Single speed - really low gear

[deejayen]

I mainly ride recumbents nowadays, but I used to ride fixies, and found that slightly heavier then 'normal' gears suited me for most rides. I settled on 86" for most audax rides (up to 600k around the Scottish Borders), although I also geared down to 65" on really hilly rides.

I have a Moulton TSR which is currently set up as a fixie, but I'm thinking about converting it to a single speed, mainly so that someone else can ride it.

The bike doesn't have provision for a rear brake, so I'm looking at a hub with coaster brake. If I go for a pure single speed (as opposed to a 2-speed Duomatic etc) my best option seems to be the Shimano CB-E110 hub. The instructions say the smallest sprocket which can be used is 15 tooth, but it comes with a 19 tooth. The bike has a 48 tooth chainring. With 20" wheels, this gives a gear of around 47". I'm not sure if this would be too low, or if it might suit the bike just fine. I obviously wouldn't be racing - I'd probably use it for general sightseeing on nice days, or for some light touring.

If I fitted a 15-tooth sprocket, this would give around 59".

Of course, I could buy a bigger chainring, but the whole project would get quite expensive for something I might not use too much. Also, chainrings start to get as large as the bike's wheels! For example, 70x19 = 68". 70x15 = 87".

So, I'm just wondering how usable/infuriating a 47" gear might be!

 

[Teamfixed]

Blimey.... 86" on an Audax?
Blimey.... 46" you'll not see your legs
I've always used about 68" (48x19)

 

[DCLane]

We run single speeds for track/grasstrack/road. In terms of gearing the grasstrack run 84" and 86" with the road single speed running 78" plus a 72" option for Medium Gear time trials.

Anything below 72" I'd find really spinny.

 

[deejayen]

Thanks! I feared as much, but thought that as I'd be freewheeling rather than spinning on the descents, 47" might just work. However, it's probably a bit too light for the flats, especially with a tailwind! I suppose I could do that thing you see BMXers doing - spinning like crazy for a few yards, then freewheeling while crouching down where the saddle should be.

 

[ColinJ]

We run single speeds for track/grasstrack/road. In terms of gearing the grasstrack run 84" and 86" with the road single speed running 78" plus a 72" option for Medium Gear time trials.

Anything below 72" I'd find really spinny.

I have 52/19 on my singlespeed, a compromise gear to allow me to get up moderate hills, but not spin out on the flat. I make that about 72".

I agree that a lower gear would be too 'spinny'. I'd prefer more like 78" - 80" but I struggle on 10% slopes as it is so I'm sticking with 72".

 

[Chris S]

A 47 inch gear is about the same as the bottom gear on a Sturmey Archer 3-speed with 46/19 gearing. It will get you up most urban hills but you will struggle to get in to the low teens on the flat.

 

[fossyant]

74" for commuting. Found that fine.

 

[tyred]

You could go for a Sturmey 3 speed as they are available with drum and back pedal brakes.

 

[deejayen]

Thanks for that.

However, I'd prefer something which didn't need a gear cable, as the bike doesn't have cable guides.

I'd also like to retain the simplicity of splitting its frame without having to split a gear cable.

Perhaps an old Duomatic might be a wiser option than the Shimano CB-E110, as second gear would be an 'overdrive'.

I know Sturmey Archer have the S2C, but I remember reading of reliability issues with these, so I'd probably keep an eye open for an original Fichtel & Sachs.

I'll need to weigh up my options again...

The current hub is a flip-flop, so I think I could buy a screw-on freewheel to see what the bike is like as a single speed. However, I obviously wouldn't have a rear brake, so not an option for long-term use.

 

[spark303]

What about a Velosteel single speed coaster? AIUI they are copies of old Sachs models and I’ve heard positive things about them. They use Sturmey style sprockets so you could go down to 13t.

Regarding the reliability of the Sturmey S2C, I ran one on my TSR2 for a couple of years commuting and it never skipped a beat. I only changed it when I switched to riding fixed.

 

[deejayen]

What about a Velosteel single speed coaster? AIUI they are copies of old Sachs models and I’ve heard positive things about them. They use Sturmey style sprockets so you could go down to 13t.

Regarding the reliability of the Sturmey S2C, I ran one on my TSR2 for a couple of years commuting and it never skipped a beat. I only changed it when I switched to riding fixed.

Thanks very much.

I had come across the Velosteel, but had ruled it out for some reason. I think I thought it was a bit too wide for the TSR 2, plus it might have been out of stock.

It's helpful to know the S2C has been reliable for you. I don't suppose you still have the wheel and are thinking about selling it....!?

 

[spark303]

I don't suppose you still have the wheel and are thinking about selling it....!?

Sadly not 🙂

Practical Cycles are selling the Velosteel hub through their eBay shop in 120mm width which IIRC should fit the TSR2.

 

[mickle]

You may still be able to find a SRAM 2spd Automatix if you trawl the big German and Dutch on-line retailers.