Gear ratios for CX

[chriscole]

I've noticed that on the climb from the bottom of the hill I currently live on, to home (which is a 4km continuous climb of 310 metres vertically = 7.75%-ish) to maintain a comfortable cadence I can be in about 2nd gear on my CX bike, or about 4th-5th gear for the same cadence/workrate on my road bike. Some of that is due to the road bike being a fully carbon-based life form which weighs about 1.5kg less than the cross bike, and has skinner higher pressure lower rolling resistance tyres on it than the cross bike, but the disparity still seemed a little too much.

On closer inspection (for the first time... never thought to look before), I notice my CX bike has an 11-28T 10-speed cassette on the back, whereas the road bike has a 11-32T 10-speed cassette.

This kind of surprised me, as I thought that with its offroad intentions in mind, a CX bike would be geared a little more like a MTB with some lower gears (higher mechanical advantage). Interestingly this does not seem to be the case. When one looks at CX-"specific" cassette options they seem to max out at 27 or 28 teeth.

Do we just assume all CX riders are harder/tougher/stronger than the average lycra-clad road wuss? Is there another mysterious reason why it's thought that a CX bike doesn't need the lowest gear options? Are they just trying to provide more closely spaced ratios in the mid-range?

Putting a new set of wheels on the CX bike currently and need to buy a new cassette... was tempted to get something to give me some lower end options... 11-32T for example... but wondering if I should just stick with the "norm" and put an 11-28T on it again (albeit a sexier, lighter one)?

[queequeg]

What crank does your CX bike have? Mine came with a 46/38 setup, with an 11-32 cassette. My road bike is 53/39 with an 11-28 cassette. There is not a huge difference at the low end as the cassette goes 21-24-28-32 and 21-24-28, so I only gain the extra bailout gear.

I did have a 50/34 compact crankset on the bike, which I mostly commute with, but I stuffed the chainrings due to neglect so I fitted the original CX crankset. The close sizes of the chainrings gives a very quick gear change and spreads the use if the cassette more evenly. I do miss the 34/32 gear on one nasty hill, but I still climb just fine in 38/32.

On my CX bike I have heavy commuting tyres, mudguards and a rack. I ride with pannier bags, and all this adds to the weight. If I stripped my bike back to the original CX setup it would weigh less than my road bike and probably be a bit quicker.

[chriscole]

Front chainrings are 46/36... with 11-28T on the back.

[queequeg]

Front chainrings are 46/36... with 11-28T on the back.

You'll only get one extra gear going to an 11-32. If you go to a 12-32 you'll find the spacing gives you more options at the low end, at the sacrifice of some high gears.

I just treat each bike on merit. My commuter CX bike is built tough as a workhorse. Reliability over pure speed.
My road bike is built purely for speed, and when I commute on it I am 7km/h quicker on my avg speed.

[Mugglechops]

If you go to a 32 just make your rear derailleur can take it. Most Shimano road ones only go to 28t max.

Might be easier to fit a 34t front ring.

[dalai47]

On closer inspection (for the first time... never thought to look before), I notice my CX bike has an 11-28T 10-speed cassette on the back, whereas the road bike has a 11-32T 10-speed cassette.

Since many rear road derailleurs don't handle a 32 rear (unless recently changed Campy short cage only handles 26t, I thought Dura ace 28t), you rarely see a 32 on a road bike. So wouldn't base road bike gearing on yours...

My road bike is 53-39 and usually 11-23 (sometimes 11-25) and the CX bike is 50-36 and 12-25. Will look at a 12-27 for my next cassette on the CX bike, as I found an the steepest and technical sections whilst racing that I could have done with the extra couple of teeth.

[cyclotaur]

If you go to a 32 just make your rear derailleur can take it. Most Shimano road ones only go to 28t max.

Might be easier to fit a 34t front ring.

I did this on my CX and now have 46/34 > 11-28 or 12-27, depending on which wheels I have on. Works well.
I don't commute or carry much gear.

[simonn]

Cyclocross is different to MTB racing in that any technical sections, run. Anything too steep, run. Run run run, they do run run (especially if you are the worlds worst offroad rider like I am). CX tends to be flatter (basing this on all my CX, ermm, experience - 3 races and much youtube viewing ) i.e. no big long climbs, so you do not need the really low gearing, but not enough straight sections to make very large sprinting gears (i.e. 50-53t front ring) worth having over being able to switch gears quickly - 46/36 is really snappy. Also, 45 to 60 min races so you only have to bare the pain so long.

Saying that, two of my races were so muddy flicking my brifters after the first lap was more like submitting a proposal to change gear at some future, probably inconvenient, moment, so I ended up riding pretty much single speed. The only reason I did not go single 38-40t on the front when I upgraded the groupset was because I commute on it almost infinitely more than I race on it (like I said, 3x) and want to be able to do audax rides on occasion on it too.

I have considered going 11-32. I would do if I had your climb to get home. I have heard that the current Shimano (i.e. 5700 105 etc) short deraillers can handle 32t and are long enough if using a 46/36. Treat that as you would anything written on the internet. Then again, try it, worst comes to worst you'd have to buy a new derailleur or just buy the derailleur anyway. The new 11-speed ultegra does 11-32.

