Re: Screamer timing chain idler bracket

"bruce" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

One more question about this. Why or how is this chain tension changing so
much the chain isn't getting longer what s moving.
I have a screamer with the new rans one roller setup.
Thanks for your comments

It doesn't take much to make it go from very tight to moderately tight
to loose. All this can happen in maybe 1/4 inch travel of the idler
wheel assembly.

So if each of the three things mentioned below wears by a small, even
almost immeasurably small, amount you can still end up with a
noticeable difference in chain tension:

1. Idler wheels. This are plastic, so they wear noticeably,
especially the upper one that is under tension (if you have that
setup--it sounds like you don't)

2. Chain. These are usually replaced when the "chain stretch" reaches
1/16 per foot. Suppose you have half of that (1/32 per foot). The
timing chain is what--4.5 feet long or something? So counting 4 feet
of chain at, say, 1/32 inch per foot of chain "stretch" you've got
altogether 1/8 inch of chain stretch. That's quite a bit!

3. Chainring wear. Chainrings will wear just a bit where each tooth
engages the chain. Especially, as the chain wears the chainring will
wear to match.

Again, in say 1000 miles the wear on each of these 3 items would be
quite small. But add them together & it's no surprise the idler wheel
assembly needs to be tightened up just a little every 800-1000 miles
or so.

--Brent
bhugh [at] mwsc.edu

Rans Screamer
Rans Rocket
Trek R200
Raytown, Missouri