Let's build a CX frame

Righto. No more mucking around; it’s time to build a frame. It’ll be my first solo frame build (I’ve only built one other during a course, ages and ages ago now). MikeD suggested a simple SS roady, which makes sense, but I don’t want a SS roady, and my CX ride sucks, and what’s so hard about vertical dropouts and a few braze ons anyway?

Designing the geo for the first time - every bit of it - is takes a lot of thought. My approach is based on a mixture of measurements from my existing favourite bike, the geo on the 55cm All City Macho Man and the wisdom of weirdo named Richard Sachs. He says:

And a bit later he says:

So here’s what I’ve come up with:

I’m thinking OS tubing with a 1 1/8" straight steerer (tapered is a bit beyond me for now). I was thinking lugged, but I’m more confident with fillet brazing. I’d like it to fir 42mm tyres, but it’ll be my race bike (That’s C-grade by the way, finishing at the front of the last quarter of riders consistently). Cantis, not disks. Straight bladed steel forks.


I’m certainly no expert on these things but I like the look of the geo - pretty straight up CX with a low BB. Maybe the fork could be slackened by a degree? OS tubes make sense for a bike that you want to be stiff.

If you build it with a 44mm HT then you’ll have a greater range of options when you come to buying a fork - for instance there’s a full-carbon Columbus Mud fork on Planet X for about $200 at the moment IIRC.

1 1/8 is ok but 44mm is better and shouldn’t be much harder if fillet brazing you may just need cups for your jig?
If you go canti’s steel fork with a crown mounted hanger should fix any shudder issues so probably a good option.
I’m not to sure on old mate RS I know that trail matters on a road bike hugely when racing, that said most big companies have it nailed now so just copy front end geo off the likes of specialized.

I’m not a fan of big saddle to bar drop but I do like to be KOPS in relation to the bb and longer in the reach as it produces a lot more power.
I like the 74 seat tube it means running a set back post rather than a inline post for me which are usually more compliant.
My only thought is that your bars are all most level with the seat and if your reach is short it’s hard to generate power at such an upright position?
Is the Tt length the same as your road?
That being said I’m still finishing building my cx bike so havnt had much time playing with its fit but I keep all my bikes the same set back on the bb of about 52mm I think and just adjust the reach with the stem.

With the cx I will start by shortening the reach by about 10mm may be 20mm compared to my road bike mainly by less saddle to bar.

Have you had a proper fit before?
Any way I will be following this closely Im stoked you’re giving it a crack

Don’t bugger around with coke can head tubes

1 1/8" forever

Dayne - Based on what I’ve seen Pete is a more ‘upright’ rider than racer. He likes to watch the world around him rather than ‘slam dat stem’ and stare at wheels. This will help on the longer days in the saddle too (or if he loads the bike with the usual hipster panniers).

if you are going cantis a crown mounted hanger is essential.

Ezy will soon ask the most important question - what colours?

What colours are you thinking Pete?

Yeah 1 1/8" steerer is locked in I reckon. I’m more comfortable with that. The idea is to build the fork too, so all steel. I might run a crown mounted hanger – just transfer the one from the Ghettro over – but being steel it shouldn’t judder with stem/headset hanger. I’d like to build a stem, but would need to make a jig first.

Ha! That saddle to bar drop will be more than any other bike I own (except maybe the Look; I should really build that up again). The saddle tip to handlebar is pretty much the same as my everyday bike. It’s shorter than the Ghettro, but that’s a flat bar bike converted to drops, and has always felt too long. No I’ve never had a proper fit before.


Excellent Pete, will follow this with interest.

I have not had any judder with my steel crosser and always had cantis with a headset hanger, so I wouldn’t say a crown mounted hanger is essential. But I suppose you want to keep your options open and be able to run both.

Oh, and ‘Bikecad’, good name.


I suggest Goosebumps as a name.


looks good but make it way more aggressive, at least 15cm saddle to bar drop. It’ll be sweet.

also waiting for smuglord to chime in.

just for you james

My old crosscheck had the worst judder of any bike I’ve owned.

Set the posts as low as possible with 85mm arms so that the pads are maxed to the top (with a little slack for wiggle room.) This will increase the arc the pad swings over and increase your rim clearance.

Cantis are dead.

Just use Mini Vs.

Is this to just race cx or gravel/trail ride as well?

Mine has zero judder, so I guess I’m lucky.

OK. They’ll handle 42mm tyres yeah?

Will think a bit more about reach/bar drop. Shouldn’t change the bits I need much. Want to order by then end of the week.

If it judders, I’ll fit a crown mount, if I don’t go with a crown mount to start with.

I’m building it to race it. I’ll probably grind it as well occasionally, hence the 42mm tyre ability.

Enduro gravel cross country in the rain.

I had either 40mm or 42mm for a while and they worked fine with 85mm mini Vs.

Heavy mud would be a problem though. And you might need to deflate the tyre a bit to remove the wheel.

I’ve got some mini V calipers in the cupboard if you ever want to try it out.

Wow, new genre. I like it!