bike gearing: What makes sense?

[gwsaltspring]

I'm trying to get a handle on the gearing that would make the most sense on an e-bike conversion. Particularly if I want to at least give the impression of pedaling while using the motor.

Since I typically seem to be either going up a hill or down one, a large front ring seems to make sense so that I could make a show of pedaling down hill or on the flat with a 24" 72V 5304 set up.

In the event that my batteries pack it in, a granny gear on the rear also makes sense to me so I can pedal home.

Has anyone paid their gearing much attention? What are you running?

Greg

 

[xyster]

Three was the most gears that would fit on the rear without requiring I try to spread a 135mm aluminum dropout wider. There were already three up front. So nine total.

I haven't counted teeth, but pedaling at the highest comfortable tempo, I go 9 mph in the lowest gear, and 26 mph in the highest. If I'm riding faster than 26mph, I keep pedaling anyway, acting like I've got a super-high gear by pedaling slowly.

The nine gears span the range nicely. A higher gear would be OK, but due to aerodynamics at speeds above 25mph, actively pedaling probably hurts more than it helps anyway.

Stock, my Currie has seven gears on the rear, and just one on the crank. The span at the same pedaling tempo is 12mph to 26 mph. I like the 3 front/3 rear much better.

 

[gwsaltspring]

Thanks X for you comments.

Do you do much in the way of hills in your neck of the woods?

As I think about this more, pedaling down hill isn't something I do all that often so probably isn't worth bothering with. As you point out, above 26mph pedaling may be counterproductive.

I need to go for a ride, as I have noticed that even my 406 with 36V (especially with a new charge), doesn't need to be in my lowest gear to climb
some of the hills around here, so I would probably be will served by doing some counting of teeth.

Cool, something more to think about

Greg

 

[xyster]

Do you do much in the way of hills in your neck of the woods?

Oh yes, lots of hills. Pedaling doesn't help much on the steeper, ~15% grades anyways because it takes every bit of my ~2500 watts to climb at a decent 15-20mph clip above the point where the motor bogs. For me, pedaling can only add maybe 10% power over any significant distance. Pedaling obviously becomes more important at lower power. My little 250w Currie, run at 1000 watts, will overheat and die in short order if I don't pedal like heck up the steeper hills -- fear of walking the bike home, and of having to buy a new motor, provides good impetus to pedal I suppose.

 

[CGameProgrammer]

I always keep the chain on the smallest (fastest) rear sprocket, and only change the front gear. So technically on a 21-speed that means I use only gears 7, 14, or 21. Works well. I did have some cases where the fuse would blow and I'd have to pedal home for around a mile, and that was annoying with a steel bike, 30-lb motor, and 36 lbs of batteries. I put it in gear 7, stood up, and pedaled home like that.

 

[Mathurin]

Something like 20-100 gear inches should cover just about every bike's needs. Also, very few bikes come with gearing greater then 52-11... Now if you just barely touch the pedals, you'll likely be more comfortable at a very slow ~60 rpm or so. If you contribute for the ride, then you can expect to be spinning at ~90. When you'll want to accelerate or push fairly hard for a few mins, say going uphill, then you'd likely be more comfortable at ~120 or so. As usual, your mileage may vary.


Bike de merde was a single speed because dérailleurs don't enjoy winter. It was geared to allow fairly comfortable pedaling for 85-90% of usage, while allowing to go faster then the motor and still leaving adequate power to climb hills. It was not intended to be used without the motor since I've already got several bikes designed for that...