Mid-Drive Motor & Mechanical 9 Speed Drivetrain - What Gear to Engage, & When?

[mail_e36]

Hi friends,

Please go easy on me, I just transitioned from a 500W hub motor to a 1,500W mid-drive Bafang Ultra (G510.1000 / M620), on a 85 pound a fat tire cruiser/hunting style ebike.

(For those curious, the bike I'm referring to goes by several names, including Bikonit Warthog (MD750 / HD750 / MD1000), Juggernaut Ultra Beast 2, Etek Hunter, Steamoon Spectre-X and other unbranded look-alikes from the Asia-based 'Leili' supplier.)

The manual transmission drivetrain on the bike is the SRAM X5 9-Speed 11x32 (11 tooth on ninth gear to 32 tooth on first gear) with the excellent trigger shifters.

I would like to understand, roughly, at what speeds (in MPH) I should be using which manual gears?

For example, most of us have initially made the rookie mistake of attempting to engage 9th gear from a complete stop, and experienced the chain slipping/cogs grinding on the smallest gear, which only has 11 teeth.

Since I am unfamiliar with which gears are best to use when, I feel like I'm often not running the motor effectively... even if it's not quite so bad as to be skipping/slipping on the cogs.

My understanding is that, unlike a gasoline motor which is most happy (and efficient) at low RPMs, a mid-drive Bafang motor is most happy at high RPMs. Is this an accurate assumption?

Thus, is the mid-drive Bafang motor most efficient when I'm spinning the cranks (in Pedal Assist) very fast going 25 MPH, in the mid mechanical gears (3-4-5-6), or when I'm spinning the cranks at a more moderate slower pace in the high mechanical gears (7-8-9), going to the same 25 MPH?

I realize these may be rudimentary questions, and that the PAS level (1-5) also plays a factor, but if anyone would be gracious enough to share their thoughts on what gears I should use when, my mechanical drivetrain would very much appreciate it!

Thank you in advance.

 

[fooferdoggie]

cadence (how fast you peddle) is the key to mid drives. You shift to keep your cadence as high as is comfortable . like for me thats around 80 rpms. so I shift to keep my legs spinning. I start off in the largest cog and work my way to the smaller ones as I accelerate. I change back and forth as terrain changes so I can keep my cadance close to the same. youn eed to anticipate hills and shift before you need to stop or slow down. also ease up on peddling while shifting.

 

[Neverlost99]

cadence (how fast you peddle) is the key to mid drives. You shift to keep your cadence as high as is comfortable . like for me thats around 80 rpms. so I shift to keep my legs spinning. I start off in the largest cog and work my way to the smaller ones as I accelerate. I change back and forth as terrain changes so I can keep my cadance close to the same. youn eed to anticipate hills and shift before you need to stop or slow down. also ease up on peddling while shifting.

Just like a normal bike

 

[fooferdoggie]

Just like a normal bike

exacltly. I shift more than most people because of years of riding a recumbent where you had to shift more.

 

[JRA]

I have found the Ultra to like a higher cadence and does not do well when lugged. Really hard to say at what mph what gear you should be in given terrain variations but in order to maintain your drivetrain it is best to anticipate your shifting so that you can let off on the power momentarily while doing so.

 

[rich c]

Have you ever driven a stick shift car? Shifting is basically the same.

 

[mail_e36]

All great responses.

I am wondering if anyone has come across any guides (generic, or otherwise) which may show MPH to Mechanical Gear mapping?

Thanks again in advance.

 

[fooferdoggie]

All great responses.

I am wondering if anyone has come across any guides (generic, or otherwise) which may show MPH to Mechanical Gear mapping?

Thanks again in advance.

you have to know your cadence and such https://www.bikecalc.com/gear_speed

 

[prestoOne]

Something to consider and you will know what I am talking about if you have ridden dirtbikes.
Rear cogs wear out and can do so fast.
Chains stretch and end up needing replaced so as not to wear out those new replacement cogs you just put on. Front Cogs wear out too.

What is the point of this post? Don't get into the habit of staying in the same rear gear. Vary your peddle assist level and the used gear for routine terrain.

 

[mail_e36]

Bumping my own thread... in a separate discussion someone mentioned the below website for calculating these types of things, it seems:

Ritzelrechner - Graphical Gear Calculator for Bicycles

The bicycle gear calculator displays graphically the gearing of derailleur gears and gear hubs. It can be used to compare different setups to find the optimal gearing for all kinds of bicycles.

www.gear-calculator.com

 

[retiredNH]

OP, what are you trying to do? Maximize motor power? Have a comfortable ride? Your link to a gear calculator makes little sense in context.
You've gotten some good advice here. Most of us experienced bike riders shift gears to maintain a comfortable pace, while cranking (peddling) in the range of 60-80 RPM. We vary gears and motor power levels depending on our personal goals - I bike for exercise, so I tend to use less power and lower gears than someone biking for speed, for example.
Experience has also taught most of us to downshift before coming to a stop, although those with throttles may use a different approach at the risk of poor control over their bikes.
As the calculator link says, it's for comparing different setups and to find optimal gearing, within the context of the rider's goals. It's not to tell you when or how to shift.

