Gear Upgrade for RadRunner

[Jrwebb]

Hey first post here! Hope I'm asking in the right place...

I had a question about upgrading my radrunners single speed freewheel. I love my bike but recently the motor stopped working while I was 5 miles away from home. The problem was just a simple wire disconnection but it was dark when it stopped working and I couldn't find the cause until I got home. So I ended up trying to pedal back home without the motor, but the bike is practically unrideable without power.

I'm not very bike knowledgeable, and even less so with electric bikes, but was wondering how easy it would be to replace the freewheel with a larger one? I don't necessarily want to upgrade to a whole derailer system, just a larger single gear to help make riding "acoustic" easier. Do they sell larger single speed freewheels than what comes on the RadRunner?

Thanks in advance!
JR

 

[Ccount]

Bump. I too am interested in this! What advantages would there be to installing gear shift ability to a radrunner?

 

[Nova Haibike]

According to Rad's specs, the bike is equipped with a 53T chainring in front and a 16T freewheel at the back. They make single speed freewheels in 13T, 14T, 15T, 16T, 17T, 18T, 20T, and 22T. Of course if you change the gear to make riding without power easier, it is going to make the bike slower.

 

[Iridebikez]

Both correct answers. You will need tools for either job, but once you have the proper tools both can be replaced fairly easily. If you do it yourself and replace the chain ring you'll also need to find a replacement with the correct bcd (bolt circle diameter), which isn't listed on Rad's website but is likely written/stamped on the chain ring itself. Normally you might also need to lenghen/shorten your chain, but since Rad uses a chain tensioner that should take care of it for you if the difference isn't dramatic. For example, from 53/16 to 53/18 or 50/16 should be ok, but if you go down to like 40/18 you will likely need to take links out of the chain to take up the slack.

Regarding more gears, the benefit would be making it easier to pedal at slower speeds with less assist and/or more cargo, as well as the possibility of increasing the top-end speed when going fast. I don't think Rad would have put gears on the RadRunner Plus if they didn't also see a benefit. As with all bikes, more gears means a little bit more complexity, so it just depends on what you want out of your bike.

However, installing a rear cassette, rear derailleur, shifter, chain, and cable/housing is a little more complicated than just swapping a chain ring or freewheel. Youtube is an excellent resource for bike repair, but if you've never done it before and are unsure you're better off taking it to a shop.

 

[Iridebikez]

It is possible, but you'll need all of the parts I listed above (rear cassette, rear derailleur, shifter, chain, and cable/housing).

And now that I'm looking at the website, the rear hub of the regular RadRunner probably won't accept a cassette. The way I can tell is that Rad lists a single speed-specific 16t freewheel on the regular RadRunner but a 7-speed freewheel for the Plus. Which means you won't be able to just throw a cassette on the regular RadRunner, you'll need the correct 7-speed compatible hub/body to accept it first. Doable, but more complicated again.

 

[rezonatefreq]

I have, or well, my wife has a rad runner single speed. I just put a electro bike world bafang 750 watt motor and bolton kt8 screen and 35a controller on it. The screen and controller replacement was relatively easy and was a big improvement since she had the low end display without the digital display. Now to give my perspective on the possibility of upgrading from a single speed to a multispeed freewheel.

When I attempted to replaced the stock rad runner motor with the 750w bafang motor, it would not fit back into the frame. The shoulder on the 750w axle was too long by about 5/16 inch. Quite disappointing after spending about $300 for the motor. Another forum member posted the correct term for the spacing of the rear wheel, OLD. I do not believe there would be adequate space between the rad runner single speed frame rails for a multi speed fee wheel using the stock rad runner motor or bafang 750w motor. Would have to measure a rad runner plus to confirm. Since I have some skills I decided to see if I could make it work. After lots of measuring I decided to move the axel shoulder by reducing the axle diameter on the freewheel side, flatten both sides of the reduced diameter shaft for the stock special lock/holding washer to slide on and then the 750w bafang motor with stock wheel wheel fit into the frame. A little fiddling with the chain tensioner for proper chain alignment and boom, the wife has quite a machine now.

