measuring chain wear (again)

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bobc
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Joined: 5 Apr 2012, 11:59am

Re: measuring chain wear (again)

Post by bobc »

The zero button is really quite handy on the digi verniers (or verynears as a colleague insists on calling them) - it's not just for setting zero... Like measuring the chain you can accurately measure distance between two (same sized) holes by using inside measurement having zero'd on the diameter of one of the holes.
another handy feature folk don't generally know about is the "step measurement" function (at the end that looks as though it's doing nothing), very handy for marking out as well as . . er . . measuring steps....
I must say I have a couple of these to be sure I always have one that works... at £9 a pop they are fantastic value!
mercalia
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Re: measuring chain wear (again)

Post by mercalia »

bobc wrote:The zero button is really quite handy on the digi verniers (or verynears as a colleague insists on calling them) - it's not just for setting zero... Like measuring the chain you can accurately measure distance between two (same sized) holes by using inside measurement having zero'd on the diameter of one of the holes.
another handy feature folk don't generally know about is the "step measurement" function (at the end that looks as though it's doing nothing), very handy for marking out as well as . . er . . measuring steps....
I must say I have a couple of these to be sure I always have one that works... at £9 a pop they are fantastic value!


I have never used one of these but after a bit of google I was able to understand how setting the zero can do the above but bobc earlier use re chains completely misses me I dont get it at all or maybe I didnt understand what was being said. measure the distance in a link setto zero then measure a number of links? dont get this at all how it works I understand that setting to zero does subtraction and understand how can be used in the hole case but the chain case dont make sense to me.
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andrew_s
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Re: measuring chain wear (again)

Post by andrew_s »

Chain rollers are a loose fit, amd move when pushed along the chain. The amount of looseness on a new chain is variable, depending on brand/model, and they get looser as the inside of the roller wears away with use.
If you measure the distance between rollers, one roller is pushed one way, and the other roller is pushed the other way, so you are measuring the distance between pins plus the the amount of roller movement.
If you measure 5 link pairs, and subtract the measurement for one link pair, the roller movement, being the same for both 1 and 5 link pairs, falls out of the measurement so that you are left with just the pin spacing for 4 link pairs. Measuring one link pair first and setting that distance as zero means that you don't have to write down measurements or do the subtraction.

You should always measure in pairs of links.
If you measure 1 link, and it's an outer link, you'll get 0.5" plus the roller movement. If you measure an inner link, you'll get 0.5" + roller movement plus twice the pin/bushing wear.
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531colin
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Re: measuring chain wear (again)

Post by 531colin »

bobc wrote:..............
Put the inside pointy things between two adjacent rollers & pull to measure the distance. SET the ZERO (while applying tension)
.....


ie. to set zero as the slop in 2 rollers, you have to measure the slop in 2 adjacent rollers, plus the distance between 2 adjacent rollers.

bobc wrote:..............
Now measure between rollers 5 or 10 links further apart.
You can directly read how many thousandths of an inch the chain has stretched.
While it's on the bike.......


but don't forget you have "zero-ed" the distance between 2 adjacent rollers, ie one half link. So to get the wear in 5 or 10 links, you need to span 5 1/2 or 10 1/2 links.

"they say" you should exclude the roller slop from an estimate of chain wear.
For me, that is an unattainable and unnecessary degree of precision. I just use a wear gauge, if I bin a chain with a bit of wear left in it, I don't care, as long as I protect my cassette. Its my observation that chain "wear" is nothing like uniform, and I conclude the uneven wear is in fact corrosion**. So just pick 2 adjacent rollers....they could be either the most or the least corroded rollers on that chain.....or maybe just average.

**where the chain sits in the jockey cage overnight, and in the morning its rusted into an "S" shape
Brucey
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Re: measuring chain wear (again)

Post by Brucey »

531colin wrote:
bobc wrote:..............
Put the inside pointy things between two adjacent rollers & pull to measure the distance. SET the ZERO (while applying tension)
.....


ie. to set zero as the slop in 2 rollers, you have to measure the slop in 2 adjacent rollers, plus the distance between 2 adjacent rollers.

bobc wrote:..............
Now measure between rollers 5 or 10 links further apart.
You can directly read how many thousandths of an inch the chain has stretched.
While it's on the bike.......


but don't forget you have "zero-ed" the distance between 2 adjacent rollers, ie one half link. So to get the wear in 5 or 10 links, you need to span 5 1/2 or 10 1/2 links.



