What's your Rohloff combo (chainring, cog)?

[Tigerbiten]

I've finally got what I think is the ideal gears for my recumbent trike.

Front:- Twin chainring, 53t/38t, on a Schlumpf HSD.
Back:- 21t sprocket on my Rohloff built into a 20" wheel.
Range 9"-172"

Small ring normal drive takes me from ~2 mph up to ~15 mph.
I then change onto the large ring for the range 15-20 mph.
It's low range overdrive then for the range 20-35 mph.
After that its large ring overdrive to ~50 mph.
It's fun being able to pedal down ~10% hills at +40 mph ...........

Main downside is that I can pop the chainrings off the HSD due to the fact they are only held on by a cir-clip if I have to much force on the pedals when I change chainrings.
If I treat it more like a hub gear change, then its ok.

[Huernie]

Hi Dan

I took your advice and changed to 36-17. Much better! Thanks.

[macspud]

I have a 36/16 and will soon be substituting a 32/16 and, if necessary, a 32/17. At my age (75) and level of fitness I have no fear of damaging the Rohloff with excessive torque.

Hello Benchman,

I was just reading through this thread again and noticed your post.
I'm interested to know how you're getting on with your set-up and where you've got to on your chainring-cog combo.

There should have been absolutely no problems using a combination much lower than 36/17 (rohloff recomended lowest (2.1:1)) as they calculate that using a 150kg max force at the pedal. to apply 150kg at the pedal whilst on a recumbant would need powerlifter strength, much easier on a diamond frame and standing on the pedals and even then would be difficult to do for anyone weighing less than 100kg.

[mickeg]

Some followup on my post from June 2013:

...
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. 
...
...  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.
...

I used the 36 front and 16 rear on a trip this past April where there was a lot of steep climbing.  It was not a loaded touring trip, instead I used the Nomad as a mountain bike with the 36t front.  After the big climbs were done and we did some car camping, I added a few chain links and switched to the 44 front for road riding.  The photo shows the Grand Canyon in the background.  I am very happy with this setup.

[rafiki]

Reviving an old thread which I found it because my Sterling feels too low-geared for me at the moment.

It's not very hilly around here and I find that I am almost never in gear 1, gear 2 infrequently and yet I feel I am spinning in gear 14 on a moderate downhill. On a typical ride of about 45km the elevation gain according to Strava is only between 40 and 190 metres.

The Sterling has 26 inch wheels of course and the chainring is a Thorn 39T, the Rohloff sprocket has 16 teeth. I don't do any touring or carry any loads.

I began reading the earlier posts in this thread but my eyes began glazing over on about page 2! I don't understand much about the physics of gearing. I'd be grateful if someone could advise me what would be the best modification to make to my setup to gear me up a bit more.

[JimK]

Gear 2 is about 13.6 higher than gear 1, and gear 3 again 13.6% higher than gear 2, or 29% higher than gear 1. Sounds like maybe a 20% increase in your gearing would get you in the range you want. You could try switching to a 47 tooth chainring.

I can barely imagine having gears that are too low! Maybe a 45 tooth chainring, just to avoid too much struggle with the occasional steepish incline?

[mickeg]

Try a 44 chainring if a 39 is geared too low in 14th gear.  A 44 would be geared about 12.8 percent higher.  

Thus when you are in gear 1 in the future, that would be very close to being in your current gear 2.  In other words you lose gear 1.  Thus, you would not lose anything on the low end because you said you never use gear 1.

And gearing up that way, your new gear 13 would be very close to your current gear 14, thus you would gain one new higher gear.

Since your rear cog is an even number, half the teeth that normally have a chain link with outer plates will wear differently than the other half of the teeth that have chain links with inner plates.  Thus, if you have a lot of distance (and wear) on your chain and on your cog, it would be best if you keep the chain links with outer plates on the teeth where you currently have outer teeth.  More on this topic here:
http://sheldonbrown.com/chain-life.html

You might want to mark the teeth some how.  I cut a notch in one tooth on the rear cog and one tooth on my even numbered chainring.  I only put the chain links with outer plates on the teeth that I cut a notch in.  It would be best to mark a rear cog tooth before you take your chain off.

