Watt about sway bars?

[C M Smith <cmsmith@domain.elided>]

The Watt's linkage is primarily to locate the axle side to side, and a 
darned good job it does. A secondary but useful feature is a high roll 
center which reduces the need for "sway" bars ( a quaint American term, 
inaccurate because the bars reduce body roll but not "sway" only harder 
suspension bushings can deal with that, or stiffer leaf springs for really 
antiquated suspensions). Ideally, a street machine should have a low front 
roll center and a higher rear roll center...the GTV6/Milano is very good in 
that regard.

As an aside SAAB used  a variation of the Watt's linkeage for fore and aft 
location of their beam axle on the 99/900 and 9000 series cars. The 
trailing arm was complemented by an upper longitudinal rod leading from the 
rear of the body to the top of the axle connected by a floating link that 
allowed the axle to compress the spring without moving fore and aft. Odd 
since they used the Panhard Rod for lateral location which is generally 
accepted to be inferior to the Watt's linkeage for that purpose, the 
Panhard Rod induces a sideways "hop" on bumps under roll. The 9000 reduces 
this negative with a low center Panhard Rod which essentially is centered 
on the axle at rest position.

As for those who impliedly criticize the use of the front anti roll bar to 
also locate the front suspension you should remember the original McPherson 
strut design used precisely this lightweight and efficient solution. If the 
rubber bushings on the roll bar bother you remember that the tension rods 
(Datsun 510), or more rarely compression struts (Triumph 2000, GT6 etc) 
that are otherwise required also must use rubber bushings on a street car. 
I find it difficult to accept that one rubber bushing is significantly 
superior to another and the elegance of one part doing two jobs is hard to 
beat.  Sure the roll bar is springy but the ends don't have to be lined up 
in their springy direction.



Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner

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