Technical > Transmission

New chain bedding in noise?

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Matt2matt2002:
After 10 months ( 1500 miles / 2500 Km )  on a KMC X1, I measured today in excess of 0.75 - so fitted a KMC X1 EPT 3/32 chain from SJS - ( 99 links  ie short ). I think it must have been on offer 18+ months ago.

As it happened - it fitted fine with only a slight adjustment of the EBB.
Q1  While loosening and retightening the 2 grub bolts on the EBB, it shifted laterally. I eyeballed it back as best I could but wondered if there is a proper way to make sure the front ring and rear sprocket are in line so that the chain runs smoothly?
Which leads me to Q2..
There is now a noise from the front ring EBB area. Like the chain is rubbing against something. It's not my Chainglider.
I adjusted the lateral movement of the EBB several times for quick test rides before a 5 mile spin.
After the quick 5 mile spin the noise has reduced and is only noticeable when the chain is under strain / I'm pushing up hill.

I can't recall this happening on previous chain refits.
There was no noise on the old chain.
The front ring does not appear worn to any degree.
While walking the bike the pedals rotate.
There is quite a lot of slack in the chain. Certainly not tight. The 2 finger grip in the middle of the chain moves it together quite a bit.

Thoughts folks?


Best Matt

Andre Jute:
The chainwheel should be set to the Rohloff chainline, which is the distance from the centreline of the bike to the centre of the sprocket teeth. There are several different Rohloff chainlines depend on sprocket type and number of teeth; check the manual for your particular sprocket. If you can't find a chainline number for your Rohloff, work with 54mm, the most common. The tolerance is 1mm, which is real tight for amateur assemblers because the measurements are difficult to take consistently.

Okay, now forget the theory of the "centreline of the bike" because in practice it is impossible to work from there. Instead put a piece of masking tape all the way around the seat tube but not overlapping at the ends, to protect the paintwork. Now use vernier calipers to measure the thickness of the seat tube where the masking tape is fitted, including the two layers of the masking tape, and the thickness of your chainring. Add the two measures together and divide by two. Call this Result A. Now measure from the outside of the chainring to the far side of the seat tube; this is Result B which consists of a layer of masking tape, a seat tube, some air, and the width of the chainring. From B subtract A and this is Result C, which is the chainline.

If you don't have vernier calipers, a less accurate measurement than with vernier calipers can be taken with a simple ruler. Look up the seat tube diameter in your bike specifications. With the ruler up against the seat tube at its nearest approach to the chainring, measure to the centre of the chainring. Add half the seat tube diameter. The sum is the chainline.

Good luck.

PH:

--- Quote from: Matt2matt2002 on April 01, 2023, 08:04:58 pm ---After 10 months ( 1500 miles / 2500 Km )  on a KMC X1, I measured today in excess of 0.75 - so fitted a KMC X1 EPT 3/32 chain from SJS - ( 99 links  ie short ). I think it must have been on offer 18+ months ago.


--- End quote ---
I don't know why you're having issues, the addition of a Chainglider takes it outside my experience.
I do know a solution - Put the old chain back on for at least another 5,000 miles!  There really is no need to be changing straight line drive chains at such a short distance, the "stretch" is irrelevant as all three components are wearing together.  I thought the purpose of the Chainglider was to prolong the life of a chain.  The KMC X1 on my Mercury, exposed to the elements, cleaned by wiping with a rag and re-oiling, is currently on 17,200 km and I'm expecting to get a good few more.

Matt2matt2002:
Thanks Andre and PH.

Andre your hint,/ explanation is well beyond my limited technical understanding. But thank you.

PH: I only mentioned the chain glider in passing since some folks say it can rub a chain and cause a noise. I heard the noise before refitting the ' glider.
Re time / mileage. I believe the 0.75 stretch limit is mentioned here quite often as the time to change a chain?  Do you have a limit yourself? Should I stop bothering?

I suspect the noise is caused by the teeth of the front ring not sitting properly within the chain links. Hence my concern at the ' chain- line.

I'll take another look later today.

Many thanks folks.

Best. Matt

PH:

--- Quote from: Matt2matt2002 on April 02, 2023, 08:34:35 am ---TRe time / mileage. I believe the 0.75 stretch limit is mentioned here quite often as the time to change a chain?  Do you have a limit yourself? Should I stop bothering?

Best. Matt

--- End quote ---
Yes, stop bothering, that's the Thorn advice, wear all three together and then replace chain and replace or flip the reversible sprocket and chainring.

It's the chain which wears the other components, as the chain elongates the teeth wear to match.  That is the reason the advice is different for a derailleur where:
1) It makes economical sense to sacrifice several chains to preserve the more expensive cassette and multiple chainrings.  If you religiously replace at .75 theoretically the other components with last forever! If you do the sums it's easy to see this doesn't make economical sense with a singe chainline.
2) The sprockets on a cassette wear at different rates, depending on which get most use, per tooth, so  the chain wear will not match them all.  On a single chainline, not just on a bicycle they're used in plenty of other mechanical applications, you can get the full life from the chain as it'll always match the teeth. 

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