[rafiki]

Thanks both. I was out today and was thinking some more about the requirement. I concluded that it is just one more gear up. I could take more but it's probably unnecessary. So 45 or 44 will do it. I take your point about the number of teeth. I'll make the marks. Much appreciated.

[mickeg]

I forgot to mention that if you do not have any left over chain from your last chain change, you will of course need some more chain to use a bigger chainring.  Or more simply a new one.

[JimK]

Sounds like you'll need a new sprocket, too! You'll be back to that gravelly sound if you put a new chain on your existing sprocket!

[rafiki]

Yes, thanks. They were both questions I was going to ask today.

I have a few links in the bag of bits supplied with the bike. Is there a formula to calculate the optimum number of links required in a chain for a chainring/sprocket combo?

I could turn the sprocket. There is some wear on the current side. Would you do that or would you fit new?

[mickeg]

There is no magic answer for whether or not you should turn the rear sprocket around or not.  But, if it has only been used on one side I would not buy a new one.  If it was me doing this, I would probably not turn the sprocket around if I added chain links.  But if I put on a new chain, I might consider turning the sprocket around depending on how worn it looks.

When I switch from the 36 to 44 (eight teeth difference), I add two links with inner plates, one with an outer plate and one quick link for a total of four additional links.  If you go with a 44, that is five more teeth, so try adding two links.  If you have a spare quick link, you could try adding one of those and a link with inner plates, thus avoiding having to use a chain tool.

[rafiki]

I'm very grateful for all this advice. much appreciated.

[Slammin Sammy]

This topic intrigues me. I understand why Sheldon Brown recommended using even numbered teeth on both chainring and sprocket, and always replacing the chain in the same phase, but I can't understand why the chain stretch is confined to the outer plate links.

Sheldon said, "Although all of the rollers, and the inner plate projections that locate the rollers wear, the wear is basically the same for all of the rollers, so the center-to-center distance doesn't change on the rollers connected by inner plates."

I'm missing something here. Can someone make sense if this?

[mickeg]

I'll try.

The links with the inner plates hold the round cylindrical parts (or rollers) that actually contact the chain teeth.  Those rollers do not move relative to the plates in use, or if they do move they do not move very much and that results in no or little wear.  Therefore the rollers in an inner plate link stay the same distance apart.  

Think of the links with the outer plates as consisting only of the plates and the pins, all other parts are part of the inner plate links.  The pins wear down over time because each time the chain wraps around a sprocket and unwraps it later, the pin rubs on parts of a link with an inner plate. In the second photo at Sheldons link you can see a badly worn down pin.  The amount of worn off metal on that pin (and also some wear you can't see because it is inside the link where the pin rubbed) is why a chain becomes longer over time.  

People (including me) refer to this as chain stretch, but it does not really "stretch" because the metal does not physically get longer, instead the parts between the links wear down and that extra slop in the bearing surfaces is where the extra chain length comes from.  And most of that extra length (or stretch) happens between the pins which are part of the outer plate links.

I hope I was clear, sorry if I was not.  I once tried to explain this to a bicycle mechanic and he thought I was nuts, so I gave up trying to explain it.  If I was not sufficiently clear here, perhaps someone else can try to explain it.

I once saw a photo of a badly worn Rohloff sprocket (or maybe it was a sprocket from another internally geared hub bike) and every other tooth was worn down more from this type of wear.

And that is why if you put a chain on a worn sprocket with an even number of teeth, if you put the chain inner plates on teeth where there used to be outer plates on those teeth, the chain will no longer be rubbing on the teeth the same way that the teeth and chain had previously worn, which can result in a noisy drivetrain.  It is best to keep using worn parts with each other as they wore down together under the same mechanical forces.

I have no idea why SJS supplies bikes with sprockets with odd numbers of teeth.  When you buy a new Rohloff hub retail, it is supplied standard with 16 teeth.  I suspect that SJS uses 17 teeth instead to try to even out the wear so you do not have to worry about keeping track of which links go on which teeth.  But, I used to work as a bike mechanic before I went to college and got an engineering degree, so I naturally think of things like how to put the chain on a sprocket properly whereas most typical bike owners don't want to think about this level of detail. The typical owner instead just wants to put the chain on and go, or maybe instead pay someone to put the chain on so they can go.