To trim or not to trim?

Manc33

I got some Claris 2400 flat bar shifters a while back (I am on 8 speed) and hated how they have a "trim" function on the middle ring and outer ring. I never really could get on with it and how there's extra clicks/positions, although I do understand the function of it, to stop chain rub in the extremes.

I used a SL-R440 left shifter, it had only one trim on the middle ring. Again I hated it, not knowing (or not being 100% certain) where it is up to, or just the ballache of always having to remember if it is trimmed or not, whether I just changed from the outer ring to the middle, or granny to middle. :roll:

Now I have got a mountain bike left shifter on and my question is why don't these MTB shifters have a trim control?

More to the point, these MTB shifters work perfectly well and do not give any chain rub despite them having no trim control at all!

Why is that... a MTB triple setup doesn't have that trim function on the shifters but road bikes do? Its not because of chainring sizes because I have a 52-38-24 triple on the bike.

It seems like a big gimmick if I can setup a chainset like that without trim and not get that rubbing when in middle>lowest. All I had to do to set it up is have a bit more cable out than normal and give it more of a shove from granny to middle, but its done so that can be fully shifted all the way without it managing to go from granny to outer.

Do people ever get used to having that trim? I never would in a million years seriously, I have said before I would rather have the chain rubbing. :roll:

We have gone from old shifters with no trim, to ones with one trim on the middle, to ones with two trims, it is a PITA to use it. If shifters exist that just don't even have the problem (like these old MTB ones) then why do shifters exist with a trim at all. You have to wonder. :roll:

darkhairedlord

have you tried posting on the MTB part of forum?

ai_1

Never have a problem with trim myself.
I'm not familiar with how it's implemented on flat bars but with Shimano STIs there is no drama. You change gear with normal travel on the left lever. If you then require trim due to an undesirable chain angle you simply apply a partial lever stroke until you get a faint click. If you want to ignore it you can do so. It's so unintrusive that I didn't realise I had a trim function on my first bike (equipped with a Tiagra triple) until a few months after I started riding it.

So in answer to your question about whether people get used to it: Yes, almost instantly. It's just a case of remembering the trim is there if I want it. Normally if I notice chain rub I'll look down, notice I'm in a poor gear combo and change to a better one with a similar ratio. If for some reason I don't want to change I'll just click the trim to provide additional clearance and carry on. If I later sweep back the other direction on the cassette and notice rub again, I simply remove the trim. It's simple as that. It's not something you need to be watching out for or worried about. I've spent far longer writing this post than I've ever spent thinking about trim on the bike over a period of 4 years.

keef66

Get yourself some friction shifters.

Manc33

My road chainset on my road bike (hence posting in this section) doesn't require a shifter to have a trim function on it. It works using a MTB shifter without having to have the chain rubbing anywhere for it to work properly.

The only shifters without trim are MTB/friction shifters. Even my entry level Shimano 2300 shifters had it.

It is a hindrance, because going from granny to middle it will need nudging out (the trim) to stop it rubbing and going from the outer to the middle again, it will need trimming, not might - will. Using MTB shifters it doesn't need to have a trim. The thing is done away with and isn't needed.

Conclusion: Road chainsets do not "need" to have a trim function on them. It isn't even an advantage from what I can see because it just introduces having to remember which way it is set all the time. Plenty of times I have thought "It seems like it needs trimming down but will this change to the granny" or whatever. Squeezing the shifter lightly then a bit harder and accidentally changing to granny because you thought you were trimming it. Why do they keep adding stuff like this to things!

If you used a bike for ages and didn't even realise it had trim, then your chain must have been doing a lot of rubbing and you must have done a lot of wondering why. The thing is it actually rubs with that trim function, but doesn't when shifters are used without it.

No one has answered why MTB triples do not have any trim but road bike triples do. :P Its not chainring sizes because I have a pretty crazy setup (52/38/24t) and it still doesn't need trimming. So then its not because MTB chainrings are smaller, which is the only reason I could think why.

desweller

I should think chainstay length plays a significant part.

A hardtail chainstay can vary from ~420mm for a short one up to over 450mm (I think - can anyone else confirm?). Road/race bikes run pretty short chainstays (~400mm), so the chainline angles are exaggerated for any given gear combination.

I can't remember what frame you're using, but if it is based on a hybrid then it probably has longer chainstays.

ai_1

I think you've got your gears set up poorly.

Manc33 wrote:

...If you used a bike for ages and didn't even realise it had trim, then your chain must have been doing a lot of rubbing and you must have done a lot of wondering why...

Nope. As I said in my previous post, I only rarely have need to touch the trim. If I have a reasonable chain line I do not have chain rub. So no, I did not have chain rub and wonder why. I think what I had was a properly indexed front derailleur!

I'm going to go out on a limb and guess that you haven't considered the possibility that there is no conspiracy whereby some mysterious "them" benefits from inflicting the terrible and otherwise pointless trim function on unsuspecting cyclists? Can I suggest you consider that you have had your gears indexed poorly or have been using them incorrectly? I'm merely suggesting that there are possible explanations for the fact that you encounter so many obvious scams and conspiracies that the rest of us are somehow incapable of recognising.

Ben6899

This forum is becoming like a Philip K Dick novel.

mr_evil

Manc33 wrote:

...having to remember which way it is set all the time...

You don't have to remember where it is set. If the chain rubs, trim. That's all.

Trim is needed on newer road groupsets because the front dérailleur cage has become narrower as chains have become narrower.

ai_1

Ben6899 wrote:

This forum is becoming like a Philip K Dick novel.

except we're talking mechanial not Di2 and there's fewer sheep

ravey1981

Mr Evil wrote:

Manc33 wrote:

...having to remember which way it is set all the time...

You don't have to remember where it is set. If the chain rubs, trim. That's all.

Trim is needed on newer road groupsets because the front dérailleur cage has become narrower as chains have become narrower.

Chain widths are the same on mtb and road bikes with the same number of gears. ie 10 speed road chain = 10 speed mtb chain. My 10 speed ultegra has trim, my 10 speed xt mtb does not. My 9 speed sora cx bike has trim, my 9 speed mtb does not.

Ouija

Lol. Whatever you do don't ever try SRAM double tap flatbar shifters, we'd never hear the end of it.

(for those not familiar with double tap shifters your required to press the paddles through two clicks to change up to larger cassette/chainrings and one click to go to smaller ones.... which would be beyond Mancs sanity threshold)

Pigtail

Just get out, ride your bike and enjoy it.

Half the time I've no idea what gear I'm in and whether I'm trimmed or not. It has reached a point where I change gears and trim without thinking about any of it.