Just to confirm something is normal
 

Hi,

I have 6 speed bike with a very basic Shimano (SIS) rear
derailleur. I'm pretty sure you can't buy it as a Shimano part.

On the lowest gear it makes a noise like the top index wheel is
running on top of the gear teeth of the lowest gear, is this normal ?

I can't see any adjustment for this, the angle seems seems set by
a bolt and a flanged bush behind the rearwheelnut. I have changed
the rear tyre, so it is possible there is some subtlety to refitting the
rear derailleur I may have missed putting the rear wheel back on.

rgds, sreten.

from your description of 'bolt and flanged bush' I believe that your rear derailer is a 'claw' type mount.
Sometimes, when removing the rear wheel this claw can get slightly moved if it was loose.
so if this noise is a new problem, check that first.

on the other hand; if this problem has been persistent in the past; it may be that you need more b-tension to pull the derailer away from the lowest/largest gear, so it doesnt grind/rub

it also sounds like you have a below-tourney-level RD, in which case there is no b-tension adjustment, and you just have to put up with it, or upgrade.


Found a decent photo online:http://bicycles.stackexchange.com/qu...-34t-megarange

Hi,

There is no B-tension adjustment, its very basic, OEM stuff.

However I loosened everything off - wheel nut - and the
derailleur retaining nut and bush/nut - and realised there
was some wiggle room of the derailleur across the axle.

Setting the derailleur bracket more anti-clockwise has
cured the problem - so I assume it is not normal.
I didn't put it back properly changing the tyre.
(But I think it was like that beforehand.)

(The derailleur is clamped by the wheelnut. The
dropouts are near horizontal - presumably for
single speed/IGH versions - and the derailleur
has a bolt and lipped bush/nut that fits into
the dropouts behind the main rear axle.
I don't know what mounting system that is.)

rgds, sreten.

The penny dropped what to try after posting.

The low end RDER's from Shimano can be a pain at times.
As you mentioned, pivoting the claw has some effect.
Proper chain length "CAN" be important also.

I think you put your finger on the problem. You moved the claw when taking the wheel off and didn't put it back as it was.

The angle the claw hangs at is set and held at two points. The nut on mounting screw behind the axle pockets into the dropout, then when the axle is in the U-cutout, it creates a center line from the center of the axle to the center of the screw, and fixes the mounting angle so it's the same every time.

Odds are the claw slipped forward or back or the back end nut slipped out of the dropout.

Remove the rear wheel, slide the claw to the back of the slot, and tighten it in position with the U lined up. Then slide the wheel all the way into the claw, centering it in the frame from the left side. If all was OK before, you should be good to go now.

http://www.babygiftsoutlet.com/image...et_BG05660.jpg

Hi,

Looks to be very near mine, and I assume its the so-called
claw mounting style, only the bracket is slightly different.

rgds, sreten.

Hi,

I think I may have missed something related to
"lining up the U". Though it seems fine I'll take
it apart tomorrow and have good look at all the
bits, there was a flat section I didn't align with
anything in particular in the dropouts, I recall.

rgds, sreten.