Just received my new chainset and BB and the bottom bracket has 3 plastic o rings with it. Firstly where do these go and how do I know if I need them?

You definitely need at least one. If your BB shell is 68mm wide then you need 2 on the driveside and one on the non-drive. If your BB shell is 73mm wide then you only need one on the dive side. They mount between the cup and the BB shell.

68mm shell 2 on drive side, one non drive side.

73mm shell one on drive side.

(assuming no funny mechs or chain devices involved)

I’d ignore the above and add 3 if you have a 68mm BB or 1 if you have a 73mm BB. Put them in whatever order gets you the best chainline, there is no set rule.

According to Shimano there is!

Many thanks guys, it’s a 73mm so jut put the one on the drive side, see how that goes

Did the chainset come without instructions?

Or put one on the non drive side and see how that goes?

Put it on whichever gives the best chainline.

According to Shimano there is!

I dont think its a set rule!

Yea the chainset came without instructions, saved a packet though!

I dont think its a set rule!

This.

I have a DW link 5 Spot & have put one on the non drive side only. As recommended by Turner bikes.

Or just rftm

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Deore-XT/SI_1J10A_002/SI-1J10A-002-ENG_v1_m56577569830680226.pdf

I have a DW link 5 Spot & have put one on the non drive side only. As recommended by Turner bikes

Which is the same as Shimano 😀

If you are running a triple shimano chainset you will want a 50mm chainline. The only reason you would move the spacer(on a 73mm shell) to the non drive side is if you had a 2×9.

davidtaylforth – Member :”I’d ignore the above and add 3 if you have a 68mm BB or 1 if you have a 73mm BB. Put them in whatever order gets you the best chainline, there is no set rule.”

as a professional bike mechanic, I’d advise you to ignore this advice^^

the non-driveside Shimano cup has considerably less thread depth than the driveside cup…

…and adding too many spacers to the non-driveside can leave your cup hanging off a couple of threads

potentially ruining your frame’s bottom bracket shell, and definitely ruining the bottom bracket cup 🙁

for 68mm its 1 spacer on the non-driveside, and 2 spacers on the driveside

for 73mm its 1 spacer on the driveside, and no spacers on the driveside

If you are running a triple shimano chainset you will want a 50mm chainline. The only reason you would move the spacer(on a 73mm shell) to the non drive side is if you had a 2×9.

I run the single spacer on the non drive side with 3×9 as it gives a much much better chain line for my set up though i lose some tyre clearance in granny with front mech.

I run the single spacer on the non drive side with 3×9 as it gives a much much better chain line for my set up though i lose some tyre clearance in granny with front mech.

How is it better? Come on share the info 😆

I get paid to fit this stuff every day and manufacturers specs rule the roost

better in that it lines up nearer to the center of the block when in the middle ring without it on the drive side.