Author Topic: What's your Rohloff combo (chainring, cog)?  (Read 116126 times)

PH

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #330 on: September 02, 2021, 05:58:07 PM »
It seems that the Rohloff shear pins weren't designed for such easy replacement.   

Wait until you discover there are nine of them.
Now that you've posted the link to https://matt.signorini.id.au/?p=198 in another thread I see that the shear pins are relatively accessible. However, I struggle to imagine that I'm strong or heavy enough to put sufficient load on the hub to break these, even if I combine the smallest available chainring with the largest available sprocket.
Yes, if you just remove the innards they drop out. 
I've never seen them listed as parts, so either it's uncommon for them to break, or Rohloff don't want you replacing them yourself.

Andre Jute

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #331 on: September 03, 2021, 01:09:25 AM »
It seems that the Rohloff shear pins weren't designed for such easy replacement. 

Wait until you discover there are nine of them.
Now that you've posted the link to https://matt.signorini.id.au/?p=198 in another thread I see that the shear pins are relatively accessible. However, I struggle to imagine that I'm strong or heavy enough to put sufficient load on the hub to break these, even if I combine the smallest available chainring with the largest available sprocket.

They certainly appear -- as has been said here -- to be the gearbox's first line of defense. This is masterclass engineering indeed, by itself adequate explanation of why I am so keen on German engineering, even if it is a fraction heavier.

However, to return to the thread's subject of choosing a chainring and sprocket for a (presumably) touring/commuting/utility bike, the first impression may be that it is an invitation to the cyclist to gear lower with security -- but in real life it is not quite unalloyed advantage for the overload boys and the stump pullers, because the limit isn't Rohloff engineering at the barrier of those torque-limiting pins, it is the cyclist's ability to keep his balance at ever lower speeds in ever lower gears. I've noticed that several parties on the forum haven't followed Herr Rohloffs more relaxed permissions all the way down to the present level, and wondered whether they were just being economical by using up components with life left in them or had already decided they were at the margin of their balance.

Personally, I stopped gearing lower at 2.35 -- 38x16, the factory default two permission expansions ago -- because I'd reached the limit of my sense of balance between 5 and 6kmh (on a 29er with 29.45in rolling diameter -- see top decision table at http://coolmainpress.com/BICYCLINGHebieChainglider.html). From there, I reversed course as cycling with the Rohloff made me stronger (after two heart surgeries) and I understood better how to use the software and torque of the electric motor in conjunction with the Rohloff, to where I'm now at a relatively (for me) racey 44x16, a very safe ratio of 2.75, even considering that I'm a masher.

Moronic

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #332 on: September 03, 2021, 06:23:32 AM »
Yes good points. I'm safely under 100kg and geared at 37-19 which is just above the minimum 1.9:1. I went there after reading Andy Blance in his Living With Rohloff screed reveal that in Thailand and carrying under 14kg he wished he'd geared lower than 41-19.

In first at 37-19 I can balance easily enough but there is a bit of steering for balance required even at a cadence I would guess at 50-70rpm with a 650bx50mm tyre (roughly 700cx30). My speed is around a slowish walk - I've overtaken people pushing their bikes up hills that I'm climbing from the saddle but it takes a long time. The ratio works out to about 15 gear inches.

As I get stronger I resort to that gear less, but I'm suspecting it would remain pretty handy if I had a load on.

The question arises Why not walk. The best answer I think is that once you start walking it's hard to remount if the grade slackens but remains quite steep. Whereas if you're still in the saddle you can click up to second and improve balance while making better progress.

As a secondary reason for valuing such a low gear is that when you're climbing in second it is nice to know the lower ratio is there. I know there's relief if I need it, and that helps me not need it.

The cost is earlier spinout at the top - and if you're over 100kg, risking a rebuff on warranty. Whether those are prices worth paying will depend on your strength and the terrain you expect to encounter. I think Andy had been off the bike with health issues for many months prior to that Thailand trip. And comparing his cycling history with mine, he was likely still stronger than I am.

