| Also known as | T1257 |
| Diagram | Fig. 2 — CRANKCASE · ref 35 |
| Subsystem | engine bottom |
| Listed in parts books | 1963–1974, 1976–1980 |
FIBER WASHER,INDEX 15/32 (12mm)
Fiber sealing washer, index 15/32 in. (12mm), used at a gearbox drain plug on Triumph unit twins.
57-1257 is a fiber sealing washer used at a drain plug point in the gearbox area, sized to fit a 15/32 in. (12mm) location. The catalog lists it under the CRANKCASE and HDP figures, and it also carries the older letter-prefix number T1257 for anyone working from an early parts book.
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These fiber washers do the simple but important job of sealing a threaded drain or level plug so oil stays where it belongs. They compress under torque and don't hold up forever, so it's a part people tend to buy a few of at a time rather than just one.
The catalog shows this washer appearing across a long stretch of unit-construction Triumph twin production, so it's a part that shows up again and again in gearbox service work. Bring your parts book or ask us to confirm the exact application before ordering if you're not sure which drain point it belongs to.
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