BBSHD LEKKIE 36T chainline issues

[outlaws]

Hi all,
I was just curious why nobody is building a chainring or adapter for 32-36 flavors for the BBSHD? One of the main reason I built a ebike was for mountain biking but everyone is riding 42T+ which I think is way too high for mountain biking. I looked at Specialized Turbo Levo and they are using 32T. I really want to fit the 36T Lekkie if that is case, but I am not sure how to solve my chainline issue as the chain drops instantly on the low gears. Any help please

 

[Chalo]

You solve the chainline issue by using a dished ring that fits around the outside of the gearbox and locates the teeth closer to the centerline of the cassette. That means the pitch circle of the sprocket teeth must be bigger than the diameter of the gearbox. I'm guessing 42t minimum.

Your desired low gearing would put the sprocket teeth inside the gearbox, if you had good chainline. Modern mountain bike gears have rear sprockets as big as 50t; how low do you think you need? In the old days of MTBs most of us were using 28/28 low gears and we didn't have 1000W motors to help us push them.

The BBSHD is a good bit wider than what's on a Specialized eMTB, because it makes a lot more power than the Specialized. If you want to use a BBSHD, you have to accept its physical shape. That means using a bigger chainring than what you'd like, or coping with horrible chainline, or using a bike with a super wide fatbike hub that pushes the cassette farther outboard.

 

[2old]

Another solution is to use fewer cassette cogs with the 42T Lekkie; 11-17-28 with 8-speed spacing are adequate for my BBS02 system. This provides a relatively straight chainline for all three gears.

 

[outlaws]

Are people just able to put 30-36T chainrings on certain DH bikes where the swingarms are a lot wider if you can't get any more offset on the current 30-36T chainrings?

 

[Chalo]

Another solution is to use fewer cassette cogs with the 42T Lekkie; 11-17-28 with 8-speed spacing are adequate for my BBS02 system. This provides a relatively straight chainline for all three gears.

I use the stock 46t chainring on my BBS02, with 14-19-24-28-34 sprockets moved into the outer 5 positions of 8. When I use any of the inner 3 cassette sprocket positions, the chain tends to derail in front. Even the 14t sprocket is mainly a place holder, because it costs too much wheel torque and only opens up a speed range I don't ride in.

 

[2old]

Usually I use the 17 and for the steepest hills, the 28. The 11 is mostly just the last cog on the cassette. I've never had a chain derailment issue (yet). BTW, this particular bike is a GT Zaskar with a Ritchey carbon fork and weighs only 35 pounds with a BBS02 and Luna 52V, 6 ah battery. I seldom go above PAS level 1 (of 5), and about half the time ride with no assist.

 

[outlaws]

Thanks for all the info! I may have been wrong with my assumption all along after I finally took the ebike out for a spin on the 42T Lekkie and the chainline was perfect going up all the fireroads, even the steep ones. If I thumb throttled going up a steep hill , the bike would even wheelie if I was not careful I had no problems on all the gears going up except the chain dropped on a really rocky section going downhill but that was probably because I didn't adjust my chain length yet. This BBSHD is way more powerful than I had ever imagined! Can't wait to convert the hardtail for a full suspension later on if it ever breaks or once I get more used to it. This is too awesome!

 

[dorndi]

Hi,
I am from Austria and new here.

I have a similar "problem" like the thread opener:

I have currently a BBS02 with the original 44T steel chainring and want to be able to climb slowly very steep trails.
The offset of this chainring is too small for riding regularly the slowest 51T cog of my Deore 11-51 11-speed cassette (much wear and chain falls off on rocky trails due to bad chain line).

In other words: the chainline is too far outside ... good for the fast gears but very bad for the slowest gear.

I don't really need the smallest two cogs because I don't need a very high top speed on this MTB.
I am wondering if it might be possible to install only the 9 biggest cogs of this 11-speed cassette (15-18-21-24-28-33-39-45-51) and to improve the chainline by using freehub spacers on the inside of the freehub (spacers which are about as wide as the 11T and 13T cog)?

Do you think that it is technically possible to adjust the rear derrailleur to such a setup (without the smalles two cogs)?
I am wondering if is only possible if I install something like a self-made "derailleur hanger spacer" to move the whole rear derrailleur more outward so that the parallelogramm of the derailleur fits to the changed position of the cogs?


(I know that there are expensive chainrings from Lekkie with 40T or 42T with narrow-wide teeth and a bigger offset to improve this situation but for now I think about the cheaper possibility to use only 9 of the 11 cogs ...).

What are your thoughts on this?

Thanks!

 

[fechter]

I'm running a 30t chainring on my BBSHD. I took apart the cassette and rearranged the gears so I have 3 between the hub and the largest cog that I don't use. This has worked out great.



This is somebody else's, but the same idea:


So now I only have 7 gears instead of 10. If the chain were to fall off the largest cog toward the hub, it would land on the unused cogs and prevent fouling the spokes.

With the 30T chainring, I can still reach 28mph in the 3 tallest gears (power limited speed). It's awesome for climbing steep fire roads at a snail's pace and keeps the motor from overheating.

 

[dorndi]

Thank you ... I will try something like that with my cassette next week and hope that I can adjust the rear derrailleur properly.