Upgrading to a BBSHD on a BBS02 based e bike

BrianK

Well-Known Member
Hi folks,
I have a BBS02 based fat tire hunting bike that was originally geared “low and slow” for off-road riding and hauling game out of the woods. I made it more roadworthy by swapping out the 34t front sprocket first with a 46t then with a 52t sprocket. That worked to decrease the pedal cadence to one I could comfortably keep up with at road speeds, but with the 52t, it occasionally causes the BBS02 to overheat and temporarily cut out when riding up long hills. I’m worried about eventually burning it out.

I decided to upgrade the bike to a BBSHD motor, something I had planned to do eventually anyway. Luna says it’s direct swap - just remove the BBS02 motor, insert the BBSHD motor and an appropriate BBSHD front sprocket, and you’re set.

My BBSHD motor is coming next week. Based on an online gear calculator, I’ll be using the 46t front sprocket and replacing the 26t rear cog on the Sturmey Archer 3 speed IGH with a 20t cog.

Any input or recommendations from anyone who has ever made a similar swap? Or on assembling the BBSHD motor in place of the BBS02 in general? Things to watch out for, or to avoid?

Thanks!
49FC97CB-3BBC-4AD1-9746-5A6273533445.jpeg
 
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voidedwarranty

Well-Known Member
Hi folks,
I have a BBS02 based fat tire hunting bike that was originally geared “low and slow” for off-road riding and hauling game out of the woods. I made it more roadworthy by swapping out the 34t front sprocket first with a 46t then with a 52t sprocket. That worked to decrease the pedal cadence to one I could comfortably keep up with at road speeds, but with the 52t, it occasionally causes the BBS02 to overheat and temporarily cut out when riding up long hills. I’m worried about eventually burning it out.

I decided to upgrade the bike to a BBSHD motor, something I had planned to do eventually anyway. Luna says it’s direct swap - just remove the BBS02 motor, insert the BBSHD motor and an appropriate BBSHD front sprocket, and you’re set.

My BBSHD motor is coming next week. Based on an online gear calculator, I’ll be using the 46t front sprocket and replacing the 26t rear cog on the Sturmey Archer 3 speed IGH with a 20t cog.

Any input or recommendations from anyone who has ever made a similar swap? Or on assembling the BBSHD motor in place of the BBS02 in general? Things to watch out for, or to avoid?

Thanks!View attachment 110693
I did a sturmey archer SX-RK3 swap on my BBSHD fat tire bike. I have a 44t chain ring and a 22t rear sprocket. Also used a 20t rear sprocket when the swap was first completed. Both ratios worked just fine but I enjoyed the added grunt the 22t rear gave me. I can max out in 3rd gear pedalling at around 26mph but it feels like my legs are going to detach from my hips. 18-19mph in 3rd gives me a comfortable cadence. First gear pulls great up inclines.

Strongly recommend tuning the start currents all the way down to 1 or 2 for throttle and PAS. This got rid of any harsh clunking inside the hub. I keep my start currents low and ramp up the current quickly once I'm moving.

My bike came with the BBSHD so I can't comment on swapping the motor.
 

BrianK

Well-Known Member
Strongly recommend tuning the start currents all the way down to 1 or 2 for throttle and PAS. This got rid of any harsh clunking inside the hub. I keep my start currents low and ramp up the current quickly once I'm moving.
Can this only be done via the programming cable? This kit has the 750c display with Bluetooth but I’m not sure what parameters I can set with it.
 

greeno

Well-Known Member
Region
USA
City
San Diego
As far as swapping motors just make sure you get the same size bottom bracket size. To program it down you will need the usb cable and you can download the software online pretty easy. The BBS02 is maxed out at 25a and BBSHD will go to 30a but it's more robust and has more heat efficient mosfets in use for heat dissipation.
Used to have an older Surly Wednesday hardtail frame and ran 4" tires . Had a BBSHD motor and also had the SA 3 spd in the rear. I had a 20t backside and ran a 36t chainring and that worked well. Didn't hunt with it but 100% off-road and I can't remember it ever shutting down because of overheating.
Look up Mike for the FREY programming guide it's pretty good.
Good luck.
 
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tomjasz

Well-Known Member
Programming can now be done by way of the internet. Very easy and there are at least a dozen .el files as guides. It’s and clean and easy swap.

52T is a big potential stressor with the 01 and 02. They overheat being lugged.

I’m a 42T fan. The HD sells extremely well to pedicab operations. Tough motor when cared for.
 
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tomjasz

Well-Known Member

See this thread for web based version. OS X, Windoze, and Linux
According to developers. Penoff’s was the first English corrected version for Windoze. He worked on it again.
 

