A frequent source of frustration for Triumph owners is the stripping of the threads holding the rear hub to the Trailing Arms (TA). The TAs are made of cast aluminum which is both soft and porous and the six studs on each side are threaded at 5/16″-24, which Triumph only rated at 14-16 foot pounds of torque. Anything more then that and you can strip the threads in the aluminum. Some people just drill and re-tap at 3/8″, but you’re still threading a steel stud into aluminum. The better solution is to use a threaded steel insert in the TA that the stud can screw in to, but the problem with doing that is drilling and tapping 12 holes that remain on center and perpendicular to the TA. If you have even one misaligned, the brake back plate and the rear hub won’t fit properly or not at all.

For those who don’t want to use inserts, I also have a kit that allows you to drill & tap for 3/8-16 COARSE threaded studs.

The solution was to make an easy to use jig that would let you drill and tap holes that were perfectly on center and perpendicular to the TA. There’s two versions of the kit that uses inserts: one for using KeenSerts and one for Heli-Coils.

**The kit has been used with great success on a number of TR6’s. The TR6 hub assembly, according to the part’s catalogs and various expert sources, is common to the TR250, TR4A IRS and the Stag so the kit should also fit those cars.

The kit described below is for using inserts but all of the kits follow the same premise: a mounting plate, a drill guide insert and a tap guide insert.