Chain wear (again...)

[brussel]

Johann parallax is an issue in the pic, the macro mode meant I was really close up and trying to hold a ruler and take a pic is not good

 

 

 

In reality it is a little over 1/32 of an inch.

[Johan Bornman]

This thread is a bit disjointed now, no doubt partially due to me consufing it with a similar tread next door.

However, I re-read it all and you say you rode in muddy conditions, the chain you have on is worn to less than 1/16th of an inch but when you put a new chain on, it skips on some of the sprockets.

 

You don't say how many chains have been used on that cassette before, but in the end, your cassette is worn beyond the poin t where a new chain will mesh with it.

 

If the issue is your surprise at how quickly it happened, then I can only say, welcome to the world of muddy riding. It is extremely hard on equipment. And yes, a cassette can wear out before its current chain is worn out.

 

 

 

[Mr Mulebar]

Personally I've been using the Parktool CC2 chain checker for the last 4 years, and have never had issues with skipping chains when replacing the chain as indicated.

 

 

 

If you are going to insist on measuring chains you should use a vernier caliper as a ruler is definitely not accurate enough for what is being measured.    

 

 

[Johan Bornman]

Personally I've been using the Parktool CC2 chain checker for the last 4 years' date=' and have never had issues with skipping chains when replacing the chain as indicated.

If you are going to insist on measuring chains you should use a vernier caliper as a ruler is definitely not accurate enough for what is being measured.    
[/quote']

 

Well, then you have never ridden enough to wear out a cassette. They have a finite life and eventually they'll skip on a new chain, no matter what checker you used. Eventually you'll wear one out.

 

Secondly, vernier accuracy is not needed. It is easy to measure accurately up to 1 1/16th with a ruler. A ruler is DEFINITELY accurate enough. The trick is to meaure over 24 links, you then divide one measuring error by 24, minimising it. Measuring one, or two links adds a relatively large error to a relatively small measurement, giving a large percentage error.

 

Vernier measurements with decimal places after one are dubious and unnecessary.

[careldurand]

careldurand2009-07-14 22:53:40

[Johan Bornman]

Cut cut cut cut

When the link goes around the sprocket it speeds up and due to the acceleration lubricant move in between the two surfaces. 

 

I don't think there is any speeding up at all. As the links go around a sprocket or idler their speed remains constant but they articulate. If they articulate' date=' the lubricant is pushed out even more, over a greater arc than initially.

 

 

 

But initially the lubricant was push out thus when it starts to speed up wear take place at a small scale.  Because the inner surface of the bush wears and the outer surface of the pin wears, the distance between the bushes enlarges.

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So? That's what we've been saying all the time. Except that we understand that the distance between the plates AND bushes increases.

 

How does this affect the sprocket?

When you start of with a new chain and sprocket both have been manufactured according to a standard.  Once you start riding your bicycle three stages of wear starts to take place.

The first phase' date=' ?bedding in?, is a very rapid change in chain length associated with components adjusting to the loads imposed on them. The degree of this initial movement will depend to a large extent on the quality of chain used. For example, good component fits, chain preloaded at manufacture, plates assembled squarely etc. Good quality chain manufactures has many features that minimise the degree of bedding in.

 

The second phase, shown as ?initial wear?, might also be described as secondary ?bedding in?. This is caused firstly by the rapid abrasion of local high spots between the mating surfaces of the pin and bush, and secondly by displacement of material at the bush ends. This localised bulge will wear rapidly until the pin bears equally along the length of the bush. Some manufactures limits this effect by introducing special manufacturing techniques. Some manufacturers maintain cylindricity by reducing the interference fit to a very low level. This reduces fatigue performance.

 

[/quote']

 

You need to modify your explanation, since modern bicycle chains don't have bushings of the type you describe. The sideplate is shaped into a vestigal bushing that doesn't resemble this description.

 

The final steady state of wear will continue at a very low rate until the chain needs renewal. In a correctly designed and lubricated system' date=' 15 000 hours continuous running should be normal.

 

[/quote']

 

Well, it isn't normal. Wear is a function of chain length, hygiene, articulation (sprocket size) and load. 15 000 hours is an arbitrary figure that certainly never works for bicycles. It may work inside clean engine casings lubricated with filtered oil but that's not what happens on our bikes.

 

On top of the stages of wear' date=' consider the following:

On a new chain and sprocket the force you place onto the pedal will transmit via the crank arm to the front cluster, then to the chain all the way to the rear cassette.  Now in this area because all are new parts the initial force will be divided by lets say 8 teeth on the rear cassette depending on witch gear you are in.  Once the chain stars the wearing process you will find that when the chain is stretched 0.25% the force is only carried by 5 teeth now and not 8 teeth. 

 

[/quote']

 

Chains don't stretch. The elongation is not from strain but from pin and plate wear.

 

 

 

Due to the increase in load on one sprocket tooth' date=' it starts to deform.  That why when you look at a badly worn motor bike cha sprocket teeth they look like shark fins.

 

[/quote']

 

Well, no. Wear on a driven sprocket results in increased pitch that doesn't look anything like a shark's fin.

 

Wear on a driving sprocket looks like a shark's fin.

 

 

When measuring a chain' date=' I don?t know who started the rule of measure over 24 links.  All chain manufactures uses one simple formula to measure the percentage wear. 

 

[/quote']

 

I did....here in anyway.  This fact was obvious to people long before I was born and is based on solid principles of error reduction, ease of reading and accuracy.  Further, it is not a rule, but a useful way of doing things. You can measure 48-links if you want, that'll be even better, but it only works on very, very long-wheelbase bicycles.

 

 

 

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Percentage Extension = {[M-(N x P)']/(N x P)} x 100

 

 

Where N = number of pitches measured

Where P = pitch

 

 

And M?  It is a rhetorical question.

 

 

The Parktool CC2 work 100% and it?s a good tool to buy.   Only they are way over priced. 

 

 

Either it is a good buy or not' date=' it cannot be a good buy and be overpriced.

 

But why don't you research it's flaws a bit before recommending it? I've posted a handy link.

 

 

 

Thus sprocket wear will always take place no matter how many chains you use.  But with good chain maintenance and checking the wear every time before or after riding one can prolong sprocket life.

 

 

 

I don't think anyone here has disputed that.

 

I hope this helps.

 

 

I just hope you haven't planted any seeds of confusion.

 

If you are looking to buy a Parktool CC2' date=' contact me as I have a similar one that I sell for R60 bucks (including postage).  A Parktool one will set you back ?R150 bucks. My cell number is 072 435 6410

 

Cheers.

[/quote']

 

Suddenly it all makes sense. You're flogging chain tools. 

 

 

 

 

[Christopher Brunsdon]

So our newly joined rep is telling me I can get a Parktool CC2 for R150 - well I'm off to my LBS then to order one !!!