105 Front shifting confusion

[gwhite]

Hi gwhite

Thanks for that yes I am following and you are right but there thats just for the middle ring, If I have understood and read correctly with the 105 ST-503 triple shifter and setup there are around 6 positions in total for the 3 rings.

As a result it requires 2 shifts down from the big ring to the middle.

Hope this makes sense !?.

No, it doesn't make sense to me. The lever has 3 positions. Starting when on the small chainring is position 1. Position 2 when on the middle. Position 3 is the trim. Position 4 is the big ring. This means 3 clicks in all for the lever and this can be checked with the cable disconnected.
From the big ring to middle should only be one click and if it takes two then the trim position has been moved to the big ring due to the cable being too tight.
Certain STI's do have a trim on the large chainring but these are double chainsets usually with a 10 speed block.
I have 105, Sora and Tiagra STI's on all four of my bikes and all are set up the way I've described. If I'm wrong then I suppose I'll have to recall all the customers' bikes I've set up.

 

[andy_wrx]

Yeah, I do agree.

You need the trim on the middle ring, as on that one you can use the whole width of the cassette.
Without trim, if you set the cable tension up so that the chain ran cleanly in the front mech when on the leftmost big cog, it would rub on the inside of the cage when you shifted-over to the rightmost smaller cogs, and vice-versa if you set it up to run cleanly on the smaller cogs it would rub when on the bigger cogs.
The trim allows two positions for left-to-middle and right-to-middle of the cassette, when using the middle ring.

But you don't need this in either the big or inner rings as you shouldn't, for bad chainline reasons, be using the whole of the cassette, shouldn't be using 'big-big' and 'small-small' so it doesn't matter if the chain were to rub (in fact, it's probably a good thing as the rubbing noise will warn you if you were doing it)

 

[bad boy]

I totally agree with the logic and its all becomming a little confusing now.

All im saying is I have found 6 positions 2 for each ring what your saying does ring true in my mind and I can trim in the middle ring but also the big and small ring aswell !.

It seems a little confusing that being as my bike is new and the shop confirmed this was correct and the shimano docs also illustrate it.

Ive got to admit I did think it was wrong when I first experienced it so hence the research I done. Im happy to stand corrected but would rather know now as the bike is going back for its first service soon.

Im just saying it cant be tension (on my bike anyway) as ive tested this and all I got was the same results but lots of chain run on the big ring as one would expect.

 

[gwhite]

I totally agree with the logic and its all becomming a little confusing now.

All im saying is I have found 6 positions 2 for each ring what your saying does ring true in my mind and I can trim in the middle ring but also the big and small ring aswell !.

You should treasure this as it has to be unique.

It's pity that you're so far away as I'd be happy to fix this for you. When it goes back for service just tell them to check the front indexing and then see what happens.

 

[pb71]

Bad Boy, i'm with you on this one! I had a problem recentely with my Sora shifter on a triple chainring. After it was sorted, the way in which it was shifting was exactly the way you mentioned, (two clicks from large to middle), When questioned, i was told that this is absolutely correct. You are able to trim on all three chainrings, and in reading the Shimano tech doc for these shifters, it does confirm this.

http://techdocs.shimano.com/media/t...001/SI_0042A_001_En_v1_m56577569830614850.pdf

 

[bad boy]

Bad Boy, I'm with you on this one! I had a problem recently with my Sora shifter on a triple chainring. After it was sorted, the way in which it was shifting was exactly the way you mentioned, (two clicks from large to middle), When questioned, i was told that this is absolutely correct. You are able to trim on all three chainrings, and in reading the Shimano tech doc for these shifters, it does confirm this.

http://techdocs.shimano.com/media/t...001/SI_0042A_001_En_v1_m56577569830614850.pdf

At last someone that doesn't think I'm going mad .

I don't know why this has caused so much confusion I cant see how the shimano docs are so wrong if thats the case.

the docs show you can trim in all three positions and I am able to do so in practise.

Ianr has the same setup and he confirmed the same thing also.

Strange can anyone else can confirm whether they have a similar setup ??.

 

[Chris James]

Bad Boy, i'm with you on this one! I had a problem recentely with my Sora shifter on a triple chainring. After it was sorted, the way in which it was shifting was exactly the way you mentioned, (two clicks from large to middle), When questioned, i was told that this is absolutely correct. You are able to trim on all three chainrings, and in reading the Shimano tech doc for these shifters, it does confirm this.

http://techdocs.shimano.com/media/t...001/SI_0042A_001_En_v1_m56577569830614850.pdf

The 105 shifter doc says the same.

There are 6 trim positions on 105 levers. One might not need six, but they do exist!

 

[andy_wrx]

Bad Boy, i'm with you on this one! I had a problem recentely with my Sora shifter on a triple chainring. After it was sorted, the way in which it was shifting was exactly the way you mentioned, (two clicks from large to middle), When questioned, i was told that this is absolutely correct. You are able to trim on all three chainrings, and in reading the Shimano tech doc for these shifters, it does confirm this.

http://techdocs.shimano.com/media/t...001/SI_0042A_001_En_v1_m56577569830614850.pdf

I'll agree, that document does definitely show trimming in all three rings, including how to trim to use big-big and small-small, which amuses me !

I've not used 3400 9-speed Sora on a triple, there was no trimming at all when I had 3300 8-speed, it was only on the higher groups.

 

[gwhite]

^^^^^ Indeed it does show trimming on all three rings. That's it then....I'm retiring.