Author Topic: What's your Rohloff combo (chainring, cog)?  (Read 48912 times)

Danneaux

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What's your Rohloff combo (chainring, cog)?
« on: July 20, 2012, 06:30:05 PM »
Hi All!

As someone new to Rohloff who is in the setup and choosing phases, I find myself wondering what chainring/cog combinations others have chosen and favor for their Rohloff-equipped bikes.  It'd be nice as a poll, but too confusing to set up and vote on...just too many combinations to be wieldy.

So, I'm hoping some of you might be kind enough to post your combo and perhaps a comment or two on...
1) How is the low working for you in your conditions/use.
2) Is the direct-drive Number 11 gear working out to be your most-used, or have you compormised on that to get the low/high you'd like?
3) How important has placement of the 7/8 split been to you?

With regards to this last, it seems best to consider "high range" (8-14) as the most-used cruising range, and the "low range" (1-7) as just that -- for slogging along at lower speeds, climbing hils, plowing through mud, going into headwinds, and so forth, with Gear 11 as the most-used direct-drive. 

If so, and with all considerations, it seems the best gearing for me might be the lowest combination permitted by Rohloff while maintaining full warranty coverage against possible breakage -- 40x17. My most-used level-cruisiing gears on my other bikes are either 58 gear-inches (early-season or if I've been off the bike a little while) or 62 gear-inches (pretty much anytime I'm riding flats) with a steady cadence of averaging around 110RPM to make up for the low gearing with fast, light revs. The 40x17 would put my Gear 11 right at 61.2 gear-inches, which is spot-on.

In reading the earlier version of Andy's "Living With a Rohloff" that appears on Sheldon's site ( http://sheldonbrown.com/harris/rohloff-impressions.html ), I see he mentioned a carefully chosen and well-reasoned 36x17 with all factors considered, resulting in a 15.4 low. While that low would be most welcome for what I so often do (ride with heavy touring loads up really steep hills and across sometimes very soft desert playa), I'm concerned about the possibility of breakage and warranty issues. It would also put me in 12th gear a lot, as 11th with that setup is a bit low for me. Given that, a 40x17 again seems like a pretty good match for my needs. My knees will never pull more than the 89.9 high it offers.

As for my overall range...
I have occasionally geared my bikes to offer low gearing in the mid-teens (15-16 gear-inches) and was delighted with the result, but do not want gears that low at the expense of reliability. At the high end -- particularly with a full touring load -- it is unlikely I'll ever use anything much above 85 gear-inches, given my high-cadence/low gear pedaling style.

Looking forward to all responses and any helpful suggestions you might be able to offer; thanks in advance! While I am familiar with derailleur bicycles, I am all-new to the Rohloff drivetrain, and learning as much as I can before my bike reaches final spec.

Best,

Dan.

wheezy

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #1 on: July 20, 2012, 06:51:42 PM »
38t x 16t, on a 700c/29er. Roughly 19-100 gear inches.

Plenty of range for an MTB and an almost brisk, flat-bar road bike. I'm rarely aware of the actual gear I'm in, unless it's top or bottom. I can tell whether it's 1-7 or 8-14 by the faint whirring and the feel through the pedals in the lower range, but that's about it. I'd say forget about the 7-8-7 shift. I personally don't notice it.


triaesthete

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #2 on: July 20, 2012, 08:16:12 PM »
Hi Dan
I would suggest as low as you can go but maybe on 38x16 for the even even sprocket combo Sheldon recommended to reduce wear. If you don't need 90"+ and want to stay within the law this is your only alternative.
My hub is quietening down very quickly due to extensive rough track hillclimbing. First is now very quiet as it has had a pounding. Two to seven whirr a bit but not annoyingly and are getting quieter. Like wheezy I don't notice the 7-8 change being any different to the others.
Most of the time now I don't know or care what gear I'm in I just use what I need when I need it,  and thats a simple choice higher or lower. No more juggling two shifters or toughing it out on the middle ring.
This sort of stuff will grow on you with familiarity
enjoy
Ian

JimK

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #3 on: July 20, 2012, 08:35:55 PM »
I have 38x16 (with 26 inch wheels).

