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CX chainring ratios are pretty close, why?

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CX chainring ratios are pretty close, why?

Old 10-28-14, 10:14 PM
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CX chainring ratios are pretty close, why?

Road bikes usually come with 50/34, 52/36, or 53/39, why do CX bikes come with 36/46? Why the 10T gap when road bikes come with 14-16?

I'm about to buy my first CX bike. Would it be possible to swap the 36 for something smaller? I'm just a little nervous because my mountain bike has a 1x10 setup with a 30T chainring and 11-36 cassette. 36 (chainring)/28 (cassette) as my lowest ratio seems a little high. Hell, even 34/28 on my road bike isn't as low as I'd like and 36/32 on the CX bike if I swapped the cassette probably wouldn't be as low as I'd like.
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Old 10-28-14, 10:43 PM
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What are you planning on doing with it? For racing, the close ratios aren't a bad thing. There's a reason 36/46 or something similar is so common.
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Old 10-29-14, 02:02 AM
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I'm hard pressed to think of an off road course where anything larger than a 46t would be all that beneficial. Riding on grass, through mud and sand... you aren't likely to get any benefit from a 50t that is typical on a road compact. However, lots of people are unhappy with the large gearing gap between a 50t and a 34t, so closing that gap is preferential. A ten tooth difference between chain rings tends to shift well, and covers the spectrum that you are likely to see on a cross course. In other words, road cranks have different chainrings because they ride under completely different conditions. Of course, if you ride a lot of hard-pack or gravel roads with longer stretches, it might be beneficial to have that 50t chainring; it all depends on the conditions your are riding in.

34t is the smallest size on a compact crank and is generally as small as you can go. There are manufacturers that offer a different bolt circle diameter, Sugino makes a nice crank that will allow you to run whatever combo you want (below 34t). TA also makes something. Neither is cheap. Alternatively, you could find a triple crank and just don't use the outer/big ring.
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Old 10-29-14, 02:13 AM
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CX bikes don't come stock with MTB low gears cuz CX racers would rather run up a short hill than grind up it with 25 gear inches.
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Old 10-29-14, 07:07 AM
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Sorry I wasn't clear--it will be my bad weather road bike and light duty XC bike. We have a ton of super well groomed, non technical trails around here but sometimes steep. It will not be used for actual cyclocross.

it would be nice to have a 30ish chainring for the steep parts and the 46 for the road
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Old 10-29-14, 07:25 AM
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Originally Posted by Alias530
Sorry I wasn't clear--it will be my bad weather road bike and light duty XC bike. We have a ton of super well groomed, non technical trails around here but sometimes steep. It will not be used for actual cyclocross.

it would be nice to have a 30ish chainring for the steep parts and the 46 for the road
You can find 46/30 combos but they are rare. IRD and Velo Orange both sell one. I think it's a great combo actually.
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Old 10-29-14, 07:30 AM
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Originally Posted by bikemig
You can find 46/30 combos but they are rare. IRD and Velo Orange both sell one. I think it's a great combo actually.
Are you saying I need a whole new crank or can I just swap the smaller ring? 32 would probably be fine too if that gives me more options. The bike will come with a 36/46 installed.
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Old 10-29-14, 07:55 AM
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Originally Posted by Alias530
Are you saying I need a whole new crank or can I just swap the smaller ring? 32 would probably be fine too if that gives me more options. The bike will come with a 36/46 installed.
No, cross cranks are 110 bcd; the smallest it will go is a 34. The IRD and VO cranks use a different BCD and a different bottom bracket as they are both square taper. Personally I'd buy the IRD crankset over the VO crank as the BCD the IRD crank uses will make it easier to find chainrings.

Talk to the LBS; they can swap out the cranks and give you a credit for the crank on bike to use towards a new crank. Alternatively, just go with the existing crank and run a little larger cassette in the rear. The latter option will be cheaper and easier.
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Old 10-29-14, 08:01 AM
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Originally Posted by bikemig
No, cross cranks are 110 bcd; the smallest it will go is a 34. The IRD and VO cranks use a different BCD and a different bottom bracket as they are both square taper. Personally I'd buy the IRD crankset over the VO crank as the BCD the IRD crank uses will make it easier to find chainrings.

Talk to the LBS; they can swap out the cranks and give you a credit for the crank on bike to use towards a new crank. Alternatively, just go with the existing crank and run a little larger cassette in the rear. The latter option will be cheaper and easier.
Thanks. What's the biggest cassette I can use on shimano 11spd road? 11-32 probably?
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Old 10-29-14, 08:27 AM
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Because of chain line, low top speeds, and the wondrous range of 11 cog cassettes. Why would you want a 50x11 when you're never going to crack 25mph in a cross race?

I've always preferred close rations on my road bikes, too: 36/46, 39/50, 42/53. The high mountains are really the place for a 34/50.

At any rate, you should spend some time riding the thing before swapping out chainrings and cranks. CX terrain is a lot faster than Mtn bike terrain.
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Old 10-29-14, 08:29 AM
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Originally Posted by Jiggle
. . . . The high mountains are really the place for a 34/50.
Hard to generalize like that; age and fitness make a difference as to what gearing is appropriate. Plus high mtns aren't necessarily the toughest place to climb; some hilly areas are plenty tough as well. Terrain matters also if one rides on gravel.
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Old 10-29-14, 08:33 AM
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I was thinking more in terms of using the 50. If you guys spend lots of time pedaling above 34mph on a gravel road, more power to you. I ain't doing that.
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Old 10-29-14, 08:43 AM
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Originally Posted by Jiggle
Because of chain line, low top speeds, and the wondrous range of 11 cog cassettes. Why would you want a 50x11 when you're never going to crack 25mph in a cross race?

