Help I've run into an issue

[Perrin21]

Re:

I hear what your saying about the BB but I've just measured it and it's within the spec you gave. The main issue is the chain catching on the chainrings making the drivetrain rough. Here's some pics but either way that's the part that needs to be sorted before I can see where I stand with the BB. I may get away with the clearance.

 

[itscervo]

From that photo your chainline looks to be around 45mm.
http://www.sheldonbrown.com/chainline.html

 

[mattr]

In what gears does the chain catch on the lift pins?
I'm guessing middle ring and top one or two sprockets?

I had that on my completely original and correctly built XTR equipped bike 18 years ago. I just avoided using that gear, it's duplicated about half way down the cassette on the big ring anyway.

I've also had it on pretty much every road bike i've ever had. And almost all the other MTBs.

You want good front shifting, you need the rings to be close to each other and you need the pins, so you are likely to get catching in some combos. Unless you have 50+cm long chainstays.

 

[scottproonly]

Re: Re:

A 8 speed chain on a mega 9 chainring should be no problem.
But it doesn't work on a 9 speed cassette.
A 9 speed chain on a 8speed cassette doesn't work either.

I've used a 9speed chain on an 8speed cassette with great success!

 

[mattr]

Yeah, going up a speed for the chain is usually ok.

 

[Perrin21]

In what gears does the chain catch on the lift pins?
I'm guessing middle ring and top one or two sprockets?

I had that on my completely original and correctly built XTR equipped bike 18 years ago. I just avoided using that gear, it's duplicated about half way down the cassette on the big ring anyway.

I've also had it on pretty much every road bike i've ever had. And almost all the other MTBs.

You want good front shifting, you need the rings to be close to each other and you need the pins, so you are likely to get catching in some combos. Unless you have 50+cm long chainstays.

Its catching in all gears which suggests its chain related. I have ordered a chain that should be here tomorrow so i will fit that and test to see how it all runs.

 

[FluffyChicken]

A 9 speed chain is slightly narrower and will work with that setup, it may/may not help.
The cranks are a nice distance from the chainstays still so not a problem ( though irrelevant info )
The chainline is too short. It'll work but when in granny or even in middle if you are on the lower cogs at the back, then it may catch. That's reading 50mm if you but it's from the middle ring you should be measuring.

You may want to tweak the chain line at the bottom bracket if there is room for it (I don't think there will be much on a DuraAce one, If you can squeeze a 2mm spacer on the drive side, give it a go. BUT it'll ram the arm into the frame :-(

Longer bottom bracket is the obvious answer if the slight chain wide doesn't help. It doesn't need to be much as it would be lifting the chain.

I will worn though, that you may get chainsuck when it does lift over bumpy ground. (I know it well)

 

[itscervo]

Don't know what make of chain you've tried or bought, but they aint all the same.

Shimano HG 7-8 speed 7.4mm
Shimano IG 8 Speed 7.1mm
SRAM 9 Speed 6.9mm
Shimano 9 Speed 6.6mm

 

[Thias]

And then you can of course add shims between the middle ring and the crank arm to gain a little distance.

 

[mattr]

Either chain or spacers (between rings) AFAIK this chainset doesn't use spacers.

9 speed chain *should* fix it.

Or at least, you'll only catch the lift pins in the top one or two gears at the back.