Anyone prefer a fixed single-speed ebike?

[Jeremy McCreary]

Jeremy, I'm sure you are happy with your current setup.

Yes, 40t has been the perfect compromise for my SL, old bird legs, stock 11-50t cassette, and local mix of hills and flats.

If you are ever in the need of improving your gearing low end, go for a 36T chainring (as I think @Rás Cnoic did on his Vado SL). That would set your granny gear at the true MTB 20 gear-inch. You could achieve 24.1 mph at the cadence of 90 pedalling on the flat or downhill.

I use a 36T chainring with the 11-46T cassette on my big Vado, as I need a really low end for some of my demanding e-races. It is 38T chainring with a 11-51T cassette for my Vado SL as I never plan exceeding 10% grade with my low power motor and weak legs!

If I ever decide to tackle the much longer 5-10% climbs found in the mountains east of I-15 (for example, around Palomar Mountain), I'd want to change both chainring and cassette. Haven't done the math yet, but a 38t chainring and 10-52t cassette might work for me.

 

[Stefan Mikes]

10-52t cassette

It is not as easy as you think, Jeremy. The 10-52T casette requires an xD driver for your freehub body, and there might be a compatibility problem (might). The 10-52T SRAM cassette is (as I can understand it) very expensive. You would only gain two teeth on the largest sprocket and one tooth for the smallest one. While going for a smaller chainring would give you the gearing you need for tough hills the easy way.

Regarding the high end of the gearing: do you actually pedal downhill at high speed?

 

[Jeremy McCreary]

It is not as easy as you think, Jeremy. The 10-52T casette requires an xD driver for your freehub body, and there might be a compatibility problem (might). The 10-52T SRAM cassette is (as I can understand it) very expensive. You would only gain two teeth on the largest sprocket and one tooth for the smallest one. While going for a smaller chainring would give you the gearing you need for tough hills the easy way.

Understood. Very familiar with all the calculations and real-world trade-offs involved in the gearing game.

Regarding the high end of the gearing: do you actually pedal downhill at high speed?

Yes. Wouldn't want top gear to go much below the 99 gear-inches I have now.

 

[Stefan Mikes]

Yes. Wouldn't want top gear to go much below the 99 gear-inches I have now.

For me, riding a descent is a good way to conserve the e-bike battery charge

 

[Jeremy McCreary]

For me, riding a descent is a good way to conserve the e-bike battery charge

Yeah, I take advantage of that sometimes. Pedaling downhill in OFF also conserves battery. Best not to have a fixed policy about such things.

 

[Stefan Mikes]

Pedaling downhill in OFF also conserves battery.

I have forgotten about that What speed do you achieve downhill?

 

[spokewrench]

I've had two single-speed e-bikes, and they worked fine. I switched off PAS and relied on a half twist throttle. You could say I used the throttle like a gear shift. On a push bike, you shift down on a hill to get more torque. On an e-bike, if I couldn't pedal hard enough to maintain speed on a hill, I'd add a little torque with the throttle.

Now I usually ride a 7-speed because I have the pleasure of tackling steeper hills without any throttle. I may end up breathing hard, which didn't happen with a single-speed.

 

[stompandgo]

I've never regretted having more gears. On a related topic, I also love manual transmissions in cars, but I haven't been able to buy one in decades because my wife only knows how to drive an automatic transmission and won't learn to shift gears. They are selling bikes with auto shifting these days: https://bike.shimano.com/en-NA/stories/article/our-automatic-shifting-technology.html

My Pinarello has a middle ground. It's not automatic by any means, but I can shift more than one gear at a time with a single button push if I want to. I love it.

 

[RunForTheHills]

My Pinarello has a middle ground. It's not automatic by any means, but I can shift more than one gear at a time with a single button push if I want to. I love it.

Reminds me of friction shifters. What's old is new again.

 

[stompandgo]

Right.

 

[Jeremy McCreary]

I have forgotten about that What speed do you achieve downhill?

Generally keep ground speed under 30 mph, braking if necessary. Legs spin out at ~105 rpm, which is 31 mph in the SL's top gear of 99 gear-inches.

Descents here are usually well under ½ mile, but 8-10% grades are pretty common. Coasted to 40 mph once. SL felt perfectly stable, but 30 mph is about as fast as I want to go.

 

[Underdog]

I took the bike out today and tried to simulate a fixed gear ride, I tried 5th gear and rode a 7 mile loop with several small hills. In torque sensor it was a joke and not very enjoyable, halfway through I switched to Cadence sensor and it was a bit better but still a very bad idea and not much fun. So that idea is out the window and back to what works, if it isn't broke, don't fix it. Thanks everyone who chimed in with logic and brought me to my senses.

 

[Stefan Mikes]

Haven't done the math yet, but a 38t chainring and 10-52t cassette might work for me.

I now fully understand your needs (these are reasonable!) So, it is SRAM GX Eagle XG-1275 (12s, 10-52T) and the xD driver. My brother has exactly this setup including the 38T chainring on his gravel bike, and that configuration is optimal. The price of the cassette is around US$230.

 

[6zfshdb]

Not for me.
If you ride at a constant speed on relatively level ground, it could work. Tough to vary the speed much without getting into an uncomfortable cadence though. A throttle might help, but if it's a true class 3, it likely doesn't have one.

I had a fixie as a kid and remember the joy I felt when I switched to a 3 speed.