EDIT: FWIW, I have 46/36 11-28

[queequeg]

On closer inspection (for the first time... never thought to look before), I notice my CX bike has an 11-28T 10-speed cassette on the back, whereas the road bike has a 11-32T 10-speed cassette.

Since many rear road derailleurs don't handle a 32 rear (unless recently changed Campy short cage only handles 26t, I thought Dura ace 28t), you rarely see a 32 on a road bike. So wouldn't base road bike gearing on yours...

My road bike is 53-39 and usually 11-23 (sometimes 11-25) and the CX bike is 50-36 and 12-25. Will look at a 12-27 for my next cassette on the CX bike, as I found an the steepest and technical sections whilst racing that I could have done with the extra couple of teeth.

SRAM Apex does 32t, and I think this has now filtered through to rival and force. Not sure about SRAM Red.

[clackers]

I have considered going 11-32. I would do if I had your climb to get home. I have heard that the current Shimano (i.e. 5700 105 etc) short deraillers can handle 32t and are long enough if using a 46/36.

Shimano won't support anything beyond 30 on the 105 (which I have on my roadie).

I run 36 SRAM on my CX.

[simonn]

I have considered going 11-32. I would do if I had your climb to get home. I have heard that the current Shimano (i.e. 5700 105 etc) short deraillers can handle 32t and are long enough if using a 46/36.

Shimano won't support anything beyond 30 on the 105 (which I have on my roadie).

I run 36 SRAM on my CX.

Have you tested this?

[clackers]

Yep. Read it in the manuals.

Your short cage theory is right out, I'm afraid.

I had a medium cage and used it with a 32 tooth cluster, but it would throw the chain every now and then. I didn't worry about it until one day the derailleur ended up in the spokes.

After consulting with support at Shimano Australia, my LBS were reluctant to let me recreate my old setup. The new derailleur was now officially capable of taking the 30 designed for 10 speed Tiagras, and I went along with it.

The CX is easy, because the pull ratios for SRAM MTB and roadie stuff are the same, so the 36 cog goes with the X9 rear derailleur and Rival front. I use it for trails, commuting, touring and of course mountain climbing.

[Mugglechops]

Yep. Read it in the manuals.

Your short cage theory is right out, I'm afraid.

I had a medium cage and used it with a 32 tooth cluster, but it would throw the chain every now and then. I didn't worry about it until one day the derailleur ended up in the spokes.

After consulting with support at Shimano Australia, my LBS were reluctant to let me recreate my old setup. The new derailleur was now officially capable of taking the 30 designed for 10 speed Tiagras, and I went along with it.

The CX is easy, because the pull ratios for SRAM MTB and roadie stuff are the same, so the 36 cog goes with the X9 rear derailleur and Rival front. I use it for trails, commuting, touring and of course mountain climbing.

Mates CX bike has a SRAM XO rear derailler so he could probably run the big 36t too.

[clackers]

Mates CX bike has a SRAM XO rear derailler so he could probably run the big 36t too.

Fo' schizzle, Mugglechops.

As was said earlier, you'd never use it in a CX race because there just aren't the climbs characteristic of a road stage (asking too much of beer and frites swilling Belgian spectators to go up a hill) and competitors run with their bikes on the real sandy bits rather than slow down.

[chriscole]

Ended up finding a local fellow with a SRAM (Red) XG 1090 11-28T cassette for about $70 less than the best online price. *woot!*

Picked up a new chain to go with it today, and will hopefully have the new wheelset on and adjusted this weekend.

[Mugglechops]

Mates CX bike has a SRAM XO rear derailler so he could probably run the big 36t too.

Fo' schizzle, Mugglechops.

As was said earlier, you'd never use it in a CX race because there just aren't the climbs characteristic of a road stage (asking too much of beer and frites swilling Belgian spectators to go up a hill) and competitors run with their bikes on the real sandy bits rather than slow down.

When it's time for a new cassette I will be going the 11-34 and the XO combo.

[clackers]

When it's time for a new cassette I will be going the 11-34 and the XO combo.

You used to be able to do this mixing and matching with Shimano, too, but not since they went ten speed, IIRC.

[silentbutdeadly]

Currently running 46/36 SRAM Rival front and 11-32 SRAM Rival medium cage rear. Next iteration will probably be an X9 or X0 Type 2 RD in medium cage - using the clutch to control chain skip and slap.

Given my recent driveline experimentation on an XC MTB, I would also be tempted to go 44/33 (or perhaps even a single 36 or 38T Wolftooth chainring) out the front simply to take some of the 'load' off the legs and maintain some stamina in this old engine...leave the big rings to the heroes and the heroically minded.

[toolonglegs]

I ran 46/38 11-32 9 speed last year with an xtr derailleur... Worked a treat. For the last two weeks I have been running the same in 10 speed on my road bike while doing some silly hills... Worked well. I will try it this season for CX... If it doesn't cope well with the mud then I will go back to 9 speed.
I actually thought it would be too low a gearing for CX but I ended up using it a lot. Yes you could probably run the sections that you need 38/32 as fast but then you have the problem of clearing the mud and grass from you cleats ( depends where you are I suppose ).