Bafang BBSHD and gear system for fast commuter bike

[Mnaq]

Hi
I live in Sweden and use my bike to commute to work and sometimes to take two kids in a trailer.

I have had a BBSHD (1000W, 52V model=around 1200-1300 W at full throttle) for almost a year now on an old 1990 bike (Swedish Crescent Positron 5, steel frame, 28 inch, regular bike). I have had a lot of problems with the gear shifting mechanisms I have tried.

The bike runs 10-15 miles per day 5 days a week all year round and in winter on snow (down to -20C/-4F). About half of that at full throttle speed of approx 40-50 km/h (25-31) MPH. The derailleurs and chain that fit bolt-on wear down very fast with skipping gears after 1-2 months since the only ones I have found that fit directly onto the bike are for cheaper junior bikes. The bike does not have the "ear" for attaching a modern mountainbike or race derailleur. I then bought a Nuvinci N171B on Ebay (USA) that unfortunately started leaking after 2 months of use. Since I had the wheel built and shipping from USA is quite costly I cannot easily have it shipped back and forth for repairs (if it at all is possible).

So now I am looking for other reasonably priced solutions. Newer Nuvinci/Enviolo hubs, like the Heavy Duty is for the moment too expensive for me. Furthermore I like to pedal for the exercise so I need the gearing to be suitable and durable for 30 MPH at the fastest gear. What gear system can handle both low maintenance, durability and high speed (being able to pedal), preferably at a low cost (second hand?)? Should I try to find a used CVT like N171B, or use Alfine/Nexus 8 or try to convert it to a modern derailleur? What systems do modern factory built high speed ebikes use? I would be grateful for any tips. //Mattias

 

[amberwolf]

I live in Sweden and use my bike to commute to work and sometimes to take two kids in a trailer.

I have had a BBSHD (1000W, 52V model=around 1200-1300 W at full throttle) for almost a year now on an old 1990 bike (Swedish Crescent Positron 5, steel frame, 28 inch, regular bike). I have had a lot of problems with the gear shifting mechanisms I have tried.

The bike runs 10-15 miles per day 5 days a week all year round and in winter on snow (down to -20C/-4F). About half of that at full throttle speed of approx 40-50 km/h (25-31) MPH. The derailleurs and chain that fit bolt-on wear down very fast with skipping gears after 1-2 months since the only ones I have found that fit directly onto the bike are for cheaper junior bikes.

Some thoughts, in case you have not encountered this before:

The higher power middrives can very quickly wear out the drivetrain, especially if it is not shifted into the correct gears for startup or other high-torque situations, and if motor power is not stopped or rolled way back during a shift. There are a number of posts and threads about this sort of problem over the years with every kind of drive and drivetrain.

The chain will wear fastest, if the chainrings and sprockets are all steel, if any of those are aluminum they'll wear faster. Depending on usage you might get a couple-three chains worn out before you have to replace the chainrings and sprockets, and those need to all be replaced at once with the last chain replacement.. If you see excessive wear on them or have shifting problems or "skipping" of the chain you should replace them more often. .

This is also true of regular bicycles, but they generall don't see the same kind of torque loads on the wrong gears that middrives tend to cause (because it is very common for people with assist to not downshift far enough or at all...unassisted bikes are more likely to be shifted correctly because it's a lot harder to get started in the wrong gear without the motor power to do it for them).

There's another recent / ongoing thread here about a middrive wheel-jam problem that also has sprocket wear, and there are some links in it that I posted that are relevant to the above with useful info.


There aren't any drivetrains that aren't going to wear significantly faster with a middrive, as far as the drive from motor / pedals to wheel go, either belt or chain and their associated sprockets and chainrings, so you will still need to replace those whenever you are having problems with that part.

The derailers, if you are shifting like you would on an unassisted bike and backing off on pedal torque during a shift, will operate the same and last the same as they would on that unassisted bike. If you are not stopping the motor during shifts, it can damage any derailer, and even damage internal gears on an IGH, even one like the NuVinci/Enviolo (I don't know if it could cause one to leak, but it could cause the friction fluid inside and the balls to wear out faster than normal). If you don't have one installed, you may want to add the GearSensor to turn the drive off during shifts, to reduce this type of problem.