 I don't notice 11 as anything special, but I definitely notice the 7-8 transition. 8 feels a lot more efficient than 7 - of course I am aware that this is probably an illusion caused by the noise in 7. Also the 7-8 or 8-7 transitions are a bit rougher/slower, but that is a very small issue. Shifting my hub is delightfully easy even then.

I use the full range of gears regularly. As I ride more I am getting stronger so I do notice I am not in 1 as much anymore, but getting up any real hill means a lot of time in 1. And we have lots of real hills in the Catskills!

On the Erie Canal ride we had a lot of flat terrain. I noticed that I was mostly in gear 9 riding about 11.5 mph or maybe gear 10 riding more like 12.5 mph. That kind of steady riding is not the norm around here where I live, where is it up and down, constantly shifting!

 

Andre Jute

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #4 on: July 20, 2012, 10:29:34 PM »
As Ian says, we familiars are superior for a reason...  :)

I too use 38x16 on 29er tyres, 60x622, because I live up a steep hill. (I didn't always have motor assistance.) It is the lowest legal ratio (2.375) and it gives me 19.5 gear inches, 5.6kph at 60rpm, to 102.6 gear inches, 29.5kph at 60rpm. In theory that's a bit short at the top end but I don't mind cruising downhill. Gear 11, 1:1, gives 69.9 gear inches, 20.1kph at 60rpm. EDIT: Unlike Jim, I liked gear 11, and most of my riding was built about it, but now, just like Jim, and despite two doses of heart surgery, I ride a bit stronger, perhaps from pure joy at being alive and out on my bike, and have been noticing that I'm all the way up into gear 14 (overdrive) even on the milder inclines quite often.

Back when I got the Rohloff, I would have gone to 36x16 if I needed it, and happily sacrificed the warranty for it. It turned out that my German dealer was not such a scofflaw; he wouldn't fit unauthorized parts or even supply them loose! But, though I've since bought the parts for some other ratios, when the opportunity arose to make a change, either way, I stuck to 38x16 because it just flat works for me.

Andre Jute
« Last Edit: July 20, 2012, 10:36:20 PM by Hobbes »

martinf

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #5 on: July 21, 2012, 07:28:55 AM »
I've done a lot of riding with SA 5-speeds, and reckon larger sprockets last longer and prolong chain life.

Not yet got a Rohloff, but I was thinking of getting the more expensive optional 21T sprocket, coupled with a 50T chainring.

50x21 ratios are about the same as 40x17, range about 17" to 90".

This is about the same as the 18" to 87" derailleur setup I had for my last loaded tour, my lowest gear was dictated by the smallest available chainring and largest available sprocket for my equipment.

I wouldn't use a 90" top gear much, and 11th gear at about 61" is slightly higher than my most-used gear on flat terrain, but with a new Rohloff I wouldn't want to gear lower than the permitted combinations for the first few thousand kms in case the hub is one of the few that have to go back to the factory for modifications.

Neil Jones

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #6 on: July 21, 2012, 08:39:34 AM »
Hi Danneaux,
I was in exactly the same position as you and spent far too much time researching chainring/cog combinations, in the end I phoned the friendly people at SJS Cycles and Robin recommended a 40x17 which to be honest I was a bit sceptical about at the time, anyway to cut a long story short they got it spot on. I live in North Wales which is very hilly and find myself constantly changing gear but on the flat I'm usually in gears 11 or 12. I sometimes wish I had a couple of higher gears (I spin out on hills once I reach about 26 mph) but as I don't wear a helmet it's probably for the best and I've never used the bottom 3 gears (I haven't cycled fully loaded} so perhaps there is room to fine tune when it's time to replace the ring and cog.
By the way I bought my RST 18 months ago and it's the best bike I've ever owned. I use it to commute to work mainly and have covered about 4000 miles in all weathers. The only thing I've ever done is changed the oil and the chain and it is so much easier to clean too.
I will never sell my RST as it suits my purpose perfectly although I do hanker after a Thorn Audax as I would like a lighter more responsive bike to ride on my days off.
Good luck Danneaux, you won't be disappointed I'm sure.

Danneaux

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #7 on: July 21, 2012, 09:00:45 AM »
Hi Martin!

Very nice having you aboard; welcome!