The added torque with a 35a controller and 750w bafang motor is unbelievable. If you are not ready its an accident waiting to happen. I did not want the bike getting away from my wife, like it did me, so I adjusted settings in the display to regulate and smooth the torque delivery to manageable levels. Now she is a demon up hills and the top speed is much greater. She really likes riding an electric bike. She was not that much of a fan of non electric bikes. Now she likes to lead rather than follow, take our grand daughter along with her puppies. If there is interest I can post a few photos of the display, controller mounting, difference between motors and the modified axle shaft.

 

[cuekwe Jones]

If there is interest I can post a few photos of the display, controller mounting, difference between motors and the modified axle shaft.

Thanks for sharing these details. Not sure I understand, exactly, the required modification to the new Bafang axle -- so perhaps a photo or two would be helpful. Specifically, you first mention that the axle is "too long," and then that it (the axle or the shoulder, not sure which you are referring to?) had to be "moved," and that to accomplish this one needs to reduce the axle diameter??? Is the "shoulder" the flattened area of the axle that fits into the dropout? If so, I think I understand what's required -- one needs to machine (flatten) new dropout "shoulders" that are offset ("moved") from the stock shoulder. Is this correct? Precise dimensions here would be helpful, as I am seriously considering this exact mod for my RR1.

Also helpful would be a listing of your display/controller settings.

Thanks!

 

[rezonatefreq]

You have deciphered my post accurately. I did reduce the diameter of the shaft and then flatten both sides of the reduce diameter shaft. I did use a micrometer to measure but the reduced diameter shaft ended up being about 5/16” long.

I have read others have just expanded the frame. I thought about this but since my son has a small jewelry lathe and mill we used it. I would have used a grinder and files if I did not have access to the equipment. Be sure and use a bag or Saran Wrap and tape to protect the motor.

The other issue is the chain tensioner alignment. I just bent the arm but their must be a better way.

Some have asked why go to the trouble. If you just want to ride the bike I would recommend you do not modify. It has been engineered to meet it goals reliably. There are those of us who also enjoy modifying and learning how the bike works on a detailed level and to make it our own. The motor and controller upgrade adds quite a bit of excitement to the bike. Kinda like driving a sports car vs a grocery getter.

 

[Ccount]

Thanks for sharing. I too am about where you are, but I dd not need to make any real modifications?? (I love your machine shop and am envious). I ordered my 750w bafang motor from EBW, and I used the 7 gear cassette (freewheel?) that came with it, and it pretty much mounted right on (I did have to spread the forks just a bit). Like you, I had to bend the tensioner a bit, and added a few washers, to get it to align on one of the gears on the cassette. And yes, like you I enjoy modifying as much as riding! To say these mods add excitement is an understatement. I have to hold on for life now, and I hav a hard time NOT poping a wheelie when starting with full throttle!

Have you considered adding gear shift ability to yours? I am quite handy, but do not know or understand derailleurs and shifters and gear sensors and such. Let us know!

You have deciphered my post accurately. I did reduce the diameter of the shaft and then flatten both sides of the reduce diameter shaft. I did use a micrometer to measure but the reduced diameter shaft ended up being about 5/16” long.

I have read others have just expanded the frame. I thought about this but since my son has a small jewelry lathe and mill we used it. I would have used a grinder and files if I did not have access to the equipment. Be sure and use a bag or Saran Wrap and tape to protect the motor.

The other issue is the chain tensioner alignment. I just bent the arm but their must be a better way.

Some have asked why go to the trouble. If you just want to ride the bike I would recommend you do not modify. It has been engineered to meet it goals reliably. There are those of us who also enjoy modifying and learning how the bike works on a detailed level and to make it our own. The motor and controller upgrade adds quite a bit of excitement to the bike. Kinda like driving a sports car vs a grocery getter.

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