IRS (hardly) defined (bare wisp of Alfa content)

["John Hertzman" <johnhertzman@domain.elided>]

Michael Smith asks "if suspending the diff is the distinction whut about fwd
cars with beam axles? Are they irs? They are technically indistinguishable
from a De Dion setup.

"And finally, what about those nifty,cheap and simple twist beam axles found
on such fwd cars as VW and Opel, as well as the new Saturn ion? Are they irs
or not?"

I have regularly (yawn) drawn parallels between the De Dion and the ubiquitous
chain-drives of virtually all cars 1885-1905 (and common for another decade)
which had the transmission, differential, and inboard brake mounted to the
frame, with the rear axle and springs taking vertical loads and cornering
loads, but no driving or braking loads. Michael now gives me the opportunity
(nay, forces upon me the obligation) to mention that with very few exceptions
(such as Bugatti, and Jano's Alfas, but not Merosi's, and the front De Dion
cars such as Cord, Ruxton, Miller et al) most cars before the forties and many
before the fifties had simple I-beam front axles with little torsional
rigidity. The rear axles of the chain-drive era were also I-beams, with no
exceptions that I can think of. If the "simple twist beam axles" or
torsion-stabilizer linked suspensions qualify as independent suspensions, then
almost all cars have always had independent suspension on all four wheels, and
the term loses almost all meaning.

I hope not -

John H.
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