odd front Ultegra derailer/shifter problem

fingerfun

Hi
I have a newish bike with a full Ultegra gear set that works well except I have an issue with the shifting on the front cogs. Its the standard Ultegra double 53/39 with Ultegra shifters. So I'm on the small 39 cog and click my shifter firmly and up I go on to the 53 cog. Lovely except I have a mystery '3rd click' on my shifter so if i shift up too hard I skip to the '3rd click' and off comes my chain, pushed over the 53 and beyond... The only way to stop this happening is to set up the front mech (using the high and low adjusters) so the only way I change to the 53 cog is using the '3rd click' (dunno what else to call it!!) but that leaves me with an unwanted shifter position in between.
Urmm, help. Any one come across this isuue and if so, what do I do to get rid of it?!

Cheers
Marcus

simmo3801

The third position is called trim. When you change up or down your rear cassette to assist the chain you need to either push the lever as if you are changing up or push the small lever as if you were changing down on your front mech. You should hear a clunk orfeel the lever moving as if you were changing chain rings but not as much and you won't actually change gear. If you don't you may hear the chain rubbing on the front mech. This happened to me and I was convinced that it needed adjusting until I realised what trim was. Obviously if your chain is coming off the ring then there's a further prob and as you said the limits need adjusted.

Sorry if I haven't explained this very well but once you try it, it should become clear.

fingerfun

Thanks, i'll investigate that as its not a full index click so that may make sense - funnily enough we have the same Planet X bike...

Meds1962

I've had exactly the same thing with 105 STI's but never knew about the 'trim'. Make sure the high limit screw is set so the mech outer plate is as close the chain as possible without touching, this will prevent the chain being thrown off when you change up and leave as much room as possible for the chain to move within the cage as you change to larger sprockets.