A Couple of Bosch Drive System Issues

[Admin]

A friend was recently talking about the Bosch drive system with me (he rides a lot of off-road terrain) and we were discussing the smaller front sprocket that the system uses (apparently this part gets built by the bike manufacturer but Bosch specs three sizes... all relatively small, ideal for higher speed racing, normal city riding and off road climbing). These smaller chain ring sizes (verses traditional larger sized front rings) seems to create mechanical advantage for their centerdrive motor, allowing it to spin at higher RPMs and achieve better torque and power as a result.

The small Bosch sprocket whirls 2.5 times faster than the crank revolves. This has several big advantages where ground clearance, weight and motor performance are concerned. However, this small sprocket is not compatible with a standard suspension frame chassis, as the lower chain position produces too much pedal kick back with standard position pivot points.

Instead of repositioning pivot points on frames to deal with the pedal kickback issues (which would make frames longer and change their handling dynamic) some full suspension ebikes like the Haibike FS 27.5" have introduced a chain routing system called a Sprocket Equalizing System (S.E.S.) that's basically a pulley wheel which link the chain up and around the pivot point. This seems pretty reasonable to me, here's a picture of the SES system from Haibike which also seems to double as a guide to reduce chain drops in rough terrain:



Okay, so this discussion is just setting the stage for one issue that my friend has experienced. Apparently in muddy situations he has found that the smaller chain ring and associated guide don't provide the necessary space or separation to avoid chain suck (which is when the bottom portion of the chain sticks to the sprocket and gets pulled up... possibly back into the top of the cog where the top portion of the chain is feeding in). He shared a picture with me recently and to be fair, since the sprockets are all made by the manufacturer and not Bosch, this may be a result of both the smaller mountain bike speck that Bosch recommends in their sizing guideline or simply the way the sprocket was made or possibly the addition of the small chain guide that hugs the front sprocket? Maybe the teeth on this particular sprocket were tighter than necessary? I discovered recently that Haibike actually uses a pattern of narrow to wide teeth that match the same pattern on the chain (it has narrow and wide slots from one link to the next) designed to reduce slipping and possibly avoid this type of issue. Here's the picture he shared from a Bosch powered electric bike that was being tested off-road along with another shot of the battery interface where some mud was leaking in.



The outcome of chain suck like that shown above is that the chain gets locked and the cranks stop turning and the rider is forced to stop pedaling at short notice. I'm sharing this because it's interesting and might be good feedback for Bosch on future design considerations or individual riders who go into mud and might encounter a similar outcome. In my opinion, rigorous terrain is bound to impact ride quality and I'm not surprised that something like this could happen but I can see how it might adversely impact a rider (they could bump their knee or have a foot slip off the pedal and scrape a shin).

Thankfully, the second issue I've heard about recently has less impact on ride quality. Apparently the Bosch Nyon display panel has a plastic bevel which gets narrow along the top and the plastic has cracked for some people (and not on impact... just as the result of being brittle or expanding and contracting due to temperature). The details on how this happens are sparse, one person said they just left the display on their counter over night and in the morning it was cracked like this:



That's about it, I'm just sharing these independently and opening up for discussion from Bosch, individuals or manufacturers that use Bosch so the product can get better or people can learn how to maintain it more effectively to avoid issues. I still thing it's an amazing system and have not had any issues with the Intuvia display that's sold in the US (apparently the Nyon is coming in 2016). Maybe there will be some updates to the design before we get it.

 

[Shea N Encinitas]

I'll probably never get mine muddy enough to suck the chain, but the chain does look long in high gear as you can see in the poster frame of this video. I would pull 4 or 5 links if I was having that problem. BTW where is the pulley in that first stuck muddy chain shot? Or is it a hardtail? -S

 

[Lumos]

This is proving to be a huge problem for me. On my Haibike AMT Pro I have frequent chain suck and it has cost me two SRMA XX1 rear derailleurs, two Iodine 3 wheel rebuilds, rear cassette, chainring, chain replacement. It seems that every time it happens it bends the derailleur hanger leading to the secondary consequences for the transmission. It has never occurred whilst shifting but it is always when it is really muddy. One week I had to use my Park Tools DAG2 seven times. Ironically I have never had this on the previous Bosch motor on another Haibike with a traditional sized chain wheel. The tooth loading on a tiny chain wheel must be huge on a normal bike, adding another 60Nm of torque makes the result inevitable rather than surprising. Did not Bosch understand the chain suck issues on granny gears?

 

[EddieJ]

Sorry to hear that Lumos.

