Optimising my chain line

[Custom24]

I don't know how to search for this, because I don't know if it's possible, or what it would be called.

Anyhow, my newish bike makes a fair amount of chain noise in gear combinations where I don't think it should.

It's a double front derailleur with a ten speed cassette. This bike http://whyte.bike/2013/product.php?xProd=116&xSec=121

When I'm in the small chainring on the front, it runs silently on the smaller sprockets on the cassette. There is some chain noise when I'm in the big sprockets on the cassette.

Most of the problem is that when I'm in the big chain ring on the front, it only runs silently on the smallest two sprockets on the cassette, meaning I don't like using the big chain ring.

It feels like the chain rings and cassette are not in the correct positions relative to one another laterally.

I don't think there is a way to adjust the relative positions, is there?

Could it be something else? I will get the bike on the stand and make sure it is not the front mech which needs its position tuning. Is there anything else that causes this?

If we label the sprockets on the cassette 1 through 10 biggest to smallest, I'd expect the small front chain ring to ring silently on say sprocket 3 and the big front chain ring to run silently on sprocket 8. Is that reasonable?

Thanks
Mark

 

[ianrauk]

You do have a trim function on the lwft hand brifter. Just press the small left hand lever one click and it will release the FD a notch, enough to trim it.

 

[Custom24]

You do have a trim function on the lwft hand brifter. Just press the small left hand lever one click and it will release the FD a notch, enough to trim it.

Thanks. Just to be clear, this trim function is to tune the position of the front derailleur mech?

 

[ianrauk]

Thanks. Just to be clear, this trim function is to tune the position of the front derailleur mech?

Indeed. Basically a short shift.
Check out the 3rd column on this Shimano Tech Doc

 

[RecordAceFromNew]

If the noise is due to front mech chain rub when on the small front then the issue is likely a bit more fundamental than trim setting, given the front and rear chainlines should allow the small front ring to work fine with most sprockets with the possible exception of a couple of outer ones without chain rub - provided the front mech L limit screw was set up properly. There should be a c1mm gap between chain and mech outer/inner cage when on large front small back and small front large back respectively. See this.

Given the noise comes about from the 3rd/4th smallest sprocket rather than the smallest with the large front ring, it is also unlikely that the front mech could have caused the noise in that situation.

Having checked the above I would suggest measuring the front chainline (centre of frame to middle of the front rings) and the width of the chain at the pin with a vernier caliper. It is also worthwhile examining the chain carefully to ensure no bent/stiff link.

 

[Custom24]

If the noise is due to front mech chain rub when on the small front then the issue is likely a bit more fundamental than trim setting, given the front and rear chainlines should allow the small front ring to work fine with most sprockets with the possible exception of a couple of outer ones without chain rub - provided the front mech L limit screw was set up properly. There should be a c1mm gap between chain and mech outer/inner cage when on large front small back and small front large back respectively. See this.

Given the noise comes about from the 3rd/4th smallest sprocket rather than the smallest with the large front ring, it is also unlikely that the front mech could have caused the noise in that situation.

Having checked the above I would suggest measuring the front chainline (centre of frame to middle of the front rings) and the width of the chain at the pin with a vernier caliper. It is also worthwhile examining the chain carefully to ensure no bent/stiff link.

It's definitely not the front mech. This appears to be perfectly adjusted and is not rubbing or even near the chain when the noise happens. I had the bike on the stand earlier. The noise does appear to be coming from the rear. I have adjusted the rear mech lateral position with the tension adjuster and left it centred between the exteremes of skipping up a gear and down a gear, if that makes sense.

I do have a vernier calipers. Should I just measure and report here? What am I looking for?

The chain is identical to the one that came with the bike, albeit with a KMC quick link now.

There is no stiff link. The noise is also continuous, rather than a regular or intermittent clicking.

 

[RecordAceFromNew]

I do have a vernier calipers. Should I just measure and report here? What am I looking for?

Since there are numerous possible reasons, we can only just go for the most likely to start off with. I think it is possible that you have the wrong sized chain, hence I am interested in knowing what the pin width is. I think it is actually quite unlikely for the chainline to be wrong with a road outboard bb, though not impossible, and it is a doddle to measure and eliminate.

 

[uclown2002]

It may be possible your front mech is not shifting far enough due to inadequate tension, thereby causing some rubbing in the big ring.

If it is rubbing in smallest gear combo then low limit screw needs loosening a touch then.

 

[Custom24]

Since there are numerous possible reasons, we can only just go for the most likely to start off with. I think it is possible that you have the wrong sized chain, hence I am interested in knowing what the pin width is. I think it is actually quite unlikely for the chainline to be wrong with a road outboard bb, though not impossible, and it is a doddle to measure and eliminate.

Hi, thanks

Chain is 6mm wide. The pins are recessed, so this is the width of the side plates at the pins as measured with my vernier. The width of the original chain is identical, and they are both marked Shimano CN 4601.

The distance from the centre of the seat tube to the small chain ring is 4.25cm and to the big chain ring is 4.93cm

I thought it might be a change in lube this week (Finish line Wet weather lube changed to Finish line Dry weather lube), so I've just relubed the chain with the Wet Weather one and the noise is the same.

