[Fot] sway bars

[Malaboge at aol.com]

In a message dated 11/3/08 5:53:07 PM Pacific Standard Time,
vintage.racer at comcast.net writes:

I am currently racing my 1962 TR4 with a > ADDCO front sway bar, the car
has been lowered approx. 2 (removed front spring spacer, de-arched rear
leaf springs), runs on Hoosier Speedster tires (185/65R15) with zero
negative camber and find the car leans over at a pretty good angle while
cornering.  I am considering trying a larger diameter front sway bar to help
minimize the lean.  Any thoughts as to a suitable diameter?  Thanks.

Gary-

As I recall you have a sway bar with a fairly long lever arm...at least 8" or
so. The lever arm length effects the roll rate as well as the diameter, so
comparing diameters will not always tell the complete story. The way the bar
is
mounted and fastened to the suspension also has a big influence on the rate.
A solid mount on a .8" bar is approximately the same as a rubber mount on a 1"
bar.  Solid mounts (Heim joints or the like) at the suspension end mounts of
the bar realize a similar rate effect.  The width of a bar has a smaller
effect on the rate, but be aware that the narrower bar of similar sizes will
have a
higher rate.  (Also a narrow bar with short lever arms will weigh less).
Finally the placement of the attachment of the bar to the suspension arm has a
big effect, not on the bar itself, but rather what forces are received to the
chassis of the vehicle.  The closer you can connect the bar to the trunion,
the
larger the lever arm through which the bar has an effect and restricts
movement.

Without going into the spring rates which obviously have no effect on sway
bar rates, but complement the size of the sway bar required, what bar rates
are
the best?
Start with the narrowest bar that you can fit.
Use all solid type mounts.
Attach it as close to the wheel as possible.
Use the shortest lever arm as possible.

Remember that the stiffness of a bar (all else remaining the same) increases
with the diameter to the fourth power.  That is a 1" bar is 16 times as stiff
as a .5" bar.  The lever arm effect is less but more direct, a 6" lever is
twice as stiff as a 12" lever arm.

So how does that relate to your TR4?

Well the bar realistically cannot be hung under the frame rails as it would
be too low and be removed at the first bump.  Mounting the bar on the top of
the frame rails could be done, but there are just too many parts in the way.
Fortunately the front of your frame is just about right.  A bar mounted at the
front will have lever arms of approximately 5 "to 6".  Make an aluminum plate
similar to the factory radiator shield between the two frame rails, but
position it forward just enough to allow solid mounts to be bolted to it. (The
factory steel piece is too close to the radiator).  Curve the lever arms (for
tire
clearance when turning) so that they roughly follow the lower a-arm and attach
them at the outermost bolt that mounts the spring pan to the a-arm.  (A
sliding mount here will make a nice adjustable bar as well).  Use 6150 steel
(or
4130) and heat treat it when in final form.  Its been a while since I made any
bars, but I recall that you want to have about a 62 on the C scale Rockwell
hardness on them.

You state that the car may have stock springs in it.  If so, these really are
too light, but if you continue with them I would suggest about a 15/16" to 1"
bar.  If you have the old left hand wound factory springs which were about
310 lbs/inch rate, probably about 15/16".  Stiffer springs up to about 500
lbs/inch I would suggest about 7/8" bar.  There are PERSONAL OPINIONS here and
in
no way will be correct for many setups, but seem to be in the ballpark for
me!

You didn't mention a rear bar and so I will not open that "bag-o-worms".

Never one to "Sway" anyone's beliefsb&
Nick in Nor Cal

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