On Mon, 8 Apr 2002, Walt Philipson wrote:
> Kevin,
Hi,
I have to chime in on this one...
> I just replaced my springs with the uprated springs from TRF. If anything,
> the car sits slightly lower, but the squat is gone.
Good. Great!
> The ride is firm, but
> not harsh.
> I think the shocks probably contribute to harshness more than the
> springs.
Well, I have to respectfully disagree with this. The springs control how
the weight is transfered around, the shocks _dampen_ the oscillations. If
the shocks cause the ride to be more harsh, they are entirely the wrong
shocks to use.
Now, by way of example, if you use stock springs in the rear, they are
maybe 350 pounds/inch. Something like that. If you put "uprated springs",
say 20% uprated - the rate goes up to 410 or so. Still not too bad. If you
_double_ the spring rate, the car will ride like a buckboard.
Why? Because the rear corner weights are probably in the 450 pound range.
If you have a spring that's rated at 600 pounds and you transfer only 450
pounds to the spring - you get something like 3/4 inch of spring
deflection. More or less. This is very little suspension movement.
The key here is that once the spring compresses 3/4 of an inch, it has to
do something with the energy. It can either rebound or it can convert the
compression into heat. As you may guess, the spring will rebound. How
much? well, it has to return to its static height but the "unspring
weight" of the wheel, tire, brake assembly etc. has a certain mass - and
the resultant inertia of this mass will make the spring rebound past the
static height until the momentum is lost until it swings the other way.
Without a shock in this scenario, the suspension will continue oscillating
until all the engery is dissapated.
So, you add a shock absorber, or as the British more appropriately refer
to the part - a spring dampener. The dampening requirements change as a
function of the spring rate, so if you uprate your springs, you should
(out of necessity) uprate your shocks. If you uprate your shocks without
changing your spring rates, you've actually accomplished nothing in terms
of the efficiency of the suspension system.
> My next step is the tube shock conversion from TRF. I'll let you
> know how that goes.
Good luck.
I will not try to dissuade you from your choice. However, I will say that
a tube shock conversion only gets you two things. It gets you a higher
unspring wheel rate (undesirable in and of itself) and it gets you the
ability to utilise different shocks. The latter is probably a good thing
because it gives you some lattitude to select shock more appropriate to
your usage.
But frankly, the lever type shocks are pretty darn good for a lot of
reasons, even if they aren't as robust as new technology shocks. But the
bottom line in that regard is that for a street driven TR6, there's not
much advantage in being able to tune the shocks to changing conditions -
at least not any where near as much advantage as it is to a racer.
Simply put - I think the shock conversion thing is overkill for a street
car. And for racers, I'd lean more towards a coil-over setup because this
allows you tune change the shocks and the springs todial the system in.
But coil overs for a street driven TR6 is _way_ overkill.
> Walt
> '74 TR6
regards,
rml
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