Avoid front small, rear small gear combo?

[nbfman]

My bike has 52/39 in the front and 12-25 (10 sp) in the back. On the 39-12 combo, the chain tends to grab the front 52 chain ring, even though there is no contact with the front derailleur chain guide. It seems that the relative positions of the front and rear chain rings need a slight lateral adustment (i.e. the sprockets need a shift towards the hub and/or the front chain rings need to move away from the bike). Are there ways to do such adjustments? The componets are Ultegra crank (the one with integrated spindle), derailleurs, and chain, and Dura-Ace wheels and sprockets. All are for 10 speeds in the rear.

I have heard that one should avoid the small-small, large-large front-rear gear combos, and I usually do. But even so, is such partial shifting behavior normal and to be expected in these gear combos? Or does this indicate a problem that needs to be fixed.

Thanks,

nbfman

 

[Rideastrong]

yes this is to be expected. you have cross chained the drivetrain. We all hit the combo sometime and it is just part of cycling. Try not to do and you will be fine.

 

[boudreaux]

My bike has 52/39 in the front and 12-25 (10 sp) in the back. On the 39-12 combo, the chain tends to grab the front 52 chain ring, even though there is no contact with the front derailleur chain guide. It seems that the relative positions of the front and rear chain rings need a slight lateral adustment (i.e. the sprockets need a shift towards the hub and/or the front chain rings need to move away from the bike). Are there ways to do such adjustments? The componets are Ultegra crank (the one with integrated spindle), derailleurs, and chain, and Dura-Ace wheels and sprockets. All are for 10 speeds in the rear.

I have heard that one should avoid the small-small, large-large front-rear gear combos, and I usually do. But even so, is such partial shifting behavior normal and to be expected in these gear combos? Or does this indicate a problem that needs to be fixed.

Thanks,

nbfman

Simply stated, you shouldn't be doing it,so don't. It happens,and happens alot more with short chainstays. It can be fixed with a BB shim or spacers between the rings,but that is the ugly way and serves no real purpose. A smart person would learn to just not do it.