Dure Ace Gears

[GoLefty!!]

GoLefty!! can't it also be that the BB sizes my differ? A narrower BB vs a wider BB...wider allowing more room for the chain...

 

 

What you're refering to is the Chainline. For road bikes this is always around 47.5mm. For MTB's it's 50mm to make room for the extra chainring.

 

Chainline for roadbikes is similar, irrespective of the BB width.

[ZippIt]

On my old Centaur groupset I could crosschain from 39->11 without a worry. Now with the Chorus' date=' I can't crosschain at all...it seems to be the teeth on the 53blade picking up the chain and then throwing it off... I suppose it's time I learned not to cross-chain [/quote']

 

My chorus begs me for 53-23..

its the best gear i have!

 

The other side (39-11) - I can do it but prefer just to slip it onto the big ring..

[Guest colonel]

I agree with Titus on this one.

[SwissVan]

I agree with Titus on this one.

 

 

Jawhol ja me 2

 

Sometimes you can get away with it, depending on how much time you (or your LBS) are prepared to fiddle around trying to find the best position for your front dr. 

Other than BB width another factor is frame size / design and the length of your rear stays (or distance from the BB to the rear axle) the shorter this is the greater your chain angle will be and more chance of rubbing on the front dr.

 

Typicaly shorter wheel base bikes will have this problem, if you have a long wheel base you may get away with no or very little rubbing.

 

But moral of the story is you should not really be using extreme opposite chain ring selections, a 39 - 11 (or similarly a 53 - 23) because it will place excessive loads on the connecting plates / pins, leading to at worst case scenario a broken chain while you are climbing  / standing.