Quote
... reckon larger sprockets last longer and prolong chain life. Not yet got a Rohloff, but I was thinking of getting the more expensive optional 21T sprocket, coupled with a 50T chainring.
I spent some time this evening with the Rohloff gear chart and it -- along with the SJS Cycles site's Rohloff cog offerings -- had me thinking along similar lines.

Thinking about Ian's reference to Sheldon Brown's even-even gearing combos, I wondered if the even-odd (40-17) setup might result in a wash, where wear is concerned. Yes, it is a mismatched combo in terms of tooth count, but the larger diameter compared to the 38-16 might come out the same in terms of service life even with greater wear due to the odd sizing. Certainly, the 38-16 is more economical -- that 21 tooth cog costs nearly twice as much. The 16T is 25.99, while the 17T is a modest increment upward at 29.99, and the 21T is 49.99 (USD$ $40.37, $46.59, and $77.66 respectively at current exchange rates).

The 21T cog and 50T chainring would have to effectively double drivetrain life to cost-out effectively. If chain life is factored in...maybe it would. Also, thinking about the sizing of the timing rings on my tandem, I think torque loads on the bottom bracket would be reduced as well. I went to far larger timing rings and now my bottom brackets last forever. Something for me to ponder further. One point Andy makes in his "Living With A Rohloff" articles is how the larger 17T cog contributes to longer chainlife because -- while there is no lateral stress on the chain compared to a derailleur application -- the chain doesn't have to wrap as tightly, saving wear. To get equivalent overall range with the 17T cog as the 16T also means increasing the chainring size, so the chain is stressed less at both ends (larger arcs) -- a less extreme version of what Martin is considering, but also at less initial outlay.

I'd love a low gear around 15 gear-inches, but like Martin, I'm concerned about compromising my standing with the Rohloff warranty. And, in the back of my mind, I'm a bit concerned about the potential for actual breakage out in the field, however unlikely that might be. It isn't a complete stopper, and it doesn't seem to be a problem in practice, but it really is possible to generate pretty high torque loads when starting from a stop on a 24% grade with 32kg/72lb of gear.

In earlier days ( <cough> late 1970s <cough>), I developed maps of routes that pioneered the Eugene Hill Tour. It was later taken up by local clubs and became an annual event and even a fundraiser for them. I was deep into gearing then and caught the low-gear bug (logarithmic graph paper days. Australians, do you remember Ron Shepard and his ultra-low gearing efforts/Low Gear Fellowship from that era? He used FW cogs up front and chainrings behind). I modified a number of older cranksets to take freewheel cogs (pre-Mountain Tamer Quad days, too, though I got one of those in due course). I found it is possible to actually ride a 12-inch low gear with a load, provided the hill is steep enough. Biggest problem was catching the pedal cage with my shoe cleat -- the crankarm whipped around so fast at that point, it usually took till the third go-'round to catch it, so I started out in second or third gear, then shifted down once underway.

The thing is, as my gearing got ever lower, torque on the rear hub and freewheel components grew greater and greater. I never broke anything, but I soon had a terrible time getting the freewheels off the hub -- they would screw on so tight, they distorted the land next to the freewheel threads. I finally solved the removal problem by coating both hub and freewheel threads with molybdenum disulphide high-pressure lube and then using crushable (sacrificial) aluminum spacers between the freewheel body and the hub. As you can probably imagine, my chain life dropped dramatically, and this was in the days when a 5-sp Regina Oro was a really robust chain. heavy, anyway.

The lesson I took from these efforts is my output remained essentially the same within anobjectively narrow range. What changed was the effective torque multiplication due to the lower gearing, and I think this is what Rohloff is concerned about. I strongly suspect even the "red" or "illegal" Rohoff gearing combos don't kill the hub outright or even for a very long time or at all, unless the rider is really strong or other factors are in play (hill slope, heavy load, etc). I'm guessing these deep ratios do eat into the service life/MTBF (mean-time between failure) ratings Rohloff have specified so there is less "cushion" or safety margin before something goes Bad. This effect is bound to be more risky when it is still early days for a hub, and the gears and internals have not worn into full mesh and contact with one another. After the hub is broken in, it seems considerably less risky.

I am still boggled by the realization that all that forward torque is countered by such a small reaction-moment arm -- the thing fits inside the dropout! Pretty astonishing when you think about it, and it makes me happy Thorn have spent so much effort to craft their left-hand dropouts with great care. Kinda makes me wonder about the aluminum OEM Rohloff dropouts, but there's a lot of "beef" in them as well, and they're really thick.

