Cyclocross Gearing with two chainrings

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Permalink Reply by Chris Mayhew on September 6, 2011 at 6:26pm

Am I allowed to comment?

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Permalink Reply by Chris Mayhew on September 6, 2011 at 7:00pm

Frankly, I don't buy it. I don't see why a 4 tooth difference would make things worse. In fact, the smaller the difference the easier it is for a front der to work.

 

The Red ders are known to be a bit flexy and most pro teams run the next one down because the steel plate (that weighs a bit more) flexes less.

 

Also, where are you going to use a 46t ring? That's a big gear for sure, like pro big. Pretty sure Powers just had a 44t on the front.

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Permalink Reply by Dan Tille on September 6, 2011 at 7:41pm

Totally agree with what chris said.  I have used both the red and the force for a 42 x 38 combo with no issues.  The Force tends to shift better for the reasons Chris listed.

 

When riding around in a 46 you have either have a really big engine to push that thing in cross conditions or race on a flat fast course to make it useful and not be in the little ring all the time.  A 42 will allow you to be in the big ring on most courses all the time with the exception of super muddy ones.

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Permalink Reply by VJ Goh on September 7, 2011 at 5:31am

It's not really about whether you need to be in the big ring all the time, just a matter of what works best. If you're in your 36 or 38 the whole race and that's fastest, go with that. 38/42 sounds too close to me just because you've only got a couple gears on either side that aren't pure overlap. At that point, you're wasting weight on a second ring and a front derailleur; just go with the 42 and a wide-space cassette.

 

 

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Permalink Reply by Andrew Rosenberg on September 6, 2011 at 7:26pm

the concept is half step gearing, many derailleurs are not set up for half step, old school derailleurs could do it but probably would not work with a indexed system....i like half step, it requires a light touch and a friction shifter. you mount a bar-con and and a smooth derailleur. it would mess with the aesthetics but that never mattered to me.

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Permalink Reply by Jared on September 6, 2011 at 9:48pm

I run a 42x38 on shimano.. the gearing works great..

 

But if I was running compact, i'd go 42x36 or 44x36. It would be nice to have the 36. I spend 90% of my races in the 42, but if a steep rideable climb is thrown in I have the 38 to go to. 

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Permalink Reply by Chris Mayhew on September 7, 2011 at 5:51pm

Not to beat a dead horse but this isn't about half step gearing. It's about having a chainring you can use a good portion of the time you're racing. But if that were the case we'd all run a single 42T. It's also about having a lower gear for the occasional steep climb or long muddy section, while also keeping in mind at a certain speed you're better off running that riding.

 

That all assumes we're talking about 'cross *racing*. Once you get into making your bike practical for say road riding there are other variables. But then you have to balance out the two things.

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Permalink Reply by andrew on September 6, 2011 at 11:19pm

Chuck, I think the question really is will this be a race-only bike?  Or do you like riding trails, some road rides (with slicks perhaps) or even jump in on a group road ride near cx season, to get used to the bike (or because you don't have a road bike)?

 

If yes to any of the above, I'd go with something wider.  I've run everything from a 34/42, 38/48, 36/46, 38/44, 36/50, 34/50 and a 39/50.

 

the only gears that I hate for cx are the 36/50 and the 34/50.  everything else can work great for CX racing - provided you choose your rear cassette appropriately.  There are lots of options for cassettes that start with a 13 or 14, making a 39/50 just as good as the popular 36/46.  the advantage? I can use my cx bike on any road bike ride/race, especially if I have an 11.  I love the 34/42 setup for trail riding, as with a low cassette in the back i can pretty much ride any mtb trail.  and if I have an 11, I can still race any course fine - so I do agree with Chris that a 42 is plenty tall for most cx races for all but the strongest racers.

 

but for race-specific gearing, I think tighter rings work well - you can spend less time using the front derailleur actually, which sounds counter-intuitive I know.  one could even argue that at that point go with one ring.  but I think i had to choose one ring combo for racing it'd be a 36/44.  that's just my preference.

 

Chris, what ring combo do you use, and what shifter/derailleur?  I do agree that you should be able to get it to work - just maybe not perfectly due to the amount of upswing the front mech takes when it travels that distance out, expecting the 13 tooth jump.  the cage would be too high in the big ring and/or too high in the small ring. An old deerhead xt front derailleur made for half step + a barcon would probably work great. 

 

I too have a barcon on one of my bikes, and it is awesome.  Infinite trim, imagine that.

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Permalink Reply by VJ Goh on September 7, 2011 at 5:28am

I agree; 36/44 sounds like an excellent combo. If you want to go with a single chainring, go with a 42, but my problem with a 36/42 is that there's too much overlap. That's okay if you've got a really narrow range of power or conditions, but 36/44 seems like it would give you some decent top-end speed on the flats, and a good range for the short climbs out of the saddle.

 

I currently ride a 36/46; fairly standard CX offering. I can turn over 1200w in a sprint (which isn't amazing, but it's not like I'm a tiny guy, either) and I still basically never use the 46. All I do is cross-chain with that ring. Besides, 36-12 is a big enough gear 90% of the time.

 

 

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Permalink Reply by stickboybike on September 7, 2011 at 6:43pm

Stick with it and use a different cassette on your other wheel set of you need lower or higher gearing.

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Permalink Reply by Blaine Krueger on September 7, 2011 at 8:52pm

damn I got a 50 on my bike

 

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Permalink Reply by stickboybike on September 8, 2011 at 5:38am

That's not so bad, at least it's a compact crank and you can swap in a 46t for a 46/34t combo.

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