Naive gear question

AllanES

Gear indexing & adjustment is a black art to me no matter how many YouTube videos I watch!

My simple(ton) question is...... When the gears are optimally adjusted, should the chain rub on the front derailleur cage (Shimano 105 although I guess that's immaterial) when I'm cycling normally? Even just a little contact? And it's not on all gear settings.

The guy at the LBS from which i bought it last week said i should pop it back for an initial check over so I'm just wondering if that's something which needs adjustment.

freezing77

AllanES wrote:

Gear indexing & adjustment is a black art to me no matter how many YouTube videos I watch!

My simple(ton) question is...... When the gears are optimally adjusted, should the chain rub on the front derailleur cage (Shimano 105 although I guess that's immaterial) when I'm cycling normally? Even just a little contact? And it's not on all gear settings.

The guy at the LBS from which i bought it last week said i should pop it back for an initial check over so I'm just wondering if that's something which needs adjustment.

No it should not rub on the front derailleur, that is what the front shifter trim position is for when at extreme positions.

forward_loop

as above....shifter trim -which you have on 105 - is the little extra push you can give to the lever which will push the Front der out just a little when on the big ring - or the small click which will let it move in a touch - without completely shifting the chain from the big to small ring - ask the LBS to show you if your not sure when you pop in, it may be you just haven't realised you have this fine tune ability

AllanES

Forward loop wrote:

as above....shifter trim -which you have on 105 - ....... it may be you just haven't realised you have this fine tune ability

I didn't!!!
Just been and tried it and hey presto - sorted!
Thanks for the replies guys.

Churchill123

Can you explain what this is, and how it works as i have the same issue where the chain in some gears rubs just ever so slightly and as I'm relatively new haven't a clue :S

CiB

Churchill123 wrote:

Can you explain what this is, and how it works as i have the same issue where the chain in some gears rubs just ever so slightly and as I'm relatively new haven't a clue :S

The front mech isn't wide enough [by design] to accommodate the full range of the chain's angle across the gears on the cassette. As you move up & down the gears on the cassette, you need to move the front mech slightly to allow for the different angle. This is called trimming.

markhewitt1978

As above can you explain what you need to do to make this work, as it seems my chain is always rubbing, and I'm not sure what I'm doing when trying to trim it - as above, with 105.

CiB

If the chain is rubbing against the front mech, try moving the gear lever a gnat's crotch, not far enough to invoke an index click but enough to move the mech slightly. If you don't have indexed gears just move it until the noise stops. If the indexing doesn't allow enough movement before it changes properly try adjusting the thumb adjuster on the cable near the lever, giving it a quarter turn either way and seeing what happens.

It's no different to tuning your guitar - you need to adjust the tension on the cable by the right amount, playing it by ear to see which way works. </boring analogy>

If your chain is always rubbing the indexing is out and needs adjustment; use the same method to fine tune it. If you can't get it even close, drop it onto the small ring, adjust the barrel thing to about halfway, release the cable then pull it hand tight whilst nipping the clamp bolt up again and have another go.

djm501

:idea: *has learned something new here* :idea:

AllanES

djm501 wrote:

:idea: *has learned something new here* :idea:

I'm pleased to see it wasn't just me who didn't know about this.


But yes, I Google'd (other search engines are available ) "Shimano 105 trimming" and found an explanation too.....which was just what Forward Loop said up there ^

Schoie81

I'm not sure it can be better explained than Forward Loop did above, not in words anyway. Have a look at the shifter instructions - mine explained it (quite badly, but explained it) and try using the shifters whilst not on the bike and watch what the deraileur does - you should be able to feel that there's two movements on the shifters, a short one and a larger one - the short movement for trimming, the longer one for changing chainring. If you still struggle you probably need someone to actually show you, a friend who does know, or your LBS (maybe try YouTube, see if there's a video?).

markhewitt1978

I get that on the left shifter I can give it a little push which I sometimes need to do if I'm running big<->small. But what if I want to run big<->big?

zx6man

I guess you push the smaller lever a little ( I have posh shimano 2300 with the thumb shifters :-) )

Schoie81

Like zx6man I have the 2300 shifters, if i'm running big chainring with 28 at the back and the chain catches I press the thumb shifter a short 'click' and it shifts the deraileur in a bit and off the chain. If i'm running small chainring with 11 at the back I puch the brake level over a little but not enough to shift chainring and that brings the deraileur off the chain.

If the chain is catching when you're running the big chainring and the smallest gear at the back then (and I'm not 100% certain about this, so take advice elsewhere first, but...) I would suggest something needs adjusting, maybe the upper limit on the front deraileur.

wongataa

markhewitt1978 wrote:

I get that on the left shifter I can give it a little push which I sometimes need to do if I'm running big<->small. But what if I want to run big<->big?

If the chain is rubbing when on the big cog at the front and the little cog at the back then the endstop is set incorrectly. It needs to be adjusted so there is no rubbing in this chain position.

markhewitt1978

zx6man wrote:

I guess you push the smaller lever a little ( I have posh shimano 2300 with the thumb shifters :-) )

Ooh that works. I never knew that. :oops:. This is good, it means I can be in the big ring most of the time instead of the little ring most of the time.

Kingsmill1

i have this problem on the front derailler when the chain is on the smallest cog at the rear and front ( I know its not the best position for the chain) my LBS tried to fob me off and tell me it was because of the distance between the front and rear mech on modern bikes. It never did this when I first had the bike and I've checked the chain and its still within tolerance on the chain checker. All the gears change fine but the noise when the chain is in this position means its not happy, I realise I should be changing up at this point but sometimes I need to hold this gear for a bit longer.

forward_loop

Kingsmill1 wrote:

i have this problem on the front derailler when the chain is on the smallest cog at the rear and front ( I know its not the best position for the chain) my LBS tried to fob me off and tell me it was because of the distance between the front and rear mech on modern bikes. It never did this when I first had the bike and I've checked the chain and its still within tolerance on the chain checker. All the gears change fine but the noise when the chain is in this position means its not happy, I realise I should be changing up at this point but sometimes I need to hold this gear for a bit longer.

probably down to a bit of cable stretch, chain stretch would't have an impact

Check the inside stop position on the front der - suspect you might need to bring it into the ring just a smidgen, re-index/tighten cable.
run cloth over chain fettle a bit with the rear index. there is smooth running and smoooooth running - concentrate on the smoothness over the middle range of the cassette.
if this doesn't work - check front der alignment, position it over the large ring (will give better perspective) - and move the rear of the cage out 1/2mm.
geo could have an impact but unlikely on most "average sizes"

gozzy

Hewitt and Kingsmill, if you run big-big and small-small it creates a chain line where you will get chain rub, which will wear your chain badly.

Kingsmill - you really should be changing up to the big ring from the small one before you get anywhere near the smallest cog.
The LBS wasn't fobbing you off - they meant that the width of a 10 speed cassette is greater than that of an old 5 speed freewheel, therefore the distance that the rear derailleur travels with respect to the front one (parallel to the frame) is greater, so the chain is more likely to rub against the front derailleur.

Kieran_Burns

Just to add, you also have the trim facility on triple 105 shifters for the middle ring as well