I think that is what Bob is saying.

mercalia wrote: I have never used one of these but after a bit of google I was able to understand how setting the zero can do the above but bobc earlier use re chains completely misses me I dont get it at all or maybe I didnt understand what was being said....


if you get some digital verniers and then carfefully follow Bob's instructions you will see how to do it and what the readings tell you. There is no substitute for actually doing something, sometimes.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bobc
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Re: measuring chain wear (again)

Post by bobc »

As brucey says, have a go. As ever, lots of ways of skinning this cat this is an easy procedure I happen to use.
It occurred to me that I'd never actually tried it on a derailleur chain, would the arm on the caliper fit in? Turns out that it does - just... but I couldn't be sure it will on yours! And a 6" caliper is big enough to measure 5 links (10 x 1/2") having zero'd on one (2 x 1/2" - a roller)
My trike chain is quite new, 5.005" - that's 0.1% stretch (or maybe typical for new chain :)
fastpedaller
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Re: measuring chain wear (again)

Post by fastpedaller »

Crikey, all this fiddling around - I'll just use the 12" rule, never failed me before :D
BigG
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Re: measuring chain wear (again)

Post by BigG »

I have always found that the best way of measuring chain wear ("stretch") is to hang it through the open link pin holes from a suitable nail. This is easily done now that we have quick release links. Any stretch above half a link from its length as new (about 0.4% - 0.5%) should put it in line for changing. There is no need to be meticulously accurate. I have a nail and mark at 110 links on my garage door post. Chains are cheap expendable items and changing them regularly saves more than their cost in the life of rings and sprockets.
fastpedaller
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Re: measuring chain wear (again)

Post by fastpedaller »

BigG wrote:I have always found that the best way of measuring chain wear ("stretch") is to hang it through the open link pin holes from a suitable nail. This is easily done now that we have quick release links. Any stretch above half a link from its length as new (about 0.4% - 0.5%) should put it in line for changing. There is no need to be meticulously accurate. I have a nail and mark at 110 links on my garage door post. Chains are cheap expendable items and changing them regularly saves more than their cost in the life of rings and sprockets.

Agreed - that's more accurate than the 12" rule as well........ but you can't do it on the bike :lol:
Psamathe
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Re: measuring chain wear (again)

Post by Psamathe »

Excuse my ignorance in these matters but, strikes me that there are two aspects to "chain wear". One is the wear on the pins/stretch of the side plates (do the side plates really stretch ?). The other aspect is the wear on the rollers (the roller thingys on the pins). I would expect both these aspects to impact the effective space between links (from the perspective of the cogs). e.g. if your rollers were 2mm thick (difference between inner and outer diameters) when new and wore down to only being 1.5mm thick then your interlink spacing would be 0.5mm per link greater (ignoring and wear on the pins).

And measuring the inter rivet distances would only check side plate stretch and would ignore wear on rollers and pins.

So where have I gone wrong ?

(Sorry I don't know the correct names for the correct bits)

Ian
Brucey
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Re: measuring chain wear (again)

Post by Brucey »

in fairness it is unclear that roller wear does impact badly on the way a chain works;

1) The roller OD varies little between chain designs, but the free play in the rollers of new chains from different manufacturers does vary a fair amount.

2) Rollers contact each tooth near-tangentially; this means that a chain with rollers that are worn on the ID may not load the teeth all that much differently from one that isn't so worn.

Re 2) I suspect that if there is roller wear, there is more scope for the roller moving slightly under load. But then it will be likely to do that anyway; few systems allow the chain to be consistently fed onto the sprocket so that the roller immediately assumes the correct position on the tooth, i.e. the exact same one as it is in when under load immediately prior to disengagement.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Cyril Haearn
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Re: measuring chain wear (again)

Post by Cyril Haearn »

I have a stock of new chains at home. I would measure the worn chain against a new one of the same make.
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mercalia
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Re: measuring chain wear (again)

Post by mercalia »

well I got my self one of those cheap digital verniers ( and also a metal ruler ) According to the guage after doing the zero adjustment I get 5 links are 5.006" thats for a budget SRAM PC41 chain after 1500 miles . ( 1% is 0.05"?) That seems to be too good to be true? The internal distance of a link I get 0.215". I have been every 100 miles or so rubbing off any grit and re drip relubing with chainsaw oil. But even so I can not say I believe the measurment.... My Park tool says it is at between .5 and .75 depending on the links tested
Brucey
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Re: measuring chain wear (again)

Post by Brucey »

with slack rollers they might both be right!

What does the ruler say?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
mercalia
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Re: measuring chain wear (again)

Post by mercalia »

well as far as I can make out the ruler says 10" is still 10". I caught the end of the ruler on the edge of a pin and measured to the same edge on the pin nearest 10". I dont believe I have a super chain that only cost me £5 10 years or so ago and has done 1500 miles with no wear. some 10" sections seem less that 10"!
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