Known Issues & Problems with BULLS Products + Help, Solutions & Fixes

Ann M.

Well-Known Member
No ebike is perfect, this is a thread dedicated to sharing known issues or problems with electric bikes from BULLS as well as any help and solutions you know of. Sometimes that means a DIY fix and other times it can mean a recall, software update or part replacement by a dealer.

Please be respectful and constructive with feedback, this is not a space for hate speech. In many cases, representatives from the company will see feedback and use it to improve their product. In the end, the goal is to enjoy riding and help each other go further and be safer.
 

LimboJim

Well-Known Member
Yesterday I let a friend ride my E-Stream FS3 27.5+. He'd only ridden Bosch ebikes before this, and didn't remember that I'd told him there were two front chain rings. Although he's an experienced cyclist, he ended up audibly cross-chaining, but I didn't think it necessary to check the chain for damage - OOPS!

A bit later, while climbing a steep hill, the chain broke and the motor spun to what sounded like well over 1k RPMs - it made a frighteningly loud, extremely high-pitched whine for maybe 5-10 seconds before shutting off. While it behaved/performed normally after we fixed the chain (chain tools and spare links are good to keep handy), I worry about the internal (belt/gear) wear and long-term effects this incident might've caused.

Any thoughts? Has this happened to any of you with other Brose (or any brand) equipped ebikes?
 
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Robie

Active Member
What is cross chaining? Is that with chain on small ring front and small ring rear ? Hope your bike is fine. That is a super e mtb.
 

LimboJim

Well-Known Member
What is cross chaining? Is that with chain on small ring front and small ring rear ? Hope your bike is fine. That is a super e mtb.
Thanks for the well wishes! Yes, that's cross-chaining as I understand it, and indeed, it's an amazing eMTB. I feel like I'm half my age riding it on my favorite old trails...

A lot of MTBs now come with a much larger "granny" gear rings than before, usually with 11- or 12-speed cassettes (this one has 11). When crossing from the large front chainring to such a large rear one, unassisted hard pedaling won't usually bend or break a chain link, but still really stresses the chain (even with a 10 speed smaller granny ring). Add up to 90Nm from the motor to that and... snap!

Hopefully I'll hear from a Bulls tech about why the motor spun out like that - and if it could've suffered any damage - soon. Knock wood, it rode fine again today.
 

Robie

Active Member
Thanks Limbojim, and, E wheels for the link for understanding cross chaining . I've noticed that I seem to be doing it a lot. Not a good habit for the torque our motors are producing.
 

LimboJim

Well-Known Member
Addendum: my Bulls had maybe 120 miles on it at the time of this incident, so the chain was relatively "young."

Last year I had a chain break on my 2015 iZiP E3 Sumo (73Nm of rated torque), but it had a few hundred hardy trail miles on it at the time. I had to walk/coast the bike 3 miles that day...

I've since bought a chain checker tool and check my chains regularly. I also carry a quality multi-tool (with built-in chain-pin breaker) and the right size connector links for my chain with me on all my rides. Sure came in handy this time!

Chain breaks seem to be more common with my eMTBs - in ~30 years of "regular" MTBing, I don't remember ever breaking a chain! Of course, my bike weighed a lot less and my legs never put out this much force.
 

Robie

Active Member
Thanks limbojim for the info. on chain care , I am building and ebike chain kit now for repairs , one question since ebike chains are built stronger, do they require a special master link required for on the trail repair ? Thanks
 

LimboJim

Well-Known Member
Thanks limbojim for the info. on chain care , I am building and ebike chain kit now for repairs , one question since ebike chains are built stronger, do they require a special master link required for on the trail repair ? Thanks
I've seen ebike-specific chains available, but never noticed offerings for separate ebike chain links or pins.

I get a lot of my parts and accessories from bike-discount.de out of Germany (where eMTBs are far more common the in the USA), and thought that if anyone would carry such items, they would. While the charge about $25 to ship here, I find that their selection and savings more than offset that fee. For instance, I got a Magura wireless dropper post, which lists for upwards of $500 on most US sites, for less than half that there.

While they have far more ebike-specific parts listed at more reasonable prices than any website I've seen yet, the chain connectors they show on their ebike chain pages don't appear to have that label... yet!

Consumer demand might change that soonly.
 

