Can someone explain the trim operation on shimano 105

1964johnr

I have a compact chain set on my new bike with shimano 105. I have set the front mech up to my style of riding and use of gears as best I can. In the big ring I can use gears one to six with no front mech chain rub which I am happy with. On the little ring I have no front mech chain rub through gears one to five, but then the rub and accompanying noise sets in on gear six. I understand that the trim function will move the front mech out slightly to eradicate the front mech rub so that I may be able to use gears six and seven without the rub and noise. Having trouble working out how to use the trim in terms of which lever do I click, the small black one which shifts through the gears or the larger silver one which moves the chain from the small ring to the big ring. Also, once you use the trim and the front mech moves out, do you then need to reset it to it's original position and if so how do you do this? A simple explanation would be appreciated.

freezing77

First of all which a gears one to six on your cassette, the smaller sprockets or the larger sprockets.
Before using the trim function you should ensure that the high and low stops are correct as well as cable tension. If these are correct you should not get rub in most combinations, big big may be problematical i.e. big ring at the front and large sprocket at the back.

andrewjoseph

the trim function on the shimano shifters i've used is via both levers. when on small ring in front, and extra little click will move the mech outboard to give more clearance on the smaller rear cogs. when on big front ring, an extra click on shifter moves front mech inboard a tad to give better clearance on big rear cogs.

duckson

I have 105 and there is only a trim position in the big ring.

In small ring i think i can access pretty much all sprockets 1 to 10 (big to small) with no chain rub, dont tend to run in 8-9-10 with the small ring though as i'm changing to the large ring by then really. You need to set the low screw so the front derailleur is as close to the chain as possible but not rubbing when in small ring - big sprocket combo.

In the big ring you should be able to trim (light touch on the lever behind the brake lever) to move the derailleur slightly so you can use the larger sprockets when in the big ring. Also make sure the H screw is set so the chain is as close to the derailleur as possible with no rub when in big ring - smallest sprocket.


My DA9000 has trim in both small and big rings, so 4 positions in effect.

Pauld100

105 has trim on both small and large chainrings if set correctly. In the small chain ring if I get to 7 or 8 I give the brake lever a push to first click (don't use small chainring to the two smallest cassette gears 9, or 10). Another push of the brake lever gets me into the large chainring. Coming back down through the gears on the large chain ring, a small push of the small lever prevents rubbing on the larger cassette gears (13, 14, not using the largest 2 gears 11, or 12).

rafletcher

1964johnr wrote:

I have set the front mech up to my style of riding and use of gears as best I can.

Why do you not just set it up as per the tech docs from Shimano? You should (assuming this is a 10sp setup) manage 7 of those gears without rub IMO.

As to which lever...

If you've shifted to the big ring you will have used the brake lever. To "trim" the mech inboard use one click of the inner shift lever. You then can either use a single click on the brake lever to move the mech back outboard, or another single click on the shift lever to change to the small ring. All with the LH sti of course.

The opposite applies if you're in the small ring - a single click of the brake lever trims the mech outboard, etc. etc.

John.T

Check the cable tension when on the little ring. It should be slightly slack. If it is tight then the shifter is only allowed back to the trim position rather than the full little ring one. Set correctly you should be able to use all gears without chain rub using the trim. If you go little / little with a compact you may get rub on the back of the big ring but you can do nothing about that other than not using that gear. You should not use extreme cross over gears anyway as has been said on here many times.

duckson

My bad, mine trims in the lower ring as well, just dont spend alot of time in it with the smaller sprockets.

BigDixter

I can explain it in mine. A 5703 Brifter. (Unless anyone knows different)

From its base position the Brifter moves the cable that moves the changer cage in the following amounts up from the smallest chainring. The numbers are mm from the most inner position of the cage.
0 Low 0mm
1 Low+ 2mm
2 Med 9mm
3 Med+ 12mm
4 High 16mm
5 High+ 18mm

You can go all the way up in these steps with a small push to get to the + and big to get to the "raw". The surprising thing is that a "wee dint" to the small lever on the brifter will go from 5 to 4 then to 3 then it just goes all the way to 0.

I'm not sure if there are funny ways to push to levers or some other "1970's video player style" complex key strokes or whatever to avoid this. Unless there is you can go up in all of these steps but you come down to the Med+ (Medium ring with trim) then you go all the way to the bottom.

Whats this mean?
Firstly the system is considerably more complex than the endless bike shop mechanics on Youtube imply. For instance where you set the High and low cage movement screws will change the availability of all of these slots and how the system works.

Secondly the full 18mm is enough cage movement to drop the chain over the edge of the largest ring and the smallest too I think.

I'm thinking I don't really need trim on High or Low so adjusting it to get trim going up on the medium would be the way to go.

I'm pleased to have found this as the front derailleur has niggled me since I got it. I kept wondering if I hadn't adjusted it right. I guess understanding what is going on I'll just get used to it.

Or maybe it's Shimanos way of saying "Should have bought a Campy"

dj58

Read this service instruction:
http://cycle.shimano-eu.com/media/techd ... 696762.pdf

John.T

Looking on here it is far easier to use than to describe. Never had any problem with it.