The spacers that you sometimes find in rear dropouts, what is their purpose? Why wouldn't you want the axle to slide in as far as possible? This is in reference to horizontal dropouts. I have an old Nishiki Seral touring frame I'm doing a build on, it had the spacers, took up about the last 3/8 inch of the dropout. Why?

Because!


Horizontal dropouts were what was available (for '70's era bikes) and people couldn't be trusted to put the axle in its proper place above the derailleur pivot.

Jeff, thanks for the response. Here are a couple of pics of the spacer and the axle in present positioning without the spacer. Does it look to you like I need the spacer? Why don't they just make the dropout so when the axles all the way back it is in the proper location? Do they play any role in centering between the stays? Just trying to understand there function. The Miyata 210 donor bike a lot of these components came from also had them.

No, it looks like you need to be mindful of where you place the wheel in the dropout..
when you tighten down the QR..

This is a bit of a guess on my part but I suspect that the longer than required slots even on the later dropouts with integral hangers were designed to be compatible with the older derrailleurs that used the old style hangers that fit into the rear section of the slot. Or possibly with the old style freewheels and shifting of the day the adjustable dropout slots were used to adjust the amount of chain wrap. With today's stuff the amount of wrap is set by the design of the derrailleur and adjustment of the B screw. But back then it seems like the standard for placement of the hanger was a trifle more fluid. By using semi horizontal dropouts that used either the fixed spacers or the adjustable screws seen on some higher end frames this could be adjusted to optimum for the parts being used.

As I say these are just guesses on my part since I wasn't riding and wrenching bikes during those times so I'm not sure. But from the parts that I've played with this almost seems like the ideas fit.

the Screw adjusters were likely a Race Convenience for team road support wheel changes to be Quick,
and the alignment preset.

+1. The spacers help locate the axle correctly with respect to the derailleur hanger, but aren't an absolute reference for the wheel.

Well, this being an 80's Nishiki Seral touring frame built with vintage Suntour ARX derailleurs and a Sachs freewheel I,m thinking I should probably go ahead and put the spacers back in. You can see from the scoring on the dropout that the axle was always further forward in this frame. My thiking in removing them was that one of the features of a touring frame was the longer chain stays and thus longer wheel base, so moving the axle forward in the dropout would somewhat negate that. This bike is going to be used as a tourer with front and rear panniers with a lowrider in the front. I was trying to achieve a little more stability by stretching the wheel base to the max. Thanks to all for the responses, any further insights would be welcome.