Radrunner upgrade to TRUE 750w Bafang hub motor

Ccount

Member
I have come to learn that the RadRunner does not really have a 750w motor, but a smaller 500 which may peak at 750w. Several online videos showing this, and it becomes obvious when you compare them side by side. So I purchased a new Bafang 750 hub motor, and am mounting it on my RadRunner. I am unable to get the chain to line up with the single gear threaded to the hub motor (which I transferred from the old motor to the new one), and with the front gear and the tensioner, even if I use spacers on the gear. The new motor came with a 7 gear cassette, so I installed that on the motor, and am able to get the chain lined up perfectly on the 3rd gear on the cassette. It pedals OK, and looks a bit silly, but works just fine. Has anyone found a way to install a true 750 motor in a RadRunner using just a single gear? By the way, I have installed a suspension front end, handlebar risers, a pan style sprung seat, 35a controller, color display, and a handfull of other accessories. I also installed 3 2000w LED headlamps, wired directly to the battery, for amazing night rides on the beach or golf course!
 

Ccount

Member
I did not realize that! I did not recall seeing that option, but I will now shop for the freewheel! You are right, it took me a lot of time to get it all to work with the cassette! Thanks!

The 750 comes in freewheel and cassette version the freewheel version would have been a lot less work.
 

AHicks

Well-Known Member
I'm not sure one version or the other is going to work better (free wheel vs. cassette)? Are you doing this without the benefit of a derailleur? Do you plan on installing a derailleur?

With all the work/money you have invested in the rest of it, seems like something like that would be a good plan to me. But then again it's your project and I can't see what you are looking at....
 

BTfl

Active Member
I have come to learn that the RadRunner does not really have a 750w motor, but a smaller 500 which may peak at 750w. Several online videos showing this, and it becomes obvious when you compare them side by side. So I purchased a new Bafang 750 hub motor, and am mounting it on my RadRunner. I am unable to get the chain to line up with the single gear threaded to the hub motor (which I transferred from the old motor to the new one), and with the front gear and the tensioner, even if I use spacers on the gear. The new motor came with a 7 gear cassette, so I installed that on the motor, and am able to get the chain lined up perfectly on the 3rd gear on the cassette. It pedals OK, and looks a bit silly, but works just fine. Has anyone found a way to install a true 750 motor in a RadRunner using just a single gear? By the way, I have installed a suspension front end, handlebar risers, a pan style sprung seat, 35a controller, color display, and a handfull of other accessories. I also installed 3 2000w LED headlamps, wired directly to the battery, for amazing night rides on the beach or golf course!
If you could, please show a picture that sounds great, thanks
 

Ccount

Member
I really think a derailleur would be a bit silly since it is a hub drive, and there is rarely a need to actually pedal the bike without motor assist, and extra gears would be rarely used, if ever. The only reason I installed the cassette was because it was the only way I could get the chain to run in a straight line from the front gear, through the tensioner, and to a gear on the hub motor. Frankly, I would have preferred the single gear from the original motor, but simply could not get it to line up with the chain path. It appears as if the case end for the original motor end and the new one are different in size. (Obviously I did not replace the entire motor case, just the internal rotor and axle, and case end. Will take pics tonight...

I'm not sure one version or the other is going to work better (free wheel vs. cassette)? Are you doing this without the benefit of a derailleur? Do you plan on installing a derailleur?

With all the work/money you have invested in the rest of it, seems like something like that would be a good plan to me. But then again it's your project and I can't see what you are looking at....
 

AHicks

Well-Known Member
Most of us (not on Runners) are using several different gears with the PAS (pedal assist) and rear hub motors. I don't think it's "silly" at all. I do acknowledge you may be using yours differently at the moment, but given a fair chance/open mind on the topic, you might find a deraileur setup would work out well for you as well - if you ever felt like pedaling - to greatly extend your range for instance.

At the very least, it would give you a "chain guide" to hold it in any of the 7 gears you have available the way you are set up now.

Do as you like. Just trying to absorb what it is you're doing and maybe provide some ideas.....
 

Ccount

Member
Thanks for your input, and perspective! I suppose you are right, but I just have never considered the possibility of actually "peddling" my e-bike, as absurd as that sounds! Now you have me intrigued. You clearly are quite knowledgeable on the topic, so I am curious, how difficult/practical/expensive is it to retro-install a derailleur? I foresee the need for a cable, gear selector, and the physical derailleur. Can I use the 7 gear cassette I have installed? Must the cassette and the derailleur and the handlebar mounted gear selector (sorry, I don't know the proper nomenclature of the parts) be "matched sets"? Sorry, but this is all new to me, but I catch on quickly! Thanks! (Frankly, I have contemplated the possibility of having to pedal home, if I deplete the battery charge earlier than anticipated!)