Sadikin

New Member
I just purchased a 2016 Bulls 29er with Brose motor. The problems with my bike is the frequent system power cut Iam getting. The power will cut off for no reason and turn itself back on after 1 or 2 sec later. What could be the problem?
 

kennyzzz

New Member
could you provide more details on the motor cut out.
is it cutting out when going uphill , down hill, or just pedaling at the same speed on flat ground at say 10 miles a hour.. also what level of assist and gear & speed will help too.
 

Sadikin

New Member
The power cut mostly occurs during going up hills. I normally use max assist or a level down. The display will turn off when the power cut and the display will turn back on 1 or 2 secs later. After it turn back on the setting on the display will reset back to no power assist. I have to set the assist back up again like everytime when I first power up the bike. The power cut sometimes happen on level ground too.
 

LimboJim

Well-Known Member
The power cut mostly occurs during going up hills. I normally use max assist or a level down. The display will turn off when the power cut and the display will turn back on 1 or 2 secs later. After it turn back on the setting on the display will reset back to no power assist. I have to set the assist back up again like everytime when I first power up the bike. The power cut sometimes happen on level ground too.
I'm no expert, but it sounds like a (hopefully) simple disconnection somewhere along the line. Maybe check for obvious loose connections in all your visible wiring first? If it's not obvious, you may need ask your dealer for help.

Maybe @BULLSBarney has as better idea...
 

jtooley

New Member
I have a Bulls lacuna evo e45. Its new, but I am having problems with the chain slipping between gears when going faster than 20 mph on the smaller rear sprockets. I think I have eliminated the motor since it happens when its on any level (0-3) of assist. I have tried adjusting the rear derailleur but I cannot eliminate it. It has a Shimano Deore XT RD-M781SGS-10 derailleur. Any advice?
 

pxpaulx

Well-Known Member
If it is new, make sure the chain is properly lubricated, and make sure you're not crossing your gears (using the small front gear and small rear gears). That is all I've got. If it is definitely the chain and not to do with the motor, any shop can help you out trouble shooting.
 

Ravi Kempaiah

Well-Known Member
I have a Bulls lacuna evo e45. Its new, but I am having problems with the chain slipping between gears when going faster than 20 mph on the smaller rear sprockets. I think I have eliminated the motor since it happens when its on any level (0-3) of assist. I have tried adjusting the rear derailleur but I cannot eliminate it. It has a Shimano Deore XT RD-M781SGS-10 derailleur. Any advice?
Hey @jtooley , chain slip happens when the derailleur in not indexed properly. If it positions the chain between sprockets because of slight misalignment, you may notice this. Any bike shop worth a salt would do this derailleur adjustment for $10. You can also watch YouTube videos and do it yourself.
You may need to adjust the limiting screws but it would be best to have a trained mechanic do it properly.
 

bob armani

Well-Known Member
Addendum: my Bulls had maybe 120 miles on it at the time of this incident, so the chain was relatively "young."

Last year I had a chain break on my 2015 iZiP E3 Sumo (73Nm of rated torque), but it had a few hundred hardy trail miles on it at the time. I had to walk/coast the bike 3 miles that day...

I've since bought a chain checker tool and check my chains regularly. I also carry a quality multi-tool (with built-in chain-pin breaker) and the right size connector links for my chain with me on all my rides. Sure came in handy this time!

Chain breaks seem to be more common with my eMTBs - in ~30 years of "regular" MTBing, I don't remember ever breaking a chain! Of course, my bike weighed a lot less and my legs never put out this much force.
Jim= I have had my MTBs for over 25 years (Trek 7000-Made locally) and have never had a chain snap! Lucky I guess. I have always cross chained with no issues.
 

jtooley

New Member
@Ravi -- I watched a few videos, and read the manual. I adjusted the derailleur today, and lubricated the chain. After several tries and tweaks I think I finally got it adjusted right. Now it rides smooth without skipping when there is lots of torque or going fast. Thanks for the advice
 

LimboJim

Well-Known Member
Jim= I have had my MTBs for over 25 years (Trek 7000-Made locally) and have never had a chain snap! Lucky I guess. I have always cross chained with no issues.
Hi Bob, cross-chaining "small-to-small" is one thing, but going from the large front chainring to an oversized, 40-tooth rear sprocket with well over 90Nm of torque is another!

None of my old MTBs ever had more than 32T sprockets (my last was a 2002 Stumpjumper, which I still have). It has a 3X9 setup, and I'm pretty sure I cross-chained it more than once, never breaking a chain, either.