Freewheel to cassette

[Jim_STEM]

Good morning Ebike enthusiasts!

I have a Blackbird. It has a 750w bafang with a freewheel. Does anyone know if it’s possible to convert the hub to accommodate a cassette? Here’s why: I went from a 42t to a 52t chainring to help with top speed ghost pedaling. I’d like to add a new 1st gear, like a 40 or 42 to allow for climbing. BTW, the 36t 1st gear was not a good climbing gear to begin with but now that I’ve added 10 more teeth and a substantial addition to my chainring radius, I know the 36t is going to perform less as a climber that it did before the swap.

Thx!

 

[m@Robertson]

You would have to change out the hub motor itself in the back wheel. What you would do is change out to a cassette version of the Bafang motor. Pull the motor core you have now and drop the cassette one in its place.

Here's the rub, though: Freewheel versions of the Bafang 750 typically have 175mm rear dropout spacing - thats the width between the dropouts. Cassette versions have 190mm spacing. You would have to be committed to trying to spread your frame's chainstays to make this fit, and doing 7.5mm on each side is one hell of a lot of spread. I have done 160mm to 175 (Bafang fat singlespeed to fat freewheel) but it was on a steel frame. Steel bends, but alloy snaps.

If you do decide to spread the frame, your dropouts will no longer be parallel to one another. Here again this can be lived with on steel (the axle bolts sort of just deal with the issue). And when you spread chainstays, you need to be very careful they spread evenly, each the same amount rather than just one of them moving. Your spreading tool needs to account for this (usually with a plumb line).

oh and also a cassette is typically at least a 9 speed. You will want to use a 9s cassette (look at the Microshift steel one which is only $39 and has a 46T big cog in back). Blackbird's spec sheet says its a 9-speed which is mighty unusual. Is it really? We're talking about a 9s freewheel here? That doesn't sound right. Are you sure you don't already have a cassette? I didn't think it was possible to do a 9s freewheel without at least two extension cogs out past the freewheel body and I thought those were a thing of the distant past.

Its not a trivial project.

 

[m@Robertson]

ugh. Go to the Blackbird page at Area13. Look at the motor picture. Its already a cassette. The closeup pic of the motor is a 9s. You just need to remove the existing cassette and put another one on. And lengthen the chain (!) The derailleur cage should be all the way back, facing rearward, as far as you can get it and still maintain slight tension on the chain. A common screwup is to use a chain that is too short and ends up pulling the derailleur cage forward on the bigger cogs.

How To: Installing A New Chain For Your 1X Drivetrain (How to do it Right!)

For this MTB How To, we are going to be focusing on setting the correct chain length when installing a new mountain bike chain on a 1X drivetrain. Making sur...

www.worldwidecyclery.com

 

[Jim_STEM]

You would have to change out the hub motor itself in the back wheel. What you would do is change out to a cassette version of the Bafang motor. Pull the motor core you have now and drop the cassette one in its place.

Here's the rub, though: Freewheel versions of the Bafang 750 typically have 175mm rear dropout spacing - thats the width between the dropouts. Cassette versions have 190mm spacing. You would have to be committed to trying to spread your frame's chainstays to make this fit, and doing 7.5mm on each side is one hell of a lot of spread. I have done 160mm to 175 (Bafang fat singlespeed to fat freewheel) but it was on a steel frame. Steel bends, but alloy snaps.

If you do decide to spread the frame, your dropouts will no longer be parallel to one another. Here again this can be lived with on steel (the axle bolts sort of just deal with the issue). And when you spread chainstays, you need to be very careful they spread evenly, each the same amount rather than just one of them moving. Your spreading tool needs to account for this (usually with a plumb line).

oh and also a cassette is typically at least a 9 speed. You will want to use a 9s cassette (look at the Microshift steel one which is only $39 and has a 46T big cog in back). Blackbird's spec sheet says its a 9-speed which is mighty unusual. Is it really? We're talking about a 9s freewheel here? That doesn't sound right. Are you sure you don't already have a cassette? I didn't think it was possible to do a 9s freewheel without at least two extension cogs out past the freewheel body and I thought those were a thing of the distant past.

Its not a trivial project.

First things first,
Thank you for a quick and detailed response. Secondly, you are a bada$$. I think you’ve forgotten more than I will ever learn.

All signs point to a freewheel. Pics, vids, literature, product specs. I have verified it is a 9 spd by looking at the freewheel and counting the gears as I pedal while someone else shifts. Thank you for the recommendation. I’d rather remove the old freewheel and replace it with an 11/46 or 50 for that matter. The next time I remove the rear wheel, I’ll confirm it’s a freewheel.

