Single Speed Conversion

I find I no longer use many gears since converting to an electric rear hub. Has anyone converted to a single speed? If so what kind of gear ratios are you using to pedal along at 30 mph?

CrazyBike2's been essentially singlespeed for a long time (2+ years?) with just a single-sprocket freewheel on the rear motor, and though I've still had a 3-speed front chainring on teh cranks, the derailer hadn't been setup to actually work (just a chain guide), until last month when I finally puta shifter on it. So now it is technically 3-speed, but it's only there for worst-case scenarios.


I cant' help with the gearing, cuz I don't go past 20MPH cuz of the laws here, and because of my knees I don't even have it geared to pedal faster than around 10MPH.

But there are gearing charts and/or calculators out there to figure it out for you, including some either on or linked on the Sheldon Brown site.

I don't bother with gears either. I find if you gear your bike for a comfortable cadence a few kph above your motors top speed it makes for the best combination of pedal and e power.

My yellow bike has 54 front and 17 rear with 175mm cranks and I can maintain 34kph comfortably and peak around 45kph
My silver bike has 52 front and 17 rear with 165mm cranks can maintain 30 kph comfortably.
My orange chopper 48 and 18 with 170mm cranks 28kph comfortably but is geared a bit low so cadence is a bit higher but due to the lower seat height is acceptable.
It pays to have a few free wheels and chain rings on hand to play with. Horizontal dropouts are a good idea or a chain tensioner.
I have just purchased a nexus 3 speed hub. Some times a few gear options would be useful. When I ride with non ebikes I find I am often geared too high and when I want to keep up down hills I run out of gear and can't keep up.
I don't want to go for a dérailleur because that is too many gears. I am not sure how successful this will be, I'll keep you posted.

I have a single speed white industries 16 tooth bmx freewheel on mine, its geared so that I can pedal it normally from a standing start, the problem with gearing it for 30mph is that its completely useless if you break down as its too hard to pedal, yet if its geared for a slower speed you can actually get the bike home then if something dies on you. I still 'clown pedal' on the roads at most speeds, but only so I look like a bike and dont attract police attention.

Single speed works fine. We build cruisers that are single speed and people really dont mind if the bike has gears or not. I would say gears are more for riders who like to pedal to get a workout.

lester12483 said:

Single speed works fine. We build cruisers that are single speed and people really dont mind if the bike has gears or not. I would say gears are more for riders who like to pedal to get a workout.

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Most casual riders have no idea how to use gears and probably why more people don't ride bikes. It spoils an otherwise pleasant experience with un necessary tech, add cheap crappy mechanisms and the bike ends up rotting away in the shed.

Optimal single speed ratios in 26" MTB wheels to start with:
42t-20t, 40t-19t, 38t-18t, 36t-17t, 34t-16t, 32t-15t, 30t-14t, 28t-13t, 26t-12t and so on... Lowest freewheel value recommended is 15t. Lower than this and efficiency will get lower.
This can be optimized for higher speed or better starting torque by going one or two values up or down on both crank and freewheel (trial and error).

Here is a list of calculated "magic single speed ratio" speeds in a 26" MTB wheel. Speeds are:
11km/h@40rpm_cadence<------This is a too low cadence
16Km/h@60rpm_cadence<-------Low cadence
21km/h@80rpm_cadence<-------This is a comfortable cadence
24km/h@90rpm_cadence <------This is a comfortable cadence
27km/h@100rpm_cadence<------High cadence
32km/h@120rpm_cadence<------This is a too high cadence
130 rpm and over<------This is an insane cadence, but some professional cyclists are going past this.

The formula for other wheel sizes is
(crank/freewheel)*wheel_in_inches=55. 55 is the constant of 140cm of travel per revolution (55inch per revolution).

Here is the Sheldon Browns calculator for ratio vs km/h vs cadence: http://sheldonbrown.com/gears/

A good start is choosing the 34t-16t. This gives one the opportunity of going one value lower down to 15t on the freewheel side, without loosing the efficiency. If not enough, it is possible to increase the crank value. It's also harder to loose the chain on rough terrain at freewheel values of 16t or higher. The thread on our hubs is english, sometimes called ISO thread. Metric BMX thread is NOT compatible, so the smallest freewheel you can buy is 15t.

Thank you Fellow. Very useful information.

To pedal effectively at 30 mph, you will need similar gearing to those who do that all day. Racers use 52-11 a lot or even higher. But yes, really small cog in the back causes some various problems.

