NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/rec/bicycles/tech/2808

Internet Message Format | 1992-12-23 | 1.8 KB

From: [e-mail] (Jobst Brandt)
Date: Tue, 22 Dec 1992 22:51:51 GMT
Subject: Re: Re: Chain Maintenance Question
Message-ID: <[e-mail]>
Organization: Hewlett-Packard Laboratories, Palo Alto, CA
Path: sparky!uunet!usc!sdd.hp.com!hpscit.sc.hp.com!hplextra!hplred!jbrandt
Newsgroups: rec.bicycles.tech
References: <[e-mail]>
Lines: 32

XiDavid Keppel writes:

> A new chain measures 12" for a dozen link pairs (one set each of
> wide and narrow link plates).  At 12-1/8" it is time to consider
> replacement.  At 12-1/4", the cogs and chainrings are being
> damaged.

I think you are giving this an excessively binary character.  As
soon as you use the chain it begins to wear and its pitch increases,
and this concentrates more load on the disengaging tooth.  This
increased load is doubly damaging because the chain rolls out of
engagement over an increasing length of tooth, as chain pitch
elongates.  It is a continuous process.

Less apparent is that only every second chain roller increases in
pitch since the link that carries two rollers is by definition
always at correct pitch.  It is the connecting link (outer plates
and pins) that develop the increase in length both by wear on the
pins and the sleeves in which they turn.  Therefore, the percentage
pitch error is actually twice as great as one would deduce just from
chain elongation (the elongation being concentrated in half the
links).

Because most bicycles have derailleurs or an odd number of teeth on
their sprocket, the sprockets wear uniformly because, although only
every second tooth is loaded, they all have their turn at this task.

I think the FAQ has enough information on this to satisfy the
subject but there are always nuances to this that may not be
apparent.

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