| Also known as | M21-2013, S2013 |
| Diagram | Fig. 18 — REAR WHEEL · ref 24 |
| Subsystem | wheels |
| Listed in parts books | 1970, 1974 |
AXLE NUT 3/4-20 UNEF - 37-3426 (THIN) Large Hex 1 5/16 - 5/16 Thick
Thin rear axle nut, 3/4-20 UNEF thread, large hex, for the timing side of the rear wheel.
This is the rear wheel axle nut, part number 21-2013, a thin nut cut for a 3/4-20 UNEF thread with a large hex head. The catalog notes it as thin with a hex measuring 1 5/16 across and 5/16 thick, and it also carries the older reference number 37-3426 for anyone cross-checking against an earlier parts book.
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It shows up in the rear wheel figure for the timing side of the axle, holding the rear axle secure in the wheel. Given the fine thread and thin profile, it pairs with a specific axle setup, so if you're replacing this nut it's worth having the axle in hand or the diagram in front of you to be sure the fit matches.
We show this one appearing in the 1973 catalog listings. If you're not sure whether your bike's rear axle takes this nut versus a different one, give us a call before you order and we'll help sort it out.
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