Fat bike chain ring offset question...

[bergsnj]

My set up:

Race face turbine crankset, 190mm spindle (widest spindle available but it allows the bike to clear any size tire).
Rear hub is 197 spacing
Eagle X01 cassette 10-50t

The chain ring is a race face cinch style, 28t. In the largest 3 gears(50t and the next 2 down) the chain line is pretty crossed up and there is noticeable noise and vibration from the chain engaging with the chain ring at that harsh angle. I'm wondering what chainring I should get to bring the chain line closer to the center of the bike. If i get one of those wolftooth 6mm offset chainrings will that do the job? I don't see that race face makes a 6mm offset chain ring but wolftooth does.

 

[Patrick]

Can't go too far in with 5" tires - the chain will rub the sidewall unless the tire is dished.

I have the same setup with a gx crank, no offset chainring.

 

[serviceguy]

I have the same setup minus SRAM (RF Cinch 28T chainring, RF Cinch 190 spindle and 197 rear hub with a 11-46T) no rubbing nor noise. What spindle spacers do you use? Maybe offset the spindle spacers would work?

 

[bergsnj]

I have the same setup minus SRAM (RF Cinch 28T chainring, RF Cinch 190 spindle and 197 rear hub with a 11-46T) no rubbing nor noise. What spindle spacers do you use? Maybe offset the spindle spacers would work?

i guess there is some adjustability with the spacers, i'll have to look into that. Its not a loud noise but it is an audible chain engagement noise in the biggest rear cogs.

 

[w_b]

First measure the chain clearance to the (largest) tire you will run, while in the 50T cog. At that point you can consider messing with the spindle spacing/chainring offset if it will remain <1-2mm after adjusting.

 

[serviceguy]

First measure the chain clearance to the (largest) tire you will run, while in the 50T cog. At that point you can consider messing with the spindle spacing/chainring offset if it will remain <1-2mm after adjusting.

The only adjustable parameters is the chainring offset, either changing the actual ring offset (RF allows to reverse the chainring to move the chainring away from the BB, by approx 6mm if I remember correctly) or moving the whole cranks one way or another. Since the noisy cog is the 50T I would assume the chain line needs to move further in a little, if the chain is already too close to the tire he's out of luck. If there's room instead, the RF chainrings have all the same offset, so either he switches to a different brand (i.e. OneUp Switch for non boost chain line) or moves the spacers. I would also worry about the chainring interfering with the chain stays...

 

[bergsnj]

I just cleaned and lubed the chain and that basically solved the noise issue. But I may still get a 6mm offset ring to bring the chain line closer to the inside. I have a lot of clearance. When in the 50t:

 

[one piece crank]

If you take your existing chainring off, you can lay it on a flat surface and measure your current offset.

For the new ring, go for Absolute Black oval.

 

[Patrick]

is that direct mount?
isn't there a spacer system for that?

 

[bergsnj]

is that direct mount?
isn't there a spacer system for that?

It is the race face cinch direct mount.I want to keep the crank spaced the way it is for pedal arm clearance with the chainstays. I'm going to give a 6mm offset absolute black oval ring a try.

 

[serviceguy]

If you take your existing chainring off, you can lay it on a flat surface and measure your current offset.

For the new ring, go for Absolute Black oval.

RF only makes 3mm offset chainring as of now. Both Wolftooth and OneUp have their proprietary system that deal with different offsets using a dedicated spider.

Not sure what the offset offering from other manufacturers is.

I spent more time than it would be considered sane researching this crap when I built my Mukluk, mostly unnecessarily as I ended up using standard RF component and it has been fine ever since. OneUp seemed unofficially confirm that their switch standard (non boost) setup would be best (they led me to write that myself in my e-mail but did not confirm not deny that was the intended use).

I guess tighter tolerances with a boost chainring makes the chain noisier when in not perfectly clean conditions?

 

[Steve Vai]

AbsoluteBLACK or Wolftooth 6mm is the move. You can also run an 11-speed spacer behind the cassette to move that out.

 

[bergsnj]

AbsoluteBLACK or Wolftooth 6mm is the move. You can also run an 11-speed spacer behind the cassette to move that out.

It did the trick. Made the chain line better and silenced the chain

 

[Steve Vai]

Chainring.