Matt2matt2002

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #333 on: September 03, 2021, 11:25:58 AM »
What a great thread.
So much to take in and learn.
Are we now going down the ( very pleasant ) road of methodological skepticism, an approach that subjects all knowledge claims to scrutiny with the goal of sorting out true from false claims?
Never drink and drive. You may hit a bump  and spill your drink

martinf

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #334 on: September 03, 2021, 04:08:35 PM »
However, to return to the thread's subject of choosing a chainring and sprocket for a (presumably) touring/commuting/utility bike, the first impression may be that it is an invitation to the cyclist to gear lower with security -- but in real life it is not quite unalloyed advantage for the overload boys and the stump pullers, because the limit isn't Rohloff engineering at the barrier of those torque-limiting pins, it is the cyclist's ability to keep his balance at ever lower speeds in ever lower gears.


My lowest-geared bike (a Brompton folder) has 14.6 gear inches. Despite the small wheels I don't have a problem with balance, and generally have enough weight in the front luggage to keep the front wheel down on steep climbs.

That gear corresponds to 6.3 kph at my preferred cadence of 90 rpm, 4.2 kph at 60 rpm if I am tired. Although not much quicker than walking, in most circumstances I find it easier.

Lowest gear on my Raven Sport Tour is not much higher at 15.2. I don't yet need this gear for road use with this bike, but it is useful when I take "short cuts" off road.

Danneaux

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #335 on: September 03, 2021, 04:55:53 PM »
Quote
My lowest-geared bike (a Brompton folder) has 14.6 gear inches. Despite the small wheels I don't have a problem with balance, and generally have enough weight in the front luggage to keep the front wheel down on steep climbs.

That gear corresponds to 6.3 kph at my preferred cadence of 90 rpm, 4.2 kph at 60 rpm if I am tired. Although not much quicker than walking, in most circumstances I find it easier.

Lowest gear on my Raven Sport Tour is not much higher at 15.2. I don't yet need this gear for road use with this bike, but it is useful when I take "short cuts" off road.
As a data point, my experience almost exactly mirrors Martin's with the exception of cadence. My "comfortable and preferred" cadence is 110-120rpm normally and falls as low as  80rpm up steep hills if I'm tired. If the slope is steep enough while carrying a heavy touring load to require me to pedal long at <80rpm where I would stress my knees, I get off and push. Pushing is something I try to avoid as I have found a loaded touring bike makes a lousy wheelbarrow, especially as the nearside pedal seems to always find my shin even with four panniers mounted.

A fast-light hummingbird cadence makes up for the low gearing by resulting in a speed I can still balance comfortably and maneuver easily -- in my case 4kmh/2.5mph. My Nomad is geared at 36x17 with 47mm tires on 26in wheels for 15.2 gear-inches; my Enduro-Allroad derailleur bike with the same size wheels and tires has a derailleur drivetrain with a comparable 15.88 gear-inch low of 22x36t.

Best,

Dan.

JohnR

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #336 on: September 03, 2021, 05:03:26 PM »
At the moment I'm running 42 / 17 on my Mercury with its 50mm 650B tyres which my spreadsheet tells me gives 1st gear as 18.6". I don't normally use that gear but it came useful on the LEJOG when my legs got weary. I've got the parts for running 38 / 16 which I reckon gives 17.8" (effectively 1/2 a Rohloff step lower), 42 / 19 = 16.6" (one Rohloff gear step lower) and 38 / 19 (= 15") which are options to accommodate either aging legs or adding significant baggage. I am, however, a masher, not a spinner (average cadence in low 50s, maximum around 19 when trying to get a bit more speed going downhill) so the issue of stability at low speed could arise. I suspect I would need to encourage the legs to spin faster if I drop the gearing.

mickeg

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #337 on: September 04, 2021, 01:56:52 AM »
I wrote the following a bit over eight years ago.  It is still accurate, when using my Nomad Mk II for touring or pretending it is a hard tail mountain bike, I use 36 and 16 chainring and sprocket.  But around home when the bike is unladen, use a 44T chainring.

I wrote  a brief note on a different thread with my gearing, might as well list it here too.

I have been building up my Nomad over the past couple months.  For normal use, am using 44t front and 16t rear.  With the tires I currently have on the bike, this gives me a range of 20.2 to 106.4 gear inches.  I normally use a chainguard/bashguard in the outer chainring position and the chainring on inner on a double crankset.  My chainline is off by about 5mm, I did not want my Q factor to be more than about 10 to 12mm wider than on my other bikes, thus I compromised on chainline.