 

[tomjasz]

peddling

I can't resist. Do you sell ebikes?
Sorry, a very good post!

 

[tomjasz]

although those with throttles may use a different approach at the risk of poor control over their bikes.

EXCELLENT POINT!! They risk serious overheating. And motor damage.

 

[AHicks]

OP, what are you trying to do? Maximize motor power? Have a comfortable ride? Your link to a gear calculator makes little sense in context.
You've gotten some good advice here. Most of us experienced bike riders shift gears to maintain a comfortable pace, while cranking (peddling) in the range of 60-80 RPM. We vary gears and motor power levels depending on our personal goals - I bike for exercise, so I tend to use less power and lower gears than someone biking for speed, for example.
Experience has also taught most of us to downshift before coming to a stop, although those with throttles may use a different approach at the risk of poor control over their bikes.
As the calculator link says, it's for comparing different setups and to find optimal gearing, within the context of the rider's goals. It's not to tell you when or how to shift.

As a rider that only rarely uses my throttle once moving, I'm offended by the assumption that my decisions regarding favorite cadence, frequency of shifting, and selection of PAS level are any different than that of somebody riding a bike that's missing a throttle. Sure there are some wannabees that ride around without even pretending to peddle, but at least locally, I find them the exception, not the rule.... ESPECIALLY when it comes to having the bike under control at any given moment....

 

[tomjasz]

As a rider that only rarely uses my throttle once moving, I'm offended by the assumption that my decisions regarding favorite cadence, frequency of shifting, and selection of PAS level are any different than that of somebody riding a bike that's missing a throttle. Sure there are some wannabees that ride around without even pretending to peddle, but at least locally, I find them the exception, not the rule.... ESPECIALLY when it comes to having the bike under control at any given moment....

Screw the throttle criticism. I’m able to ride only because I have a throttle. I have days I can pedal but I have more days I can do my errands without spewing climate destroying fossil fuels.

 

[retiredNH]

As a rider that only rarely uses my throttle once moving, I'm offended by the assumption that my decisions regarding favorite cadence, frequency of shifting, and selection of PAS level are any different than that of somebody riding a bike that's missing a throttle. Sure there are some wannabees that ride around without even pretending to peddle, but at least locally, I find them the exception, not the rule.... ESPECIALLY when it comes to having the bike under control at any given moment....

Where you got the idea that I'm condemning all throttle users IDK. I'm just pointing out that some riders (of course, not you, who is above reproach) can overuse throttle when starting out leading to control issues, especially in heavy traffic situations.
Other posters here (see alaskan, for example) have made the case that throttle for them can be a very positive feature. Maybe if you spent time explaining to others how throttle helps you, rather than mis-interpreting and bashing other posters, you might actually add value to the discussion.

 

[AHicks]

Where you got the idea that I'm condemning all throttle users IDK. I'm just pointing out that some riders (of course, not you, who is above reproach) can overuse throttle when starting out leading to control issues, especially in heavy traffic situations.
Other posters here (see alaskan, for example) have made the case that throttle for them can be a very positive feature. Maybe if you spent time explaining to others how throttle helps you, rather than mis-interpreting and bashing other posters, you might actually add value to the discussion.

I've done that on countless occasions. It would seem that info goes in one ear and out the others of a given anti throttle mind set. For proof of that, read my preface to the condemnation of your assumption in the same sentence!! Here, I'll save you the trouble of looking for it -

"As a rider that only rarely uses my throttle once moving, I'm offended by the assumption that my decisions regarding favorite cadence, frequency of shifting, and selection of PAS level are any different than that of somebody riding a bike that's missing a throttle."

That same thought in mind, maybe you could more closely define those you are speaking of when mentioning anything to do with your well known often repeated anti throttle comments?

Or better yet, stop bringing those thoughts up completely and trust others to make up their own mind on the topic? Like @tomjasz mentions, it's none of your damn business if he (or anyone else for that matter) is using a throttle or not.

You don't want/need a throttle? I'm fine with that. It's your call, just like riding a throttle equipped bike is my call. You start making disparaging remarks about others using a throttle, even going so far to say that they might not even have their bike under control? Who the hell do you think you are? You think you are adding to any discussion with blather like that?

 

[retiredNH]

^ AHicks, did you forget to take your meds today?

The pot calls the kettle black. At least this board has an ignore feature! Very useful for those who over-contribute in a negative way, and have answers for everything....

 

[AHicks]

^ AHicks, did you forget to take your meds today?

The pot calls the kettle black. At least this board has an ignore feature! Very useful for those who over-contribute in a negative way, and have answers for everything....

No, thankfully I'm only on 1 and that's just to control a minor blood pressure issue. You do whatever you feel necessary, as I plan on doing the same....

 

[tomjasz]

^ AHicks, did you forget to take your meds today?

The pot calls the kettle black. At least this board has an ignore feature! Very useful for those who over-contribute in a negative way, and have answers for everything....

Jeez, really? Another one bike wonder. zero to expert in a single bound.