Tips Please on using TRIM Function on 105 Groupset

[RideToWorky]

Hi All,

Tips Please on using TRIM Function on 105 Groupset

The Shimano user manaual PDF I downloaded was a bit vague
URL:
http://si.shimano.com/#seriesList/18/56


Trimming for lowest gear. (34 front, and 32 back)

Can I check specifically:
1. If I change down the front ring - from largest to smallest ring - Does that reset the Trim function back on ZERO? OR does it hold any original setting before changing down the fron ring?
2. How do I invoke the trim function? The Diagram talks about "Click" and HITS?!
3. How many position can I trim down? 3 times did I read?
4. If I'm a bit cack handed, and nudge the lever too much, does that mean the TRIM won't happen at all?! (Ie, I've tried to go down another front ringht, 105 says no and ignores lever nudge)

Its' all a bit hit and miss for me, so I'm trying to tidy up my technique!


Regards
Martin

[Paulatic]

I've never read any manual so maybe I'm wrong but this is how I use/ understand it.
When you drop from big to smaller ring yes your trim will be at zero. Assuming you are in a rear sprocket from large to about 6or 7 then there should be no scraping and no need to trim. If you move the rear into a higher gear scraping will start and you trim by giving a short push.
A big push will put you into the bigger ring at the front and if you are in say 3-10 on the rear then there should be no need to trim. You will need to trim. if you were to use the three biggest sprockets at the back then a small short click will trim and stop the scrape. A full length click will drop it into the smaller ring again.
Hope you follow that. Someone could demonstrate it to you in a couple of minutes.

[cycleruk]

There are 2 positions per ring.
My 105 is a triple so there are 6 positions all together.
I find the shifting to be quite touchy and needs a slight delicate touch to trim.
A hard push will swap rings up or down.
Going from big to small ring will usually shunt the mech' all the way over requiring a "trim" back if still on the smaller sprockets at the back.
If going up to big from small ring, and just using gentle pressure, the ring-pins will pick up the chain and will still leave the "trim" function for the smaller cassette sprockets. A hard push will shift the chain and also go through the "trim" as well requiring a gentle click back if on the large rear sprockets.
This all supposes that the front dérailleur cable is set up correctly.
Hope that helps.

[Brucey]

shimano used to publish a little chart that showed how the trim functions worked on the various STI models, and you know what, they were all bloomin' different to one another. So what works for one model of STI mightn't work for another and in some, if there is a triple and double version of the same shifter, they can work differently too.

However, on a lot of double STIs, the protocol is 'downshift in one click, upshift in three clicks'.

The three upshift slicks are not evenly spaced; from the bottom there is a short push for a trim click, a longer push for the shift onto the big ring, then a short push for the high gear trim click.

A single downshift click onto the small ring puts you back at the start again, i.e. set right for bottom gear.

cheers

[Samuel D]

However, on a lot of double STIs, the protocol is 'downshift in one click, upshift in three clicks'.

I think that’s how it’s supposed to work (though as you say they vary), but I have found that I can successfully go from outermost position (i.e. trimmed for top gear) to the inner trim position of the same chainring (i.e. trimmed for big-big) without dropping to the small chainring.

The technique is to command the downshift but catch it with the upshift before the chain has actually dropped to the smaller chainring. With button shifters (e.g. ST-2300 or Sora ST-3300) it is rather easy to start upshifting (taking the slack out of the system), then push the thumb button to downshift (releasing the cable) and then quickly swiping further to ‘upshift’ to the desired trim position.

This sounds more complicated than it is in practice. There may be some risk of the upshifts and downshifts interfering, like pressing two keys on a typewriter, but I did this for years and never experienced any trouble.

To me, fooling around with trim defeats the purpose of indexed shifting. I much prefer friction shifting at the front.

[Stevek76]

Certainly the newer paddle stis, if not all of them have a double click mechanism on the front downshift allowing you to trim without dropping to the small ring. As you press the paddle in there is first a lighter click which drops to the lower trim position. If you then follow through a second click will drop to the small ring (though always to the bottom trim)

That said, I've never found the trim positions to really be necessary, particularly if not severely cross chaining. I've got 105 5700 2x10 setup on a bike (admittedly with sightly longer 415mm chainstays) with no rub in any combination and only using the lower trim position for each ring.

2. How do I invoke the trim function? The Diagram talks about "Click" and HITS?!

That manual is a pretty horrendous explanation, I've absolutely no idea what the hits part is on about. Basically what it's saying is that if you're in the shaded gear combinations and the chain is rubbing on the front derailleur then press the shaded lever for a single click.