BrianK

Well-Known Member

See this thread for web based version. OS X, Windoze, and Linux
According to developers. Penoff’s was the first English corrected version for Windoze. He worked on it again.
Excellent, thanks. I only have an old MacBook Pro so I need that.
 

BrianK

Well-Known Member
Used to have an older Surly Wednesday hardtail frame and ran 4" tires . Had a BBSHD motor and also had the SA 3 spd in the rear. I had a 20t backside and ran a 36t chainring and that worked well. Didn't hunt with it but 100% off-road and I can't remember it ever shutting down because of overheating.
Look up Mike for the FREY programming guide it's pretty good.
Good luck.
Thanks. A fellow I know locally uses the Luna 1000w program on his builds. He stated, “Problem is going to that bbshd with the sturmey archer, it will destroy it with my program.”

The BBSHD I’m getting has the Luna 1000w tune. Do I need to be concerned regarding my SA 3sp?

My hunting days are long past. I found this bike leftover two seasons at an archery shop and they just wanted it out of their store, so I got it “new” for $1200. I bought it to covert it for road and rail trail riding.
 

tomjasz

Well-Known Member
Yes. I dislike Gearsensors but would definitely use one with the SA hub. Do a bit of Google time to find programming discussions with BBSHD and SA users. The are spread sheets with varied settings as well as .el files with settings. I’m pretty sure the spread sheets are posted here. PM and I’ll email what I have. Not sure I’ll get to it today but surely within 24 hours or so.
 

BrianK

Well-Known Member
Yes. I dislike Gearsensors but would definitely use one with the SA hub. Do a bit of Google time to find programming discussions with BBSHD and SA users. The are spread sheets with varied settings as well as .el files with settings. I’m pretty sure the spread sheets are posted here. PM and I’ll email what I have. Not sure I’ll get to it today but surely within 24 hours or so.
Ok thanks, PM sent.

I ride conservatively and mostly in third gear, except hills and starting out, and I’ve trained myself not to shift with the motor engaged. It doesn’t like to shift then anyhow, so it wasn’t difficult.
 

greeno

Well-Known Member
Region
USA
City
San Diego
Whats nice about the SA 3 spd is the parts are pretty cheap to rebuild or repair if you need to. I think the rear cogs are like 8 bucks or so. They are easy to open up and work on if you need to. I think Modern bike and universal cycles carry all the spare parts. I think the whole rear hub is like $150 that's for the SX-RK3 which has the rear dropout size of 170mm. Cant tell by your pic but you might need a chain tensioner if you don't already have one. If you don't PM me I think I have a spare on my shelf that I will never use, just pay for the shipping and it's yours as I am riding a full suspension 11spd and won't be going back. Have fun brother.
 

BrianK

Well-Known Member
Cant tell by your pic but you might need a chain tensioner if you don't already have one.
Thanks, but I think a chain tensioner is only needed with an IGH when the bike frame has vertical dropouts for the rear axle, and no way to adjust chain tension. Mine had an IGH from the factory so it has horizontal dropouts, and the chain is tensioned by moving the rear axle forward or backwards in the horizontal dropouts.

Fortunately everything I’ve been able to find regarding using the fat SA 3sp IGH with a BBSHD has been very positive, and they seem to hold up to the increased demands of this motor well.
 
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greeno

Well-Known Member
Region
USA
City
San Diego
Spoiler alert! My Surly had horizontal dropouts too but the torque of the motor would make the axle slip under load and move forward and then your chain will loose tension and it will skip. I know all about sliding the wheel forward, setting the chain and then sliding it back and then tighten I used to race track at the local Velodrome out here in SD way back when. Track bikes, horizontal dropouts, fixed gear, no brakes.
Anyways I had to always have my axle slid all the way forward so it couldn't get slack and be hard up against the notch so I had to use a tensioner to keep it all in place.
Another thing the SA axles have the flat notch in most of them and they are on the smaller side as far as fitting snug in the dropouts. I had to use 10/12mm spacers to make it fit better in the opening.
Another thing with horizontal Dropouts is you will probably need a torque bracket to keep the axle from shifting. I made some of those for my ride to.
Maybe yours will be fine the way it is but I'm just given you a heads up in case it isn't.
Good luck.
 

BrianK

Well-Known Member
Spoiler alert! My Surly had horizontal dropouts too but the torque of the motor would make the axle slip under load and move forward and then your chain will loose tension and it will skip. I know all about sliding the wheel forward, setting the chain and then sliding it back and then tighten I used to race track at the local Velodrome out here in SD way back when. Track bikes, horizontal dropouts, fixed gear, no brakes.
Anyways I had to always have my axle slid all the way forward so it couldn't get slack and be hard up against the notch so I had to use a tensioner to keep it all in place.
Another thing the SA axles have the flat notch in most of them and they are on the smaller side as far as fitting snug in the dropouts. I had to use 10/12mm spacers to make it fit better in the opening.
Another thing with horizontal Dropouts is you will probably need a torque bracket to keep the axle from shifting. I made some of those for my ride to.
Maybe yours will be fine the way it is but I'm just given you a heads up in case it isn't.
Good luck.
Excellent advice, thank you greeno for taking the time to explain! I’m so new to all this it’s embarrassing. I need to listen more and talk less.
 