Most of us (not on Runners) are using several different gears with the PAS (pedal assist) and rear hub motors. I don't think it's "silly" at all. I do acknowledge you may be using yours differently at the moment, but given a fair chance/open mind on the topic, you might find a derailleur setup would work out well for you as well - if you ever felt like pedaling - to greatly extend your range for instance.

At the very least, it would give you a "chain guide" to hold it in any of the 7 gears you have available the way you are set up now.

Do as you like. Just trying to absorb what it is you're doing and maybe provide some ideas.....
 

AHicks

Well-Known Member
This would be all new to me as well. I've never purchased a single speed, so everything I've been/worked on was already set up.

Regarding using the cassette, my bet on how well it will work is going to depend on chain to frame clearance on the one side, and chain to tire clearance on the other. You might be able to scope that out in advance to get some idea of how it will work?

Cable is almost a no brainer. People re-cable all the time to freshen their bikes, and maybe allow for taller handlebars or something.

As far as matching the control to the derailleur, again no experience, but my bet is that if you stayed with a single manf. they SHOULD cooperate with each other. Hard/daunting part of the project may be coming up with a functional place/way to mount the derailleur.... No clue what your frame looks like, or if it might be all set up to allow you to just bolt one on?
 

rezonatefreq

New Member
When I did this same upgrade to the bafang 750 on a single speed rad the new motor’s axle would not even fit back into the frame! Seems you did not have this problem? Where did you buy you motor and what is the O.L.D spacing? I had to modify the axle shoulder to fit. I did have the same problem with the chain alignment but that was corrected by carefully bending the chain tensioner/derailleur bracket. Really like the added power and speed of the motor, controller and display upgrade. There are a few gotchas but that’s what we get when we modify engineered equipment.
 

Ccount

Member
I purchased my new motor (and controller and display) from electro Bike World. I made the false assumption the cases were the same size,,and obviously they are not. I was able to wedge the motor into the space with a little persuasion, and it is snug! I too bent the bracket a bit to get my final chain alignment, and added a washer (spacer) or 2 between the mount and the tensioner mount arm, to get the chain perfectly lined up on one of the middle gears on the cassette. I was afraid to push the bending too much, as I imagine that is a difficult part to source if I broke it! It is all working perfectly now. I think I will wait a while on upgrading to a gear shift setup. See my next post for a summary of my modifications and some impressions!

When I did this same upgrade to the bafang 750 on a single speed rad the new motor’s axle would not even fit back into the frame! Seems you did not have this problem? Where did you buy you motor and what is the O.L.D spacing? I had to modify the axle shoulder to fit. I did have the same problem with the chain alignment but that was corrected by carefully bending the chain tensioner/derailleur bracket. Really like the added power and speed of the motor, controller and display upgrade. There are a few gotchas but that’s what we get when we modify engineered equipment.
 

rezonatefreq

New Member
I bought my motor from EBW also. I thought about widening the frame but chose to reduce the shaft shoulder on the free wheel side by 5/16 inch.

I believe the term for the gear set on the rad runner is free wheel hub not cassette. The mechanisms are different. Either a single speed or multi speed sprocket.

For the single speed the “derailleur” is called a chain tensioner vs a derailleur and they are many styles available.

How did your brake caliper fit after the upgrade. Mine needed to be adjusted but did seem to fit ok.

Want suspension forks and hydraulic brakes now. Maybe a spare battery once we buy another rad. Like the rad runner plus.
 

Ccount

Member
The brake disk slid right in, it was the other side which was a bit tight. Very minor adjustment needed to allow the wheel to spin freely. I love my suspension fork, and dollar for dollar was a good upgrade. I have no issue with my brakes being adequate, but I ride on flat land only here in East Central Florida, we really have no hills, and the brakes seem to do just fine. I thought about adding hybrid brakes, but so far have not gotten motivated to proceed. I also want to get another battery, but there is SO MUCH to learn about them, to figure what is and is not a good buy and what is and is not a good battery. The guy from EBW told me to ONLY buy a battery with Samsung, Panasonic or Sony cells, and never buy one with Chinese cells in it (even though he sells them). Apparently the Chinese cells are way over rated (amperage) and have low C ratings and other unfavorable features (most of those triangle batteries are Chinese). There is a big price difference for certain. At first I thought I wanted a 52v battery, but there are a lot of benefits in having 2 batteries with the same voltage (including parallel hook-up). But frankly, the bike is fast enough for me now, and I would prefer a little more life per charge than a little more speed. Heck, I may even take a shot at building my own battery pack. I think a 48v 20A battery would be ideal, but the cost is STEEP!