Regards,
Jim

 

[Jim_STEM]

ugh. Go to the Blackbird page at Area13. Look at the motor picture. Its already a cassette. The closeup pic of the motor is a 9s. You just need to remove the existing cassette and put another one on. And lengthen the chain (!) The derailleur cage should be all the way back, facing rearward, as far as you can get it and still maintain slight tension on the chain. A common screwup is to use a chain that is too short and ends up pulling the derailleur cage forward on the bigger cogs.

How To: Installing A New Chain For Your 1X Drivetrain (How to do it Right!)

For this MTB How To, we are going to be focusing on setting the correct chain length when installing a new mountain bike chain on a 1X drivetrain. Making sur...

www.worldwidecyclery.com

Thanks. I see the picture but the specs and videos , terminal ology used by staff, etc all point to a freewheel. I think that’s a generic photo. If you are right, this will be great.

Thank you,
Jim

 

[rich c]

First things first,


I have verified it is a 9 spd by looking at the freewheel and counting the gears as I pedal while someone else shifts.

Regards,
Jim

Huh? I just look at the gear set and count them.

 

[Jim_STEM]

Huh? I just look at the gear set and count them.

Forgive my ignorance.

 

[rich c]

Ease up there Jim_Stem. I tried to interject some humor. Like how many eBike riders does it take to count gears?

 

[Tom@WashDC]

If the motor is a screw-on freewheel and not a cassette motor, Bafang does make an outer motor cover that has the Cassette mount for some of their IGH motors. You may be able to source it out somewhere.

https://www.aliexpress.com/i/3256801385085798.html?gatewayAdapt=4itemAdapt

bafang fatbike rm g06 motor/sondors cover with cassette base for replacement-Greenbikekit.com BBS, ebike batteries, Bafang M620, Bafang M600, Bafang M500, Bafang M510, KT controller with display-GreenBikeKit.com

Bafang fatbike rm g06 motor cover for replacement. The cassette base is included.

www.greenbikekit.com

 

[Jim_STEM]

If the motor is a screw-on freewheel and not a cassette motor, Bafang does make an outer motor cover that has the Cassette mount for some of their IGH motors. You may be able to source it out somewhere.

https://www.aliexpress.com/i/3256801385085798.html?gatewayAdapt=4itemAdapt

bafang fatbike rm g06 motor/sondors cover with cassette base for replacement-Greenbikekit.com BBS, ebike batteries, Bafang M620, Bafang M600, Bafang M500, Bafang M510, KT controller with display-GreenBikeKit.com

Bafang fatbike rm g06 motor cover for replacement. The cassette base is included.

www.greenbikekit.com

View attachment 134549

Thank you! So helpful.

 

[Jim_STEM]

Gents,

I ended up calling Area 13 and I did speak to Kyle. He verified that it is a cassette! M@Robertson, You were right! You know more about my bike than I do. Much respect! In the event that anyone else wants to change their Black bird, here is some quick community info: The max 1st gear is 36t. 36t is already on there so if I want to change to a 11/42t or an 11/46t, I would have to change the derailleur to accommodate the taller 1st gear. Because I have a 52t, 50t and 42t chainrings, I think the less invasive thing to remedy my climbing issue is to revert back to the 42t chainring when I plan on finding hills.

A big shout out to you guys for the work and assistance as well as the humor from rich c. After counting everyone up, the answer is 4. It takes four ebike riders to count gears. Lol. Enjoy your day.

Jim

 

[m@Robertson]

If the motor is a screw-on freewheel and not a cassette motor, Bafang does make an outer motor cover that has the Cassette mount for some of their IGH motors. You may be able to source it out somewhere.

Yes but the axle will still be for 175mm rear spacing, so that translates to about 7.5mm shorter on each side, best case. About a bolt's length. Not going to be so easy to get around that. But worse, the 750 has an oversized power plug that can oly be threaded thru as a bare wire. He would have to cut off each of those very thin motor wires and individually solder them back on. Not a novice job unfortunately.

Thanks. I see the picture but the specs and videos , terminal ology used by staff, etc all point to a freewheel. I think that’s a generic photo. If you are right, this will be great.

Well there's no way to not tell you this and avoid being a name dropper... I know Kyle Chittock who is the owner over at Area 13 (formerly known as Bolton Ebikes). I just asked him and yes, the web site is correct. The Blackbird has a cassette motor. All you have to do is change the cassette and lengthen the chain. That bike already has a SRAM drivetrain with a long cage so that puts you two steps up over most ebikes out there on the market in terms of quality components.

EDIT: HAH! I think you posted right when I started typing this.

 

[Tom@WashDC]

All's well that ends well!

 

[Jim_STEM]

Yes but the axle will still be for 175mm rear spacing, so that translates to about 7.5mm shorter on each side, best case. About a bolt's length. Not going to be so easy to get around that. But worse, the 750 has an oversized power plug that can oly be threaded thru as a bare wire. He would have to cut off each of those very thin motor wires and individually solder them back on. Not a novice job unfortunately.