BrianK

Well-Known Member
I’m a 42T fan. The HD sells extremely well to pedicab operations. Tough motor when cared for.
The BBSHD arrived yesterday. The previous owner ordered it January 1, 2021, with the gear sensor and a 42t Bafang bling type front sprocket. I thought he had the 46t front sprocket, so in anticipation I ordered in a 20t rear cog for the SA IGH.

I re ran the numbers at the online gear calculator, and it seems the 20t won’t be quite small enough now for my needs. (I can’t keep up higher pedal rpms due to prior strokes and residual left leg weakness. I can do short spurts at higher pedal cadence but I can’t maintain it for long.) I’m considering 18t or 16t rear cogs so I can ride at round speeds of 14-16mph comfortably but at lower pedal rpms (60?)

Any thoughts on rear cog size with 42t front sprocket?

This is the rear cog options at 60rpm:
0C842FD6-9C1A-4270-9111-2C30A949F916.jpeg

This is the rear cog options at 80rpm:
952FE163-737B-42C2-8192-5CAEB051B83B.jpeg
 
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voidedwarranty

Well-Known Member
What was your old chainring size? Were you always using the 20t rear cog? Do you use throttle? What would you want your max top speed to be if using throttle?
 

m@Robertson

Well-Known Member
Region
USA
You might try bikecalc.com. I used to use that same gear calculator but bikecalc.com gives you some much better displays and data like speed at cadence and cadence at speed, in increments you choose for both.

52T is mighty big for a BBSHD, although the rear cogs are going to have something to say about that. I have HDs running in 36T (purely offroad) 42T (best mixed use) and 52T (flat ground only, supplemented by a front motor in a 2wd combo). I have also used 46T and 48T. Your motor will be a LOT happier if you let it spin at high rpms. A 42T and an 11T should typically let you pedal reasonably up to almost 30 mph. However your SA will change how all this is calculated/figured out.

There is no single one best set of settings, but I strongly recommend you invest in the tools necessary to change the factory settings on your BBSHD. The blog entry above is the bible for this sort of thing. I added my own 0.02 on what I like to do on mine.

 

BrianK

Well-Known Member
What was your old chainring size? Were you always using the 20t rear cog? Do you use throttle? What would you want your max top speed to be if using throttle?
I only use the throttle to get the bike rolling (due to my weak left leg.). I normally ride in PAS 1 & 2, with PAS 3 very rarely for big hills, and prefer to ride around 13-16mph.

Original rear cog was 26t and front sprocket was 34t. I couldn’t possibly keep up with the pedal cadence at road speeds, so I replaced the front sprocket with a 46t, then a 52t. Even with that, I’m pedaling too fast at 16-18mph to keep it up for long.

If I am using unlimited throttle, top speed could be as high as it’s safe, but its not a big concern as I’m not going to use it much. But I’m coming off multiple Honda Sport Touring and Adventure type motorcycles so no matter how fast it goes, it’s not much in comparison.
 

BrianK

Well-Known Member
You might try bikecalc.com. I used to use that same gear calculator but bikecalc.com gives you some much better displays and data like speed at cadence and cadence at speed, in increments you choose for both.

52T is mighty big for a BBSHD, although the rear cogs are going to have something to say about that. I have HDs running in 36T (purely offroad) 42T (best mixed use) and 52T (flat ground only, supplemented by a front motor in a 2wd combo). I have also used 46T and 48T. Your motor will be a LOT happier if you let it spin at high rpms. A 42T and an 11T should typically let you pedal reasonably up to almost 30 mph. However your SA will change how all this is calculated/figured out.

There is no single one best set of settings, but I strongly recommend you invest in the tools necessary to change the factory settings on your BBSHD. The blog entry above is the bible for this sort of thing. I added my own 0.02 on what I like to do on mine.

Thanks, I’ll give that link a try.

This BBSHD has the 42t bling type Bafang front sprocket. I had the 52t on the BBS02. They can’t be swapped between the two.

I mostly ride country back roads and rail trails. This is a big heavy bike, and with the adjustable stem riser I have on it and swept back handlebars for a more upright position for back trouble, I really don’t enjoy riding it very fast. These steering changes have made it a little more twitchy at higher speeds so I generally keep it under 20mph.