Wednesday, December 31, 2008

Rear suspension

Several years ago I replaced my Herald's original swing axle with a Canley Classics swing spring. This was to eliminate the original suspension's tendency to sudden oversteer - a tendency that is often over-hyped, but a trap for the ham-fisted or unwary nonetheless. The new swing spring improved the handling, but as standard made the rear sit too high. I lowered it with a Jigsaw 1" block between the diff and spring, and have driven it that way ever since. The 1" lowering created its own problems, though. The car had about 4 degrees negative camber, putting a lot of strain on the halfshaft UJs, and the swing spring's central box sat so high it occasionally contacted the diff inspection plate behind the back seat. So this week I substituted a Canley Classics 3/4" lowering block to raise the ride height.

The first task was to shorten the four bolts holding the spring to the diff. The threads were extended up the shank with a thread die, and about 1/4" was removed from the ends.

The spring box now sits slightly lower, and no longer makes rubbing noises on the inspection hatch. The two plugs in the diff (Heralds originally used six bolts to retain the spring) are still in place and haven't moved over the last few years. The protective grease on the spring box seems to have worn off. If I'd been more motivated I would have taken it out, derusted and painted it. Oh well, next time.

The old Spax shockies were replaced with Konis. The Spax went on in the mid-nineties - I'd ordered Konis from Rimmers, but they sent some yellow ones instead. When I complained, they sent a second pair free! Postage from New Zealand to the UK made returning them too expensive, so they went on the car, and the spare pair were sold to a friend.

The final tweak was to remove the swing spring's second retaining loop, as it sits very close behind the brake cylinder (I've got Vitesse brakes). The flexible brake hose has to connect to a short length of steel brake line, a setup I've always viewed with concern as the small metal line has to be free to slide as the cylinder moves back and forth. This means it's poorly supported and can flex, creating a potential fatigue failure point. Removing half the outer spring loop means I can reattach the brake line to the wheel cylinder, eliminating a potentially catastrophic failure point. I didn't move the brake lines yesterday, as I want to get a one-man brake bleeder before tackling that particular job.

(I should point out that Canley Classics' kit includes Kunifer (copper nickel alloy) hoses which run aroud 270 degres of the backing plate, and are less prone to fatigue than steel. Kunifer's illegal in New Zealand and Australia, though).

The spring's second loop is designed to help retain the top of the suspension upright if the spring fails - not something I've heard of happening. I've left half the loop though, which should hold the upright if the inner spring leaf does fail.

Happy New Year to all Heralders and Triumphologists!


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