Need help identifying small part behind rear axle
 

Could someone tell me what the small part immediately aft of the rear axle is called so I could purchase for the one that is missing on the left side of the bike? It appears to act as an axle stop when setting the rear wheel in it's place within the rear dropouts.

Thanks!

P.S. Bike is 87 Schwinn Sierrahttps://cimg6.ibsrv.net/gimg/bikefor...19edbe32c0.jpg
The part in question is the small silver part with a screw through the center of it, located at the rear most section of the axle dropout. I am missing the one at the left side dropout and would like to replace.

I believe it is adjustable fore and aft to align wheel. None needed on the other side.

Yes, it's an axle stop. And it's not strictly necessary. Just pull the wheel back until it stops against the drive-side stop, then center the rim between the frame stays, and tighten the quick-release.

The part of the process you describe that I do not enjoy is "then center the rim between the frame stays". I find it a fiddly chore. My thinking is if there was an axle stop on the other side the rim would self align or almost so.

I see no point of having an axle stop on one side only. Why does the axle have to be stopped in that particular place anyway?

So far "axle stop" brings up nothing resembling part on Google. Could it possibly go by another name?

Dropout Spacer

Previously those got included when the derailleur hanger was a bolt on addition on the drive side ..

Its D shaped Nut occupies a similar amount of he back of the dropout.


On the bike, shown, its quite superfluous ..

For symmetry, remove it, rather than seek a 2nd one ..

Some derailleurs and shifting systems (particularly indexed shifting systems) are sensitive to where the derailleur sits in relation to the cluster. That's one reason why many manufacturers have moved to using vertical dropouts.

Have you tried asking a bike shop if they have an axle stop you could put on the other side?

Thanks for your wonderful help everybody! I just placed an order so I will have one on each side.

It is good to have the stop in the dropout to provide consistent placement of the axle in relation to the RD hanger. With index shifting, the alignment of the RD to the cogs helps to provide reliable shifting. Shimano has a recommended alignment for this, which appears to be about correct in the pic, with the wheel axle slightly forward of the center of the RD hanger bolt. Inconsistent placement of the wheel would require constant adjustment of the RD's "b-screw" to optimize shifting.

Inconsistent placement could also put the brake pad into the tire or spokes.

It's probably best to keep the part in the dropout so you don't have to eyeball the placement. Even without a similar part in the other dropout, placement is close enough when you try to center the wheel between the stays the brake pad alignment is usually close enough.