# 54T/42T chainrings



## rasputinlv (Aug 27, 2011)

I'm planning to install 54/42 chainrings instead of 53/39.
Would I need different chain and front derailleur?
Thanks and advance.


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## Daren (Jul 25, 2008)

Chain, maybe, fd, no. You may need to move the fd up a little for tooth clearance. I'd get a new chain, especially of your current one is old. That said, if there are enough links that the chain will shift onto the 54 and the biggest cog in the back with out jamming, you're good to go


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## JCavilia (Sep 12, 2005)

The answer to both your questions is simply "no."

My question is "why?". Just curious.


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## rasputinlv (Aug 27, 2011)

ok, thanks guys.
why? to go faster downhills


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## Sheepo (Nov 8, 2011)

Maybe hes one of those "Florida guys".


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## wim (Feb 28, 2005)

rasputinlv said:


> why? to go faster downhills


May not be worth the expense. One tooth more on the big ring doesn't get you much. The reduction in cadence would be a measly and almost imperceptible 2 rpm. I'm assuming you're "spun out" in the biggest gear you have when descending.


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## Salsa_Lover (Jul 6, 2008)

TT bike, it just goes smother on a 54/42 for flat courses.


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## wim (Feb 28, 2005)

Salsa_Lover said:


> TT bike, it just goes smother on a 54/42 for flat courses.


Well yes, I can see how the change from a 39 to a 42 would smooth things out when shifting the front. I'm a big fan of 10 or less teeth difference in the front. But if the OP's spun out in the 53 on a descent, a change to a 54 isn't going to do much of anything for him.


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## cxwrench (Nov 9, 2004)

changing to the 54 isn't really going to do anything for you, as all the others have said. if you don't have an 11t cog, get a cassette w/ that...much bigger difference losing 1 tooth on your small cog then adding 1 to the big ring. 
if you already have an 11-xx cassette, spin more. you should be able to pedal a 53/11 to over 45mph w/o too much effort.


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## Icycalm03 (Nov 2, 2012)

I changed from a 39 to 42 and it really helped me


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## Icycalm03 (Nov 2, 2012)

Is it possible to get a 43??


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## spade2you (May 12, 2009)

Salsa_Lover said:


> TT bike, it just goes smother on a 54/42 for flat courses.


Assuming minimal wind.


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## cxwrench (Nov 9, 2004)

helped you what? Specialties TA probably make a 43, not sure who'd have it.


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## rasputinlv (Aug 27, 2011)

Thanks guys for advice.
I'm in Vegas and we have lots of hilly rides with long downhills. My friend on 55 always pulls away on downhills, I want to keep up with him.
I have 11/27 on the back.
I will rethink that idea thou


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## spade2you (May 12, 2009)

I would think the 42 makes going up a lot more difficult.


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## Kerry Irons (Feb 25, 2002)

*Big gear*



rasputinlv said:


> I'm in Vegas and we have lots of hilly rides with long downhills. My friend on 55 always pulls away on downhills, I want to keep up with him. I have 11/27 on the back.


100 rpm in a 53/11 is 37 mph. You would definitely be faster to get into a tight tuck and coast. Going to a 54 would give you 0.7 mph. That one tooth is NOT your issue.


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## cxwrench (Nov 9, 2004)

Kerry Irons said:


> 100 rpm in a 53/11 is 37 mph. You would definitely be faster to get into a tight tuck and coast. Going to a 54 would give you 0.7 mph. That one tooth is NOT your issue.


i agree about the single tooth not making a bit of difference for the OP...but you always talk about the speed at which coasting in a tuck is faster than pedalling. you're saying here it's 37mph...i don't see how we can know w/o knowing the size of the rider and his positon...and the percentage of the grade he's going down. i regularly ride down a descent that varies between 6 and 10%. coasting (yes, in a tuck) i'm usually seeing 39-42mph depending on conditions. pedaling a 53/12 or 11 i can easily get 47-48mph. i think there are way too many variables to really say for sure. 
all we really know is that a 54 won't get this guy any more speed. learning to pedal will help a lot more.


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## Sheepo (Nov 8, 2011)

Just put a 54t on it and be done with it. 

Only condition is you gotta make people riding a 53t hurt or youre a pansy.


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## Kerry Irons (Feb 25, 2002)

*Coasting speed*



cxwrench said:


> i agree about the single tooth not making a bit of difference for the OP...but you always talk about the speed at which coasting in a tuck is faster than pedalling. you're saying here it's 37mph...i don't see how we can know w/o knowing the size of the rider and his positon...and the percentage of the grade he's going down. i regularly ride down a descent that varies between 6 and 10%. coasting (yes, in a tuck) i'm usually seeing 39-42mph depending on conditions. pedaling a 53/12 or 11 i can easily get 47-48mph. i think there are way too many variables to really say for sure.
> all we really know is that a 54 won't get this guy any more speed. learning to pedal will help a lot more.


I have looked at a number of different rider weights and descent grades and it will be faster to coast (tight tuck) virtually any time you get over 35 mph. Based on wind tunnel tests tight tuck cuts aero drag by 1/3 compared to "racing position" on the drops. I used the 37 mph number because that is what you get at 100 rpm in his current top gear and for sure he would be faster in a tuck at that speed.

And as you say we can be almost certain that the OP has not learned to spin out his gears.


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## rasputinlv (Aug 27, 2011)

42 already arrived, waiting on 54.
Do I need to pull the crank, or can swap them without pulling the crank.
Thanks guys.


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## wim (Feb 28, 2005)

rasputinlv said:


> 42 already arrived, waiting on 54.
> Do I need to pull the crank, or can swap them without pulling the crank.
> Thanks guys.


No need to pull the crank. The holes inside the rings are big enough to tilt the rings around whatever obstruction they encounter. And don't come crying to us if after installation of the 54T, your (prolly heavier) friend still pulls away from you on those long downhills .


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## Max09 (May 3, 2011)

When I replaced my chainring removing the cranks made the job easier for me either way make sure you have the right tools and torque the chainring to specs.


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## tom_h (May 6, 2008)

If you were a hardcore TT racer, and looking to shave seconds on long TT, large chainrings are advantageous because you can use a larger rear cog, keep similar gear-inch ratio, and it will reduce drive train losses (chain bends thru larger radius = less friction).

Shimano and mechanical engineers from Johns Hopkins University did a drivetrain efficiency study ~10yrs ago. A well maintained drivetrain has >99% efficiency. Different lube types (eg, wax, plain oil, or fancy-schmanzy) were virtually all identical on efficiency (they did not evaluate longevity or durability).

IIRC, about the only thing that made a measureable efficiency difference (another 1% ?) was larger chainrings and cogs.


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## Kerry Irons (Feb 25, 2002)

*Easier?*



Max09 said:


> When I replaced my chainring removing the cranks made the job easier for me either way make sure you have the right tools and torque the chainring to specs.


It is SO easy to remove the chain rings from the crank without pulling the crank it is not clear what you are saying. It seems like removing the crank is a LOT harder than removing a chain ring.


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