| Also known as | 99-3517 |
| Diagram | Fig. 11 — CHAINCASE AND CHAINS · ref 4 |
| Subsystem | primary |
| Listed in parts books | 1960–1970 |
Bolt
A 1/4 inch, 26 TPI, 1/2 inch long general fastening bolt used across many Triumph assemblies, superseded by 99-3517.
DS57 is a general-purpose bolt that Triumph used all over the bike during this era. The alias 1/4X26X1/2D tells the size story plainly: a 1/4 inch bolt with 26 threads per inch, half an inch long. This part number was later superseded by 99-3517, so if your parts book shows the old DS57 stamp and you're ordering today, 99-3517 is the current number to ask for.
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What makes this one worth stocking a few of is how many jobs it covers. The catalog shows it turning up in chaincase and chainguard assemblies, footrest mounts, mudguard and fender fittings, battery carriers and toolboxes, engine fittings, exhaust brackets, swinging fork and suspension hardware, ignition and coil mounting, and speedometer and tachometer brackets, among others. It's not a part tied to one job on the bike - it's the small fastener Triumph reached for across dozens of different assemblies.
Given how many places this bolt shows up, don't assume every DS57 you pull off a bike is doing the same job as the last one. Check the fitting it came out of before you toss it in a generic hardware bin, and if you're replacing a bunch at once, it's worth grabbing a handful since they tend to get used up fast on a full restoration.
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