The derailleur does not hang exactly vertical from the rear cassette. It hangs probably 2 to 3 degrees inboard, towards the wheel. I don't know if this is normal. I've not crashed the bike or otherwise damaged or pressured the derailleur, so it was either like that from the shop 3 weeks ago, or someone has kicked it in the bike stand at work, or it's fine and normal.

The only thing I did do was that when I put a new chain on it (trying to rotate chains frequently), I routed the chain the wrong way through the rear derailleur (around the outside of the halfway connection between the plates of the jockey wheel cage) and rode on it for 15 miles. I only noticed something was wrong because the quick link was catching and clicking. I've rectified that now, but the chain is the same as the one I routed wrong. Maybe I've damaged something?

I've got some photos and video, which I'll post tomorrow.

The bike will go back in for its 6 week service at the LBS where I bought it in a couple of weeks, but I'd rather sort this myself so that I can continue to ride it in the meantime. So thanks for your suggestions.

 

[Custom24]

Video uploading, but in the meantime, here is a photo.

I am pretty sure that the problem is that the rear derailleur is out of alignment. An alignment tool isn't too expensive, so I will probably order one today, unless anyone thinks I am barking up the wrong tree?

Also, I am thinking that it would be best to use my other bike until this problem is sorted out?

Thanks
Mark

 

[solidthegreat]

The mech does look a little out to me, pushed inwards towards the wheel. Personally if it were me and the bike was new, I would take it in to where I bought it for its service and tell them the issue and you have not done anything.
Chances are they will change the hanger and/or mech dependant on what they think.

 

[RecordAceFromNew]

Is the cable clamped in the groove correctly at the rear mech like this (I think behind/under rather than in front/on top of the bolt)? If you can put it on a stand it is also worth watching whether the top jockey is centred directly under each sprocket as you shift through the gears.

It is not uncommon for a chain to be routed through wrong in the mech, but I have no idea what damage if any 15 miles in that circumstance might do to it - since it is your second chain (despite having owned the bike for only for a couple of weeks) you could perhaps swap the original chain back and eliminate that possibility.

If you don't have an alignment tool most rear hubs made by Shimano have an M10x1mm fine thread qr axle, which is exactly the right thread for the hanger and can be used to help spot (as well as correct with care) a bent hanger.

Your front chainline is a bit greater than I would expect for a road double/compact (usually 43.5mm), but not great enough to cause the noise I think.

 

[Custom24]

Is the cable clamped in the groove correctly at the rear mech like this (I think behind/under rather than in front/on top of the bolt)? If you can put it on a stand it is also worth watching whether the top jockey is centred directly under each sprocket as you shift through the gears.

It is not uncommon for a chain to be routed through wrong in the mech, but I have no idea what damage if any 15 miles in that circumstance might do to it - since it is your second chain (despite having owned the bike for only for a couple of weeks) you could perhaps swap the original chain back and eliminate that possibility.

If you don't have an alignment tool most rear hubs made by Shimano have an M10x1mm fine thread qr axle, which is exactly the right thread for the hanger and can be used to help spot (as well as correct with care) a bent hanger.

Your front chainline is a bit greater than I would expect for a road double/compact (usually 43.5mm), but not great enough to cause the noise I think.

I will look at the cable clamp later.
Top jockey wheel I have played with the adjustment and it doesn't seem to affect the noise.
I could use the rear wheel off one of the other two bikes as you suggest, but I am unclear what to do. Is it basically to use the whole rear wheel off another bike, with its axle screwed into my derailleur hanger, to manipulate the derailleur hanger until the two wheels are parallel? I guess I can use my vernier calipers to check the distance between the rims at several points. I think both rims are true

Here are some videos, from the side and back.

View: https://www.youtube.com/watch?v=-62EbvBmwOI

View: https://www.youtube.com/watch?v=M2764XpLfX8

 

[RecordAceFromNew]

I could use the rear wheel off one of the other two bikes as you suggest, but I am unclear what to do. Is it basically to use the whole rear wheel off another bike, with its axle screwed into my derailleur hanger, to manipulate the derailleur hanger until the two wheels are parallel? I guess I can use my vernier calipers to check the distance between the rims at several points. I think both rims are true

I wouldn't advice you use the whole wheel, especially with tyres on, because the weight can easily damage the thread of the hanger which is usually alloy. If you are familiar with adjusting cup and cone hubs it is no big deal removing the axle use it and putting it back afterwards, but I keep a spare Shimano axle on its own for this purpose - once it is in it is easy to spot deviation by looking from above and from behind.

 

[Custom24]

I wouldn't advice you use the whole wheel, especially with tyres on, because the weight can easily damage the thread of the hanger which is usually alloy. If you are familiar with adjusting cup and cone hubs it is no big deal removing the axle use it and putting it back afterwards, but I keep a spare Shimano axle on its own for this purpose - once it is in it is easy to spot deviation by looking from above and from behind.

Oh, thanks. I have a spare axle, I think. I guess in that case, it doesn't matter if it's from the front or rear wheel, although I suppose for this purpose, the longer the better. So, do you manipulate the hanger with the axle, or do you just use the axle as an indicator and use something else to manipulate the hanger?