Oh! While writing this, I see Neil has posted on this very topic -- talk about timely! Good having you weigh in also. Neil, I'm glad to hear the 40x17 has worked so well for you in practice, and to hear it does so on the kind of hills you reference is reassuring too. Thanks so much for your "user report" and now...boy! Now, I need to ponder all the input and come up with a spec. This is all outstandingly helpful, and I do so appreciate all your efforts and responses and kind wishes. Keep 'em coming, please! All sounds very promising to get an ideal ratio for my needs.

All the best,

Dan.

Danneaux

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #8 on: July 21, 2012, 09:07:46 AM »
Thinking about it more, Wheezy's post is going to have me running a quick comparison of "forbidden" gears between 700C and 26" wheels in the Rohloff charts. The larger 700C/29er diameter is bound to result in added stress that can be calculated (thinking about Shimano's cautions related to using their 12-36 cassette on hubs made specifically for it if 29er wheels are used). If the forbidden ratios are the same, I can get an idea of the safety margin Rohloff allow. If they are different, then Rohloff are making an adjustment for diameter-related torque increases on the hub internals.

Late enough now, so off to bed. A fine project for when I awaken.

Best,

Dan.

il padrone

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #9 on: July 21, 2012, 09:13:15 AM »
42-17 gives me a nice ~65" gear for gear 11 which is very nice as a comfy flat road gear. The 17 sprocket also reduces chain wear apparently - larger sprockets and chain-rings always wear slower as well.

il padrone

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #10 on: July 21, 2012, 09:44:12 AM »
With regards to this last, it seems best to consider "high range" (8-14) as the most-used cruising range, and the "low range" (1-7) as just that -- for slogging along at lower speeds, climbing hils, plowing through mud, going into headwinds, and so forth, with Gear 11 as the most-used direct-drive.  

This recommendation is the best guide you could use. I had a 42-16 to begin with and gear 11 was too high for me to use on flat roads mostly. I found myself using gear 10 mostly. The current high gear (with 42-17) is 94" and I will spin out at about 55kmh on steeper descents. This is rarely a real concern as by that speed, especially when fully-loaded, I will get more speed from going into a tuck than by pedalling.



In reading the earlier version of Andy's "Living With a Rohloff" that appears on Sheldon's site ( http://sheldonbrown.com/harris/rohloff-impressions.html ), I see he mentioned a carefully chosen and well-reasoned 36x17 with all factors considered, resulting in a 15.4 low. While that low would be most welcome for what I so often do (ride with heavy touring loads up really steep hills and across sometimes very soft desert playa), I'm concerned about the possibility of breakage and warranty issues.

My bike has a low gear of 17.9" and that is fine for  all sorts of loaded touring up to about 20% grades. I am quite amazed by the gearing Andy Blance runs as it looks to be about a 21 sprocket with a 38 or lower chain-ring. This is well below the specific recommendation from Rohloff.
« Last Edit: July 21, 2012, 09:46:02 AM by il padrone »

Andre Jute

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #11 on: July 21, 2012, 10:02:15 AM »
... with a new Rohloff I wouldn't want to gear lower than the permitted combinations for the first few thousand kms in case the hub is one of the few that have to go back to the factory for modifications.

Probably a smart consideration. Also, the hub will be run in, a little less likely to break from a sudden stress. I see Dan has also addressed the point.

Thinking about it more, Wheezy's post is going to have me running a quick comparison of "forbidden" gears between 700C and 26" wheels in the Rohloff charts. The larger 700C/29er diameter is bound to result in added stress that can be calculated (thinking about Shimano's cautions related to using their 12-36 cassette on hubs made specifically for it if 29er wheels are used). If the forbidden ratios are the same, I can get an idea of the safety margin Rohloff allow. If they are different, then Rohloff are making an adjustment for diameter-related torque increases on the hub internals.

The lowest ratio Rohloff permits has nothing to do with wheel size. It is specifically and exclusively the ratio of teeth between drive sprocket and chainring, as in 38/16 = 2.375 or 42/17 = 2.471 whereas 36/16 = 2.25. If you think about it carefully, the power that goes into the box is localised at that point by this ratio, regardless of the rolling radius of the wheel. The wheel size selected is thus a "free multiplier".

