> From: Jim Altman [mailto:jaltman@altlaw.com]
> Sent: Wednesday, September 29, 1999 5:28 AM
>
> According to Bentley's data 3000 RPM should be 75.3 MPH
> on an A type and 78.3 MPH on a J type. I presume many of
> us have close, but no cigar, tire sizes that will induce some
> variation. Roger Elliot's data is very similar. He said 25.3 for
> the A type whereas Bently sez 25.1 MPH per 1k RPM.
Don't know about A-type ODs but my J-type with stock Michelin Redlines turns
2500 @ 70mph <http://www.gumbi.com/peterz/tmp/70mph.jpg>.
Another interesting point about Laycock de Normanville ODs...
If you look underneath the car at the O/D unit, you will see an ID plate
with a bunch of text on it (sort of like the commission plate on the body).
Part of this plate text is a number. For example mine (J-type) is 25/115876
002757.
Apparently the number at the start of the sequence (25 in my case)
represents the percentage by which the engine speed is reduced by the O/D.
So for mine, when the O/D is engaged the engine RPM decrease by 25% from the
direct drive RPM (in the same gear and at the same speed of course).
The last number sequence (002757 for mine) is the unit serial number. I
don't know what the middle number (115876) represents.
I think A-types on Triumphs used a 22% reduction. Other cars with ODs
(Volvos, MGs, Healeys, etc) might have used different ratios.
--- Peter Zaborski CF58310UO ---
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