Mitchell027

Howdy folks!

I've been trying to find solid information on this across the web, but have had little success.

I'm converting an old Trek 970 Single Track that I picked up for $50 to a e-cargo bike using the Xtracycle Free Radical kit (not the LEAP). To start, I'd like to just get the cargo bike operational and get a good feel for things before I electrify it.

The first question I have is, what do people recommend for gearing on an e-bike or in particular an e-cargo bike? I won't be doing many big hills, but I will be carrying heavy loads. It has a triple chainring crank on it right now that I'd like to convert to a 1x setup. Looks like most ebikes have this as a 1x7 or something of the like. I especially want to do this because the existing FD is bottom pull, requiring housing the whole way. The housing stop is on the top tube for FD...I guess they only had a bottom pull FD available! What sizing do people recommend in the front and back? It looks like RadWagons use a 46T chainring and a 11-34 freewheel.

Thanks!

andychrist

I take it then you’re planning to replace the rear wheel on that Trek 970 Single Track with a motorized hub wheel, rather than installing a mid drive? Because the latter choice would come with a single chainring crankset, available from 48T on down and most commonly 750W. OTOH hub drives now commonly support up to 9-speed freewheels/cassettes, and are easy to find in 48V between 250-1200W. As the Xtracycle supports both rim and disc brakes your choices are wide open.

On my own e-cumbent cargo bike with dual 500W Bafang hub drives, kept the original 50-39-30T crankset and slapped on an 11-28T 9-speed cassette. Now, for some odd reason I can’t get any FD to reliably shift onto the smallest chainring, so just alternate between the 50 and 39T rings. With the chain the largest ring and sprocket, can climb pretty steep grades, though am a bit more comfortable maybe on the inner chainring and middle to like 7th gear on the cassette — don’t recall ever having had the need to shift into the 28T cog when in that 39T ring.

So I’d be willing to bet that with a single 46T chainring, an 11-34 cassette would certainly suffice.

BTW I happen to have a NOS top pull Deore FD sitting around here, in case you’re interested.

andychrist

Also, not sure what’s the BCD on your Trek’s crankset, but you might have to replace the chain arm if not the whole unit in order to move up to a larger chainring such as the 46T.

2old

You have the triple now. Why not build the bike and try the three front chainrings in order to decide? One thing to remember is to have a system where you're able to ascend the steepest hill at half of top speed or too much energy is transferred to heat which could be deleterious to the motor.

Mitchell027

Thanks for the replies.

Yes, I am planning on using a rear hub motor.

Perhaps the best option for now is to leave the triple on there and just experiment with different sized chainrings until I'm sure what size(s) I need. I saw one person recommending that you can manually move the chain to different chainrings as needed so you don't need the FD or shifter/cables/housing. Personally, I'm excited about having a 1x setup and would love to learn about that process. This would be a good way to trial that.

So assuming the above, what steps do folks recommend for moving forward with a 1x?

• If it's a 4-bolt 104 BCD crank, should I just slap the correct size chainring on there once I know?
• Do I need new/shorter bolts for the spider?
• Do I need a new BB to get the chainline in the center of my rear cassette or just use spacers?
• Should I get a narrow-wide chainring to avoid chain drop?
• Do I need a chain guide or can I just use my FD by adjusting the limit screws?

Thanks all!

cat0020

What is your budget for the conversion?

How much weight do you plan on hauling with this cargo e-bike?

How much do you weigh yourself?

What kind of operating temperature is in your riding area?

What kind of distance do you plan to cover per ride or battery charge?

All of the above can help determine what type & capability of e-bike you need for the conversion.

I'm about 170-180 lb. fully dressed,
I carry about 20-60 lb. of donated food between schools & homeless shelters.
I ride in air temperature ranging from 20F to 90F.
Distance I cover per ride is about 12-14 miles one-way, 25-40 miles per day.
I ride mainly in congested NYC traffic, top speed with PAS rarely get above 20 mph, mostly staying under 15 mph, but still need brakes better than standard cable actuated V-brakes.
Terrain that I ride is 99% pavement, hop on & off curbs onto sidewalks, potholes & metal plank are plenty.
Hills are gentle, but some can be as long as 1/4 mile long, at low gradient.

andychrist

Yeah you can manually shift front chainrings but not on the fly and kind of a PITA to do with your bare hands (or even with gloves on).

