How to adjust front chain ring gear shifting

[petmcgratt]

was out for a cycle today and haven't been out now for a few weeks. When I go up through from the small, middle and large chain ring everything is fine. However when I begin to click back down the chain the chain rings the first click (i.e. large to middle ring) does not send the chain down to the middle ring but instead stays on the large ring but with a terrible rattling noise. As soon as I click again it then goes down into the middle the ring. Do I need to tighten or loosen the gear cable. what is the best way to do this. I have the campagnolo xenon 9 speed gear system.

thanks
peter

 

[Garz]

Im guessing this is so you can use your rear cassette range to better effect, i.e. no catching when your in the lower zones. The experienced guys will know the terminology for this I just cant remember the word for it right now.

 

[petmcgratt]

I don't think this has anything to do with the rear casette. I just can't get the large front chain ring to go into the middle chain ring when I press my gear to shift it downwards. The first press only brings the front derailleur to rub against the chain on the large chain ring and then I have to press the gear button again to move it to the the middle ring.

 

[GrasB]

Okay I'm assuming you have a double chainring. So what is happening?

On the bottom chainring the front mech has one position because if the chain goes any across towards the outside it'll clip the top chainring, a rather undesirable thing as the chain will be picked up by the top chainring. This is shown in the left diagram below.

On the top chainring there's no problem with clearing the bottom chainring, being smaller. Because of this a shifter can employ trim, this shifts the front mech a few mm towards the inside so it the chain can reach all sprockets on the rear cassette. This is shown on the right diagram, the blue rectangle shows the 'normal' position of the FD, but the green rectangle shows the mech trimmed to allow access to the low range of sprockets.

What this means is that when you change down to the bottom chainring the first click will only go into low range trim & it requires another click to move all the way to the lower chainring. If you're on a triple the same principle applies & you may have some trim on the middle chainring but if present not as much as the top chainring.

The way to adjust the tension is in low range trim let the chain pass the front mech to the lowest gear by 1-2mm, on a triple you want to use the chainring with the least clearance for the front mech. To move the mech further out you increase the tension, to move the mech further in release some tension. To me it sounds like you may not have enough tension & the front mech isn't far enough out in the low range trimmed position.

 

[Garz]

That's the word, trim. Thanks GrasB

 

[petmcgratt]

Apologies GrasB for only getting back to the forum now. I read what you put in your message and to be honest it was a bit too technical for mee. I did however go and read up on trimming. Spent quite a few hours playing with front derailleur last night but ended up going to a repair shop this morning. The first thing he said to me was "that is not a racing bike chain set" to which I was very surprised. He went on to count teeth etc and told me the chainset was more geared towards a moutain bike with the largest sprocket having 48 teeth. He was surprised that the set up was working. Maybe that is why I starting encountering problems. He said the gaps between the chain wheels were too big for a racing bike set up. He therefore fitted a 53T 39T double chainset and showed me the difference in the gap between the chain wheels. Everything seems to be working well now. It just worries me that as time goes on there is something else spotted that doesn't appear to be quite right with the bike. He said the parts that were used were also quite old (i.e. end of line ranges etc).

Thanks alot for your help and advice.
peter

 

[Garz]

Hmm seems like you left off your bike setup as we cant guess what age it is and spec etc. I was assuming it was a recent purchase..

 

[GrasB]

I can't see how mixing & matching road & mountain front setup is a problem. The reason being is that they're interchangeable! I run Shimano 105 mechs, Dura Ace bar end shifters & cassette with an XT 26/36/48 chainset on my mountain bike without any issues.

 

[petmcgratt]

I only got the bike (Vitus Alios triple) in august this year. However alot of the parts (e.g. handlebars, stem, gears etc have been out for several years and some parts have been discontinued). I suppose that is why I got it for £299.

I have also read reviews from other people who bought the same bike and have thay have said that when they got the bike the spec quoted was not what they got on the bike. I'm not complaining necasue it is a learning experience for me and now I know what to look out for when I decide to buy a more expensive bike.

thanks for the advice

 

[Ivan Ardon]

Did you want the bigger gears that the larger chain rings have given you? Can you still get up hills? If you were happy with your ratios before the LBS changed them, then they may have done you no favours.

 

[petmcgratt]

I can still get up the hills Ivan. Went out today and enjoyed the cycle as you were definitely having to work harder but in a good kind of way. To be fair the LBS did ask me before hand "Are you fit enough to use this chainset?". The gears are shifting between the chain rings alot smoother and I can also use all the gears without any rubbing on the front derailleur cage unlike the triple set where the most extreme indexing would have caused rubbing of the chain.

 

[redjedi]

I'm no expert, but I think the LBS took the easy route by selling you a new chainset (I assume you had to pay for it). I don't believe there is any difference between MTB and Road chainsets.

Do you know what make/model the shifters and front derailleur are?
Is the front shifter indexed i.e. does it have lots of positions or just the 3 "clicks", one for each chainring?

As you've got your bike running smoothly you may not be bothered, but it could be worth finding out if your LBS has just made a quick buck out of you or made the correct decision.

 

[redjedi]

I'm no expert, but I think the LBS took the easy route by selling you a new chainset (I assume you had to pay for it). I don't believe there is any difference between MTB and Road chainsets.

Do you know what make/model the shifters and front derailleur are?
Is the front shifter indexed i.e. does it have lots of positions or just the 3 "clicks", one for each chainring?

As you've got your bike running smoothly you may not be bothered, but it could be worth finding out if your LBS has just made a quick buck out of you or made the correct decision.