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Discussion Starter · #1 ·
typical chainlines for a boost bike is 52mm but as we all know that there's more wear and friction when you're in the lowest and largest cogs. Why shouldn't we move the chainring as far in as possible allowing chainstay clearance to get a smaller chainline so you're more centered in your climbing gears for less wear and friction? When I'm descending I'm not pedaling and when I'm cruising I don't push that hard. Wouldn't this be best for wear and reduce friction for most of the times you're grinding? This of course is limited to the size of your chainring. I run a 28t so I have quite a bit of space to play with.
 

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Discussion Starter · #3 ·
You're referring to this article

It makes sense. A standard 52mm is to give space for a 32T chainring and clearance when running on the smallest cog.
I guess you can move your chainline inwards as long as you have at least 3mm clearance to the chainstay and the chain doesn't catch the next cog when it's in the smallest cog.
I'm going to try it and see what the smallest chainline I can get away with.

If you go through your gears you can see how the chain is rubbing in a 1x system. I'm guessing that's a lot of wear on the chain as well as loss of wattage. As long as we understand the limitations and how 52mm was derived, we have optimize it for out specific builds.
 

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When moving the chainring inboard there is a chance you can pick up a small stone that can get caught behind the back of the ring and the stay, causing damage. Don't ask me how I know! There is a lot more to calculating chainline than you might think. I have a Yeti ARC which has a 55mm chainline. I tried a 52mm chainline and while it was possible, it was so tight that the little stones were continually being caught behind the chainring, So be careful!
 

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Discussion Starter · #6 ·
I've just tried moving it closer and I don't feel comfortable. I think 52mm is the best I can do. I can move the chainring closer with at least 3.5mm of clearance but if my chain drops and gets stuck it'll scratch up my chainstay. My 11sp chain is about 5.6mm and it probably should be larger than that. Right now with a 52mm chainline, I have about 7.5mm of gap space for the chain to fall in and out.
I was thinking if that gap is less than the chain width, it won't fall through, but I think it can still get stuck and cause damage.
Go ahead and try it. Take off the NDS crank arm and just move the chainring inward and outward.

@beastmaster, yeah I agree with you on this one. I dont want to scratch the carbon. Seems like maybe the frame mfg did some homework but it's good to know why as consumers.
 

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Interesting blurb from Wolf Tooth. I converted an old 3x9 bike to 1x11. The cassette centerline is around 43-44mm on this bike. The middle ring mounts on the old 3x crank are at 50mm. I was able to use 4mm of spacers to get it to 46mm. If I understood that Wolf Tooth piece, that's right about where it should be.
 

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bin there done that.

there is a previous post by me w some pics


bike works great or as expected now. 6mm offset

ended up w a 28t chainring and then removed two links. (just because of the drop from a stock 32t.)

note run the older n/w chainring tooth pattern as the new chain ring has a design flaw where the thick tooth makes improper contact w the edges of the chain. chain plates drive into outside edges of the base of the thick tooth. cant be good for chain life, etc.

seen this on other brand chainrings also.
 

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I had a 2x10 Boost bike with 36/22 chainrings. I converted to 1x11, kept the crankset, mounted a regular old 28t chainring (not narrow wide) on the inside position of the crankset, no spacers. I think that ends up as around 48 mm chainline. Works great, never drop the chain backpedaling, chain is relatively straight while in the biggest cogs, of course. I have dropped the chain a total of 3 times in two and a half years of riding this setup. The frame would probably fit a 30t but I like the 28t.
 

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Fwiw I just fitted a non Boost crankset (48.8mm chainline) based on the Wolftooth article. I've also gone from a 30t to 32t n/w chainring.

My bike is Boost with a 1x11 set up and came as stock with a Race Face crankset with a 51mm chainline. Had good clearance to play with and still consider that I have good chainstay clearance (around 6.5mm) after the changes. Not dropped a chain in two years.

Side note all works well so far except my chain derails off the biggest cog after a couple of back crank rotations, weirdly it didn't do this before with 51mm chainline. Put this down to it all being brand new and/or an 11-46t instead of a 11-42t cassette, I guess it will wear in a little and settle down. 🤔
 

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Fwiw I just fitted a non Boost crankset (48.8mm chainline) based on the Wolftooth article. I've also gone from a 30t to 32t n/w chainring.

My bike is Boost with a 1x11 set up and came as stock with a Race Face crankset with a 51mm chainline. Had good clearance to play with and still consider that I have good chainstay clearance (around 6.5mm) after the changes. Not dropped a chain in two years.

Side note all works well so far except my chain derails off the biggest cog after a couple of back crank rotations, weirdly it didn't do this before with 51mm chainline. Put this down to it all being brand new and/or an 11-46t instead of a 11-42t cassette, I guess it will wear in a little and settle down. 🤔
I think the backpedal chain drop is related to the larger 46t cog, how it mates with the derailleur, or the chain length (you would want a new, longer chain if you went from 30t front/42t rear to 32t front/46t rear).
 

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I think the backpedal chain drop is related to the larger 46t cog, how it mates with the derailleur, or the chain length (you would want a new, longer chain if you went from 30t front/42t rear to 32t front/46t rear).
Yeah, I guess it's probably the bigger cassette @paramount3.??

All new chainring, jockey wheels, new chain cut from scratch based on big/big plus 3 links and master link, (hardtail) pretty sure length is okay.

Not something that will effect my riding or get in the way just sort of thought it was strange especially with the non Boost chainline.?
 

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I have sometimes (not always!) had some luck correcting this by using the B screw adjust to increase the gap slightly (2-3mm) between the upper derailleur pulley and the largest cassette cog.
Yes, worth thinking about @Sssteveyoung. I did adjust b-tension gap, it's around 5-6mm and it seems fine but I will look at it again, tweak it and see if it helps. Thanks!👍
 
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