| Also known as | W1691 |
| Diagram | Fig. 13 — SWINGING FORK AND SUSPENSION UNITS · ref 31 |
| Subsystem | bodywork |
| Listed in parts books | 1966–1970 |
LOCK NUT 5/16 X 26 (BRAKE DRUM TO HUB)
A 5/16 x 26 self-locking nut used to secure the rear brake drum to the hub on Triumph twins, PN 37-1691.
This is the 5/16 x 26 lock nut Triumph used to secure the brake drum onto the rear hub, part number 37-1691, listed under the older W1691 form in earlier books. It's a self-locking nut, so it holds itself against vibration without needing a separate lock washer stacked underneath it.
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It shows up across a wide spread of figures in our records - swinging fork and suspension, frame, fenders, gas tank and seat, and both the rear wheel and mudguard sections - which tells you this same small nut got used in more than one spot on the bike wherever a self-locking 5/16 fastener was called for, not just at the brake drum. The catalog appearances run from 1966 into 1970.
It's a cheap part to keep a few of in the parts drawer since it's easy to lose track of one when you've got the rear hub apart. Confirm the exact location you need it for against your own parts book, since this number turns up in several different assemblies.
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