CX cranks?

[josephr]

doing a little research on CX bikes as thinking about replacing my touring/gravel bike. I noticed a lot have CX specific 46/36 cranksets --- there's even an Ultegra CX specific crank. Other than the chainrings being 46/36, is there any difference b/t this and a compact Ultegra (6800) or 105 (5800) crank? I'm thinking the added range of a 34/50 would be much more beneficial. Just wondering if there's any actual difference/limitations/advantages or if this is just more creating more solutions to non-existent problems?
Joe

[AngryScientist]

well, the cx70 crank, for example takes standard 110 BCD chainrings, where the 6700 compact crankset has a 110 bcd, but uses the 50t chainring with the "wings" on it, so standard 110 bcd chainrings would look weird on it.

https://media.performancebike.com/images/performance/products/1500/50-7515-NCL-TOP.jpg

[Bruce K]

Dream setup:

Wickwerks chain rings

Put them on any decent 110bcd crankset

Then find a mechanic who knows how to set the derailleur up to work with them

You are set

BK

[Mark McM]

well, the cx70 crank, for example takes standard 110 BCD chainrings, where the 6700 compact crankset has a 110 bcd, but uses the 50t chainring with the "wings" on it, so standard 110 bcd chainrings would look weird on it.

https://media.performancebike.com/images/performance/products/1500/50-7515-NCL-TOP.jpg

Well yes, they do fit the cranks with matching chainrings, but as to the poster's original question, the only functional difference between cranks labeled "CX cranks" and other 110 BCD cranks is the sizes of the chainrings they come with. Occasionally we'll see a 130 BCD crank with 48/38 chainrings also labeled "CX cranks", but again, the only functional difference is the size of the chainrings they come with.

[shinomaster]

Just pick the gearing that suits the terrain and your fitness. A regular compact would be just fine.

[seppa]

Really depends on the terrain but ive found the 36/46 offers the far best versitility, a 50t on a regular compact becomes a real tough gear to roll over well, especially when you fatigue.

[Bruce K]

Lots of folks swap the 46 for a 44 and some even swap the 36 inner ring for a 34

As was said above fitness can dictate minor adjustments

Then there is the whole discussion of 1X

BK

[gavingould]

i've been riding a 6800 crankset this year. ordered the "cx" version with 46/36t rings. for road use i got a 52t and swap the big ring as needed. shifts fine, just adjust FD height.

there's no differentiation within model level with the newest 4-bolt cranks (ultegra, D/A, 105) as there is no standard vs compact BCD. you can run 50/34, 46/36, 53/39, whatever all on the same cranks.
the choices are just chainring combo and arm length.
same for DuraAce 9000, Ultegra 6800, and the incoming 105 5800.

differences/limitations... if you pick up an older series (5 bolt) crankset you will need to pay attention to BCD, if you get "standard" 130 bcd that'll limit your small ring to 38t as the smallest. 110BCD you can do 34t to get up those hills. if you buy 46/36 straight away, you can go a little smaller on the inner ring, larger on the big ring, or both.

[brando]

I'm thinking the added range of a 34/50 would be much more beneficial.

This is the main difference. CX cranks are a narrower span optimized for racing speeds. I've had both. 50/34 is probably a better bet for longer rides.

[vav]

When I set up my Zanc CX, I had in hand already a Shimano R700 compact 50-34. Bought a 46 ring and I have been running 46-34. Paired with a CX70 FD shifts very very well. I run a 11-32 cassette and I almost never I am out of gears.

edit: if I could find a 110 bcd 48t ring I'd love to try that configuration.

[zennmotion]

46T large ring for racing CX is for fools and heroes, which are you? Or are we not really discussing cyclocross?

[RobJ]

To answer the question directly - no there is no difference between a compact and cx crankset. They are one and the same thing - a crankset with a 110BCD. On a road bike it might be geared 50/34 or 52/36 (mid-compact) and on a cx bike run 46/36. The smaller the gap in number of teeth between the chainrings the crisper/quicker the shifting, which is preferred when you are racing cx. Plus you don't hit any major hills requiring anything over 46. Now SRAM has cx-specific crank that is a single chainring.

doing a little research on CX bikes as thinking about replacing my touring/gravel bike. I noticed a lot have CX specific 46/36 cranksets --- there's even an Ultegra CX specific crank. Other than the chainrings being 46/36, is there any difference b/t this and a compact Ultegra (6800) or 105 (5800) crank? I'm thinking the added range of a 34/50 would be much more beneficial. Just wondering if there's any actual difference/limitations/advantages or if this is just more creating more solutions to non-existent problems?
Joe

[josephr]

46T large ring for racing CX is for fools and heroes, which are you? Or are we not really discussing cyclocross?

very perceptive...no, not really talking cyclocross -- this bike is marketed as a cross bike with commuter/off-road potential and has eyelets for fenders and rack mounts. It comes off the showroom floor with an 11 speed FSA CX crank/bb30. The immediate conversion would be to a Wheels adapter with a Shimano 105 (5800) crank in the 50/34 configuration.

My point to this post is to confirm (which sounds like has been done) is that there's no funky business with the Q-factor or some other unknown-to-me factor which would render this a dumb idea.

Part of my wonder is why Shimano has very limited chainring options for the new style Shimano cranksets ...just doesn't seem like there's a lot of options for 11sp.

[Gummee]

...just doesn't seem like there's a lot of options for 11sp.
You can get 36/46, 34/50, 36/52, and 39/53 ...and that's just 6800!

Same crankarms, same BCD with all the rings

M