Triumph T140 Rear Rim Retrofit and Service Bulletin 4-77
Triumph T140 Rear Rim Retrofit and Service Bulletin 4-77
After reviewing some old Triumph Service Bulletins, I came across one that may be of interest to restorers of the 1976-1977 Triumph 750 twins, number 4-77, dated December 7, 1977. The bulletin details the running change of specifications to the rear WM3-18 rim and spokes due to the common spoke failure on the 1976 and early 1977 T140V and TR7RV models. These machines were originally supplied with long 10 gauge spokes, which in some cases were unable to adequately cope with the additional power generated by the 750cc powertrain. In service, they had a tendency to work loose and snap, necessitating a change to the more robust 9 gauge spokes.
The original WM3-18 rear rim carried the part number of 37-7018 and was pierced for .250” OD spoke nipples. The original 1976 factory Replacement Parts Catalog (99-2257) showed the 37-7018 rear rim, along with the thinner 37-7009, 37-7008, and 37-7007 10 gauge spokes. The revised parts catalog is also associated with part number 99-2257, but states “Revised August 1977”, which included the specifications for the 1977 models.
The updated specification for the 1977 TR7/T140 rear wheel assembly is listed as 37-7030 for the rim, 37-7031 for the 9 gauge inner spokes, and 37-7032 and 37-7033 for the 9 gauge outer spokes. Of course, the nipples were changed to suit the thicker spokes and carried the part number 37-7034. The nipples now had an outside diameter of .300” and the new rim was pierced to suit the larger nipples.
Interestingly, the service bulletin makes no mention of the reason for the change in specification, perhaps due to the avoidance of a broad and expensive recall during a difficult financial period at Meriden. The revised 1976/1977 replacement parts catalog shows part numbers for both the 1976 and 1977 models. The listed part numbers for the 1977 models are the current condition that most wheel goods suppliers are offering the replacement rim and spokes in for the 1976-later Triumph 750 twins.
We are pleased to introduce our new line of Devon Rim Company wheel goods and are offering rim and spoke kits for some of the more common applications, including the disc-brake 750 twin models. As it relates to the uprated TR7/T140 specification, we are supplying a complete rim and spoke kit for both front and rear wheels with Devon “Valtru” chrome rims, stainless steel spokes, and brass nickel plated spoke nipples.
