Radrunner upgrade to TRUE 750w Bafang hub motor

claybear

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.
How did you shorten the axle shoulder ? I'm lookimg at doing the same upgrade. I haven't boight motor yet because I've read that motor is 175 mm and rad runner drop out is 167mm.
 

Ccount

Active Member
How did you shorten the axle shoulder ? I'm lookimg at doing the same upgrade. I haven't boight motor yet because I've read that motor is 175 mm and rad runner drop out is 167mm.
The only reason I lengthened the axle was to accommodate the fender struts. I ended up having the fender on backwards, and in fact there are built in mounting points on the Boltol forks, and all you must do is do some wire bending to match them up!
 

Ccount

Active Member
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.
I ride on the beach a lot, and in soft sand, it is VERY helpful!
 

Ccount

Active Member
The only reason I lengthened the axle was to accommodate the fender struts. I ended up having the fender on backwards, and in fact there are built in mounting points on the Boltol forks, and all you must do is do some wire bending to match them up!
It ends up that step was not necessary, i just failed to notice there were available places on the Bolton forks to mount the fender struts. I mounted them to the axle, and needed extra length on the axle.
 

ZRider

New Member
Region
USA
How did you shorten the axle shoulder ? I'm lookimg at doing the same upgrade. I haven't boight motor yet because I've read that motor is 175 mm and rad runner drop out is 167mm.
Not sure if this has been fully answered. I bought a 750W from https://electrobikeworld.com/products/48v-750w-bafang-geared-rear-hub-motor and installed it on a single speed Radrunner (not plus). My original motor had a bent axel, and the threaded side broke.

I shortened the axel's shoulder (wired side) 8mm (4mm will not be enough since you will rub the brake rotor against the frame) by taking the motor to my local machine shop. You can also use a dremel if you are handy with it. Just use proper PPE.

You will need a freewheel spacer (https://www.ebikekit.com/collections/small-parts/products/freewheel-spacer-for-1-speed) to offset the single speed freewheel. I swapped my freewheel from the stock one, and I used washers to shim the tensioner. This allowed proper alignment. It is very difficult to remove the stock freewheel. If you want to then you need to buy the single speed freewheel removal tool from Rad. Good luck. Make sure you use grease for the spacer and freewheel's threads so you can remove them in the future.
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Also remember you will need a security Torx T20 (it has a whole in the center) you need this to remove the screws from the new motor.
 
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It is very difficult to remove the stock freewheel.

For what it's worth, I was able to remove my freewheel using a center punch and hammer. The stock Rad freewheel has notches on it (for a freewheel removal tool), which can be used as bearing points for the punch. Hold the punch on a notch at an angle, and make sure you are driving it counterclockwise to remove. While this method marred the notch a tiny bit, the freewheel is made of hardened steel and can easily survive several good blows (I've done this a few times now).

Btw, given the space between the 750w motor and the freewheel, looks to me like you could easily fit a seven speed sprocket to this bike if you so desired. I put a three speed sprocket on my RadRunner with the stock motor, yet which has a boss cast into the motor casing that acts as the spacer (and thus can't be removed to make way for a wider sprocket stack). But I can say that even having just three speeds is a lot better than one.
 
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ZRider

New Member
Region
USA
For what it's worth, I was able to remove my freewheel using a center punch and hammer. The stock Rad freewheel has notches on it (for a freewheel removal tool), which can be used as bearing points for the punch. Hold the punch on a notch at an angle, and make sure you are driving it counterclockwise to remove. While this method marred the notch a tiny bit, the freewheel is made of hardened steel and can easily survive several good blows (I've done this a few times now).

Btw, given the space between the 750w motor and the freewheel, looks to me like you could easily fit a seven speed sprocket to this bike if you so desired. I put a three speed sprocket on my RadRunner with the stock motor, yet which has a boss cast into the motor casing that acts as the spacer (and thus can't be removed to make way for a wider sprocket stack). But I can say that even having just three speeds is a lot better than one.
Hi,

Yes, I the motor comes with a 7-speed freewheel as part of the package so you could use it instead of a spacer and single speed--I suspect you would have to bend the frame though. There are RadRunner owners who bend the aluminum frame's dropout distance to fit the 750W motor w/o shortening the motor axle's shoulder. I wouldn't bend 6061 aluminum. I personally don't have any interest in adding the overhead of cables and adding gears; however, if people decide to go that route they will need, in the future, another Rad provided or modify a freewheel removal tool for the 7-speed freewheel (not sure if your center punch and hammer will work to remove that one). A Park Tool one's inner diameter won't clear the motor connector/hex nut (I think Bolton machines and sells his own now for this purpose https://boltonebikes.com/collection...wheel-removal-tool-made-in-usa-by-bolton-labs).

I had the local bike shop take my freewheel off, but putting the tool in a vice and turning the wheel would also work. I wasn't sure if hammering would damage the bearings. Note: the stock Rad single speed freewheel the notches are wider than a standard single speed freewheel. Rad's tool tool is better designed to account for this and remove it. I had the machine shop modify a Parktool (notches are better designed/located) for a standardized single speed freewheel. The Rad tool is the one above in the picture, middle is the stock freewheel, and bottom is the modified Park Tool.
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... another Rad provided or modify a freewheel removal tool for the 7-speed freewheel (not sure if your center punch and hammer will work to remove that one).

Correct. I also own a RR+ with the 7 speed freewheel, which I could only remove using the split freewheel removal tool from RPB (and even then it was a royal pain-in-the-$%#@ to remove because that tool does not fit snugly/securely inside the freewheel without slipping -- the diameter of the tool is too small and so must be wedged apart further with another tool, like a flathead screwdriver).

To repeat, I installed a 3 speed freewheel to my stock RR1 motor -- fit fine without any frame modification. But notice again that the stock RR1 motor comes with a single speed freewheel spacer already cast into the motor casing, yet which is absent in the upgraded 750W Bafang motor and buys you another 1.5+ inches of clearance for a wider 7 speed freewheel. Thus, I suspect (but do not know with certainty) that the frame dropouts need only be spread a tiny bit more to accommodate the 7 speed freewheel. In other words, I believe this mod is doable with a bit of tinkering.

In my view, the extra gears have several benefits, including (1) they make hill-climbing much easier, and (2) they increase battery range by providing more efficient peddling when matched with an appropriate pedal assist level. As compared with my fully stock RR1, I used to get at least 10 miles of further range on my RR+, and I am convinced this is mainly due to having the extra shiftable gears. But of course if riders are not especially concerned about range, hills, and/or don't usually ride these bikes as bicycles (i.e., with a fair amount of peddling), then none of this will matter much.
 
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