Triumph & BSA 3-Spring Clutch Thrust Washers

BSA & Triumph Clutch Thrust Washers Explained


As time passes by over the years, there seems to be a bit of confusion on the Triumph & BSA twins 3-spring clutch thrust washers. In fact, there are two types of thrust washers and two types of clutch hub sleeves that where fitted to many Unit Triumph & BSA twins. Below I would like to show you in detail of how to identify what parts you currently have, and also what parts you need. 


 Triumph Early & Late Thrust Washers

 Shown is the "early" version and "late" version of the clutch thrust washer as fitted to Triumph & BSA twins, also singles.


First off, there are two types of clutch thrust washers. We often refer to them as the "late" and the "early" variety. The later Triumph clutch thrust washer has one part number as also shared with the BSA models under 57-3931. The early thrust washer has two part numbers, one Triumph, and one BSA, both are the same part. The Triumph clutch thrust washer part number is 57-1735 (T1735) and the BSA part number is 68-3278. The Triumph & BSA early clutch thrust washers where fitted to twin cylinder models including the 350, 500, and 650 twins with the 3-spring hub only up to approx 1969. According to factory parts books, the "late" clutch thrust washer was fitted to Triumph & BSA twins from 1970 & on.



Triumph Clutch Hub Sleeve Early & Late
 Left sleeve is the "early" type and the right sleeve is the "late" type. Notice the inner grooves are different? That is what dictates what thrust washer you need. 


You are probably wondering... what is the difference? The difference is that both "early" and "late" thrust washers have a different I.D. (internal diameter). The clutch hub sleeves themselves where machined differently to accept the different thrust washers. As shown in the photo above, the left hand side sleeve has a smaller O.D. machined "step", that is to accept the early 57-1735 / 68-3278 thrust washer. The right hand side sleeve is the "late" version. You can clearly see that both look the same but the "late" sleeve has a wider machined O.D. Look at both red arrows to visually see the difference. You must use each thrust washer with the correct sleeve in order for them to work and fit properly together. 



If you are performing an overhaul on your clutch, and you not sure which thrust washer you need or not sure which sleeve you have, use the specs below and compare with your hub. I have seen many cases where an early sleeve has been fitted to a late model and vice-versa. Sleeves are interchangeable for all 3-spring clutches, but you must use the correct thrust washer in conjunction. 


 Thrust Washer Types                                        I.D. (approx)         O.D. (approx)

Early Clutch Thrust Washer (57-1735 / 68-3278)        1.836"                   2.608"

Late Clutch Thrust Washer (57-3931)                        2.020"                   2.608"



Original Triumph Thrust Washer

Original Triumph clutch thrust washer. Notice that one tab is missing / broken?


The original clutch thrust washers where made from two types of materials into one piece. The back half was a steel type material and the front half was made of bronze. The problem with the "early" original types, as shown above, the factory used metal tabs to secure the thrust washer from rotating. The metal tabs would eventually break off and get crushed by your clutch chainwheel. Original thrust washers never had a precise fit, they where also marginal.  


Triumph Clutch Thrust Washers & Sleeves



The new thrust washers we stock are made here in the USA and they do not use the tabs, they are precision machined and rely strictly on the chamfer design to prevent rotating and to offer a perfect fit. In my opinion, they are 10X better then what the Triumph and BSA factory use to fit. Clutch thrust washers do wear over time and should be replaced. You can purchase the "early" 57-1735 clutch thrust washer and you can also purchase the "late" 57-3931 thrust washer on my site. Click on the red text above as they are links and will take you directly to each part. 


  • Bob Cottam

    But what about me?…. I have an April `62 Star, so a very early bike. In my clutch, there are no separate bronze washers at all. The clutch sleeve is part number 68-3212- it is not machined to accept a thrust washer on its front side, it just runs directly against the clutch drum bearing face. There is no separate thrust washer fitted behind it either because the six hole retaining plate at the back (68-3235) is solid bronze – so no need for a separate washer there. I assume BSA thought this too costly , so introduced the later steel, recessed rear plate ( same part number 68-3235!) and bronze “insert” washer. I would be interested to know if the front washer ever made much difference to the clutch operation, as there is no wear at all in mine after 60 years, so there cannot have been much friction there anyway?? Anyone else got this early set up?

  • Ray

    Thanks for the write-up and description Good info. however unless I misunderstanding something you are using OD when you should be using ID in the description. The OD is identical on both early and late washers. The ID is what is different.

  • david elston

    Hi if the wrong thrust washer is used will this make my clutch slip thanks Dave

  • Skippy

    How much oil goes in the clutch side on a 1969 a-65 bsa lightning

  • Classic British Spares

    @Harold Moore – yes

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