Last summer there were a couple days of very steep climbing in the USA rocky mountains.  With my Sherpa having a lowest gear of 19.2 gear inches, I wished I had lower gearing.  With this in mind I thought that when I set up my Nomad, I would want to be able to switch to a different chainring for the days when I know in advance that there will be some very steep climbing.  I am not using a front derailleur, instead the plan is to only switch chainrings when absolutely necessary.

So, if I go on a trip where I anticipate steep climbing, I intend to remove the chainguard and put a 36t on the inner and the 44t on the outer positions on my double crankset before I leave home.  I also put an extra quicklink in the chain so I can remove (or add) a few links, adjust the eccentric and have lower (or higher) gearing with only a few minutes of work.  The 36t front with 16t rear will give me a range of 16.6 to 87.1 gear inches.

With the low gear of 16.6 gear inches, I find that the slowest that I can ride the bike and keep myself balanced upright correlates to a cadence of about 72 rpm, which I find is an ideal cadence for me.

Since I am using chainrings and Rohloff cog that all have an even number of teeth, I am going to try this theory:
http://sheldonbrown.com/chain-life.html

The only change to the above is that I bought a proper chainguard or bash guard that is sized better for the 36 chainring, so when I use that I do not have the 44T chainring serving that purpose anymore.

And I wrote the following in Jan 2016:

...

For touring on my smaller chainring, I sized the chainring to provide a lowest gear with a cadence of 72 at 3.5 miles per hour (5.63 km/hour) because that is the slowest speed that I can easily maintain balance and that cadence is on the low end of my preferred range. 

With a Schwalbe Marathon Extreme 559X57 tire, that is 16.46 gear inches with 36 chainring and 16 tooth cog (2.25 chainring to cog ratio).  I weigh about 80kg, so that is an acceptable ratio for me.

I have spun out the rear tire on loose gravel in my lowest gear, when climbing a hill that slow it takes no time at all to come to a halt.  And if the hill is too steep for me to sustain 3.5 mph, a lower gear will not help me because I will be walking.

I do not have heart problems, but at an age of 67 I think it prudent to not overly tax it.  So, when my heart rate monitor tells me that the hill is too steep to keep pedaling, I get off the bike and walk at a slower speed.

I walked almost the entire hill in the attached photo, 13 percent grade was not worth the struggle to try to pedal up it for 3 km.  The inclinometer on my bike tells me that the sign was accurate, a constant 13 percent grade.


Andre Jute

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #338 on: September 04, 2021, 02:14:23 AM »
John has a good separate point about aging legs and the lowest ratio useful to the individual cyclist, already addressed by others too, so that I'll just make a point at a tangent.

There was a time when I could hold my balance down to 3.5mph, but I seem to have lost it either by aging legs or lack of practice during the two years of a bad winter and then the pandemic when I hardly cycled appreciably, and when I did cycle, the steeper hills were outside the officially permitted limits of my circular rides. This brought home to me that sooner or later my Rohloff's gearing will have to be changed again. Meanwhile:

It's not all bad news, though. It turns out my electric Bafang/8FUN BBS central motor's software has a setting called "Parking" (1), which can be used for walking the bike, especially when heavily loaded with my painting gear, up hills at 5-6mph at 1:1 ratio, and other speeds at Rolloff-mediated ratios. It's another consideration in determining your Rohloff's gearing if you're getting on in years.

(1) For those with a Bafang/8FUN BB central motor and the C65 control set: with the motor switched on, put the controller of the motor in "0" by pressing the "gear down" button, hold the handlebars tight, press the "gear down" button and hold it, after a few moments see a "P" appear in the controller window, and walk with the bike as the motor moves it forward; it stops when you let the button go (or you pull a brake, which operates the motor cut-out -- you do have cut-outs fitted, don't you?). You can arrange the speed the bike moves at by changing the Rohloff or other gears before holding the "gear down" switch to get "P". Good for stair climbing too if you're a cyclist who lives in an apartment.