And yes, you'd be screwed when you break down.

One good way to go is to leave your gears in back, but switch to a friction shifter that takes up less handlebar real estate than most shifters. Then if you do need a low gear to limp home, you got it. Put the biggest gear you can fit on the crank. My cargo bike is 56-14. It can be pedaled to 35 mph, but by then you are just throwing off your balance clown pedaling. It pedals smooth and effective to about 25 mph, and mostly I ride it 20-25 mph.

Or, just gear 48-16 , 48-18 whatever. screw pedaling once going 30 mph or more. Seriously, at 30 mph you are using about 1000w. by then your 100w of pedaling is nothing but 10%. Why bother?

Some of what dogman and and fellow are saying does not make much sense.

As far as I know you can't get a 15tooth freewheel to fit onto a 700c or 26 inch wheel only BMX which is a smaller thread.
If you can please let me know where I can get one.

If you need to "limp " home you can easily do so with a big gear since going slow does not use much energy. It might be tough going on a hill but do able. You can also get off and walk up a hill. A good Ebike should be a good bike first. If you can't do 20km on it without the motor leave it at home and take the bus.

100 watts can be the difference between 32 and 35 kph which is not insignificant when you are being left behind.
It can also mean another 5km to 10 km out of your battery.

The gear ratio will have a lot to do with your fitness level, if not sure ride around on a regular multi gear bike to find what is comfortable, you will find you will settle on a 2 or 3 gears most of the time. The motor fills the gaps for the lower gears making them obsolete. If you like going fast choose the bigger gear and work a bit harder. If you want to cruise choose the lower gear.

The nice thing about single speed is the simplicity. No annoying missed gears and indexing problems. Less clutter on the bars. No compatibility issues with group sets. You can use just about any chain you have.
I often beat all the multi geared bikes off the line because they are fiddling with gears and cleats instead of pedalling mean while I am way ahead. The down side is they pass me later because I run out of gears because I only have the one. It is not ideal for riding in a group. It is great for commuting since you can focus on traffic instead of gears. The bike is also a bit lighter, up to a kilo or more depending on your set up and a little more efficient, only a few watts, since the chain is not going throug an s bend. Not significant on a 10km ride but glad of it after 60km.

As you get fitter you can up the gearing, some wheels have a flip flop hub, usually one side is for a fixed gear but you can also fit a second freewheel with a different size gear so you can flip the wheel if you want to change the ratio.

I've been riding single gears for Over a year now and it's a lot of fun.

I find 46T front and 11T rear not enough for pedalling at 30mph on a 29er/700c ( i like to pedal as well ). I don't touch the front derailleur but run through my 9 speed rear a lot. During my commute I punch it off the line pretty hard - using MTB pedals and heaps of gears to cycle through. My gear is maintained pretty well so it shifts like silk.

My next upgrade is a 48T front.

edit. 46/11t is ok for 30mph, but its at the edge where you want higher gearing.

Sounds like you like a very high cadence Raged. Many of us can't do that anymore, for one reason or another. Before my health failed, I liked a high cadence too, but for 27 mph I liked 48-11, or 56-14 which I could pedal to 30 mph.

Limping home in a high gear never worked for me. My house is 1000' higher than town. So in my case, walking pushing the bike for about 6 miles up a hill is kinda harsh. So I keep the bike in high gear, but preserve the ability to shift down in an emergency by having a friction shifter that takes up less handle bar space.

It's still no fun to limp home, without battery, the cargo bike weighs 130 pounds.

Definitely though, if the motor works you tend to ride in one gear for weeks or even years at a time, the highest gear you have.

Modbikemax said:

Some of what dogman and fellow are saying does not make much sense. As far as I know you can't get a 15tooth freewheel to fit onto a 700c or 26 inch wheel only BMX which is a smaller thread. If you can please let me know where I can get one.

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You are right! It seems that 15T english threads are gone for ever, could not find them on my quick search. That makes 16t the lowest one (for the english=ISO threads).

The freewheel type depends of course on the hub. My Q100H uses english=ISO thread. Other hubs may use other standards. Ratio of 55 inch per revolution, is almost de-facto standard (public acceptance) as a starting point and very suitable for a limp home backup system (it's flat but windy here in Sweden).

It's not suitable for fast speeds, and it does not suit everyone. 16t can be bought on aliexpress, ebay and such.

True, the original poster is talking about a lighter bike than mine, and perhaps doesn't have to limp up 1000 vertical feet to home like I might.