If your current outer chainring is only 44T or less, and what ever FD you have on now is matched correctly as to size, it’s quite possibly a MegaRange which won’t work on a larger chainring because of the way the cage is shaped. (Road cages for larger chainrings are long and shallow while Mtb cages are shorter and deep.)
Again, I have a spare vintage Deore top pull FD with a road cage — guess it was manufactured before the advent of 34T+ cassettes when even Mtb cranksets had relatively large rings.

If you’re not going to shift out of the largest chainring then you might not need a chain guard at all, but I don’t have experience with that setup so can’t say for sure. One kinda crazy idea might be to get either something like this steel 48T outer chainring or an aluminum alloy 46-48T single and install it in the middle position. Then you could replace the current outer ring with a spiffy Driveline 48T chain guard. Again, dunno for certain whether your crankset would support this mod but as outer and middle chainrings share the same BCD might very well be possible. Anyway you could inquire about this in the Bicycle Mechanics sub-forum.

Bafang display switches do all seem designed for left hand use so a bit of a challenge to position along with both a throttle and FD shifter (not to mention requisite brake lever!) That said, managed to work it out on my own dual drive cargo bike, even with a Mirrycle bar end installed. Secret was to go with half twist throttles and SRAM Rocket triggers:



Come to think of it, I also have spare SRAM left-side triggers in case you decide to keep a FD and lack a compatible shifter (because you wouldn’t want a twist shifter alongside any kind of throttle, and Shimano triggers suck donkey balls.)

For a cargo bike though you’d probably want to go with something more powerful than Bafang’s 500W hub drive, such as the 1000W kit offered by TheeBikeMotor — a brand with which I have no experience. But there’s this great YouTube about it by Augustine EBikes:

2old

Don't know whether I remember all the questions, but as stated above you could use the outer ring in the middle if it helps the chainline. You'll need shorter bolts for a single chainring (or possibly washers); I always use the shorter bolts ($10 Amazon). Definitely use a narrow/wide chainring; I've never had a problem with one dropping a chain and without any other "keeper". It is easy (but dirty) to stop and change from one front chainring to another; just push the cage at the bottom of the derailleur forward to "loosen" the chain and move it one way or the other. You shouldn't need to space anything with the new cassette, but make sure the derailleur can handle it. Usually (FME) a rear derailleur can accommodate two more teeth in the cassette than specified.

Mitchell027

cat0020 - I'm not sure how those questions help answer my questions...Maybe I'll just say I'm not hauling or living or needing any extremes...

andychrist - thanks for the offers and ideas! I think I'm gonna try to use my outer chainring in the middle position and the FD as the chain guide and see how it goes without a shifter.

2old - thanks for the reply. Do you think I need new chainring bolts? or can I just use the inner chainring bolts that are shorter?

Thanks all!

cat0020

Well, battery range can be affected when rider weigh varies, 140 lb. vs 180 lb. or 220 lb. rider; 40 lb. e-bike or 80 lb. e-bike; your budget would help determine what kind of e-bike you may afford.

If your riding area is tropical vs 3-4 months of snow covered tundra, would make a difference in e-bike performance.

If you plan on riding 40-60 miles every single day, you may want to consider an extra battery or even dual battery on your e-bike.

2old

M, you can use the shorter bolts if the "nut" is short enough that it doesn't protrude through the crank mount and chainring, but that's improbable. It's possible to locate the correct washers to use the longer "nuts" or file them down, but I've always just purchased the "one ring" ones. Might ask question in the mechanics section to determine what others have done.

sloppy12

Depending on wattage I would go 40-46 on chain ring assuming you can clear those on a 1x.. I would see what works with the triple but I can pretty much guarantee over 750 watts you will want more that 40t.
Yes a narrow wide on middle ring
yes or spacers.
if the gear you pick clears on middle ring the chain line should be ok
YES! I am riding my winter bike without a narrow wide I do drop chains from time to time. I would not even consider it on a ebike.
On a normal bike I would say no. But on a cargo bike a chain guide or locking the FD in the middle might be a good idea. its a long chain you will get chain slap.

