I have my bb fitted (68mm shell, band on mech) with two spacers on the non drive and one on the drive, the opposite to what Shimano say, I reckon the chainline is better (middle ring sprocket 5 is straight)

Does anyone else do this, am I wrong, is their way actually better for some reason I am not getting, does it really matter?

Interested as fitted new chainset and mech catches (new ones are a different profile cage) a new mech should sort it but this got me thinking about my spacing of the bb….

Is the thread shorter on the non-drive side cup?

Mech catches what? Tyre?

No it doesn't catch the tyre, though with the 2.25 Ardents it is very close i noticed last night..

Obviously the spacers as Shimano detail will move the mech further from the tyre when in the granny ring, though that is not a gear I use a lot so not sure it is too much of a convern.

Mech was catching on the crank arm itself when in the big ring, the M960 mechs have a bend in the cage, the M970 are straight. I bent the cage and it is not straight, everything shifts on the stand and it is clear of the crank, will see if all is well when i get out and test it under load.

Was more interested in why Shimano are right and I am wrong, is there a valid reason why I should do it their way and not mine?

Sorry Jim, cups are same thread both sides, more of a chainline reason i imagine, though mine looks better, i think….

It is middle ring and middle sprocket as a good indication of chainline right, straight chainline from the chainset to cassette is good yes?

Shimano put two spacers on the driveside so if you need to run a BB mounted mech you can remove the extra spacer to accomodate this. By flipping the extra spacer to the non-drive side you are moving the chainset 2.5mm to the left, the cranks won't sit equally spaced to the frame. However in practice you are unlikely to notice this difference.

Yep I ran mine off centre last year, and it was fine, as you say the chainline was better, and you could use a road front mech. I'd watch out for any knee pain or anything like that, but on an MTB I doubt you're likely to notice a 2.5mm offset in the pedals.

I do exactly the same. Couldnt get my front mech to shift down into granny, removing a spacer did the trick……dont think you need to run 2 on the non-drive though I do so I dont lose the damn thing….

I always thought MTB's used to be 47.5mm chainline (back when everyone ran 110mm UN52 bb's 😆 ), now everyone seems to run 50mm chainline with HT2 cranks and if anyone asks about square taper a 113mm bb is reccomended.

So i know what you mean about trying to line up the middle ring on the cassette but TBH id not worry and just set it up however it works best.

Well all seems fine, will ride on it and test it later but nice to know i'm not the only one….

Never noticed the cranks being unevenly spaced, did have knee pain, ditched the XTR pedals and started using Time Atac Roc pedals, all pain gone now…

Oh, and is it me or did front mechs never rub on the chain as much back in the day as they do now?

I ran M970s offset for the second half of 2007. I still suspect it to be one of the reasons for the knee injuries that made 2008 a total washout.

Dougal, mmmmmm food for thought….

Though been like that for a good number of months, maybe the change to Time has disguised the real issue, that being the offset cranks?

That possible?

where you put the spacers shouldt affect you too much. I used to run 2 on the NDS, and a chain device on the DS.

Most cleats have a bit of side to side adjustment, certainly enough to accomadate 2.5mm. Times IIRC float this way, shimano you have to fix in the psoition you like.

Another thing that is worrying me now as every bike i look at has acres of room compared to mine….

Inside of RH Crank arm is sooooo close to the mech cage in the big ring, all other bikes seem to have loads in comparison…..

Not sure what is different that makes mine so close. Not touching though so don't imagine it's a problem, i'm just picky and want to know why mine is so close…..

Cage sitting squarely over the chainring, not excessively adjusted out…

Methinks i'm thinking about this tooooo much!

The LBS I use recommends setting them up with 1 drive side spacer as it improves the chainline and he seems to know what he's doing.

went for quick spin with the set up now sporting a 'modified cage' xtr mech and one drive side spacer, all good, no rubbing, I'm happy.