Drives like the Rohloff and other high-torque-capable IGHs can more easily take the slamming on of power from a motor (if yours doesn't ramp power up at least a bit to take up any gear lash before applying higher torque), but they are really expensive and will still not resolve any chain / sprocket problems like skipping, etc.; they only help with shifting system wear...but if shifting is done under power they'll still wear out faster than if you don't do that.

 

[Mnaq]

Hi! Thanks for your thoughts. I think I am quite good at not shifting gears under power, though I normally do that by applying the brake to cut power, or just by stopping pedaling. I also down shift when running slowly or stopping, like I would without motor assist. My derailers seem to have taken their main beating when the chain has been slipping at high speed. It seems the derailer folds back (or rather forward) quickly when this happens. Probably due to weak spring in the chain tension joint. I liked the internal hub I had because that limited the wear to a simple single speed sprocket and chain, which both are cheap in comparison with cassettes and derailleur parts and chains. I will get the bafang cable for programming the controller, but I think it has a little ramping up of power with factory setting also.

 

[amberwolf]

My derailers seem to have taken their main beating when the chain has been slipping at high speed. It seems the derailer folds back (or rather forward) quickly when this happens. Probably due to weak spring in the chain tension joint.

There are two typical causes of the chain slipping on the sprocket teeth:

If this happens equally all the time even with brand new chainring, sprockets, and chain, it means there is insufficient tension on the chain to hold the wrap around the sprocket (usually this only happens on the smallest sprockets with fewest engaged teeth). That you can fix by using less chain links as long as there is stil enough chain to wrap the combination of the largest front sprocket you'll ever use with the largest rear sprocket. If that doesn't fix it and/or it's already as short as will still work, then you can try increasing tension via the derailer with the tension adjuster screw on the derailer if it has one (but not all of the older type do). If it has no adjuster you can see if there is any way to force the derailer to sit where it will pull differently on the chain to cause more pull on the wrapped chain/sprocket, or perhaps adding a spring (like from a screen door closer, etc) from the derailer to the frame in the right place at the right angle. Also, if the derailer and it's shifter isn't adjusted correctly to line up with the sprockets, it could wear or damage things.

If it doesn't happen at first with new chain and sprockets, but only after time passes and gets worse over time, then you will need to replace at least the chain as soon as the problem starts. If it's already damaged the sprockets they'll have to be replaced at the same time. Any worn part will wear the new parts faster...

I liked the internal hub I had because that limited the wear to a simple single speed sprocket and chain, which both are cheap in comparison with cassettes and derailleur parts and chains

As long as you can be sure of shifting between power applications, you can use any of the IGHs that support your gearing ratios and torque levels...but like any other derailer system it'll need to be adjusted correctly to properly shift fully into each gear. Chalo has a recent post in another active thread describing the differences between most IGHs and the Rohloff in shifting being that the Rohloff uses detents inside the hub, while the others have them in the shifter...so the shifter not being adjusted correctly can mess up the gears in the others, but not the Rohloff.

 

[pomah]

I also live in Sweden, commute 5 days a week, I aswell was using a my bike to hitch two kids in a trailer to and from school/pre-school, but those days are now past

But to answer your question: for the last year I have been using the linkglide drive train, I just did my fist chain change, that is 1500km, I have noticed that running my chain to 0,75 on the chain wear meter, is not recommended for the linkglide drivetrain, 0,5 is a better value and then I would most likely get around 1000km of use out of a single chain. The cassette is still great, I do need to replace the 11t cog now since the missuse of the chain, but that can be done easily,

So to summarize, try to get a more moden frame, both for handling the speeds you are going in and to brake properly. It is not fun/ok to travel at the speeds you are doing with inadequate break power and/or frame stiffness. Use a nexus 5 speed IGH or the shimano linkglide shift systems, depending on what you prefer.

Get a chain extension meter to check your chain, and do not forget to regularly add lubrication to the chain and clean. I have been using squirt wax which makes the cleaning process super easy but I need to reaply it every 2 weeks, but that takes 5 min so not much work.

Summary:

Get a good frame that can handle the power you are putting.
Get IGH or external gears made for e-bikes, linkglide or shimano nexus 5 speed are tested and good.
Get tools to measure chain wear and also a good chain lubrication product
Ride your bike and enjoy

Or you get a frame with a belt-drive and just live happy ever after