I will add make sure whatever hub you go with make sure it will take a cassette, I would also scrap the 7spd and go to a 8spd using the microshift acolyte. It has a "clutch" and can either use a 12-42 or 12-46 cassette and its under 80 bucks for system. a clutch on a cargo bike with a 1x is a good idea IMO.

I pretty much have your bike minus the hub motor a rock hopper with free radical(I will most likely add a motor). I also have a rad wagon, and a Raleigh lorry that is converted to ebike. the raleigh is I think a 42 with the same 11-34 freewheel as the radwagon, that bike spins out easy. the rad wagon I think mine is a 50t on chain ring they may have changed with new model. Honestly it can be lacking on the low end on steep climbs but that I think is more stock controller than anything else.

andychrist

Mitchell I just discovered in my parts bin a 4 arm 104BCD chain guard that should fit a 46-48T chainring, it’s yours for the asking. Might save you the trouble of switching out the bolts if you install an outer or narrow-wide chain ring in the middle position. Just PM me your mailing address if you want it.



Though AFAIK the only problem with chain drop on e-bikes is with mid-drives, which put additional strain on the drive train. Hub motors OTOH reduce load and actually make shifting easier than on an unassisted bike. So if you go with a hub motor and a single chainring middle position, shouldn’t make any difference in performance whether it’s an outer triple or narrow-wide single. More important issue might be durability, as narrow-wides are generally only available in aluminum alloy while that 48T Truvative comes in steel. Remember, on a triple crankset the wear is distributed over all three rings, at least the inner two of which are usually steel. So limiting the crank to a single alloy ring will decrease its overall longevity. Of course rings are easily replaceable and adding hub motor assist does generally reduce wear on the drivetrain so maybe not such a big deal.

On my 26” wheel cargo ‘bent with a 44T outer chainring, 11T smallest sprocket, I spin out over around 24mph. Similar model e-cumbent cargo bike with 50T ring and 11-28T cassette, I can pedal to 30mph. Thus pretty sure you’d be fine with a 48T chainring and 11-34T cassette, which any long cage RD should be able to handle. Might be helpful to install a return idler though to take up chain slack, I have a used bolt-on unit that might fit the chain stay on your Free Radical.

andychrist

Also this Park Tool Chainring Bolt Wrench for Slotted Nuts will help a lot too. (Sorry I don’t have a spare.)

MNebiker

Rather than making big changes initially, I would suggest that you retain the triple, and ride it for a while. It will give you a chance to actually "feel out" how the conversion works for you and you may find that it gives you options that make for easier riding, particularly since it will be a cargo bike with heavy loads. Even on an ebike some hills can be nasty. Try it out before you invest in some changes that you may, or may not, need.

Then if you do decide to go with a single, you will have some info to use in choosing the chainring size, rather than just estimating what might be the right one.

Mitchell027

Hey all,

So I went ahead and tried moving the outer 46T chainring to the middle and borrowed some single chainring bolts from another crankset. Unfortunately, the 46T doesn't clear the chainstay in the middle position. The crankset is a triple 175, 5-bolt (didn't check BCD) square taper The bolts I borrowed were from a double 170 (4-bolt 104 BCD) square taper, which has a chain guard on the outer and 42T on the inner. I installed the double and it fit well and cleared, but the chainring is bent and I didn't have a matching 170 crank arm with square orientation instead of diamond, so I put the triple back on. Before that I tried the 42T on the triple in the middle position, but it was mere microns from the chainstay and too close for comfort, so back to the original chainrings (46T and 38T).

So, this is what I'm thinking and would love input:

• It seems that the chainline is better in the middle position, but maybe it doesn't matter. Is there a problem (more likely to drop the chain) if I keep my only chainring on the outside of the triple?
• Why did the double clear at 42T, where the triple did not with the same chainring?
• I'm concerned 42T will not give me enough high end, but perhaps I should throw it on (once I find a matching crank) and see...
• Are there 1x specific cranks that would work better for this?
• If I have trouble with chain drop, then I'm gonna go with a narrow-wide chainring. Can I do that with my 8-speed setup now or should I upgrade to 9-speed?

Thanks!