I have a mtb currently a 8 speed rear casette. I am converting using a BBSHD which I ordered yesterday. I know my issue will end up being that I might need to backspace the motor to clear the chainstay. In an ideal world, if I want to maintain for sure use of most gears and for sure the lowest gears, where should the chainline fall? the middle of the gearset, like 3rd or 4th? I keep hearing that this is a major issue, however This does not make too much sense to me as most bikes come with 3 chainrings up front and the largest one is easy 6 mm further out than the innermost ring and they still work in all gears no matter what chainring they are on
chain line
- Thread starter Cavi
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Retrorockit
New Member
Usually with a BBSHD you need an inset chainring to get a good chainline. This means a range of 42-48 teeth. To space outwards any of the chainring adapters for the various bolt circles will do that, and the sizes can get smaller. You didn't say what wheel size and intended use. Wide/Narrow chainrings help in a 1x8 situation as they tolerate chain angles better.
A derailer can be used as a chain guide ( this is why crosschain "works") if you have chain drop issues. Be aware that chainrings run on the inside of the adapters so avoid rings that can't be mounted reversed. Cheap rings won't have a counterbore on the bolts and can't be spaced in as much. The stock BBSHD chainring is junk. If you need the lower gears a 42t inset W/N ring set close to the chain stay should work for you. Sunrace makes 11-40 and i've heard 11=42 8 speed casettes that are very inexpensive. I put Shimano or SRAM cogs in the 11t and 13t positions. They hold the chain better under power. A derailer hanger mod may be required to run these. The lower gearing is needed to make up for the lack of the inner chainrings. An 8 speed chain can run in a 9 speed derailer so maybe you can find a wide enough range 1x9 derailer.
I would suggest buying a Park Tool CC-2 chain checker. This lets you stay ahead of chain wear to protect your expensive chainring from the stretched chains you will surely produce.
Clean and lube you chain regularly. Keep a supply of master links ( carry spares), they don't last long.This is mandatory with a BBSHD. FWIW I rivet my chain. A shift sensor, and softer reprogram of the motor firmware are recommended also. The factory program really isn't suitable for offroad use as is. Power comes on @ 25% after 1/4 turn and doesn't stop right away when you quit pedalling. PITA in parking garages also.
Luna Eclipse, and Lekkie Bling Ring are 2 popular inset chainrings.
A derailer can be used as a chain guide ( this is why crosschain "works") if you have chain drop issues. Be aware that chainrings run on the inside of the adapters so avoid rings that can't be mounted reversed. Cheap rings won't have a counterbore on the bolts and can't be spaced in as much. The stock BBSHD chainring is junk. If you need the lower gears a 42t inset W/N ring set close to the chain stay should work for you. Sunrace makes 11-40 and i've heard 11=42 8 speed casettes that are very inexpensive. I put Shimano or SRAM cogs in the 11t and 13t positions. They hold the chain better under power. A derailer hanger mod may be required to run these. The lower gearing is needed to make up for the lack of the inner chainrings. An 8 speed chain can run in a 9 speed derailer so maybe you can find a wide enough range 1x9 derailer.
I would suggest buying a Park Tool CC-2 chain checker. This lets you stay ahead of chain wear to protect your expensive chainring from the stretched chains you will surely produce.
Clean and lube you chain regularly. Keep a supply of master links ( carry spares), they don't last long.This is mandatory with a BBSHD. FWIW I rivet my chain. A shift sensor, and softer reprogram of the motor firmware are recommended also. The factory program really isn't suitable for offroad use as is. Power comes on @ 25% after 1/4 turn and doesn't stop right away when you quit pedalling. PITA in parking garages also.
Luna Eclipse, and Lekkie Bling Ring are 2 popular inset chainrings.
tomjasz
Well-Known Member
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- USA
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- Minnesnowta
Huh? It has a decent offset, designed for the BBSHD, 46T, and you can run heavy EBike chains from Connex/Whipperman that won’t run on narrow wide Lekkie or Luna Eclipse. Lekkie now has a 40T kit with offset. Lekkie looks better and is lighter. I’ve never seen a failed OEM 46T. EVER.
typical MTB chainstay widths, 1.95-2.40 tires widths are seldom a chainline issue. Fatbikes are another story. I alwayd suggest using Google with the brand, model, and year of bike to be converted. More often than not you’ll find another build log/post discussing any issues, or lack of problems.
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Retrorockit
New Member
Dropping the chain is the issue. Mostly over bumps. It sort of worked with a derailer as a chain guide. Mine will never fail. It will never be on my bike again EVER. Maybe my need to run an 8 speed chain was part of the problem? On a single speed, or IGH with no derailer I could see it working. I went to a stainless steel Surly 50T for my puposes on a 130BCD adapter. I finally went with a roller chain guide. I tried narrow wide and removed those too. It's crosschained in the low gears, but I don't use power there, just for pedaling near pedestrians. I run the Wippermann 8SE chain, riveted.
Here's a forum hosted by Luna. You can find lots of BBSHD builds there.
My challenge was getting high enough gearing to use the power of the BBSHD on a 35mph 26" street bike, with low enough for urban sidewalk crawling.. 46t was never going to cut it in the first place. 50tx11-40 8 speed, Wippermann to hold it together. Med. cage XTR Rapid Rise (low normal) derailer with Shimano grip shift so I can dump many gears at once sitting still in traffic.
Here's a forum hosted by Luna. You can find lots of BBSHD builds there.
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