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Author Topic: Redshift SM Gearing  (Read 354 times)

Ireek

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Redshift SM Gearing
« on: September 29, 2017, 03:05:15 AM »

Okay, I'm new to electric bikes, but I have a question.  What affects does gearing have on the Redshift SM, I know on normal ICE bikes, lower gearing helps acceleration but hurts top speed, I'm considering trying a larger front or smaller rear sprocket to help on top speed or at least, higher cruising speeds, I can afford to lose a little bottom end power, does gearing changes affect electric bikes differently than ICE bikes?  I will say that the dealer where I got my SM said that he would gear the SM higher (for higher speeds, lower rpms) for longer range and less wear on the motor ultimately giving the bike more longevity, again, what he recommended, I am not questioning him but would like to hear your thoughts.
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rayivers

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Re: Redshift SM Gearing
« Reply #1 on: September 29, 2017, 08:26:04 PM »

For a given throttle setting, higher gearing (more top speed) results in increased loading on the front sprocket.

If I had an Alta - either SM or MX - I'd ride it stock for a while to determine what the lowest max top speed I could live with for my particular usage was, then gear it for that speed at slightly below motor redline.

On my 'MX' dirt bike, gearing down at the front sprocket for more RW torque has improved range slightly due to reduced WOT usage, and also significantly decreased front-sprocket noise.  Re longevity effects, the new reduced loading probably keeps wear and tear at the same level or maybe a little less, excepting the smaller front sprocket.

FWIW, on my ICE bikes sprocket choice has always been about fine-tuning acceleration for a given gearbox & set of track/trail conditions, but my electric setup has been purely a search for more low-speed torque.

Ray
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'14 Zero FX 5.7 (now 2.8, MX), '14 Zero FX 2.8 (street), '08 YZ250F, '82 RM250Z, '75 MR175, '74 CR125M (175cc)

Judaslefourbe

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Re: Redshift SM Gearing
« Reply #2 on: September 29, 2017, 09:54:13 PM »

One thing you need to consider with EVs is the motor efficiency also.
The Redshift sweet spot is between 6,000 and 8,000 RPM.
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rayivers

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Re: Redshift SM Gearing
« Reply #3 on: September 30, 2017, 12:43:05 AM »

Quote
One thing you need to consider with EVs is the motor efficiency also. The Redshift sweet spot is between 6,000 and 8,000 RPM.

Thanks very much for that info!  It would be outstanding to have torque & hp / thermal / efficiency / etc. curves for the Alta powertrain, so owners could make informed decisions about potential changes rather than just having to try-it-and-see.

Ray
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'14 Zero FX 5.7 (now 2.8, MX), '14 Zero FX 2.8 (street), '08 YZ250F, '82 RM250Z, '75 MR175, '74 CR125M (175cc)

Ireek

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Re: Redshift SM Gearing
« Reply #4 on: September 30, 2017, 05:08:04 AM »

One thing you need to consider with EVs is the motor efficiency also.
The Redshift sweet spot is between 6,000 and 8,000 RPM.

Thanks, this is what I was getting at, I've re-geared normal ICE bikes for years with road racing and such so I know the obvious but electric bikes are totally new to me, I'm not seeing a gain in longevity for the power unit but efficiency is a concern, if the battery has to work harder to accelerate with taller gearing, I'm guessing range will suffer, but maybe have an advantage at higher speeds with small throttle (cruising) openings so maybe it'll even out.  I feel that this bike accelerates so hard to 82mph that if I geared it slightly taller that the dip in efficiency would be negligible and might hit a higher top speed before the next corner, I'm running out of speed between corners is my biggest problem.  I think I might try a 2 tooth drop on the rear just to see what happens.  Thanks for info!! 
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Judaslefourbe

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Re: Redshift SM Gearing
« Reply #5 on: October 02, 2017, 09:52:35 PM »

Quote
It would be outstanding to have torque & hp / thermal / efficiency / etc. curves for the Alta powertrain, so owners could make informed decisions about potential changes rather than just having to try-it-and-see.
Ray

You're very welcome!
As for the graphs, they won't be available to the public for a while but I will make sure to share as soon as I get the green light.
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SuburbanDad

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Re: Redshift SM Gearing
« Reply #6 on: November 30, 2017, 12:47:17 AM »

I have a spare KTM wheelset that I have setup with tubliss that I am planning on switching over to on my MX.  I was thinking I would take the warp9 wheels and put some heidenau's or some other more street biased tires on them so I can commute on my redshift without killing my knobbies (it is dead easy to plate a redshift MX in Oregon btw).

I am having trouble finding the sprocket and counter sprocket tooth count for the SM online.  I presume the counter sprocket is the same between SM and MX, and just the rear sprocket is a bit smaller to reach the higher speeds.  Anybody have the SM sprocket tooth count info handy somewhere?
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Judaslefourbe

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Re: Redshift SM Gearing
« Reply #7 on: November 30, 2017, 10:55:58 PM »

SM: 15x50
MX: 12x53
EX: 13x53
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