Well there's no way to not tell you this and avoid being a name dropper... I know Kyle Chittock who is the owner over at Area 13 (formerly known as Bolton Ebikes). I just asked him and yes, the web site is correct. The Blackbird has a cassette motor. All you have to do is change the cassette and lengthen the chain. That bike already has a SRAM drivetrain with a long cage so that puts you two steps up over most ebikes out there on the market in terms of quality components.

EDIT: HAH! I think you posted right when I started typing this.

Not to correct you, sir. My apologies. The SRAM X5 will not accommodate a larger than 36t sprocket. I need a new derailleur. I’m thinking about Box Prime.

 

[m@Robertson]

Not to correct you, sir. My apologies. The SRAM X5 will not accommodate a larger than 36t sprocket. I need a new derailleur. I’m thinking about Box Prime.

I have an X5 on one of my bikes but its cluster maxes at 32T. Too bad as thats a great derailleur.

I use both Box and Microshift derailleurs. Box Two Extra Wide will do the trick for you. It has a very high level of fit and finish and shifts butter-smooth. I believe you have to match it with a Box shifter, and on my most recent build I chose a Box One because of its uber smooth cable and cable housing. I do have a Box Two with a Box Two shifter on another bike and there's nothing wrong with that setup, either. On that setup I use the Box 3 11-46 cluster. You don't want that cluster. Its largest two cogs are each pinned to the next smallest cog and to fit the freewheel, because of this, a spacer (which they include) is required. I called Box and talked to a product guy and asked whether a setup like this would work well with a powerful mid drive and he wasn't sure. No fault of theirs as they are building for analog MTBs and not ebikes. FYI this cluster is a Sunrace CS-M983 with a Box label on the lock ring.

I also have Microshift Advent drivetrain components and they are much cheaper than Box, and perfectly functional. The derailleur is not as premium-looking as the Box, with a slightly less refined powder coat finish vs. the top-drawer Box finish, but you are never going to notice that after you install it. The Box does shift slightly more smoothly, but that may be because I have the Box on a cargo bike with some chain alignment challenges. The Advent has a fantastic clutch on it. One thing that stands out big time is the Microshift Advent 11-46T all-steel cluster (the 11-42 uses alloy for its biggest cogs). It is head/shoulders over the Box/Sunrace since it is 1-piece steel (no spiders at all) and also pinned together. It is also about half the price. It works great with the Box derailleur/shifter or the Microshift Advent. Its absolutely the cluster you want in conjunction with a Bafang mid.

Note the pins and the 1-piece construction. $39 retail IIRC.

This is the Microshift cluster with the Box 2 X-Wide derailleur

...and the same cluster with the Microshift derailleur

Box seems to be frequently out of stock on their web site but you can find them on Jensen USA and to some degree on Amazon. Also the SRAM EX1 chain is 144 links, made specifically to be mid-drive strong and is on sale for $19. A far cry from the $40-$50 you'll pay for the typical mid drive chain. Its advertised for 8-speed but it is actually a 10s chain and will work fine for 8, 9 and 10.

Amazon.com : SRAM Chain Pc Ex1 Solidpin 144 Links Powerlock 8 Speed: Sports & Outdoors

Amazon.com : SRAM Chain Pc Ex1 Solidpin 144 Links Powerlock 8 Speed: Sports & Outdoors

amzn.to

 

[Jim_STEM]

Matt,

I can’t thank you enough for you insight and knowledge. Enjoy your day.

Jim

 

[Jim_STEM]

A big thank you! It's all done. I got in two test rides and one crash. So funny. I learned a lot. I had some difficulty, made some mistakes, used box tech support via email which was great. I sent them pics and they told me what was wrong with my install and how to fix it. I followed their instructions and everything works perfectly. I bought a KMC, 126 link, 9 speed E bike chain ($47) and some tools ($50) to change the cassette. All in all, I have about $355 invested in this drive train ($215) and tools. I ended up with a 52t chainring ($30) and an 11/50t cassette. 1st gear is 1:1.04, from 1:1.53 and 9th gear is 1:4.73 from 1:3.82, which is not dramatic on paper but when climbing a steep hill, it is much easier and I can get up the hill much further before falling or adding electric power. The top end on the other hand is very noticeable. I cannot run out of pedal resistance on flat ground and have reached a top speed of 33 mph on the flats.

Box three, Prime 9, X-wide, Multi-shift, 11/50t group set

Happy pedaling,
Jim

 

[manman]

Hi, could anybody tell me if I take the motor out of a Bafang rear hub motor which is originally a Cassette version could I place just the motor into a freewheel casing both are 175mm drop-out.