I've always preferred close rations on my road bikes, too: 36/46, 39/50, 42/53. The high mountains are really the place for a 34/50.

At any rate, you should spend some time riding the thing before swapping out chainrings and cranks. CX terrain is a lot faster than Mtn bike terrain.
Where did you get that I want 50x11? I want a smaller than 36 chainring and I'm fine with the 46 for when I ride it on the road
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Old 10-29-14, 08:54 AM
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The gearing on bikes has never really been about what the end user needs. They have always been about marketing, what racers use, and keeping costs down. CX bikes make great all around machines but for a lot of users, a 36/32 may not be optimal.

I like this IRD double, New Albion Cycles: New IRD Wide Double Crankset

It's a smart crank and chainrings are available. At $200, it isn't cheap. I run a triple on my cross (48-36-26 chainrings).
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Old 10-29-14, 09:32 AM
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Originally Posted by Alias530
It will not be used for actual cyclocross.
Meanwhile, the company probably thinks they are making "actual cyclocross" bikes. You can see where the confusion can arise.

I'd just buy a 34T ring for the inner and get a cassette with a slightly-bigger low cog and call it a day.
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Old 10-29-14, 09:47 AM
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I'm running a 46 /34 and that's plenty of low range for steep fire roads. (a 36 wasn't quite low enough) One thing to consider is that CX geometry doesn't put your CG as far back over the rear wheel so anything steeper than you can get up with a 34-32 standing on the pedals, your weight is far enough forward that you are at the limits of where you can keep the rear wheel from skipping, unless you are on pavement or clean rock.

A 33 is as small as will fit on a 110BCD compact and there's only one source for it. 34's are relatively common.

The 46-11 puts you at 31 mph @ 90 rpm so that's plenty fast enough for the flat.
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Old 10-29-14, 10:41 AM
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Its all about getting around the CX Race course as quickly as possible , the people that get on the Podium are very fit, and skilled bike handlers .

You are just buying that style of Bike .. want different chainring sizes than stock , ask the Bike shop to change them as they set up the Bike .

even a whole crank-set can be a Point of Sale swap.. some take-off credit is offered , since the parts will be New.

Component choices are the Product Managers choice , and the factory has the best price on truckloads of what the component manufacturer sells .

You at the retail end are free to make what changes you desire.

A single chainring is also an option CX Racers use .. depends on the course.. yes the run up , is often faster than granny gearing down

and watching your self get dropped and being a Lap Down before long..


people tour on midrange cross bikes these days .. thinking a proper.. touring bike frame is too heavy.

Last edited by fietsbob; 10-29-14 at 10:51 AM.
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Old 10-29-14, 07:39 PM
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Originally Posted by Alias530
Sorry I wasn't clear--it will be my bad weather road bike and light duty XC bike. We have a ton of super well groomed, non technical trails around here but sometimes steep. It will not be used for actual cyclocross.

it would be nice to have a 30ish chainring for the steep parts and the 46 for the road
Not sure I have seen many other but I have a Cannondale Coda super compact crank. It's a 94bcd compact with a 29/44tooth double, could easily be swapped to a 46t, although I'm not sure how well it would shift. 94bcd is sometimes hard to find rings for but they are still out there.

Last edited by wesmamyke; 10-30-14 at 04:57 AM. Reason: Bleh
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Old 10-29-14, 10:23 PM
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Originally Posted by TGT1
I'm running a 46 /34 and that's plenty of low range for steep fire roads. (a 36 wasn't quite low enough) One thing to consider is that CX geometry doesn't put your CG as far back over the rear wheel so anything steeper than you can get up with a 34-32 standing on the pedals, your weight is far enough forward that you are at the limits of where you can keep the rear wheel from skipping, unless you are on pavement or clean rock.

A 33 is as small as will fit on a 110BCD compact and there's only one source for it. 34's are relatively common.

The 46-11 puts you at 31 mph @ 90 rpm so that's plenty fast enough for the flat.
I hope the bike I'm looking at comes with a 11-32 cassette... it doesn't say on the website. Is that the standard for CX bikes? I'm looking at the 2015 Felt F65x.
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Old 10-29-14, 11:15 PM
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Originally Posted by Alias530
I hope the bike I'm looking at comes with a 11-32 cassette... it doesn't say on the website. Is that the standard for CX bikes? I'm looking at the 2015 Felt F65x.
The Felt website says it comes with an 11-28.
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Old 10-30-14, 07:06 AM
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Originally Posted by Andy_K
The Felt website says it comes with an 11-28.
Ah, thanks. I'm on my phone and the mobile version of their website doesn't say
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Old 10-30-14, 08:53 AM
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Stock cassette size seems to vary with spec level and intended use. I've seen 11-30, 11-32 and 12-30 on lower end less racing oriented CX bikes with SRAM Apex or Shimano Tiagra 10. Higher spec "racier" stuff tends to run a 12-27 or 11-28. I would double check the OE derailleur's cage length if your bike has a stock 11-28 and you plan to go 11-32. Also budget for a new chain.
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Old 10-30-14, 09:16 AM
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A 12-32 would be even better.

I'd trade the 11 for a 16 any day to get tighter spacing in the 16-20 mph range where you really need it.

the SRAM WiFli maxes out at a 32, the Shimano medium length equivalent is I think the same. A short road cage RD isn't going to accommodate a 32.
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Old 10-30-14, 11:55 AM
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I'm building up a bike with 1x11 using SRAM's CX1 group. Front ring is 38 (also have a 40), and the cassette is 11-32. Not an actual racing bike, however.
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