Smallest Chainring?

[Thomas777]

Wondering what the smallest chainring some of you are using  with a 16t sprocket?
What is the smallest that can be used?
Thanks!

[mickeg]

I assume this is for a Rohloff bike.

Most on this forum use a 17T sprocket, as that was standard from Thorn.

I use a 16T which was the standard shipped with most hubs.  For touring, I use a 36T chainring, that gives me a low gear that at 3.5 mph has a cadence of about 72 with my 559X57 tires.  Slower than 3 mph, I walk the bike.

But for riding around near home where the most weight on the bike is a bag of groceries, I use a 44T sprocket.  That gives me a much nicer range of gears for unladen riding.

I add or subtract four links when I change chainrings, use two quick links when using 44T.

Rohloff does not specify teeth, they specify a ratio of chainring teeth divided by sprocket teeth.  Do a word search for ratio at this link.
https://www.rohloff.de/en/experience/technology-in-detail/specifications

My 36/16 ratio is 2.25 for touring, or 44/16 ratio is 2.75 for use around home.

[PH]

30T, assuming that fits on the cranks.
But what's the purpose of the question?  if you're looking for lower gears, then changing the sprocket might be a better way to go, cheaper and kinder on components, unless there's some reason you can't. 36/19 is going to be close to 30/16, either will give a really low gear, about 14" on a 700c wheel. OK on a trike, but I can't pedal that low and balance, plus I'd be spinning out on the top gear.

[Thomas777]

My wife's  bike,with 26" wheels,  currently has a 38-16. We will be cycling  across the US and in Idaand Washington there are some long steep grades. She has ridden this combo for a while.  So since we are riding east to west maybe her legs will be strong enough when we get to the mountains!
Thanks for your responses!

[JohnR]

A bigger sprocket should be cheaper than a smaller chainring and a pair of bigger gears is marginally more efficient than a pair of smaller gears with the same ratio. Changing the sprocket from 16T to 18T is approximately the same as one gear step on the Rohloff hub (as is changing the chainring to 32T). However, if thinking of changing the chainring you also need to check the size of the spider. If it's 130mm BCD then 38T is the minimum chainring size.

[PH]

My wife's  bike,with 26" wheels,  currently has a 38-16. We will be cycling  across the US and in Idaand Washington there are some long steep grades. She has ridden this combo for a while.  So since we are riding east to west maybe her legs will be strong enough when we get to the mountains!
Thanks for your responses!

Sounds like a great adventure.
You could take a couple of chain links and a 21T sprocket, change it when you come to the hills. With a snap ring it's much easier to change the sprocket than the chainring.  I know of someone who cycled across the US on a single speed, they changed sprockets a couple of times, though I think they had a tensioner so didn't have to bother changing the chain.

[Thomas777]

PH, now that's an idea!

[Moronic]

In case it helps, I'm still running 37-19, which is inside Rohloff's spec, on my Mercury with 650B wheels.

Every now and again I think of going up a few teeth on the front, and then I find myself tired on a steep grade and congratulate myself on my procrastination.

For 26-in even I might want a little longer top gear.

[martinf]

I use 150 or 155 mm cranks, with these I pedal faster than I did with standard 170 mm cranks. So I set my gearing lower than most people.

On my Raven Tour touring bike, used mainly for loaded touring, I currently have 38x21.

This gives me a range of 13 to 67 gear inches. The input ratio of 1.81 is slightly lower than the minimum of 1.9 recommended by Rohloff, but as I put less torque on the hub with the short cranks I reckon I am unlikely to break it.

The lowest gear of 13 inches equates to 5.5 kmh at 90 rpm. With this gear the limiting factor on steep hills is keeping balance (front panniers help to keep the front wheel on the road) and tyre adhesion. A gear this low is only useful on a steep hill when I am really tired at the end of a long day.

The top gear of 67 inches seems low, but equates to 29 kmh at 90 rpm, a speed that I can only rarely maintain with a loaded bike on the level. If necessary, I can up my pedalling cadence to about 120 rpm for very short periods to get the top speed up to about 40 kmh, for example when negotiating roundabouts, where I reckon it is best to match the speed of other vehicles as far as possible.

____________________________________________________________

On my Raven Sport Tour, used for lightly-loaded day rides, the gearing is higher. 42x19 with a range of 15 to 80 gear inches.

At 90 rpm, this gives 6.6 kmh in lowest gear and 35 kmh in highest gear.

Max speed is about 46 kmh at 120 rpm.

[mickeg]

My wife's  bike,with 26" wheels,  currently has a 38-16. We will be cycling  across the US and in Idaand Washington there are some long steep grades. She has ridden this combo for a while.  So since we are riding east to west maybe her legs will be strong enough when we get to the mountains!
Thanks for your responses!

Are you are still running the threaded sprockets?

[John Saxby]

Hi Tom,

A slight variation on the valuable detail above.  I hope this is useful:

In my tour North-to-South through the Rockies & to the Washington coast in 2016, I used a 17 x 36 combination on my Raven, with 26" wheels and 1.6" Marathon Supremes.  That gave me a gear-inch ration of 15.6 in my lowest gear.

There were a lot of hills on that tour, but they tended to be long (say, 25 kms) with a moderate grade (4-6%). If memory serves, I used my 1st gear only 4 times in about 2200 kms -- twice on the Icefields Parkway, once south of Canmore in Alberta, and once in the States, west of Montana (would have to check the detail.)

Each time I used low gear, it was for about a kilometre to reach to summit of a particular pass, and the climb was no problem.

As a comparison:  On a 5-day ride in the hill country NW of Ottawa in 2021, I used my low gear about 15 times in 175 kms -- the hills were steeper (usually around 8-10%) and shorter, and on the whole, more demanding than what I encountered in the West.

Good luck to you & Kathy, and enjoy!

John

 

[Thomas777]

My wife's  Ike does not have the threaded sprocket.
So after we had a discussion about the gearing my wife said she is fine with the current setup.  She said after riding from Ohio to the Rockies she would be stro g enough!
One less thing to carry!