Cassette chainline rework

Hi all. I have just ordered a BBS02 and a Luna mighty mini ring that will go on my fat bike with 100mm BB and 197 rear hub spacing. From what I have been researching, the mighty mini ring is going to put my chain line way out of whack.
My bike will be used for singletrack riding mostly in the snow so top speed isn't a priority and I don't think I will need more that 5-6 gears but want my biggest cassette cog to be at least 34t maybe 36t.
Can anyone recommend a rear cassette that can be easily reworked to move the largest cog as far out on the freewheel as possible to improve chainline?

Choose an inexpensive cassette compatible with your drivetrain with as few useless stock ratios as possible. The geometry of your bike is unknown and will restrict how far a given size sprocket can be moved outboard by an unknown amount. Also, the biggest cogs are generally attached to each other for support otherwise the mechanical advantage from large radius and bad chainline can deform them. You probably want a more moderate sprocket for your riding as the largest gears on a mtb cassette will be too slow.

Anyway you can move the group of biggest gears down and simple pack the back with the smaller gears you don't plan to use. Obviously you don't want to shift past the hump you've now created, but it won't necessarily ruin your ride if you do.

Any inexpensive cassette that doesn't have a spider for the large sprockets can be reshuffled to put the larger sprockets closer to the outside end. You might have to grind or drill the heads off of some rivets to separate the sprockets. Use the derailleur's limit screws to keep it from shifting past the biggest sprocket.

For the outermost sprocket position, you can do one of three things. You can use the 11-13t sprocket that came with the cassette originally. You can find and buy a special larger size sprocket (intended for Junior racing) and use that instead. Or you can substitute a metal spacer from a cassette, freewheel, or bottom bracket for the outer sprocket.

To make the derailleur work right, it may be necessary to use a Wolf Tooth RoadLink or similar hanger extender to keep the derailleur from crashing into the sprockets.

I already have a 10 speed shifter so preferable to get a 10 sp cassette. Problem is I can't find one that the two larger gears aren't riveted to a central spider. The only thing I've found is a 9 speed Sunrace CSM98 that all of the gears can be separated.
I'm riding mountainous terrain in Colorado, pedal assist only and no throttle so I'm thinking I will need the 36t large sprocket.
Would like to arrange the gearing something like this, 36-28-21-17, maybe 13 and stack the unused sprockets behind the 36. I currently ride this bike legs only with a 28t front ring and very rarely shift into anything smaller than 15t in the rear.

If you take out the spacers from the 9sp cassette and substitute 2.2mm thick spacers, you can probably make it compatible with 10 speed shifters, at least across a half dozen gears.

Dura Ace 11 speed uses 2.18mm spacers, or you could stack a 1mm spacer with a Shimano 1.2mm spacer in between each sprocket. For 10-speed, each sprocket plus its spacer should be as close as possible to 3.95mm thick.

Have you looked at the Shimano xtr m980 the 6 largest rings are riveted in pairs the rest are individuall.

@dirtgoon:
You might want to check out the webpage of electroncycles.uk:
https://www.electroncycles.co.uk/product/bbshd-hot-rod-controller-asi-bac-800-36v-90v-foc-90a-peak/

They give some nice informations on setting up a good chain line together with a BBSHD using a standard Shimano 10 speed cassette.

I'm running a 30t chain ring on my BBSHD fat bike and had the same issue. I spend a lot of time in the lowest gears climbing hills. I took apart the cassette and reconfigured the gears:



Now the lowest gear is where 4th used to be and the chain line is acceptable. I adjusted the stops on my derailleur so it doesn't go past the largest gear. On flat ground, I find my top speed is the same in the top 3 gears as it is power limited. The downside is you can't pedal fast enough for human input above about 15mph.

Taking apart the gear cluster required drilling out some rivets and the two largest gears were riveted in a way that I didn't want to disturb, so they stayed together.

I found a 10 speed XT (I think) cassette in my spares bin that I can mod to suit my needs pretty easily. Found quite a selection of cassette spacers on eBay that should make for a tidy modification. Will post some pictures when I get it all set up. :thumb:

I think it's good to have a cog that's not used on the spoke side of the cluster just to catch the chain if it comes off the low gear. It's never happened to me, but a chain in the spokes generally produces a bad outcome.

That's where those plastic deflectors inboard of the sprockets, usually clipped to teh spokes, can help; you'll know really quick when the chain comes off so it doens't have to survive very long, just long enough to stop moving the chain.

Balmorhea said:

If you take out the spacers from the 9sp cassette and substitute 2.2mm thick spacers, you can probably make it compatible with 10 speed shifters, at least across a half dozen gears.

Dura Ace 11 speed uses 2.18mm spacers, or you could stack a 1mm spacer with a Shimano 1.2mm spacer in between each sprocket. For 10-speed, each sprocket plus its spacer should be as close as possible to 3.95mm thick.

Click to expand...

He's right, assuming that...

The question nobody asked you (but was probably assumed): which 10-speed groupo are you using? If Shimano or SRAM then 3.95 is the pitch. If Campy, well, it's complicated...
https://www.sheldonbrown.com/cribsheet-spacing.html

With Shimano 9-speed space gears, the exact spacer needed to get to 3.95mm is 2.17mm. 2.2mm will work fine if you tune it for the center of the (gear 5). Using the Dura Ace 11 speed spacers is definitely the easiest approach. If you end up needing 0.1mm then you can cut them out of a Coke can; it's tedious but it works.

I ended up using 6 of the lowest cogs from a Sram 10 sp cassette I had laying around and a OneUp 42t extender cog for a total of 7 speeds. Only had to space it out about 6mm to achieve a perfect chain line with the Luna mighty mini ring. I did have to use a derailleur extender, found it on eBay for $10 works great.
It's perfect for trail riding, I'm glad I have the 42t for technical uphill sections, and it has plenty of speed for most trail riding.

That looks great.