Author Topic: Chainrings, which & why?  (Read 2161 times)

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Ian Schmidt

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Chainrings, which & why?
« on: January 18, 2011, 05:51:22 PM »
So, I'm curious... what size chainrings do you guys run?

I'm switching to 165 cranks tonight, and I'm considering trying bigger chainrings, or at least going to a 42 inner.
What size chainrings do you use, and why did you switch? Do you find there to be a difference?

Most of the timetrials are flattish, and even the ones with big hills don't tend to be anything that I couldn't get over with a 42.


FWIW - I'm anticipating racing at 142lbs this year, average height, and I'm in no way a diesel... I'm much more likely to be pulling the group on climbs.
My goal this year is to be fast enough in the Stage Race TTs that I'm not chasing 2-3' GC gaps when we do get to the climbing parts... anything beyond that is gravy.

shovelhd

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Re: Chainrings, which & why?
« Reply #1 on: January 18, 2011, 06:02:54 PM »
I use a 172.5mm 39/53 standard DA 7900 crank. In the old days I used 170mm 42/53 Super Record. My question would be why are you switching to 162.5mm cranks? Do I remember something about it being a recommendation from your fitter, or am I having a flashback?

I went to 172.5mm to get a little more torque, and on the recommendation of several people I trust.

EDR

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Re: Chainrings, which & why?
« Reply #2 on: January 18, 2011, 06:23:57 PM »
I run a 54 or 55/42 (21/11 cassette) and for hillier races TT's I'll run a 23/11 cassette.  172.5 arms.

Ian Schmidt

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Re: Chainrings, which & why?
« Reply #3 on: January 18, 2011, 06:44:11 PM »
yes - recommendation from fitter.
My position is low enough that my legs are compressing my diaphragm as I pedal, and it feels like I'm not able to breathe as well as I'd like.

Also, when I'm doing the appropriate turtle/chin.out/back.low position, my legs get really close to (or run in to) my chest.

EDR - 11-21? you are a crazy man... or you don't live near many mountains :-)
« Last Edit: January 18, 2011, 06:46:18 PM by Ian Schmidt »

EDR

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Re: Chainrings, which & why?
« Reply #4 on: January 18, 2011, 06:57:48 PM »
We normally don't TT up any mountains..and when we do I use a road bike.  Most TT's around here are either flat or have some rollers...for the most part a 42x21 will get me up and over most of them if not I'll throw on a 23/11.

Tom Anhalt

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Re: Chainrings, which & why?
« Reply #5 on: January 18, 2011, 07:17:18 PM »
I'm using a 54/39 with an 11/23 cassette and 170mm crank length.  I went up to the 54T big ring after noticing not being able to keep the power up on moderate downhills in a 53/11. 

For some reason I need to drop my cadence slightly below my typical TT average of 95-100 rpm to keep power up in "high kinetic energy" situations...

esammuli

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Re: Chainrings, which & why?
« Reply #6 on: January 19, 2011, 01:01:33 AM »
Same here. I run a 55t because I tend to drop my cadence quite a bit on fast descents.

Offline <gmt>

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Re: Chainrings, which & why?
« Reply #7 on: January 19, 2011, 09:46:20 AM »
54/42 and 11/23


for very harsh hills I switch out the cassette to one of my 12/27s, but I am considering going the racer ex route of leaving the cassette and switching to a 39 ring instead.
o-meter

Ian Schmidt

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Re: Chainrings, which & why?
« Reply #8 on: January 19, 2011, 11:42:54 AM »
okay - thanks all.
My shop had a 42t ring for 5 bucks, so I'm going to give it a try.

Quel

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Re: Chainrings, which & why?
« Reply #9 on: January 19, 2011, 06:13:16 PM »
I run a compact (with 170mm cranks) on my tri/tt bike.   No descents, so I'm not worried about spinning something out.  In the 23-27mph range I'm looking to go, the 50t with an 11/23 sticks me in the mid range of the cassette.

I run 175mm standard cranks on my road bike FWIW.  There I need a bit more for descents and fast pace lines.

Ian Schmidt

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Re: Chainrings, which & why?
« Reply #10 on: January 24, 2011, 01:35:18 PM »
I put the 42 inner ring on yesterday, and it sure seemed like I was either much weaker than I expected riding up the steep hill on the way home from the shop.

it wasn't until that evening I remembered that 48 gear inches is not the same as 44... good times.