI with two chainrings will have a couple of empty clicks, but I don't think it's that big of a deal.

What I don't have is a frameset and brake calipers. I have some old beat up wheels I could use to start, but I'm wondering if it wouldn't be smarter to start with dics brakes right away and build a cheap disc wheelset. Question is, do cross frames have a 130 or 135mm spacing for the rear hub?

Thoughts?

[Fibre-Lyte]

I don't know much about cross bikes but firstly, don't most use rim brakes rather than discs? Secondly, just based on chainring/guard sales, 39 seems a bit on the small side. 42-44 seems to be the regular sizing with an occasional drop to 40, so I'd be tempted to run a 42/32 (or 42/30 if you want to keep the little ring).

I also get the impression that (in the UK at least) most cyclocross frames are set to take 130mm hubs but some frames can be specced to run wider (may be for the difference between rim and disc brakes?)

[Ypsylon]

Yeah, as of now most use rim brakes, but the UCI just legalized disc brakes for use in competition, so I'm sure that'll change in the future. I think useing them makes perfect sense, as I assume they just work better in the dirt and I'd hope brake pads and tracks wouldn't wear out that quickly.

I'm looking into this topic more and more, and indeed most frames appear to take 130mm hubs, but especially with the ones that accept disc brakes you can't really be sure, it could be 135mm or something in between to be able to fit both.

I'm not too familiar with imperial measures and I could be wrong, but I think 28 (road/cross) and 29 inches (mtb) are actually the same, when it comes to rim and tire diameters, which I find a little strange. Can anybody confirm that?

So now I'm looking at rim widths and what tires you can use on each rim, like could I use a 33mm cross tire on a KinLin XD-230 disc rim which has an inner width of 17.5mm, or would it likely feel spongey or even roll off when run at a low pressures?

Does anyone know if there is a 28 (29?) inch disc specific tubular rim?

Stephen, 39 is definetly on the small side, and I wouldn't go out and buy it like that, but it's what I have. I could leave the 50t on and use the crank as a true triple setup, since the left shifter is a triple anyways, I'd just have to pick up a triple FD. But I think a bash guard would be cooler and I have a feeling a triple setup with a ton of dirt in it will just not work all that well. Also, I don't see myself useing a 50 in the woods, but I honestly don't know, that's why I'm asking.

Could be good to develop leg speed, too. This is not meant to be a full on race machine either, I just want to go out and have some fun. If I really like it, I can always upgrade stuff over time.

[rlpaul]

You are correct, 700cc and 29ers are pretty much the same size - MTB rims are wider. You see a lot of interesting wheels in the high end cross market, including Zipp 404s, so I don't think a lot of people are necessarily using wider rims.

I don't remember if Zipp specifically sells Cross wheels, but I do know Reynolds does, and the only difference is the spokes - same spoke count, but DT Rev/Comp instead of Aero-lite/Rev.

I've only seen one or two cross bikes with discs, so not sure if the trend is to run 'regular' rims with a disc hub, or if there's a non-rim brake track rim they're using, like maybe a Stan's.

[Fibre-Lyte]

Funny that you mention the 404's. The local riders I know who do cyclocross all either use or recommend 404's although I'm not too keen on them after seeing some repairs we've had to do on them.

Andy, I would very much doubt that you'll use the 50. I would definitely replace that with a bash guard.

[Ypsylon]

Interesting and objective opinion.

Now, which one would you recommend?

I'll shoot you a pm if I'm able to get my hands on a frame.

[Fibre-Lyte]

I wouldn't dare recommend a wheel for a sport I've never done. Guessing, if you need a tough,durable wheel with some kind of deep rim and alloy braking surface then the Mavic Cosmics are reputedly bullet proof and we've never seen one for repair (surely a good thing). However, I've never seen the point of a deep rim wheel in cyclocross. May be someone could educate me?

If it helps I know a cyclocross rider who races for Hope technology (he's also a good tt rider) so he may be able to offer a few pointers.

[fasterisbetter]

You certainly have the bits to build a cross bike out of that.

First thing I'd do is ditch the inner and out rings on the crankset and make it a single ring. A typical cx set of rings is either 38/46 or 36/46 (with 44s for bad mud days), so having a 30 on there is well near pointless. The somewhat nice thing about the triple is that if you can find someone (like Fibre-Lyte) to make you an inside guard for the smaller bcd of the triple you can run two guards without using spacers and a guard bolted outside the big ring.

This also solves the issue with a 3-ring shifter and 2-ring setup/derailleur.

For brakes I think it will be a while until disc brakes carch on with cross except in extreme conditions with very well funded riders. They weight too much (about an extra 1.5kg) and don't offer that much benefit over a good, stiff low-profile canti with nice brake pads most of the time. As a starter bike, I'd go for cantis.

With wheels - particularly if you aren't going disc - you can have your pick of options. The only clincher cx wheels I own are built with Stans ZTR Olympic 29er rims. They are wide and make changing to race wheels more difficult, but if they are your race wheels, they are light, stiff, and they support the tire very well. 130 spacing. Tubeless is the only thing to do if you are not going tubular.

If you're on a budget look for some good used tubulars - alu tubulars seem to go fairly cheep (as long as they aren't ambrosio rims) these days on something like Ebay. The tires are more expensive, but the ability to run low pressures and have the confidence of a well glued tubular is worth the extra shekels and hassle.

Great thing to do with extra bits. Look forward to hearing how it goes for you...

[Ypsylon]

Thanks for all the advice.

Those aren't the actual shifters, but that's my progress for now.

It's hard without a frame.

I've looked at KinLin TB-25 rims, but they might be a tad narrow for cross tubies.

[dunlinii]

I think that, given the lack of frame, you have made an excellent start.

[rustychain]

Major Tom rims are great for cross. I also use them for winter training on my road bike with 25 tires
They have a good brake surface and the glue surface is designed with bigger tires in mind.
I also would not jump on the disc bandwagon for cross. Tubulars are absolutely the way to go for cross
Cross can eat up drivetrains so stay flexible in your setup. You will be replacing parts often
Have fun!

[Ypsylon]

Well, this one is taking shape quickly now.

In a vid of Todd Wells winning cx nats someone comments on how he was the cleanest guy out there.

After every MTB race I've been in I was the dirtiest guy around, so I opted for disc brakes.

The frame will be a couple more weeks, but I'm really looking forward to start practicing mounts and dismounts.