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CX bike on the road -- chainring size?

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CX bike on the road -- chainring size?

Old 12-28-09, 08:19 AM
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CX bike on the road -- chainring size?

Hi Folks-
Might be sacrilege, but I am picking up a CX bike with the intent of riding it hard on and off the road. Would switching from a 48/34 to a 50/34 hurt me much on the trail? I don't want to lose the ability to really hammer on the road. More noob threads to come. Thanks,
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Old 12-28-09, 09:21 AM
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Originally Posted by mjdwyer23
...I am picking up a CX bike with the intent of riding it hard on and off the road. Would switching from a 48/34 to a 50/34 hurt me much on the trail?
You really should ask the question the other way around, what do you think the bigger chainring will
give you on the road?

A brief look at Sheldon Brown's gear calculator shows that your current setup will let you reach more than
30 MPH/ 48 KMH before spinning out, that should be plenty for most people.
Assuming some sort of
"average" course, you'll only be off power a few seconds at a time during serious descents.
Doing the same math for a 50T will only give you something like 2 KMH/ one-and-a-quarter MPH more
in top speed.
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Old 12-28-09, 09:44 AM
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Awesome -- thanks for the info! I think I will pick up the bike and see how it rides, my local cross community is pretty awesome.
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Old 12-28-09, 09:59 AM
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You're probably aren't going to miss anything if you're only talking 2 teeth. This is what I run on mine and I never have a problem keeping up with others on it. Plus I like the smaller big ring as it seems a little more useful to me. I routinely stay in this ring even when climbing.
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Old 12-28-09, 10:00 AM
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Cool. I think I was just a little weary of switching to a bike with a 48 from my road bike which has a 53. Thanks again,
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Old 12-28-09, 12:02 PM
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With a 53 I can't really use 14t and smaller effectively unless I'm on a downward grade. Maybe I'm a wimp but that's me.
I've got a 53/39 coming and may go with a 50 instead.
Of course I'm using a 12-27 rear cassette so I could go to a larger rear with a long cage RD as well. There seem to be many ways of getting the same thing out of your gears.

Then there's the whole 1x9 argument...
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Old 12-28-09, 12:40 PM
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Here's mine. It's geared for the road - 53 x 39 / 11-28 cassette:

[Click pic for a larger version]

With studded tires, I can still get through 8 inches of snow. Much deeper, I get bogged down.
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Old 12-28-09, 12:43 PM
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My largest gear is a 44 x 11. (This is on a 1x9)

I have no problems keeping up on fast group roadie rides. Granted I can't pedal on steep downhills, but at those speeds no problem tucking in behind and drafting.

Let's just say that unless you are SUPER HAMMER, you will be fine with a 48t in front.

-Z
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Old 01-01-10, 10:24 AM
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Compact chainring, 50/34, and a 12-27 rear cassette work great for the road and trails. IMO 48/34 is not as good on the road. There are good reasons why a 48/34 is not offered for road bikes.
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Old 01-01-10, 03:11 PM
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Originally Posted by pharding
Compact chainring, 50/34, and a 12-27 rear cassette work great for the road and trails. IMO 48/34 is not as good on the road. There are good reasons why a 48/34 is not offered for road bikes.
Thanks for the info -- update: looks like I will have one of each!
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Old 01-01-10, 07:03 PM
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Originally Posted by pharding
There are good reasons why a 48/34 is not offered for road bikes.
what reasons are those?

-Z
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Old 01-04-10, 04:54 AM
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Originally Posted by thenomad
With a 53 I can't really use 14t and smaller effectively unless I'm on a downward grade. Maybe I'm a wimp but that's me...
Nah. That's anatomical limitations and physics. Play around with Sheldon's gear calculator a little, see what speeds you get at different ratios and recommended cadences.

IMO having a really big ring in front taps into the same vein as having a 300+ HP car, or a 200 W home surround system. For most of us, and most situations it's more of an ego boost than actually useful.
Originally Posted by thenomad
. There seem to be many ways of getting the same thing out of your gears.
Well, yeah, that's another near-unavoidable consequence of the basic setup with rings and cassettes. Avoiding redundant or returning ratios is hard.

Last edited by dabac; 01-04-10 at 05:15 AM.
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Old 01-04-10, 04:28 PM
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Originally Posted by pharding
Compact chainring, 50/34, and a 12-27 rear cassette work great for the road and trails. IMO 48/34 is not as good on the road. There are good reasons why a 48/34 is not offered for road bikes.
Huh?

So a 50/12 would be great, but a 48/11 is not as good?




My commuter is a 1x10 with a 48t front and 12-26. Sometimes I coast down a big hill. So what.
Big gears exist because people seem to freak out if they run across a hill they can't pedal down.

And yes, I also have some 53t bikes.
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Old 01-04-10, 06:25 PM
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Hey guys-
Great discussion here. Turns out I got a deal and can keep both bikes. Woohoo!
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