On 2018-11-23 06:52, Sir Ridesalot wrote:
On Thursday, November 22, 2018 at 7:05:29 PM UTC-5, Joerg wrote:
After installing a new Sunrace 40-11T cassette (minus one cog), a
new chain and a new rear derailer the road bike can now climb hills
much better. 40T as biggest cog versus 32T before. Woohoo!

However, on the middle and three larger cogs (it's now a 7-speed)
there is a distinct vrrrt .. vrrrt sound when under heavy load.
Maybe from the chain because with a derailer setup it'll never run
100% straight. Hard to say. The noise appears briefly twice per
pedal crank rotation and always on the power strokes.

The chain is a KMC Z50 that should be suited for 7-speed and I
looked, it doesn't rub against a neighbor cog. Maybe a "teeth exit
grinding"? On the 3rd cog from the largest it's really weird
because that has an almost perfect chain line when on the small
chain ring up front.

Anyone heard that before? Can it simply be ignored? Or maybe it'll
go away over time?

-- Regards, Joerg

http://www.analogconsultants.com/

Frame Flexing a bit allowing the chain to touch those cogs? That
could be why you don't see the chain touching the cogs when the bike
is stopped.


It's a fairly rigid steel frame but this could certainly be a
possibility. I'll have a buddy who is a machinist take a close look
while I step on it full tilt with the brakes applied.

Weird thing is, to test for that I cocked the rear wheel slightly left
(it has long dropout slots with vernier peg screws) and the sound did
not change at all.

If my buddy doesn't see anything skewing I am tempted to just go riding
with that. I guess a 1982 bike is allowed some clunker sounds. At least
then cyclists will hear me coming when I want to pass them :-)

--
Regards, Joerg

http://www.analogconsultants.com/