Author Topic: 40T vs. 38T  (Read 3600 times)

Beave

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40T vs. 38T
« on: November 09, 2006, 03:28:45 AM »
Well, I guess when you have the perfect drivetrain, if you are looking for things to complain about, you really have to start nit-picking!

So since the installation of my Rohloff, I have been running a 40T chainring and 16T sprocket. Noting various gear-calculators, it seems this is about equal to a 22T chainring and 31'ish tooth sprocket.

I really miss my 22/34 granny gear on some of the bigger forest road and singletrack climbs that I do. I still feel like I have plenty of high gears to go as fast as needed on downhills etc.

Would swapping from a 40T to 38T be a real noticable difference as far as climbing real steep trails?? Maybe even a 36T?? Anybody out there running these combos with favorable results??

Pic of my bike:
http://www.flickr.com/photos/climbercraig66/292827541/
 

john28july

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Re: 40T vs. 38T
« Reply #1 on: November 09, 2006, 02:05:34 PM »
Would swapping from a 40T to 38T be a real noticable difference as far as climbing real steep trails?? Maybe even a 36T?? Anybody out there running these combos with favorable results??
Hello,
I had a 42 teeth fitted with 16 cog. This was a calculation based on my other bikes gear ranges. I should have read the Thorn blurb more carefully! I have now purchased an expensive 38 tooth chainring and fitted it. I have been out for a ride today.
How was it now? PERFECT.
Moral? Listen to Andy Blance.
John.
www.pbase.com/john28july

john28july

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Re: 40T vs. 38T
« Reply #2 on: November 09, 2006, 02:10:28 PM »
quote:
Originally posted by john28july

Would swapping from a 40T to 38T be a real noticable difference as far as climbing real steep trails?? Maybe even a 36T?? Anybody out there running these combos with favorable results??
Hello,
I had a 42 teeth fitted with 16 cog. This was a calculation based on my other bikes gear ranges. I should have read the Thorn blurb more carefully! I have now purchased an expensive 38 tooth chainring and fitted it. I have been out for a ride today.Gear 11ow the most used as it should be.
How was it now? PERFECT.
Moral? Listen to Andy Blance.
John.
www.pbase.com/john28july



Beave

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Re: 40T vs. 38T
« Reply #3 on: November 27, 2006, 02:46:45 AM »
Well, this turned out to be interesting. I ordered a 38T from a friend at the bike shop. Took it home and got to work on the install; I got the old ring and bashgaurd off, wiped off the grease and to my embarrasment, found I ALREADY had a 38T ring. I guess I'm just not in that great of shape!!
 

stutho

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Re: 40T vs. 38T
« Reply #4 on: November 27, 2006, 06:58:26 AM »
LOL Sounds like just like the sort of thing I would do!  Are you now going to go for 36?

paulhipwood

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Re: 40T vs. 38T
« Reply #5 on: November 27, 2006, 11:08:32 AM »
Hi

Well you could put it in the "For Sale" section!!!!!!
 

freddered

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Re: 40T vs. 38T
« Reply #6 on: November 27, 2006, 03:49:18 PM »
22 front/34 rear*26" wheel = 17" gear (approx)
A 40x16 Rohloff = 18" gear (approx)
May be cheaper to fit a 17tooth rear sprocket to get 17" gear although there is not much difference between the 17" and 18" first gears.
See http://www.thorncycles.co.uk/thornpdf/ThornLivingWithARohloff.pdf
 

simonsydney

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Re: 40T vs. 38T
« Reply #7 on: November 27, 2006, 09:31:01 PM »
Low gears
36*16 * 26" = 16.3"
38*16 * 26" = 17.2"
40*16 * 26" = 18.1"

does less than an inch make much difference in such low gears? Would a gripper rear tyre, to reduce any slip make more of a difference if climbing ?
 

stutho

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Re: 40T vs. 38T
« Reply #8 on: November 28, 2006, 07:59:12 AM »
quote:
Originally posted by simonsydney
Low gears
36*16 * 26" = 16.3"
38*16 * 26" = 17.2"
40*16 * 26" = 18.1"


You probably know this already but the minimum allowed gearing is
  • 42*17
  • 38*16
  • 36*15
  • 32*13

quote:
Originally posted by simonsydney
Does less than an inch make much difference in such low gears?
I would say yes.  I use 42*16 and occasionally 42*17 although the difference is only 1/2 of one Rohloff gear change I can notice the effect.  However I agree with you changing the tyres may have more effect.

Beave

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Re: 40T vs. 38T
« Reply #9 on: November 30, 2006, 03:20:22 AM »
Well, now that I have it, I believe I'll hold onto it until the current ring is ready for replacement.

And no, I won't be trying to get different gears as apparantly I already have exactly what I was looking for. I just need to keep turning those cranks until it *feels* like a 22/34 setup. ;)