Gear adjustments.

[nickp]

Hi.

Sorry for all the questions but i'm as little stuck agian.

I'm having trouble with the chain rubbing on the front derailleur when it's on the biggest chainring.

Also when shifting the rear gears its missing the first 3 cogs when shifting up and jumping straight to the 4th.

I have have been looking at videos and tried all the adjustments but can't seem to get it right.

Any advice.

Cheers

 

[Paul_Smith SRCC]

Hi.

Sorry for all the questions but i'm as little stuck agian.

I'm having trouble with the chain rubbing on the front derailleur when it's on the biggest chainring.

Also when shifting the rear gears its missing the first 3 cogs when shifting up and jumping straight to the 4th.

I have have been looking at videos and tried all the adjustments but can't seem to get it right.

Any advice.

Cheers

If you have followed the videos I assume to have adjusted the cable tension and made sure mech' stop screws are screwed either in or out enough, although the latter generally effect largest/smallest sprockets and not those mid-range.

A common error can be the the way the cable is clamped via the pinch bolt, it must follow the correct path, there is normally a little groove to show where it should go, plus make sure the clamp section has not rotated, as this again may change the path of the cable, which may pull the mech incorrectly.

Also make sure the cable guide under the bottom bracket is not moving, they can come lose, which effects the cable tension.

Paul_Smith
www.corridori.co.uk

 

[Paulus]

Firstly, is it a new bike? If it is the cables have stretched a bit and need tightening. If not then a bit of TLC is needed. If the chain is rubbing on the front mech then either the limit screws need adjusting or the cable needs tightening or loosening. It sounds like the rear cogs are the same, and the cable needs a bit of adjustment. if it is a new bike the shop should give you a first free service to correct these problems. Look here.

http://www.sheldonbrown.com/gearing/index.html

 

[nickp]

Thanks for the advice guys, it's an old bike which i have just fitted with new cables.

I have been adjusting the limit screws for what seems like an eternity now but either the chain rubs or it won't shift the chain to the high or low chainring.

 

[peanut]

Its much better if you continue to post in the original thread because then everyone would know all the previous suggestions and what you had tried.

In order to help you we will need to know the following .
Shimano or campag ?
8-9 or 10 speed ?
53x 39 Double or treble chainset ? or is it a 50x34 compact ?

What ratio is your cassette ie 12-27

There are many possible reasons why your chain is rubbing on your front mech but we need all the info to stand a chance of solving your problem.

I've checked your previous thread and you have Shimano Sti levers. Are you sure that the new cables you have fitted are specifically for STi ?
If not they will be useless. STi cables have specially wound steel so that they are not compressable .

 

[nickp]

Cheers peanut, i didn't post in the other thread as that was about repacing cables and i didn't what to confuse it.

In answer to your questions, it's shimano, 9 speed and treble chainset. I#m going to sound stupid now but how do i find out the ratio?

Thanks

 

[accountantpete]

Cheers peanut, i didn't post in the other thread as that was about repacing cables and i didn't what to confuse it.

In answer to your questions, it's shimano, 9 speed and treble chainset. I#m going to sound stupid now but how do i find out the ratio?

Thanks

The ratio is the number of teeth on the small cog ( usually 12/13 ) and the number of teeth on the biggest cog (25/27 and upwards). You will have to count them!

 

[peanut]

well the cables are an essential part of adjusting the transmission. if you have fitted new cables they will need to be tensioned otherwise they will need readjusting after a few days of use .

I usually grab the gear cables mid tube and pull them away from the frame and gradually increase the pressure and hold them for a few moments.
This has the effect of pretensioning the entire cable system, all the slack in the cabling, ferrules, cable clamps etc.
IMPORTANT
Make sure you operate the gear levers first untill all the gear cable is out as far as it will go and the lever is at the end of its travel ie the chain will be on the smallest rear sprocket and the smallest front chainring .

Then you'll need to re-adjust the gear cables either with the barrel adjusters or by re-clamping the cable on the front and rear mechs.

 

[peanut]

ok if you have a triple chainset you will need a compatable triple front mech Are you sure it is the right mech ? they are usually wider to accommodate the increase in angle of the chain line ie biggest back cog and biggest front chainring or smallest rear sprocket and smallest front chainring.
They also have staggered front and rear cage plates

Shimano STi systems usually have what is called a 'trim' feature on the gear lever. This is a single click which just moves the cage of the front mech away from the chain when the chain is at extreme angles.

Which combination of sprocket and chainring causes the rubbing ?

 

[nickp]

ok if you have a triple chainset you will need a compatable triple front mech Are you sure it is the right mech ?

Which combination of sprocket and chainring causes the rubbing ?

The mech is ok, it hasn't been changed.

It is rubbing when on the top chainring and first 3 rear cogs, if i adjust the derailleur enough to stop it rubbing it will no longer move the chain to the smallest chainring (Does that make sense?)

Thanks

 

[peanut]

best to use the description big and small so there is no misunderstanding.
So its rubbing when the chain is on the biggest chainring and the smallest sprockets yes ?

If thats the case it must be because either the front mech isn't adjusted correctly to let the mech cage over far enough or
the cable is adjusted too tightly and hasn't sufficient slack to allow the mech cage to move over far enough or
the chainring is not at the correct distance from the bottom bracket ie wrong axle length . ie could be a triple on a double BB

 

[nickp]

So its rubbing when the chain is on the biggest chainring and the smallest sprockets yes ?

yeah.

Thanks again peanut, i'll try losening the cables tommorow and see how it goes.