JohnR

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #339 on: September 04, 2021, 09:00:20 AM »
I do not have heart problems, but at an age of 67 I think it prudent to not overly tax it.  So, when my heart rate monitor tells me that the hill is too steep to keep pedaling, I get off the bike and walk at a slower speed.

I walked almost the entire hill in the attached photo, 13 percent grade was not worth the struggle to try to pedal up it for 3 km.  The inclinometer on my bike tells me that the sign was accurate, a constant 13 percent grade.
My ticker seems to be OK with the legs being the weaker link. If they are feeling enthusiastic and demand more blood and oxygen then the heart can usually deliver. Yesterday was one of those occasions when the legs worked well and the heart rate got up to 161 on my worst local hill (about 1/4 mile of ~15%) and is almost 3 x my resting heart rate. Not bad, I reckon, for someone who recently became a septuagenarian.  :) Normally the legs aren't feeling so fresh and the peak heart rate is lower but were motivated by being passed by a couple of cyclists who made that hill look easy.

PH

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #340 on: September 04, 2021, 09:38:23 AM »
The question arises Why not walk. The best answer I think is that once you start walking it's hard to remount if the grade slackens but remains quite steep.
Just on this point - It's another Rohloff advantage, it's usually easier to re-start in a higher gear than the one you stopped in. Just a couple of pedal revolutions to get going before dropping down and settling into a more comfortable rhythm.


mickeg

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #341 on: September 04, 2021, 10:29:37 AM »
The question arises Why not walk. The best answer I think is that once you start walking it's hard to remount if the grade slackens but remains quite steep.
Just on this point - It's another Rohloff advantage, it's usually easier to re-start in a higher gear than the one you stopped in. Just a couple of pedal revolutions to get going before dropping down and settling into a more comfortable rhythm.

On one of my tours with a loaded bike and lots of hill climbing, I found that if it was too steep to start in gear 5, I had to keep walking.  Gear five gave me enough time to pedal a half crankset revolution and get my other foot onto the other pedal.  Lower gear, my pedal got to the top of the stroke too early for my foot to get there and that brief pause would allow the bike momentum to dissipate. 

But I can't tell you what percent grade that steepness was, but with lots of trial and error, I found that when trying to re-start on a hill, I had to be in gear 5 or higher.

The day I came to that conclusion, it was a difficult road in the middle of Iceland interior, lots of gravel and cobbles, and in first gear my torque on the rear wheel frequently caused tire slippage on the steeper sections.  And once you lost a bit of traction at that slow speed at that steep a hill, you came to a halt so fast you could have trouble getting one foot on the ground.

I use shoes with SPD cleats when touring, pedals have one side platform and other side to mate with the SPD cleat.  On those steep hills, I try to avoid getting cleated in and use the platform side, I wanted my foot to be loose enough on the pedal I could get a foot on the ground really fast.


GamblerGORD649

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #342 on: September 04, 2021, 07:33:26 PM »
I have never used cleats on any bike. On a tour bike they are just plain stupid, especially for an old guy. JMO. How many hundreds have broken clavicles and hips, not even on a tour?? My sister's BF clumbsily just fell off his MTB, broke his clavicle right in front of his house. Hospital said we won't do anything. Never healed.
I have started in 1st more than once. I also had a half dozen minor calamities in Vietnam, that could have been major, if I landed on my shoulder or hip. One was a kid walking in front of me on a wet street. I braked on a manhole, so the bike instantly slid out. I landed on all four hands and knees.
Minor discomfort. My glasses got bent, but there was a store right near and got it fixed. Several times the bike tipped, so I had to instantly stick out my leg.

At home I had a slow slide because of sand. So I thought it would be OK to land on the side of my knee. Wrong, I cracked the top of one of the leg bones. Was sore to touch for a month and had a lump for 6 months.
 