I hope that all of your repairs have been carried out under warranty, and that you have received a big apology from both the dealer and Haibike.

It's certainly a potentially lethal issue, as I came close to finding out whilst try to cut across a fast blind intersection/ Junction. Half way across and the rear wheel locked up solid. I have now modified my bike in the hope of stopping it from happening, but why should an end user have to do the job of Bosch. They need to sort this out, before someone gets injured or worse.

 

[Lumos]

No, nothing fixed under warranty, it wasn't until I came across this thread that I discovered that I was not alone in the chain suck problems. Probably paid for £1000 of transmission repairs so far in a 12 month period. I have had the wheel lock up a number of times when the derailleur enters the spokes. Strangely this has always been at some speed and not at the lowest gears. Do MTB riders stay inside when the bridle paths are really muddy. In England that would put the bike of the road for significant parts of the year. How is your mod working out?

 

[EddieJ]

I'll take some photos of the mod when it's back on the bike. I'm just waiting a Bosch spider tool to arrive, so that I can fix it onto the motor cases from the inside. It's currently a bit of a prototype mod, but after a bit more testing, I'm going to get some machined out solid nylon block. I'll happily send one across to you if it works out.

Ref the riding off road. Many shy away from venturing off road when condition turn nasty, but I try to get out at least three to four time a week, in all conditions. I've recently met up with a lad from my home town who does similar rides to me, and is also out three to four times a week. Meeting up has been a good thing, a sit gives a bit more motivation to get out.

What I do hate though, isn't getting the bike wet and muddy and having to clean it after each ride, I just hate coming back after a ride in complete darkness, and then having to remove wet and muddy clothing. That's the tough part about riding over here in the UK at this time of year.

Poor old bike.

 

[Lumos]

Yes, no matter how cold and wet I may be the bike gets cleaned and oiled before I can get in the shower. I really like riding with friends and I am more mindful of the hazards of riding alone especially at night in the woods. After going over the bars I found myself unable to get up and had to drag myself up the hill to reach my bike so I could call an ambulance. It is so sociable being able to share the ride with someone. I have, however had some stunning rides in the mud and the rain at midnight in the woods. My 4500 lumens on my head means that it is pretty much daylight. We are on clay in the chilterns and it has been super slippery after the rain over the last two days.

I really appreciate the offer of the mod, even though I cannot quite work out how it works.

 

[Shea N Encinitas]

It seems that every time it happens it bends the derailleur hanger leading to the secondary consequences for the transmission.

If you have the clutch type of derailleur that holds the chain in tension perhaps you should unlock it when going into the bog, bending RD's into the spokes is pretty extreme. Or if this makes chain suck worse dedicate and extra water bottle to occasional rinsing of the muddy bugger. -S

 

[Lumos]

Yes, the Sram XX1 has a clutch, but I would have thought that engaging it would reduce the derailleur tension when what I really what is to increase the tension to counteract the mud holding the chain to the chainwheel. I had considered increasing the tension using the B screw on the derailleur. However, I think that your suggestion about the water bottle is a good one. This week I did stop to clear some of the crud with a stick before I ran into trouble. There is no real space for a water bottle on the AMT Pro so I carry the water on my back. It would be on add spectacle to see be squirting water out of my mouth onto my chain wheel. I appreciate your suggestions.

 

[EddieJ]

I have also now taken to carrying a small metal hook/pick on the bike, and every now and then, I unhook the chain from the front sprocket and clean the mud out from either side of the sprocket. It's surprising just how little that it takes in the way of sticky clay or chalk, to create the chain suck issue. I'd like to see a representative from Bosch come on here, and explain what they propose to do about the situation.

Lumos, I hadn't realised that you were from the UK. I've never been to the Chiltern Hills. Most of my riding is either carried out on the chalk/ clay of the South Downs, or the occasional trip to the Surrey hills, which are more sandy and free drainage. I live next to Ashdown Forest, and the soil here is Wealden clay, with sandy area on the forest. The forest soil is highly corrosive though, and it's only a matter of hours before components start to corrode if the bike isn't washed. Leave a chain over night, and it'll be bright orange by the morning.

Here is an example of the pleasure of riding on the South Downs at this time of year. Not my bike or photo.

 

[EddieJ]

Lumos, next in the line of Bosch related issues. 630miles in, and this bearing has failed.

I also noticed that the front sprocket now needs replacing as well. I'd have expected more mileage than this from a sprocket.

I beginning to think that Bosch haven't made any effort in respect of research and development of the Performance Line motor.

