Shimano Dura Ace STI lever problem

dieselgeezer

I think I'm going mad. Just had my first ride on my summer bike. It's kitted in Shimano 10, 4 years old & probably done 14k miles.
My issue is with the gear change when going down the block ie to a larger sprocket. If I press lightly on the lever it doesn't change gear. It only changes if I give it a more hefty shove. There is no problem going up the block ie to a smaller sprocket.
Have tried adjusting cable tension, new inner & outer cable, different rear mech. I then tried a relatively lightly used Ultegra lever & got exactly the same problem.
The reason I think I'm going mad is that I don't remember this issue when I last rode the bike in 2010.
Any of you guys got any pointers?

Many thanks

CarlosDSanchez

Have you ever replaced the gear cables? They could be worn out which would lead to poor shifting. Also try cleaning and lubricating the derailer, they get all gunked up after a while.

dieselgeezer

As I said, new inner & outers fitted & tried a different rear mech & then different STI's, albeit not new. I'm now almost convinced that all Shimano levers can do this trick of being able to do 2 sorts of movement ie gentle swing (& light click from lever) & no gear change or heavier swing (& a more pronounced click) & the rear mech moves fine.
Anyone else tried it?

ChrisSA

Yep - same here (with DA7800 STIs).

I had replaced the cables in Jan, and thought it could be down to road crap under the BB guides. I had some issues on a duathlon, where I had to change down 2 and up 1, instead of just down 1 gear.
In the end I replaced the rear mech, and it is better, but still needs the extra effort to change down a gear.
I may try to clean up the STI internals (or as much as one can without dismantling).

onbike 1939

To change "down" a gear i.e. from a smaller rear sprocket to a larger one, does mean that this change is not assisted by a spring so will always require more push than going from a large sprocket to a smaller (where this is aided by spring tension). In the case of "bottom-normal" RDs the opposite prevails but these, thankfully are rare.
That said, there should be no need for having to use undue pressure to change to a lower gear, especially on the rear, as the gear change is operating on the bottom (relatively un-tensioned) part of the chain.

dieselgeezer

Hi Onbike,
I don't have to use any undue pressure on the lever at all. In a way, I could do with a little more resistance so that there would be a definite click. At present if I don't push the lever over hard enough I get a part click & the rear mech doesn't move enough to change gear. I'm beginning to think that all Shimano STI's are like this.

Mike67

Have you checked/set the indexing?

I had a similar problem with mine until I did it properly.

Put it into 5th or 6th gear at the back.
Slowly unscrew the derailleur adjuster whilst turning the pedals until it just changes down a gear (larger sprocket) at the back.
Screw the adjuster back in (still turning padals) until it just changes back up (smaller cog) and give it an extra 1/4 turn for good measure.

Worked great for me...I now have crisp downshifts whereas before it could take a couple of clicks then back one etc as you describe.

dieselgeezer

Mike67,
Absolute genius!!
I think the issue is now sussed or at least it's lots better than before. I've always set the indexing in relation to the shift from 12 to 13 & haven't really had an issue with this method before. I'm just surprised your method works as you'd think there would only be one correct tension for the cable for everything to work OK. Where did you get your method from?
Again, cheers my man

Mike67

Glad to be of service

I'm sure I remember it from some Shimano docs somewhere or other that I read ( I was bored!) in the distant past.

I guess there's an optimum position for setting up indexing...do it at one extreme or the other and it drifts out as you go up the cog or something....not really sure why that should be though