Author Topic: rolhoff input gear ratio for loaded tour south america  (Read 143 times)

PRP

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rolhoff input gear ratio for loaded tour south america
« on: January 11, 2019, 03:46:47 AM »
hello,

currently i have 42/19 [2.21] for my nomad, i have chainrings & sprockets for  2.09 and 1.90 input ratios
any suggestions for loaded tour south america. i prefer a  cadence around 100
also..... is there somewhere a table of gear inches and cadence versus speed?
i would like to have topspeed around  35km/hr at cadence of 100, but am often wanting one or maybe 2 gears lower than the current 2.21 input ratio allows [which allows top speed around 40km/hr]
thanks
prp

JimK

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Re: rolhoff input gear ratio for loaded tour south america
« Reply #1 on: January 11, 2019, 04:06:24 AM »

Danneaux

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Re: rolhoff input gear ratio for loaded tour south america
« Reply #2 on: January 11, 2019, 04:11:34 AM »
Hi PRP!

I prefer a fast, light cadence of 110-120rpm and have my Nomad setup with 36x17 gearing and use 26x2.0 tires. I've been very happy with it for heavy loaded (expeditionary) touring as well as for day rides. This gives me a Gear 11 of 55 gear-inches and I spend most of my "cruising time" in either Gear 11 or the 62-inch Gear 12.

In the 36x17, a cadence of 110rpm nets me a top speed of 29.9kmh/18mph. 120rpm results in a top speed of 31.6kmh/19.64mph

You would need to gear higher than this to get the speed you want at the cadence you desire in direct-drive Gear 11. Of course, there are 3 gear higher than this in my drivetrain, so if I wish to go faster, I just upshift.  :D

My favorite calculator for speeds in gears is this one: http://www.bikecalc.com/speed_at_cadence

Best,

Dan.
« Last Edit: January 11, 2019, 04:14:21 AM by Danneaux »

martinf

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Re: rolhoff input gear ratio for loaded tour south america
« Reply #3 on: January 11, 2019, 08:02:31 AM »
I maintain a lower cadence than Dan (on average 90). I use 38 x 16 on my Rohloff-equipped Raven Tour.

This gives me a range of about 17" to 89" with the 26" x 50 mm tyres I use. At 90 rpm that is about 7.4 to 39 km/h, it would be about 8.3 to 44 km/h at 100 km/h.

I very rarely use the highest gear, and although the lowest has got me up anything rideable so far, I never say no to lower gears, so will probably drop the gearing when I wear out the 16T sprocket, either slightly to 38 x 17 or more substantially to 38 x 19. The 38 x 17 combination has the advantage of being compatible with my Chainglider. 

On my last long loaded tour in 2011 I had a derailleur setup with 18" to 86", the highest gear wasn't really useful but I did use the next-to-highest 75" gear quite often on the flat with favourable winds and on slight downhills. Lowest gear was used a lot while climbing mountain roads and on off-road stretches.

Andre Jute

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Re: rolhoff input gear ratio for loaded tour south america
« Reply #4 on: January 11, 2019, 11:05:47 AM »
For a loaded tourer I think you need to look first to the lowest gear you will need at your preferred cadence, with consideration of the lowest speed at which you can keep your balance, and then you have to take what's left at the top, which is much more on the Rohloff than on any other hub gearbox. You've in fact told us as much already:

Quote
am often wanting one or maybe 2 gears lower than the current 2.21 input ratio allows

PRP

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Re: rolhoff input gear ratio for loaded tour south america
« Reply #5 on: January 14, 2019, 01:02:37 AM »
thankyou for the replies.
the link to the Sheldon Brown calculator has answered my question exactly.
 40 tooth chain ring plus 21 tooth sprocket gives 6.6km/hr @ 100rpm in Rolhoff 1st gear, 34.4km/hr in 14th gear.
thanks again
prp