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aquateen 03-12-14 12:25 PM

Compact to cyclocross crank?
I have a Shimano compact crank (50/34) and was curious if I could change the rings for a more cross-style gearing (46/36) while maintaining the same crank. Is this possible? I wasn't sure with the different ring sizes

Barrettscv 03-12-14 01:03 PM

You should change both rings for best results. Aftermarket chainrings are so overpriced that a new crank can be cheaper. You should be able to sell your compact on fleabay to reduce your investment.

Sportster2009 03-12-14 02:52 PM

I actually just had the opposite done. I bought a Cannondale CAADx Ultegra Disc. I had them change the small chainring from a 36 to a 34. I now have 46/34 because I need the granny climbing gears as I'm primarily using the bike on the road. It works like a champ.

User1 03-12-14 02:56 PM

46/34 sounds sweet! Can someone give an idea of what the range is on the two rings? That type of info is not really that easy to find. I have to rely on retailers for a clue!

Barrettscv 03-12-14 03:20 PM

Use this tool to calculate all kinds of data for your drivetrain: Mike Sherman's Bicycle Gear Calculator

Andy_K 03-12-14 03:26 PM

Price may be the thing that kills the OP's plan (or at least makes it painful). For Shimano rings (as an example) it looks like the cost is around $80 for the pair. I got a CX50 crankset from Jenson USA for that cost not long ago.

On the other hand, switching to 46-34, which is what I'm running on my CX bike for gravel grinding rides, is cheap. You can get and Ultegra 34T ring for around $12.

I would expect that the market for lightly used rings is pretty good, but they might be generally worthless enough that you have to send out a WTB message to get them. I know I've got a pile of chainrings in my garage at any given time.

Rumpled 03-12-14 08:49 PM

Both sets of those rings should be 110 BCD and can interchange at will.
I've changed both my CX bikes from 46/36 to 46/34.
If you think you might be changing back and forth, just buy rings.
If not, swapping cranks might be easier.
I've found used rings for ~$20 or so on EBay and various forums.

I've got the two 36t FSA rings that are both lightly used.
I would easily let one go for $20 or other items of need of similar value.

User1 03-12-14 10:18 PM


Originally Posted by Rumpled (Post 16572901)
I've found used rings for ~$20 or so on EBay and various forums.

Wait, you're buying stuff on forums??? Which ones? I've been looking for frame and or a CX bike for ages! So far my sources has been CL, sometimes coast to coast, and ebay.

Rumpled 03-12-14 10:48 PM has a very active classified forum. (Triathlete forum) Got shifters, a tribelt and cranks there.
EBay got CX frame, stem, seat post, pedals,,34t ring.
CL for an Ultegra wheel, bars and saddle.
Brakes from a member of a group on FB.
Derailleurs I bought new online, they are pretty cheap on EBay.

All but the frame and derailleurs were very budget priced.

Took many hours of searching over a couple of months.

Still looking for more Ultegra wheels and repair stand and a garmin.

User1 03-12-14 11:44 PM


Originally Posted by Rumpled (Post 16573154) has a very active classified forum.

Slowtwitch looks pretty good. I'll keep an eye there. I'm up on my local CL here. One thing I forgot to mention was REI used gear sales are pretty good sometimes. I've gotten parts there. I picked up a returned Feedback stand for $75 that ain't bad at all. I've yet to use it, but I do have 3 bikes I have to build up.

fietsbob 03-13-14 12:34 PM

Out of the box , manufacturers choose for you , 36-46 is common ..

already got a 110bcd crank? get 2 chainrings of your choice for the course.

NZier 03-13-14 01:53 PM

I scope Slowtwitch from time to time as well. I bought a couple really nice ultegra cassette's on there shipped for $45, I'm going to use them on some Tubeless wheelsets (some day in the fall when I get these bikes paid up).

Chainlove (timed deal site) is a hit or miss site, but I picked up two pairs of 2013 Aksium wheelsets (with tubes and tires) shipped for like $360. (gearscan website is a decent way to track it)

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