Gearing - Single front ring issues

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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Devon
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by Devon

I want to achieve similar gearing as my road bike running 53/39 with 12-22 cassette. I have done the maths comparing to a 12-26 cassette to allow for harder climbs within CX.

So, I have worked out that a 48 chainring with 11-32 cassette will provide the same minimum/maximum ratios as the theoretical road bike.

Would I have any issues running such a gargantuan cassette on a single front ring? i.e. cross chaining or chain length issues. Would I need a mountain bike rear mech?
Campagnolo; because it's a bicycle, not a fishing rod.

thisisatest
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by thisisatest

You would need a SRAM wifli or mountain bike (can be short cage) derailleur to guarantee that it will clear the 32t cog. sometimes, a road derailleur will clear, it mostly depends on the derailleur hanger geometry. Some Specialized derailleur hangers are available in a "long" model, for instance.
You don't need a long cage, because you simply don't need to take up that much chain slack in the small cog vs the chain length requirement in the large cog. If you also had two chainrings, that would be a different issue.
You would ideally need a guide of some sort.
If you go Shimano, remember that you need a NINE speed Mtb derailleur for its pull ratio to be compatible with road shifters.

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Devon
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Location: Oxford, England

by Devon

So Campag is basically out of the question? Is this more hassle than just using a regular dual setup? I was trying to simplify but it seems it is making things more difficult...
Campagnolo; because it's a bicycle, not a fishing rod.

mattr
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by mattr

Would just query why you need similar gears to your road bike on a cross bike. You are likely to be travelling slower. Whether you are racing or not! Most of the single ring CX racers i know are using a wide ratio road cassette (11/28 ish) and something around the 40 tooth mark.

If you are just using it for gravel road hacking and the odd bit of tarmac, something like a 44/46 and 11/28 will give you a wide enough set of gears for 99% of what you are likely to do. And will use a standard road mech, with less big steps between ratios (my main bugbear with mtb cassettes in any application!)

You could even use an 11/29 campag cassette if you were that way inclined.

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Devon
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Location: Oxford, England

by Devon

mattr wrote:Would just query why you need similar gears to your road bike on a cross bike. You are likely to be travelling slower. Whether you are racing or not! Most of the single ring CX racers i know are using a wide ratio road cassette (11/28 ish) and something around the 40 tooth mark.

If you are just using it for gravel road hacking and the odd bit of tarmac, something like a 44/46 and 11/28 will give you a wide enough set of gears for 99% of what you are likely to do. And will use a standard road mech, with less big steps between ratios (my main bugbear with mtb cassettes in any application!)

You could even use an 11/29 campag cassette if you were that way inclined.


It was basically for the top speed. The bike will be used as a general mess around/commuter bike on road/gravel with a bit of recreational cyclocross mixed in during the off-season. The reason I was looking at existing ratios was to keep my high gear for descending, as I tend to spin out with my 53/12 as it is so didn't want to go any lower really. However there may eb some merit in what you say, off-road at least, regarding top speed.
Campagnolo; because it's a bicycle, not a fishing rod.

mattr
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Location: The Grim North.

by mattr

alexh wrote:It was basically for the top speed.
Tuck in and coast ;)

High 30s is doable on a 46/12 without too much pain (done it on my CX bike) and my muck about roadie runs a 49/13 (i think, might be a 14), which i've not (yet) run out of legs on.......

Have a rummage through this and see where you end up.
http://www.gear-calculator.com/#

But if you are keen for a single ring, i'd focus more on what you do most of the time, rather than what you do once or twice a ride. (and maybe having a lower top gear will improve your leg speed....... :wink: )

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Devon
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Joined: Fri Apr 12, 2013 1:19 pm
Location: Oxford, England

by Devon

It's all about low cadence and powerrr for me ;) but yes you are right. That looks like a brilliant tool - not seen that one before. Will check it out, thanks!
Campagnolo; because it's a bicycle, not a fishing rod.

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