Re: Timing belt vs Drive belt question

[bolhuijo@xxxxxxxxxxxx]

On Mon, 3 Aug 1998, Cam Nguyen wrote:

> I notice that Drive Belts are usually worn out at 30-40 K intervals and
> need to be replaced, but Timing Belts are only replaced at 60K (or higher).
> 
> Does this mean Timing Belts are better designed?

 I would say that timing belts are differently designed, and hopefully
of higher quality as well, given their function.  Regular drive belts
are V-design, and they run on friction with the sides of the pulleys,
which eventually wears them out.
 Timing belts are cog belts that function more like a chain or a gear
in that they rely on positive teeth engagement to transfer power and
avoid slippage.  After enough flexing however, they too give out.
 The higher interval given for timing belts is most likely related to
the cost and hassle of replacing them.  Automakers opt to use a higher
quality belt and keep it covered up and mostly clean so it will last
longer.  It's still cheaper to manufacture and quieter than a chain
drive, even if it's not cheaper to maintain over the long run. 
 The last 2 timing belts I broke (in a Mitsubishi engine designed
without valve/piston interference) just delaminated themselves,
started shedding teeth, and eventually snapped.  Both times, as I
remember, I was shifting down.  I surmise that the rapid engine
acceleration brought on by declutching into a lower gear puts more
strain on the belt than normal operation, so one might draw the
conclusion that proper smooth driving techniques will enhance the life
of your timing belt. 

- --
  John Bolhuis    | These are no ordinary monkeys --
 bolhuijo         | these are mean, spiteful, butt-biting
  @domain.elided   | monkeys with an obvious mission: conquest.
                                        -tabloid.net

------------------------------