Sora front derailleur probs.

[DooDah]

Hi all,

Being mechanically challenged I had the front and rear derailleur adjusted by my LBS after owning the bike for 4 months. The gears had started to have problems due to cable stretch. The bike was running sweet, but now when in the largest cog on the front and smallest on the back the chain rubs slightly on the outside edge of the front chain guide. Also seems to rub when on largest front cog and largest rear cog, but on the inside of the guide. The front derailleur does is not marked H and L so I am not sure what to adjust (and to be honest how to do it). Is this the problem or could it be something else.

Last time I attempted any adjustments I made it much worse, hence why it went to the LBS. This time though I would like to sort it out myself.

 

[mrandmrspoves]

Ok - its easy honest! If the LBS set your gears up right there shouldn't be a need to adjust the stop screws again. What has happened is the cable has stretched a little bit more so all you need to do is adjust the cable tension a little to tighten up the slack and your front derailleur will pull across a little more to the right. You can test this by putting the gear lever so the chain is on the large chain ring and then just seeing if the derailleur will move over any further by pulling on the exposed wire.
The easiest way of knowing how much to adjust the cable is to put the gear lever into the position for the smallest chain ring and then with the chain has moved onto the small chain ring adjust the cable so that all the slack has been taken out of it but the front derailleur hasn't moved.

Problem 2 is also easy - you should never be on the largest chain ring on the front and largest sprocket on the rear at the same time. When you do this you put a huge strain on the chain because it has to bend so far - this causes increased wear on the chain ring, sprocket and chain and actually doesn't achieve a gear that could not be achieved (approximately) by dropping to the smaller chain ring on the front and smaller on the rear.
I assume you have a triple on the front because most front derailleurs would cope with Big/Big - even though they shouldnt have to. So as a basic rule try and keep the chain as straight as you can with the minimum deflection - which means for easy gears small front + large back, for middle gears middle front + middle back, for hard gears Large front + small back.

Hope this helps - re-post if you need further instructions.

 

[DooDah]

Thanks Mranmrspoves, I will have a go at this tomorrow. I will sort out problem one first and see. It is actually a compact rather than a triple, so not sure if that makes any difference to problem2.

 

[DooDah]

Sorry, mr naive back again, how do I tighten up the cable for front derailleur problems, is it still turning the threaded thingy at the rear derailleur anticlockwise!! Sorry for all the questions

 

[mrandmrspoves]

No worries. If you follow the front derailleur control cable back from the front derailleur you will find somewhere along the cable there is an adjuster. It will depend on the type of bike you have as to where it is. Some have more than one adjuster. Likely places to look; where the cable enters the lever, slightly further along in front of your handlebars, on the frame where you have a cable stop (where the outer cable fits into a lug on the frame and the inner wire is exposed) When you have identified the adjuster it will need to be screwed anti-clockwise to take the slack out. It probably won't need much adjustment so go half a turn at a time until the derailleur clears the chain. If you cannot find a cable adjuster you can take the slack out by gently loosening the cable clamp nut on the front derailleur until the cable can be pulled tight then tighten the cable. (If you have to do this put the gear lever so the chain is on the small chain ring and the lever is as far into this position as it can be - also only slacken the clamp enough to allow the cable to be pulled tight......but as a precaution take a photo of the exact position the cable is in on the derailleur so you can replicate it if the cable detaches)

As for problem 2, the same principle applies. Supposing you have a 10 speed cluster on the rear wheel you would ideally use the larger 5 (nearer to the hub) on the small chain ring and the smaller 5 on the big chain ring. It wouldn't be harmful to go one or 2 either way - but certainly I would't recommend greater extremes than that. Do let us know how you get on tomorrow..

Poves

 

[deptfordmarmoset]

Odd, I understood the problem to mean the limiter screws were adjusted just a bit too narrowly. Anyhow, if it is a cable tension thing as Mr Poves suggests, and my memory serves me right in thinking it's a Boardman road race, the barrel adjuster is on the down tube close to the LH fork.

