acg@hermes.dlogics.com asks:
>Any typos above are the responsibility of the Sun-Times! Maybe someone
>can enlighten me about what the "-IRS" suffix means. Nice to see an ad
I've always assumed that "IRS" stood for independant rear suspension.
Have I been laboring under a false impression?
No, the IRS designation does mean that the TR4A has independent rear
suspension. Most TR4As did; I know that TR4s were solid-axle but I
seem to recall that a very very few As also came with leaves.
Not a very few, in fact.
As with the "TR3B" before it, the solid axle leaf-spring TR4A was a
response to the USA Triumph importers and their market predictions and
reaction to a new model (and cost of same). IRS was first mentioned for
a TR project in 1955, prototype built in 1957, was a serious proposal
for the TR4, but was abandoned in 1960, with the 4 built with a
conventional layout (and the axle passed over the frame, severely
limiting suspension movement.
When the 4 came out, with its new light and precise rack-and-pinion
steering, the rest of the suspension problems started showing up --
most notably bump steer at the rear. So there was talk again of
producing an IRS forthe TR. This couldn't be done as an easy conversion
to the existing frame. Thus the TR4A project was born.
The problem was that the Americans were willing to buy the car (that is, the
importers were going to be able to sell it) with a solid axle -- no matter how
much pressure was applied, the importers insisted that they could still sell TRs
with live axles at the right price, that ultimate roadholding was not yet
critical to sales over here, and that i.r.s. was bound to be more costly.
So ... the new chassis was designed to be built with both layouts. The live-axle
cars have long half-elliptic leaf springs and no semi-trailing arms. The
4A ended up weighing about 200 lb more than the 4, and the irs unit
weighed about 50 more than the solid axle version. There was some engine
tweaking and a new set of manifolds to get a little more power, but
the end of the four cylinder engine was at hand. (Road racers didn't
seem to think terribly much of the irs, either -- many teams thought
that the solid axle built a better car. But I don't know of any that
did a real side-by-side test.)
Some 28,000 TR-4As were built. I can't find the figure now, but I seem
to recall that about a quarter of those were solid axle units for the
States. (I can find the figure that says only about 3000 4As stayed in the
UK, the rest for export...)
(Gee, mjb, maybe The White Car was a more rare beast than your 250...)
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