I'm attempting to refurbish a bike that I was given, it has a (not sure what brand) coaster brake, which according to sheldon brown's site has a peculiar kind of cone nut. The wheel might be 10 years old, it's hard to say.

I've been able to remove the otherwise butchered nuts (see below) using a tap & hammer and an axle vice, now that they are free I'd like to know what they are, so that I can replace them, do they have a special name?

I've only ever seen mention of cone nuts resembling a regular washer, but with two flat sides (sorry for the poor explanation) - these that this bike is fitted with are something different, see below:

cone nut?

Apologies for my dodgy graphics work, the middle is threaded, and sized to fix the (slightly larger than the wheel nut thread) centre of the coaster brake axel, the outsides smooth (very much resembling a washer) except for the two grooves.

The entre part is perhaps 20mm in diameter; unfortunately my bright idea of drawing the part, and then using Google image search has failed me!

In the end, I'm sure this particular bolt is a strange european relic designed as some kind of "security" bolt; not dissimilar to the Apple style 5-point start, or similar, to discourage people against fiddling with their coaster brake. But I would really like to rebuild the brake!

I'm sure I could replace them with regular "cone nuts" - that is the ones with two flat sides, but the term "cone nut" seems to refer more to the purpose than the design of the nut itself.

All information appreciated, thanks in advance!

1 Answer 1


The term "cone nut", on a bike, generally refers to the nuts that comprise the outer half of a bearing race (the inner half being formed into the wheel hub or whatever). The "cone" side, which faces inward, has a concave profile so that the balls will roll smoothly in it.

It's hard to tell what you have from your description. I do vaguely recall some cases of nuts on coaster brakes with slots like that, apparently intended to be operated by a "spanner wrench" (which is a redundant expression in the UK, but means a wrench with pins rather than flats in the US). Presumably this allowed the nut to be more readily adjusted while everything was assembled. (Current bikes require a thin "cone wrench" for the same adjustment.) If this is all it is then a hex-sided/flat-sided nut (with similar thread/profile) should work just fine.

I've also seen, internal to some coaster hubs, various plates and nuts with slots or teeth, intended to engage mirror-image features of the hub or an internal rotating piece. These would be quite specific to the particular hub.

And it may be that this nut is a cone nut for internal bearings, such that the nut cannot be reached for adjustment with a regular wrench (even a thin one). In that case you'd have to figure out something.

It's remarkably hard to find a good image of a cone nut. Here is the best I could find:

enter image description here

This one has a sheet metal dust shield fastened to the outer diameter -- the nut itself is inside of the inner flange of the shield. On the back side is a regular (though fairly thin) hex nut or (more often) a cylindrical body with two flats, sized to take a thin open-end wrench.

(It should be noted that it's become common to refer to any nut that secures a bike bearing as a "cone nut", even though it may be securing a sealed bearing cartridge and hence lack the conical extension. This adds a lot to the confusion.)

  • I was able to take two further snaps of the nuts cl.ly/1S3w0G3j121z2I0a1M3z and cl.ly/2O3L3W0e0y3j1P3M1X3L. In this case it looks like I'm misusing the term "cone nuts". In the second picture, the third piece on the axel from the left is the "cone nut" using the correct terms. Jun 3, 2012 at 13:29
  • Strange that these nuts are so unusual, I've never seen a tool for working with those, but I will replace them with the flat-sided, should we say modern cone-adjustment nuts. (which seems like a better name for them) Jun 3, 2012 at 13:30
  • I can recall as a child that my father had several wrenches for working on this sort of nut (though probably in larger sizes). Yeah, replace them with thin regular nuts (assuming you can find some with the correct thread). (Worst case you can get the right tap and rethread nuts that are a hair smaller.) Jun 3, 2012 at 13:37
  • Here is an "adjustable" version of the spanner. The more common style was fixed -- designed for a specific diameter. Jun 3, 2012 at 13:40
  • Thanks Daniel, I also have a fixed hook spanner for a singlespeed lock ring, hadn't expected that there'd be a small enough hook spanner to work with these, but now that they're gone, I'll keep my eye open for a small enough nut! Cheers, accepted & upvoted for a good answer. Jun 3, 2012 at 13:46

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