If adjusting that doesn't solve it, the limiter screws may need a tweak. I can't remember which screw does what but if you put the bike onto the big ring so that the cable is under the least tension the outer limiter will be the one holding it in place. Pick a screw, give it half a turn, if it moves, you've got the right one. If not, return it to where you started and pick on the other.

 

[DooDah]

Thanks Guys for the help, I will certainly have a go today. It is a Boardman Road Race, you do have a good memory.

 

[mrandmrspoves]

Odd, I understood the problem to mean the limiter screws were adjusted just a bit too narrowly. Anyhow, if it is a cable tension thing as Mr Poves suggests, and my memory serves me right in thinking it's a Boardman road race, the barrel adjuster is on the down tube close to the LH fork.

If adjusting that doesn't solve it, the limiter screws may need a tweak. I can't remember which screw does what but if you put the bike onto the big ring so that the cable is under the least tension the outer limiter will be the one holding it in place. Pick a screw, give it half a turn, if it moves, you've got the right one. If not, return it to where you started and pick on the other.

You would be right - but if they were recently set up correctly they should not have gone out of adjustment. The stop screw will limit how far the derailleur moves across - but if the cable has stretched it will not reach that point - hence my suggestion that it is more likely to be cable stretch....... Diagnosis over the internet is never going to be 100% fool proof though........

 

[deptfordmarmoset]

You would be right - but if they were recently set up correctly they should not have gone out of adjustment. The stop screw will limit how far the derailleur moves across - but if the cable has stretched it will not reach that point - hence my suggestion that it is more likely to be cable stretch....... Diagnosis over the internet is never going to be 100% fool proof though........

Good points there. Mind you, I have seen posts on here about odd scrapings after the LBS has been at it. You're probably right but we'll have to wait until the OP reports back to know for certain.

 

[DooDah]

Thanks for the info. guys. Mrandmrspoves was dead right. Limiter screw was on max. so tightened the cable and hey presto. Have not had chance to ride yet but tested on a bike stand and all seems well. Thanks again.

 

[mrandmrspoves]

Thanks for the info. guys. Mrandmrspoves was dead right. Limiter screw was on max. so tightened the cable and hey presto. Have not had chance to ride yet but tested on a bike stand and all seems well. Thanks again.

I love being right!
Glad to help..... Poves

 

[AndyPeace]

Not quite the same problem as the original poster, but also a front derailier problem. Having read the thread above I may just be choosing bad gears, i.e. big ring on the front and rear. Anyway it seems to be getting worse so here it is. My chain sometimes randomly comes off when in the lower 3 gears when running the outer chain ring. I've tried adjusting the front derailier but with no result. generally my gears shift well but every once in a while the chain drops off- not whilst shifting but after, ussually under slight effort. It goes back on just by peadling. Any ideas?

 

[DooDah]

I cant help you there, but I am sure the wise guys above will sort you out. Good luck and let us know the solution.

 

[mrandmrspoves]

Not quite the same problem as the original poster, but also a front derailier problem. Having read the thread above I may just be choosing bad gears, i.e. big ring on the front and rear. Anyway it seems to be getting worse so here it is. My chain sometimes randomly comes off when in the lower 3 gears when running the outer chain ring. I've tried adjusting the front derailier but with no result. generally my gears shift well but every once in a while the chain drops off- not whilst shifting but after, ussually under slight effort. It goes back on just by peadling. Any ideas?

Hi Andy certainly the basic advice about gear selection will help. Where does your chain come off from?

 

[AndyPeace]

Hi Andy certainly the basic advice about gear selection will help. Where does your chain come off from?

I understand about chainline, I just have bad habits and often use the lower gears when it's only a short climb as it's quicker to shift back up at the top. The chain comes off from the front and heads inward but not engaging with the middle ring, a couple of spins of the pedals and it mounts back on the big ring. I have checked the front derailier adjustment and any adjustment outward is going to derail the chain the other way, on to the crank arms.