I bought my motor from EBW also. I thought about widening the frame but chose to reduce the shaft shoulder on the free wheel side by 5/16 inch.

I believe the term for the gear set on the rad runner is free wheel hub not cassette. The mechanisms are different. Either a single speed or multi speed sprocket.

For the single speed the “derailleur” is called a chain tensioner vs a derailleur and they are many styles available.

How did your brake caliper fit after the upgrade. Mine needed to be adjusted but did seem to fit ok.

Want suspension forks and hydraulic brakes now. Maybe a spare battery once we buy another rad. Like the rad runner plus.
 

AHicks

Well-Known Member
Would you be willing to do a little peddling, nothing terrific, to achieve much better range? What kind of range do you think you're getting now, on average?
 

Ccount

Member
I actually pedal a lot, but mostly for appearance. There is a fine line between bicycles and motorized vehicles on the beach in my town, so going through the motions of pedaling makes me look like a bicyclist! But of course, I would love to achieve more range. I have not even taken a long ride yet since I installed the new motor. I need to get the controller settings right, first, as I am still getting wheelies every time I start from a slow or dead stop. It is hard to say what my range is, because I ride on the beach and some soft and some hard packed sand, on a golf course on paved cart paths and on green grass fairways, and occasionally on asphalt streets. As such, I have no real idea what my range is.

So, what are you thinking? I have noticed that if I simply pedal with no real "input" of power (just simply rotate the pedals) I draw less wattage than I do at the exact same speed using the throttle only. I am open to all suggestions!
 

AHicks

Well-Known Member
If range is going to be of any importance at all, that derailleur plan discussed earlier would be the place to start. Bonus would be it would let you "ghost pedal" at ANY speed the bike is capable of, fast or slow, by simply having it in the right gear - appropriate for your speed. ANY effort you put into pedaling will translate directly into more range.

As far as taming that initial acceleration, are you messing around with the different parameter settings?

If so, suggest you try P3=1 to turn on "imitation torque control" and see how you like that regarding this problem.

I've messed with this control a bunch. Pretty familiar with it and what it's capable of. My bike is equipped with a MAC 12t geared hub motor, conservatively rated at 1000+ watts and 100+nm. It's completely tame at any speed.

I have noted that the throtle behaves very differently when pedaling vs. not pedaling. Not sure that's typical of all KT controllers or not, so check yours. When pedaling and adding hardly any throttle, indicated wattage will go well over 1000 watts and we REALLY start to scoot. If not pedaling, the throttle is MUCH easier to control. Depending on throttle position, adding 100 watts to what it was already using, on up to over 1000 at wide open throttle.

If you haven't done it yet, I can tell you first hand that having the bike wheelie right out from under you is going to hurt, even if you aren't on pavement....
BE CAREFUL! -Al
 

Ccount

Member
Thanks AHicks! Yes, the first time I rolled the throttle, it literally shot out from under me. Fortunately I was able to control it without falling or wrecking the bike. Yes, I am just now beginning to play with the controller settings. I ONLY just became aware of the detailed programming guide, and have been working with online suggestions, the Bolton video, and the 2 page pamphlet that comes with the controller. The more I think about it, the more I am starting to like the idea of the ability to shift gears, so that likely my next project. The front wheel drive idea can wait! Thanks!
 

ExPatBrit

Active Member
A lot people seem to dislike the "soft start" of the standard Rad. I actually wish it was available on the Bolton mod.

I also think throttle is overly aggressive with the mod, no dead-band and about 1/4 turn and you are at Warp Factor 9. Easy to catch you out.
 
The more I think about it, the more I am starting to like the idea of the ability to shift gears, so that likely my next project.

I'm sort of curious why you were keen on upgrading to the 750w Bafang motor? From what I understand, this mod adds lots of toque but little to no additional increase in top speed. The extra torque would be useful for hill climbing. But if you're riding on mostly flat roads/trails, I don't see the big advantage??? Getting up to top speed a bit quicker, maybe? (but at the price of hanging on for dear life :))

Same goes for gears. I now own both a RadRunner 1 (RR1) and RadRunner Plus (RR+). The gears on the RR+ offer a significant advantage over the RR1 when it comes to hill climbing. But apart from this, using only the pedal assist settings is akin to switching gears when traveling relatively flat surfaces. If it weren't for steep hills, I'd be content with just the RR1.