qclfd

Hi everyone,

The rear shifter on my bike won't stay on the lowest gear. Reading some of the threads online, I was tightening the screw on the shifter when I found that there is a crack on the top plate/washer, the plate right beneath the friction adjustment screw, on the shifter (I might have cracked it while tightening it I'm not sure).

But I don't think friction is the problem as down shifting requires A LOT of pulling on the lever, significantly more so compared to the front derailleur. I'm not sure what's going on here.

What should I look into? If I have to replace the cracked part, is there a cheaper modern part? These older parts are stupid expensive.

Thanks

tomtomtom123

You can buy cheap index shifters for $10.

Andrew R Stewart 

No brand or model, no location or style of shifter.

With friction levers when the friction "pack" (the various washers/spacers and lever that are snugged up tight to provide the friction) is allowed to slightly rotate with the lever's movements the amount of it's friction will decrease with each lever movement. In short time this loosening can reduce the lever's ability to stay put and the der spring will over power the lever's friction. Is the top plate/washer plastic or metal?

If the rear der's low gear limit screw if right on the cusp of enough travel to get into low gear the slightest cage movement back (to the high gear end) can cause the chain to try to shift.

Do you have a bike coop or bike kitchen locally? If so their stash of old parts might be far less costly then an eBay item is. Andy

qclfd

Ah sorry, newbie mistake.

The bike is a late 80s Bianchi Campione D'italia. The rear derailleur is Ofmega masters and I believe the downtube shifters are Ofmega masters as well. It certainly looks like the pictures on velo-base. (Sorry I haven't posted enough to link urls)

With the crack on the top plate, you're saying that it's possible the pack is shifting every time I move the lever? I'm not sure about the material of the top plate, it's all black, I'd say it feels like plastic? There is another metal washer wedged between the screw and the top brake.

I'll give the local bike coop suggestion a shot.

Thanks Andy.

AnkleWork

Check for excess cable friction.

Andrew R Stewart 

Don't expect any shop or business to have the OEM lever parts as these Ofmega components were pretty uncommon even when they were current. But with friction levers one can mix and match far more readily then with indexed stuff. So any friction lever should substitute, excepting the fit to the lever boss if brazed on. Andy

bikeaddiction1

That was my first thought and have seen it often. Since it is easy I would check that first. The same could happen if the derailleur hanger or derailleur is bent and the chain is again "right on the cusp of enough travel to get into low gear" and drops back a gear when pressure on the shifter is released.

Homebrew01

Is the lower 'L' limit screw allowing the rear derailleur to fully engage the largest cog ? If not, that can cause it to shift to the next gear.
A slipping shifter will often slip in other gears, not just the lowest that you mention.