Dave,
My wisdom in this area is limited, but I'll tell you what I think I
know.
First of all, I, like you, have built a lot of bicycle wheels but
have been stymied by spoked wheels for cars. There are two huge
differences between the genera.
First, you can pull an out-of-round or out-of-true bicycle wheel
back to true and round with spoke tension (within limits, of course). This
is the fine (and enjoyable) art of bicycle wheel building (I've tweeked a
lot of nipples in my day). You cannot do this with a car wheel. If the
rim is bad you are SOL. Spoke tension cannot be used to straighten a bad
car rim.
Second, the first point doesn't matter anyway because the nipples
on a car wheel are invariably rusted onto the spokes and cannot be turned.
A good application of heat, WD40, and curse words will sometimes work, but
then you have to repaint, etc, etc..... You end up destroying half of the
nipples and creating more work than you can fix (don't ask me how I know
this. OK? Just trust me on this one).
"Trueing" a bicycle wheel involves using spoke tension to put the
rim where you want it to be (round, true, dish). "Trueing" a spoked car
wheel involves making sure that all of the spokes in a wheel that already
has a round and true rim have the same tension (usually determined by
sound--at least that's what the books say). In the latter case, spoke
tension is not used to move the rim--the rim is already true and round and
spoke tension is used merely to equally distribute the significant stresses
that the wheel experiences. As I understand it, you can replace spokes on
a wheel that has a good hub and a straight rim but if the hub and/or rim
are bad then forget it.
In short, bicycle wheels and spoked car wheels are two very
different animals--they do not follow the same rules.
So what are your options? 1. Buy a bunch of used spoked wheels
and drive on them until they collapse or the wobble drives you crazy
(remember, any "used" wheel is upwards of 40 years old and has probably
been driven hard on modern, "sticky" tires--see below). 2. Buy new wheels
from Dayton (wait for the TRF winter sale and buy one or two a year). 3.
Send your old wheels to Dayton for rebuilding. I have opted for the
latter. Dayton cuts out all of the old spokes, and rebuilds a new wheel
using your hub and rim (if they are reusable). The cost is essentially the
same as buying new Daytons (but, hey, if these cars were cheap, then
everybody would own one, right?).
As long as I'm on the subject, why were spoked wheels ever used?
The story, as I understand it (I'm waiting for Andy Mace to correct
me--remember the TR10 issue?) is.....
1950's sports cars had front drum brakes and lousy bias-ply tires.
These two features kept them slow in the turns because:
a) Fast cornering wasn't possible because the drum brakes heated
up so bad that you couldn't come into a corner fast anyway (major
down-shifting and brake pumping were needed). This forced slow cornering
and meant less stress on wheels, thus favoring spokes. b) The front
brake drums needed cooling and spoked wheels were better than disc wheels
in this regard (more air circulation); again favoring spokes. c) Cast,
one-piece, lathe-trued, magnesium alloy wheels (i.e. "mags") were not
available so the only other option was welded-up disc wheels which had a
well-earned reputation for coming apart under hard cornering (welds do not
particularly like repeated stress). d) The bias-ply tires of the day
limited the speed at which you could take a corner (even if your brakes
were nice and cool) thus lessening the stress on spoked wheels. Radial
tires (combined with advances in sticky rubber compounds) and spoked wheels
did not evolve in the same time era and do not co-exist very well. e)
Finally, race teams could afford to replace their spoked wheels every 500
miles. In 1997 we are trying to get 20- to 40-year-old wheels with maybe
100,000 rough miles on them to perform up to like-new spec. It ain't gonna
happen.
The bottom line is that 1950's tire and brake technologies greatly
limited cornering speeds thus favoring spokes as the wheel of choice. Now
we drag out a set of beat-up spokes, mount sticky radials on them, throw
our beloved Triumphs into a sharp corner, and then act surprised when the
rim collapses or the car shimmies like crazy at 45 mph.
Sadly, I have concluded that this is a problem only money can fix.
Cheers
Bob
Bob and Nancy Wise
946 East Pacific Street
Appleton, WI 54911
(920) 733-9003
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