7mm BB spacer???

[ee1337]

I'm trying to move my BBSHD unit to the right by 7mm in order to fit a large chainring (Eclipse 48T), and clear the chainstays of my bike. I ran out of space to add spacers between the motor and the new chainring. if I add any more, the chainring will not sit around the flange of the motor at all.

Long story short, I would like to add a spacer between the BB and the motor on the drive side, which will solve all issues. I don't want to stack up a bunch of spacers, but instead use only 1. Most BB spacer kits I'm finding top up at 2.5mm, requiring the use of 3 spacers. How can I procure a 7mm spacer (+/- 1mm, that's ok), with an ID of ~34mm and an OD of about ~44mm?

[AZguy]

Probably would have to fabricate. Why not stack?

[Dshue]

I wouldn't hesitate to stack them. I have some spacers up to 3mm. So a 3mm and a 2mm bb spacer combined with a common 2mm chainring spacer would give 7mm.
Or just 2 3mm spacers.

The spacers I have are cheap ones from Amazon. They are fairly parallel and were close fitting to the bb housing on my BBS02B.

https://www.amazon.com/gp/aw/d/B07F2...b_b_asin_image

[AZguy]

I have around 7mm of stacked up spacers on mine

[73Eldo]

Do you already have the Eclipse? If no then maybe a BCD adapter and use standard chain rings? That way you could go bigger than a 48t if you wanted to. The stock 46 is about 19mm offset the BCD's should put you around 9mm so that gets you your 7 and chain ring spacers easily.

[AZguy]

You can also just leave the motor where it is and shim the chain ring out... or do a combination of both

[ee1337]

Yeah I already got the Eclipse, I considered the BCD adapter for a while, but I forget what the problem was with that idea that made me abandon it. Hard to tell the fit without the parts in hand, and these days mail order is the only possibility, nobody carries a thing anymore. Custom builds can be annoying with trial and errors like that.

I felt like stacking a bunch of spacers wasn't optimal with the potential for flex, or misalignement of spacers resulting in partially supported load. But this is more of a theoretical problem that I have not proven. If there is no known parts that are 7mm or so, I guess I'll just stack them.

[AZguy]

I run the BCD adapter and like mentioned have at least 7mm of BB spacer - lucky that I have a good chainline

Bought a almost unused eclipse for good deal but still haven't installed it. I will likely need to space it out from the motor but I don't see that as a big deal either.

[ee1337]

Now that you mention it, I think the offset was the reason why I didn't get the BCD. Someone had a post comparing the various offsets. Lekkie was another possibility with less offset, but because it was 50 teeth it would have hit the chainstays anyway. Somebody, send me everything for free and I will report back

[AZguy]

The BCD has a lot less offset - around 14-15mm

My chainline is good but not perfect with the BCD, centers at about the fourth or fifth smallest cog on 11sp cassette - no trouble at all with any gears but "prefect" would likely be fourth or fifth largest cog and that's about splitting the difference between the two so I'd need to shim the eclipse around 7mm

[TNC]

Chainline...possibly one of the biggest headaches of mid-drive conversions. And then take into account the extreme variety of bikes and other conveyances that these motors are attached to, and it's nearly impossible to give specific advice without being preset to see and measure what's going on. Then take into account what the bike/conveyance will be used for, and that either adds another layer of complexity or simplicity depending on application.

Chainline is relatively critical for any bike, and in some cases it requires spending whatever to get a perfect or at least more than acceptable chainline. I hated spending nearly $100 for a Luna Eclipse for my MTB, but without it I would have miserable issues on the trail for aggressive mountain biking. As is, I was able to get a perfect chainline, dead-center on 73mm BB full suspension frame with an 11-50, 9-speed rear cogset.

OP, on your concern about spacing out the chainring with spacers...at least like the 5-hole units you get from Luna...unless you get ridiculous, those should securely fit the chainring with no issue. Between Luna chainring spacers, Eclipse chainring, and when you have an option to push the motor over in the BB a bit, one should be able to fit the motor and achieve an excellent or at least decent chainline. If all these factors won't let you achieve that, maybe the frame just isn't suitable.

[AZguy]

Funny thing is they don't need to be "perfect"... as long as you can hit all the gears that's "good enough" IMO... it's one of the reasons that even though I've got the [expensive] stuff to make it "perfect", I haven't gotten the spacers/washers/bolts and spent the 2-3 minutes to do so... oh well...

[TNC]

Shame on you, AZ, for having nice parts sitting on the bench that need to be installed for perfection...shame...LOL!

I agree with you on the "perfect" description. With narrow/wide chainrings, a clutched derailleur, proper setup, a multitude of sins can be covered...LOL! But it's so nice not to have grinding, hard shifts, chain dropping, and unnecessary wear with the kind of power these motors can deliver.

[AZguy]

Agreed and I would consider those faults as not "good enough"... as long as the chain is lubed mine shifts quietly, smoothly and quickly through the whole range and likely the only thing that might be different if I were to make it "perfect" is that now rolling it backwards when in the lowest two or three gears causes it to move to the smaller cogs... but that's just such a non-issue for me!

[Dshue]

The spacers I have are plenty flat and parallel. I haven't put a tenths reading micrometer on one but they are well within .0005" of parallel judging by what I see on my dial calipers.
I don't think it would weaken the setup at all to use 2x 3mm spacers.
Any weakening will be due to the cantilever effect and would be the same with 1 spacer as with 2.

We use spacers on race vehicles of all types, and even on axles for wheel spacing. We've sheared off 3/4"solid cromoly spindles in crashes with the race karts and the spindles don't usually bend.

[Dshue]

Just because of boredom I got out the tenths reading micrometer.
the variance I measure is .0003". That's perfectly acceptable for the task in my opinion.
I didn't bother doing it scientiscientifically and find an average over many data points but the dozen or so points I checked were all between .1174" and .1177".
so like I said I wouldn't hesitate to use 2 spacers. And these are just random spacers bought on Amazon because they are cheap.