Andre Jute

julk

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #12 on: July 21, 2012, 12:15:00 PM »
Dan,
I have ridden the basic 38x16 combo for 4 years (bike stolen) then a further year, because that was what SJS were fitting as their basic recommendation.

I am 65 years old and fairly fit still.
I ride with a 20-30 kgs load quite often, camping or shopping.
I pedal at around 80 revs a minute and was finding gear 10 the most comfortable for level loaded riding.
I have tried but never found gear 1 usable, I would get off and walk at that stage on a hill!

I seem to be the odd man out here, or possibly more reckless, as I have now moved to 43x21 to get gear 11 to be what suits me best. I still do not use gear 1 although I have used the new gear 2 on a recent fully loaded ascent of a 'wall of death' type hill until common sense prevailed and I got off and walked the rest.

Moving to the larger cogs was expensive and I also needed a longer chain. I suspect I will see less chain wear now but not enough to recover the extra costs. I was surprised to see some wear on the 16 cog after just a year and a couple of thousand miles use.

I would suggest going with the lowest recommended 40x17 and running the hub in.
By that time you will have confirmed your choice or have a good idea of what to change to.
Julian.

Danneaux

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #13 on: July 21, 2012, 05:32:53 PM »
Hi Julian!

Very helpful comments, as well; thanks!
Quote
I am 65 years old and fairly fit still.
I saw the pics of your last tour, and you are indeed fit! Well done!

Your post, along with Andre's and a few others interests me in a different way, too -- It seems people do fnd themselves getting stronger after "Riding Rohloff" awhile and begn to use the lowest gears less often than at first. This puts paid to the idea of greater friction, and it may be the Rohloff's gearing and shifting encourage more riding (and perhaps more frequent shifting which also encourages more riding), and so greater fitness. A nice positive-feedback loop.

It really helps to hear how the gearing you chose works with the weights you carry, too. Groceries and camping gear are both loads that have to be hauled, so very useful data for me.
Quote
I would suggest going with the lowest recommended 40x17 and running the hub in.
By that time you will have confirmed your choice or have a good idea of what to change to.
Yes, this is good advice and is confirming my thoughts for a "starter setup". Once I get some distance on the bike, I'll better know my needs in practice and can always make an adjustment with either the chainring, the cog, or both.

The more I read, the more I think it is probably a good idea for me to go with a basic setup, get the gearbox well broken-in, and then reassess my needs and make adjustments as necessary, just as suggested. This gives everything a chance to wear-in nicely, keeps the warranty in effect, and allows me to learn what I need while still having a combination that will be usable in a very broad range.

Fantastic help, everyone; thanks so much. Still looking forward to fresh posts on the topic. As a Rohloff newbie, and I suddenly realize these are the very things I've always wondered about. Learning more brings the picture into clarity.

All the best,

Dan.
« Last Edit: July 21, 2012, 05:37:08 PM by Danneaux »

Relayer

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #14 on: July 21, 2012, 05:50:10 PM »
So, I'm hoping some of you might be kind enough to post your combo and perhaps a comment or two on...
1) How is the low working for you in your conditions/use.
2) Is the direct-drive Number 11 gear working out to be your most-used, or have you compormised on that to get the low/high you'd like?
3) How important has placement of the 7/8 split been to you?

I run 42 x 16 on my RST.

1)  I use gear 5 for an extended 10% gradient, seldom below gear 3 which does for about 15% gradient, and I know of only one hill where I use gear 1 which is somewhat over 15%. My Garmin only reads gradients up to 15% then it goes blank.

2)  I don't know if 11 is my most used gear, but given I do the vast majority of my cycling in 8 - 14 (by design) then it may well be.

3) the 7-8 split is very important since I prefer to remain in 8-14 for most of my riding, I can start off from stationery on a reasonable uphill slope in gear 8 - otherwise on level I start off in gear 9.

With regards to this last, it seems best to consider "high range" (8-14) as the most-used cruising range, and the "low range" (1-7) as just that -- for slogging along at lower speeds, climbing hils, plowing through mud, going into headwinds, and so forth, with Gear 11 as the most-used direct-drive. 

That is exactly the way I see it.