7, 8, 9, 10 speed inefficiency

[Will]

When riding my 21 (7x3) speed Schwinn C-lyte 409 commuter, I mainly use 4th to start off, and progressively shift up to 6th to cruising (large front ring only). Occasionally, if I want a climbing gear, I'll stay in 4th and shift down to the mid-ring. I thought this was equal to staying on the big ring and downshifting 2 gears in the back because it was noticably easier to pedal. Recently I was directed to 'Sheldon Brown's' gear calculator page. I was surprised to learn that 4th gear mid-ring yielded 11.8mph just as 3rd gear big-ring yielded 11.8mph (@80 cadence) though the latter is noticeably more difficult to pedal. Equal speed yet different required effort. Apparent in this situation is how the chain drive lines up. The big ring lines up with 5/6th gears, the mid-ring with 4th gear, and the small ring with 3/2nd gears. If the big ring loses felt power transfer efficiency at 3rd gear, then what good is an 8 or 9 speed with only a single front ring? With a 7 speed, I would hope to never need to use 1st, and only occasionally use 7th gear (7speed) on down hills with minimal pedalling torque applied, but wouldn't an 8 speed, single front ring to 8 rear freewheel, be an ineffiecient addition of gearing? To me, seems crossing the chain, right side front ring with left side rear sproket, makes a BIG difference. What have others on this forum experienced with cross chain pedalling?

Oopps, my bad, I used standard gearing from a chart and my bike has unique gearing. So, 4th gear mid-ring = 11.6mph & 3rd gear big-ring = 13.1. Yet, excellent remarks made by forum members below are worth reading :?

 

[Ypedal]

Pedal ?...my god Y !?

 

[Link]

Pedal ?...my god Y !?

^ This. I STILL haven't gotten around to replacing the derailleur hangar so I can put the thing back on...

Also I didn't really notice that much difference between what should have been equal gear ratios before I converted to electric. Though I tended to use the fastest gears a lot, since my rides were relatively short.

 

[Ypedal]

ok, ok , on a more serious note.. resistance cause by chain deflection on a 50 to 80lbs ebike .. i can't imagine it being remotely significant, on a weight weenie rig.. maybe but even then as long as the derailleur cage is not tweaked and the chain is properly oiled.. good practice to run a gear that keeps the chain as straight as possible..

 

[cargo]

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[vanilla ice]

Build a front triple with all the rings the same size. Then you could tell.

 

[cargo]

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[Mathurin]

I've noticed power loss using small/small vs large/large for same ratios, also a good improvement for a given ratio from not using a derailleur. Haven't noticed power loss from cross chaining, only noise and poor shifting.

 

[Will]

OK, Ok, .. I took the time to count all rings/sprokets, there's some ratio differences. 13.1mph vs 11.6mph for the intro example. As well, the consensus here is that a single ring to 8 or 9 speed is somewhat doable/adequate. Anyhow, no one was baited by my wrong assumption of gearing. Conclusions; some e-bikers loathe to pedal; some e-bikers have either large legs or egos; e-bikers have a Zen with their machines and aren't to be misled, there's minimal gear efficiency loss with cross chaining, and wear/tear being the greater concern. Still, 7 speeds is ample for my use, 5 speed probably better if available somewhere. I'm pretty economical with my riding now, getting 20+ miles out of my 8.2ah 36V Li-mg battery. Think I'll kick up cruising to 7th gear which drops it to about 16 mile per charge. I love to pedal 8)

 

[Miles]

The most significant factor (after oiling the chain... ) seems to be the absolute size of the sprockets. Below 15t the efficiency starts to drop off significantly. A chain driven power-assist bike can benefit from the greater efficiency gained at increased torque transfer.

 

[vanilla ice]

5 speed probably better if available somewhere.

You can still get brand new falcon or pyramid 5 or 6 speed freewheels. Or its pretty common to find them on junk freebie bikes.

http://www.niagaracycle.com/product_info.php?products_id=10904

 

[cerewa]

On an e-bike that you pedal, yeah, 5 speeds should be enough.

E-bikes can keep much more consistent speeds with up-hills, compared to regular bikes. So there's generally no need for ultra-low gears.

 

[Will]

Therefore; Niagra is shipping me a nice Shimano 6 speed freewheel for a future build. Found a custom 5 speed for $40 but am hesistant to spend $$ just now. thanks V-ice

 

[Russell]

Basically any combination that produces the same ratio will require the same effort for the same speed. For example the following road bike triple combinations 52/26, 42/21, 30/15 all produce the same ratio though they will likely feel and sound differently due to the different chainline each combo produces. Your particular bottom bracket and crank type along with the rear wheel spacing and cassette all affect your chainline

I pay VERY close attention to gearing and chainline when I select components for my bikes. I think triple front rings produce far too much redundancy so I don’t use them. When I was younger I ran almost exclusively in a big 52 ring even with a 13-24 rear freewheel. I also ended up blowing up both knees so I changed to a spinning style and now don’t use anything higher than a 42 front ring. Of course age, I’m 50, and 30 extra pounds also means I can’t mash gears like I used to.

I built up one lightweight 1x9 flat-bar road bike with a 39 front chainring and 11-28 cassette. The ring is mounted on the normal inner position of a double road crankset with special short bolts. The 5th gear lines up perfectly with the front and I have no problems with 1st or 9th gears though they are at the extremes. This is the (non-motorized) bike on which I’m the fastest. It’s nice not having the front shifter; I just shift up and down with the rear shifter.

The bike which I have just motorized with a front 250W Bafang is more of a hybrid bike. On this bike I use a 52-42-30T triple road crank but have removed the big ring and replaced it with a bash guard. I mainly use the 42 ring just shifting up and down the cassette which is a 12-32 8 speed. I can of course tell when I have it in 4th and 5th which are in the sweet spot, chainline-wise. They are also the gears I spend the most time in, which is the way I set it up. I haven’t ridden the bike with the motor yet since I have a few details to finish…and we’re in the depths of winter here but I plan on riding it pretty much as I have before with the motor just assisting on hills and into headwinds.