Mountain Bike Reviews Forum banner
1 - 10 of 10 Posts

·
Hack Racer
Joined
·
2,559 Posts
Discussion Starter · #1 ·
So I have here a Lynskey Titanium frame. 68 mm bottom bracket shell. Token 108mm ISIS bottom bracket

I bought a 1mm spacer to move the drive side bottom bracket cup out as my chainstay to 42T chainring was pretty close.

The original without 1mm spacer... clearance between the chainring & chainstay was aprox 1.55mm


The new chainring to chainstay with 1 mm spacer. So the clearance is about 2.55mm.


But by adding a 1mm spacer to the drive side bottom bracket cup I have scraficed space between the non driveside crankarm to the chainstay. There is now only 2mm space between the arm and the chainstay. I can flex the crankarm with my hands and have it contact the chainstay while the bike is in the stand. Mind you on the upstroke of the non driveside crankarm, it should not ever see force, so the arm may never flex. But will the back end of the titanium frame flex enough to make contact with the crankarm during one of the rotations of the crankarm?



reference: https://forums.mtbr.com/showthread.php?t=477909&page=2&highlight=lynskey

Advice is greatly appreciated.
 

·
Hack Racer
Joined
·
2,559 Posts
Discussion Starter · #4 ·
with the 108mm bottom bracket, the theoretical chainline is 43mm. So if you add in the 1mm spacer, the chainline is 44mm? Too far inboard?

Middleburn claims if you run a 113mm bottom bracket with their RS7 or RS8 Duo than the chainline is 48mm.
 

·
ups and downs
Joined
·
15,599 Posts
48mm puts it into a better position for the cassette. 44mm is almost one whole chainring space inboard (5mm spacing on the chainrings) so your biggest ring to small cog is about like middle ring to small cog.
 

·
Super Moderator
Joined
·
6,784 Posts
Yeah, that looks scary tight. Just don't go full WW and start grinding stuff down now...
 

·
Hack Racer
Joined
·
2,559 Posts
Discussion Starter · #9 ·
liam2051: Yes I can squeeze the crank arms and make it flex and contact the frame...

Thanks everyone for their insight... I bought a 113mm bottom bracket. A NOS American Classic ISIS. I know some people here don't like it, but I like the fact you can replace the bearings easily.
 
1 - 10 of 10 Posts
Top