George Haynes and I have been discussing TR4A suspensions, and since I
just went through a round of mods I thought I'd describe it for the
whole list ... George told me about work that Dave Brady (hi Dave, I
don't think we've met) did to his TR-250, complaining of rear axle
wiggle, as told to the Digest last year sometime:
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George,
I contemplated using nylon bushings but decided to be kind to my
frame and went for the heavy duty rubber bushings instead. TRF
sells a stock bushing and a hard rubber bushing, I'm now using the
hard rubber bushing and the rear axle locating has been reduced
considerably, although axle locating is still present. To further
enhance rear suspension control, I had shorter and stiffer springs
made for the car and am now using the tube shock conversion with
adjustable Konis. I think the problem is exacerbated by the jacking
effect of the rear suspension when cornering hard. Shorter springs
changed the rear roll center height and reduced the jacking effect.
I'm still working on the cars handling characteristics but I have had
good success with the above modifications along with a front roll bar.
The roll bar makes a huge difference in the way the car feels. Much
better even in straight line. My next task is stiffer and shorter
front springs and a rear roll bar. With Yokohama 008R tires on
Panasport 15x6 wheels, the car really corners.
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Here's my suspension saga. Given what Dave has done and my recent
history, I'm not surprised that he's getting rear end wiggle!
I rebuilt the suspension front and rear about three years ago to stock
specs. That was all well and good, but the car was never really great
at handling. I have (for various reasons) Dunlop SP4s in 165-15 on the
original steel wheels, so I don't have a lot of tire - and the SP4s are
built for longevity, not stick. So I got a lot of squeal on moderate to
hard cornering, though they never let go without warning.
The real problem was that the car was very disconcerting at speed, especially on
long downhill sweepers. It always felt like I'd turn, and something would
happen, and then half a second later the suspension would finally take a set.
Made me nervous. I diagnosed part of this as worn upper A arm bushings, and
decided that it was time to upgrade. I put Konis in front a long time
ago, set to full soft, and they helped a bit, but not enough.
The first thing I did was fit a stock TR6 front bar (I swapped the TR6 radiator
protection panel which was drilled for the bar mounts and the oil cooler, which
I also installed). This made a huge difference in the stability and
predictability of the car. I could get into nice controlled four wheel drifts
going around my favorite corners, but I could really feel the rear end bottom
and tramp when it got deflected, either because I stepped on it or hit a dip in
the road.
OK, I'd ordered a set of uprated springs from British Parts NW (the "red"
springs which are stock ride height and 30% stiffer) as well as a passle of
urethane bushings: lowers from BPNW, and the one piece uppers from Ken
Gillanders. I left the rears stock, because I didn't feel like
dismounting the trailing arms.
I did the easy job first: I swapped in the rear springs. Sure enough,
the rear was under better control, but the car was no longer neutral -
I was getting understeer, I couldn't easily drift any more, and I just
wasn't as comfortable driving and knowing what would happen. And mostly
it felt like the rear end
wasn't in good control. (I also drove the car around a bit on
oversized, roughly 225/60-15, old Goodyear Blue Streaks for a while,
both with and without the new springs - that was fun and it was cool to
have relatively grippy tires, but it didn't help the rear end problems).
I decided to solve that with uprated rear shocks; I had the original
leaky shocks that I'd taken off years ago rebuilt to "heavy duty" specs
by Apple Hydraulics. A month ago, I started installing everything
remaining: rear shocks, front springs and urethane bushings.
The difference is amazing. Some of it is certainly because the front is better
located by the new hard bushings, but I think the biggest difference is
that the wheel rates front and back are much more balanced. I like
these springs a lot - they transform the handling of the car from way
too soft to just about right, without lowering the ride height (I have
enough ground clearance problems, thank you) or making the ride as
harsh as my autocross GT6+. I only got the car
aligned yesterday (a saga in itself due to some old crash damage) so I haven't
had much chance to drive it hard, but I was able to get a nice balanced four
wheel drift on my favorite corner into work this morning (and yes, guys, the
tire squeal is pretty much gone).
I don't know what I'll do for rear bushings when I have to replace the stock
ones. I'm not sure that the high durometer ones will cause that much less frame
stress than the nylon ones, and the nylon ones have such lower maintenance...
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