'Standard' CX gearing on a 2x system would be 46-36 and 11-30/32. The availability of standard rear road sprockets bigger than 30 started about the same time as 1x so most people who have gone big at the back have gone 1x at the front.

The main thing you will notice is that you will never be the 52. As a 1x system 36 and 11-34 isn't a bad choice for CX. If you need a smaller gear you should probably be running and you are unlikely to need a bigger gear.

What he said. you will be fine with a 36 x 11-34

Thanks. That makes me feel better about dipping my toes in the CX pool.

You'd be much better off with a 53/39 crankset so you could use the 39 instead of a 36. If it's a fast course you'll probably spin out using the 36.

Agreed that road gearing would work (36<39<42 inner chainring and the outer is a guard), but is this on a road bike? With whatever gearing you'll need wider tires (33mm or more, preferably) and clearance for mud, so trying cx on a road bike isn't really cx.

My road bike is quite old, so I'm wondering if a gravel or CX bike with road gearing and two sets of wheels would serve me well.

I asked similar question and got good advice

https://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Gearing_upgrade_for_Cx/Gravel_P7213153/


(Apparently I don't know how to link. Search Gearing upgrade for Cx/Gravel April 2020)

Unfortunately, no races to test my set up!

I race on the standard gearing that came on my Crux (46/36 & 11-28) and have no trouble. You you should be fine.

Enjoy CX! I love it!

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I have deceptive speed.........I'm slower than I look!

Location and type of races is important. Racing in Scottsdale is going to be a lot different than racing in Boston and could affect your choices.

Benefit from my stupidity and please also consider the safety aspect of having that big chainring on a bike that is probably going to be crashed (into you and your buddies) - I once got lazy and kept road cranks 39-53 on the cx and spent a couple unplanned hours in urgent care getting a shin stitched up. Deep gash + grease + embro + mud results in a wound cleaning experience you should skip. Salsa makes a Toothless outer ring ‘blank’ is normally run with the 39 as a single but got lazy.

If you are planning to use your old road bike you need to see how big of tires will fit inside the fork and chain stays. I had a 70s bike that I ran 28mm CX tires on but didn't have much clearance for mud. With all the gravel bike options you probably could lose the roadbike and just put skinny tires on the gravel bike for road riding. I found the sweet spot for me is 32mm tires on the road and decent gravel and 38mm on rougher stuff. Much over 38mm you feel yourself pushing rubber on the pave, but floating nicely on the gravel.
Since CX season seems to be a bomb this year, I am wondering if the Gravel King 38mm size will be a thing on rough dry courses in 2021. I have been noticing the gravel bikes getting used a lot at local CX races with bigger tires than the 33mm size..

If I had to I could use my gravel/CX bike as a road bike but the downside is mainly gearing.

Many Gravel and CX bikes are coming are 1x setups these days. Mine is setup with a 40T chainring and a 11-42 or 10-42 cassette depending on which wheelset I am running. For off road riding 40x11 is more then enough for me. On the road the 40x11 is pretty easy to spin out a little above 20MPH. The 10 tooth cog solves that problem for me, I don't spend much time riding in big groups that ride fast enough that I can't keep up. I could solve that with a larger chainring but I would lose that low gear I love on steep climbs.

If I was building up a 2x gravel/CX bike to use on the road I would probably just throw a 50/34 crankset on there and an appropriate range cassette. Its larger jump in front than standard CX gearing of 46/36 but will probably work better on the road.

If you end up liking CX having a second set of wheels is a good thing. Its nice to have a second set of wheels or bike in the pit in case you flat.

If you have never raced before, any gearing will be fine. The gearing will not be tourture, it’s cyclocross, the whole event is supposed to be torture. 52-36 is fine. Really.

If you’re strong you’ll need the big ring occasionally for short periods. If you aren’t strong, you won’t need it at all. If you’re strong or you’re not, but you enjoy it, you’ll be buying two new bikes with whatever gearing you think will work better next year. The year after that you’ll be buying new gearing that you think might work better than that and 8 sets of wheels.

Been running Ritche Megabite 38s on 26mm ID rims for the past few seasons on my ss rig. LOVE the extra girth as a lot of Front Range courses have significant portions of the course that are basically just mowed paths through fields.

I bought a Specialized Crux last year thinking I might do just that. It came stock with 46/36 rings and 11-28 cassette. When I did my first CX race I found I never used the big ring (obviously course-dependant), but I also found that the 46/36 combo wasn't great on the road. Swapped out the rings for 50/34 which has proven to be pretty versatile for road riding and local gravel. I have to ride pavement to get to any gravel in my area so I wanted something that performed well on both.

I never ended up selling my road bike (Giant TCR) though. There's something about the Crux that just doesn't feel as crisp and snappy on the road - I think it's the slightly slacker front end. It doesn't handle poorly, just not like a road race bike which I guess is obvious, but I've been glad I still have my TCR. Just something to keep in mind if you're going that route.

That's some pretty relevant feedback, thanks!

Depends on location & condition, but I'd say +/- 4 teeth should get you started.

In Chicago I use 38 x 10-33 for nearly every race. It's predominantly flat here, but our grass fields get very heavy & water-logged, not including mud. 38 x 33 gets me up anything that's reasonable to ride, I think that if you need an easier gear then you're better off running it anyhow. Likewise, 38 x 10 gets me through anything fast & flat, and is plenty enough for 95% of finish line pavement sprinting (assuming tire nominal @ 32, 100rpm in 38 x 10 is 30.5mph).

Once you wrap your head around gearing (assuming you are into it & stick with 'cross), you'll go down the wormhole that is tires. Clincher, tubeless, tubular, file tread, mid, mud, pressure, etc :)

Yea Mr. Tim, I seem to like a little bigger tire on the ss rig as well. Not too sure why but I seem to go faster on the balloons. Actually in my case I go less slow with balloons on the ss rig. Fast isn't exactly a part of the nearing 70 year old cx rider vocabulary. But I use ta could.

1x up front 40T and 11-32 or 11-36 out back, clutch RD and narrow-wide chainring.

or

I would recommend a single speed and learn how to corner and maintain speed without a bunch of gears to bail out on.
If you are in the granny gear in a CX race you should probably be running anyway.