I just did 3 century miles rides in 13 days on my old CCM with new SA RD3 650B wheels. LOL.
It has 48/ 63/ 84 GI. Goes up 10% hills just fine. Came home way fresher than recent Rohloff rides, bike at 25 lbs heavier. It's now 44/ 16T, I'm done going lower for sure.
« Last Edit: September 04, 2021, 08:21:54 PM by GamblerGORD649 »

John Saxby

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #343 on: September 05, 2021, 03:14:48 AM »
Just returning to Forumtalk after a couple of weeks away, including a 5-day mini-tour in the extended neighbourhood: heat, humidity and hills ['appily, the 4th aitch was missing -- no 'eadwinds  :) ]

I had plenty of opportunity to reflect on gearing, cadence and breathing going up & down a lot of hills. My outbound leg from Ottawa was 185 kms, the first 80 kms of that pretty flat, but the remaining 100 kms took me into the hills of the Canadian Shield. Contrary to the forecast, I had three days of high heat and humidity, and was drinking about a litre of water (with electrolyte) per hour of riding.

In my two-and-a-half days in the hills, I found myself looking back on my monthlong ride in the Rockies & Cascadia five summers before.  Then, I used my first gear on the Raven (17 x 36T, mated to 26 wheels with 1.6" Marathon Supremes, for a low gear of 15.3 gear-inches) just four times in 2300-plus kms: three times on passes in Alberta, and once in Washington state. Each time was for about a kilometre.  By comparison, in my last 60 kilometres climbing into the Madawaska Hills towards my friends' old farmstead, I used my low gear about 15 times. The longest stretch was about 500 metres.

This was in part a matter of topography: the rollers two weeks ago were both shorter and steeper than the big hills of the West. Only a couple were more than 2 kms, but grades of 8 - 10 - 12% were standard issue.  Climbing the Highway to the Sun in Glacier National Park in Montana, by comparison, took me about three hours, but most of the time I was in 4th or 5th gear. The roads I was riding in Eastern Ontario were originally tracks laid down half a century or more before the automobile, and often have been improved and tarred only relatively recently.

The weather played its part, too: With high humidity pushing the humidex into the mid/high 30s, I stayed within my limits, finding deep shade for regular pauses, inhaling my home-made energy bars, and keeping myself hydrated.

The weight of bike and gear for my long ride in the western mountains was only a little more than I carried on my mini-tour.  This time, I carried a maximum of 43 lbs, plus up to two litres of water.  That included food for three days: my route had only one café, at the 75 km marker.

Notes & a few photos to come later.


Dunroving

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Re: What's your Rohloff combo (chainring, cog)?
« Reply #344 on: September 06, 2021, 01:04:46 PM »
Hello All, thanks for accepting me onto this forum. I am not a Rohloff owner at the moment, BUT my retirement bike is in the making and I'm at the point of choosing a chainring/sprocket combo for the Rohloff.

Being new to the Rohloff world, it's been a steep learning curve, and I've found this thread fascinating (yes, I have read all 23 pages!). I wonder if somebody would kindly answer a few questions.

Q1: After reading this thread and using the Gates Sanity Check page (and Sheldon Brown's gear calculations page), am I correct in thinking that, for a certain gearing, there is more than one chainring/sprocket combination that would work (approximately)?

Q2: If I'm correct in the above, from reading this thread it seems that a "big-big" combination has the advantage of less chain wear, but greater likelihood of chainring strikes on lumpy terrain? And that conversely, a "small-small" combination raises the chainring (less chance of chainring strikes), but causes faster wear on the chain?

Q3: (most important question!) So far, I've been trying to match the gearing on my new build to the gearing on my 1997 Litespeed Obed. It's a 2x (42/22 with 11-33 cassette), which gives a low of 99.3 gear inches (3.1 mph at 60 rpm) and a high of 17.3 gear inches (29.5 mph at 100 rpm). I'm wondering what will be the effect of shorter crank arms (165mm on new-build vs. 175mm on Litespeed) on the actual riding experience? If I match the same low speed on the new build, at 60 rpm, does this just mean I'll have to "push harder"!

I hope I've explained the situation clearly. My physics isn't great (though I did get a "B" at O-Level back in 1973!) ;-)

Other factors that may not be relevant: (a) Litespeed has a 26" wheel with 2.2 tyres, new build will be 27.5 weels with 2.3" tyres, and (b) I realise I can't match the Litespeed's gearing exactly, as it has a 574% gear range whereas Rohloff can only go 526% - the lower end is where I'm matching to, and truncating the upper/faster end.