 

[Lumos]

That is pretty sad at such low mileage. I have done over 2000 miles and that bearing is holding up well. I am meticulous about cleaning that out well and lubricating it. I changed the sprocket, chain, rear cassette and chainwheel all together a three months ago at around age 8 months. My wheel and steerer bearings are gone. Bosch have done so much right with the performance line and the electrical side is pretty good (although my remote stopped working last week). The small chain wheel is a problem that they must have known about. Part of my problem is the 11 speed rear cassette has fine tolerances but last week I came back the the derailleur hanger was off top to bottom by 3cm on the gauge. I understand that they are keeping this design for the 2016 bikes as well so I am not sure what to buy were I to try something else. I actually have two of the AMT Pro haibikes (identical) and even the US one that I bought from Chris Nolte has eaten a derailleur resulting in a new Sram XX0 and wheel rebuild. This was is a bone dry Colorado. My wife's classic Bosch Haibike hardtail just ploughs through the same mud and I have never touched the transmission and it is shifting al good as new. My 750W fatbike has a Nuvinci sealed hub transmission but I just do not like the feel of it even though it is unbothered by snow and mud.

How long to get yours fixed?

Ian

 

[EddieJ]

The Rotwild range of bikes look very appealing.

Just an example.

http://www.rotwild.de/en/hybrid/r-e1plus-fs-27-5

I only sent my motor off this morning, so sadly have no idea when it will be back. Hopefully not long though.

I actually prefer the Classic line of motor, to the Performance Line. I know that it had it's issues, but the performance and torque were fine, and I found that it had far greater battery range.

 

[Shea N Encinitas]

Just shy of 2K miles and running like a clock here. I was much harder on bikes in my youth, and the amounts of mud in some of these photos shocks me. Best of luck with your repairs and maybe consider a real motorcycle if you are going to ride in the thick of it. -S

 

[EddieJ]

The mud is just your typical European winter.

The novelty of it is just beginning to wear a bit thin now though. Arriving back at home at roughly 10.00pm in the evening three to four times a week after evening rides, then having to clean yourself and the bike, does become tiresome.

Ref riding a motorcycle, it wouldn't be legal or right to ride on the public areas that I do. I'm happy sticking with a pedelec and the freedom that it offers.

 

[John J.T.]

before reading all of this I was going to sell my Giant mountain bike and test and maybe buy a Haibike fs 27.5 I will still test it But now you have made me even more likely to buy a stromer st1 with a city kit and keep my Giant for the mud, the blood, and the beer.

 

[Mike leroy]

the torque sensor can detect when the chain jams. The console could flash or beep to warn you.

Ford Motor Co. has some innovative features in their Smart Mobility eBikes. The handlebars vibrate to communicate with the rider. The feature is used to provide turning directions without looking at the console.

Also, the bike has an ultrasonic sensor that detects when cars pass. The handlebars actually flash to warn overtaking drivers. No reason why Bosch handlebars could not flash when the drivetrain is jammed.

 

[EddieJ]

It takes less than a split second, for the drive to lock solid.
No warning is required, as it happens too fast to prevent it, but any rider is very lucky not to end up on either their backside or under passing traffic. It's a potentially lethal and dangerous design fault, and one that Bosch are choosing to ignore. I guess that is until someone is killed because of it.

A warning device would also simply be something else that might potentially go wrong*.


To extend the thread even further. I am now about to take delivery of my third battery in almost as many months! Bosch have been trying to get out of supplying the latest one, claiming that there is dirt inside of the battery case. This coming from a company that promotes the use of their products on e-mtb's and in extreme conditions. Clearly yet another example of poor design.



*Remember that we are talking about Bosch here.



.

 

[Mike leroy]

It takes less than a split second, for the drive to lock solid.
No warning is required, as it happens too fast to prevent it, but any rider is very lucky not to end up on either their backside or under passing traffic. It's a potentially lethal and dangerous design fault, and one that Bosch are choosing to ignore. I guess that is until someone is killed because of it.

A warning device would also simply be something else that might potentially go wrong.

You mean the mud does not build up slowly? All of sudden a big clump of mud jams the gear?

 

[EddieJ]

Just a few slightly dirty puddles can be enough to cause it, and riding without the rear mech clutch engaged is an impossibility.

Clumps of mud don't tend to really create too much of an issue, but add a bit of water and it's then a different story. It's created as soon as the chain becomes slightly tacky, which in the winter is most of the time. If you look at the first photo of the chain suck, you will see that there aren't any clumps of mud, and that the bike is actually relatively clean.