48-16 wouldn't be so bad to pedal home on, on the flat. But if he really gears to pedal 30 mph, then he'd be looking at 60-16 or something, and that would be less fun to limp home in.

SS geared to ride 20-25 mph is one thing, geared to ride 30 mph would be another.

Thanks for all the advice. I think in the end I will leave all the gears and simply install a larger chain ring on the front so I have the ability to pedal with the motor. Right now in the highest gear my feet are whipping around and going no where.

All my bikes are single speed, and none of them are geared to pedal as high as 30 mph right now. I find more useful to gear low, to pedal the heavy bike when unpowered. To pedal at high speed I like to have 2 speed, best with a planetary crank. A Schlumpf HS drive gears up 250 %. The advantages are: a very wide difference between the 2 speeds that permits both very low and very high ratios, a very compact and robust drive train, the ability to shift at rest, and shifting gears that are not exposed to elements. The downsides are weight and price, and when you have a performance bike it is just about useless to add pedal power at high speed (feeling like a fly pushing a horse :wink: ).

On the rear, a quality single freewheel that is not too small will last much longer. I like to use a 18T, a White Industies Trials ENO with a Shimano Alfine chain tensioner makes a rear drive that is almost indestructable.

If you are riding an ebike that will do 30mph (48kph) on the motor why are you bothering with pedals? It's probably really heavy and you are just kidding yourself about pedaling it anywhere, hence all the suggestions about low gearing.
What you really need is a license plate and a motorcycle licence and dump the pedals and carry a reserve battery to get you home. :lol:

Pedals are needed for legal purposes and as a last resort in case the bike stops working and your stranded.

Walk of Shame or Pedal of Pain. For me both ache, I prefer to Call and Bawl. You choose. :lol:

The only chance of having it all is to pay a lot (in both money and added mass) . Schlumpf high speed drive (chainring 34t in the front, 16t freewheel) in a 26" MTB wheel gives:

1st speed 24km/h at 90rpm cadence
2st speed 60km/h at 90rpm cadence
2st speed 80km/h+ at the insane cadence.

This should cover most of the situations one e-biker can face.

lester12483 said:

Pedals are needed for legal purposes and as a last resort in case the bike stops working and your stranded.

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I guess we are looking at this from opposite ends of the spectrum.
My bikes are electric assisted bicycles
Yours are pedal assisted motorcycles.
If I were to build a heavy ebike with 1kw motor capable of 30mph I would be gearing the pedals low or retaining the gear cluster. Unfortunately get caught riding it on the road in Australia is just going to lead to it being confiscated by the Police and heavy fines.

Mad has it right, why bother to pedal at higher speeds? Above 25 mph, you really are into a speed where your pedaling extends range 10% or less. Gearing for 20-25 mph is still pedalable if your battery conks out, or you fry your halls. At 20-25mph your pedaling can extend range enough to be worth it.

I'd say gear a SS for about 18-20 mph with a reasonable cadence, and forget pedaling when going faster than 25 mph. 48-16 close enough for that.

That's for a strong person. A sick guy like me needs a very low gear to limp home if the bike motor won't run.

If you are very strong, then go higher gear. If your ride has no hills, and you are young and under 150 pounds, hell yeah gear it bigger. Big as will fit on that frame that is. a road frame will easily take 52 up front, but MTB's often can take no bigger than 48t. But if you go big, bear in mind that all you can give pedaling won't extend range much at all if you are riding 25mph +.

We're 'sposed to pedal? I live on the flats and use 46t front with 11tx34t 7speed. Bike came with 14x34 i found i use the bottom 3. I use 11t most rides nearly exclusively. Unless there's heavy traffic an I need to obey stops. Now reconsidering a hub drive again if I can get a drive comparable to the 11t. I am going to configure one bike as a 16t single.

I fitted a Shimano Nexus 3 speed over the weekend and I must say I am pretty pleased with it.
The low gear is good for up to 28kph
2nd gear is one to one is good for 30-35kph
And top is for over 35kph.
The Nexus comes with a 19 tooth cog and the front is 53 teeth, wheels are 700x23.
I am not too fussed on the twist grip changer, it makes my wrist sit at an odd angle. I might do something else there.
I did need to take 2mm off the nuts on both sides, on the lathe, to get it to fit into the rear drop outs without too much bending of the rear stays. The nexus I got was for 130mm dropouts. I believe they do have one for 120mm which would have been better.
You see what I mean about single speed being easier!