Last updated 13 July 2008
Steering Rack Rebuild
Refurbished steering racks are readily obtainable, and reasonably priced. I had two racks and decided to rebuild one using the best parts from both. There's nothing particularly difficult involved, but you do need a supply of shims during reassembly. Having two sets of components gave me enough to play with.
I used coloured tape to keep parts together, as shown below.
The steering rack consists of four assemblies:
Tie Rod Components:
Pinion Thrust Pad: Each thrust pad, on the extreme right in the photo, had some were marks, though one was much worse than the other.
Pinion: The pinions were both in good condition, but the bearing surfaces were scored, and one had a reasonable step in it. I used the les worn one, and it's corresponding rack.
Steering Unit:
After cleaning everything and determining the best components to re-use, the first part of reassembly was to determine the end-float on the pinion, having already placed the rack into the housing. The components are initially assembled less the o-ring and shims. The end float can then be measured using a DTI.
Sufficient shims need to be added to give minimal end float but free rotation of the pinion shaft.
The pinion thrust pad is assembled next, less any shims. The main nut is tightened sufficiently to eliminate all end float. Feeler gauges are then used to determine the gap between the underside on the nut and the housing. This is then the total thickness of shims required, plus 0.004" (0.01mm).
When correctly set up a force of 2Ib (0.91kg) is required to rotate the pinion shaft at a radius of 7.9" (20.3cm). Shims under the cap nut can be added or removed to adjust this force. Not having access to the specialist tools I bolted a piece of flat bar onto a dismantled universal steering column joint, and used a small bucket filled with enough water to give the required weight.
The above bucket was similarly used to verify the shim for the tie rod couplings.
Full, detailed descriptions of the procedure are shown in the Triumph Workshop Manual, as here.
Bump Steer
Ideally, as the front suspension moves through its entire travel, from full droop to full bump, the front wheels should continue to point in the same direction. In reality they usually move somewhat. This undesirable movement is known as bump steer.
To determine the bump steer associated with the standard setup, I clamped a straight edge to the vertical link, with a pencil strapped to the end. Crude, but it did the job.
With no spring fitted it was easy to move the suspension through its full travel, and describe an arc on a piece of white faced hardboard. The change was a total of 26mm a distance of 710 mm from the centreline of the vertical link. This equates to a change of ± 1.05 degrees [arctan (13/710)].
I need to move the steering rack forwards by around 15mm, to clear the engine and front pulley. This will effect the bump steer, probably adversely. At least now I know where it started!