The more I think about it, the more I think this question is silly (in
that it is irresolvable within reasonable parameters). No one is arguing
that lever shocks produce a noticeably inferior ride or poor handling on
a street MGB. Neither has anyone produced evidence that the tube shock
conversions are noticeably inferior in either category. Some people even
think they are superior, but again, no quantitative evidence is
available. What can we deduce from that? That either setup is acceptable
for street use, and individual preferences may reasonably vary. If you
are determined to have the fastest track set-up, you'll have to do what
you always have to do -- see what the fast guys are running and copy them.
But as far as lever shocks vs. tube shocks in principle, I don't see how
there can be any question. Look at it this way: lever shock development
essentially ended in the early-to-mid '60s. The tube shocks that were
available at that time must have been competitive in terms of ride and
performance, since nearly all world automobile manufacturers switched
over, sooner or later. Since that time, tube shock technology has been
improving steadily for THIRTY-FIVE YEARS! If you were seeking ultimate
shock performance, you wouldn't go out of your way to find a set of
35-year-old Monroes or Konis, would you? Of course not. So I think it
would be ridiculous to argue that lever shocks (unchanged since 1962) are
superior AS SHOCK ABSORBERS to modern high performance tube shocks.
I will now proceed to back down from this statement, insofar as MGBs are
concerned. Because the conversion process from lever to tube shocks may
have its own disadvantages, and it could be argued that they overwhelm
any advantages of the tube shock technology. I am sure that these issues
have been on people's minds during this discussion, but I thought I would
try to lay them out.
One is increased unsprung weight -- since the front lever shock is left
in position as the upper arm, the entire weight of the tube shock and its
bracket is additional unsprung weight (I would guess 5-10 lbs/side). The
more expensive coil-over kits replace the arms, and probably do not
suffer this penalty. In the rear the weight is harder to calculate, but I
would guess it's a wash.
Another possibility is sub-optimal positioning and geometry. The lever
shocks are designed into the suspension, and their pivot points are
precisely and optimally located (they could hardly be otherwise or the
whole suspension would bind up). Many kits locate the front tube shock
off the rear of the front lower arm -- in the ones I have seen the
vertical axis is slightly canted both from side to side and from front to
back. The lateral angle is typical of tube shock systems and probably has
little effect on efficiency, especially as it is slight. The fore and aft
angle, although even smaller, seems to be an unintended consequence of
poor tolerances, and would seem to potentially cause some binding in the
rubber bushings. Whether this affects performance or just shortens the
life of the bushings, I don't know. Again, the coil-over kits wouldn't
have this problem. The rear tube shocks seem to pretty much duplicate the
attachment geometry of the lever shocks, with the only difference being
potentially more suspension travel with the tube shocks (unless the
rebound strap is the limiting factor).
A third possibility is that, assuming the lever shocks specified for the
MGB are "optimized" to the suspension characteristics, mass, resonant
frequencies, etc, of this application, and that since tube shocks were
never original equipment, then no particular brand or model of tube shock
would be completely, perfectly tailored to the MGB in all of these
factors. One would have to decide how much one was willing to believe the
first assumption, and how much difference one would expect to see from
the second one.
In summary, I don't see any overwhelming reason to reject the tube shock
conversion on these issues. It will be up to the individual to decide if
the cost, effort, and non-originality are worth whatever potential but
unquantified benefits may accrue from trying to take advantage of decades
of tube shock development.
Whew! sorry that was so long...
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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