I'm building an old 531c touring bike into a City bike. I intend to add a coaster brake (nexus 8 coaster, which I already have). Do I need to worry about the chain stay being strong enough for the reaction arm? I know coaster brakes are more usual on heavier tubes than this.

Thank you

IMO as long as the clamp is in the right place and not moving you should be ok, by the way I would put something in the stay to protect it from scratches, maybe a piece of foam or something.

I used one on a plain old peugeot mixte for a long while, and it was one of SA's 90mm drums so I imagine it put out a bit more than the smaller drums did... never noticed any kind of distortion in the tubes. I would imagine if you were really worried you could lengthen the reaction arm so that it would put less leverage on the frame but I don't think it's anything to worry about.

Once upon a time, I put a Bendix coaster brake on a Paramount track bike as an experiment. (I bet there's a few people who would burn me at the stake for this.) It worked fine, but I was concerned about bending the chainstay so I undid the mod.

Maybe put a small plate under the clamp? The old (60's-70's) Raleighs came with those. It was an oval piece of metal about 1.5"x3/4" that was curved to fit the stay.

Aaron

Good recollection.
Distributing the stress over a larger area w/ this fab can/might avoid denting a stay that was not designed for this application. Those fitted plates were OEM for a good reason.

-Bandera

I concur with Bandera. The stays were designed for tension, compression and maybe a little bit of torsion, not for bending with a point load. An appropriate reinforcement is highly recommended.

Thanks for the advice. I'll see what I can do about a spreader plate.

I think u have nothing to worry about