tigers
[Top] [All Lists]

Re: Speedo calibration

To: laifman@flash.net (Steve Laifman)
Subject: Re: Speedo calibration
From: Roland Dudley <cobra@cdc.hp.com>
Date: Thu, 22 Jan 98 10:32:57 PST
> Roland,
> 
> The Tiger Speedometer is, maybe, different from a Cobra. Firstly, even
> though it is an English speedometer, the cable attach is American style,
> not normal British, so the Ford cable can be mated. The cable is
> American size because of the speedo drive gear.
> 
> The internal speedo gears are all British, don't you know, and not
> plentiful, or cheap. American speedometers have a distinct commonality.
> They are all set to be 60 mph at 1,000 revolutions. The transmission
> teeth are selected to accommodate that standard for the rear end and
> tires of the car design. Any modifications are usually handled by a
> change in the cable end drive gear.
> 
> Not the British. As pointed out, the speedometers can be labeled "980",
> "1020", etc. The Alpine O.D. speedometers are particularly odd. All
> american speedometers are "1000" by standards.
> Bless the Empire.
> 
> Don't know what's inside the Cobra, but if you've been able to put
> American inner pieces into the works, you are fortunate. The rest of us
> are stuck with the high price solution. Additionally, unless you want
> "1000", the American gears will give the wrong calibration, even if they
> did fit.
> 
> Steve

Steve,

I should have been clearer about what gear I was referring to.  I meant
the plastic gear that is driven by the gear on the output shaft of the
transmission.  They are available with a number of different tooth
counts.  I don't recall the specifics, but I may have some info on this
stashed away somewhere.  They also come with left- and right-facing
gears.  It's best to take your old gear along or ask someone who knows
for sure if you plan to buy one with a different tooth count.  It may be
necessary to experiment to get the correct gear count, but, as I say,
they're not that expensive.  I got one left- and one right- facing
gear because I didn't know which was correct for my car and I didn't
have the old one as a reference.

As it turns out my speedo reads a bit high because I have lower profile
tires than what originally came on the car, but I can live with this
since the ratio between RPMs and MPH is very close to 1000RPM/20MPH in
4th so its pretty easy to figure out how far off the speedo is.

FYI, early Cobras (up to about CSX2200) came with mostly Smiths gauges,
including the speedo, as did all big-block Cobras.  Most 289 Cobras had
all Stewart Warner gauges, except for the clock.  My car has Stewart
Warner gauges.  Shelby didn't think much of Smith gauges, but had pretty
much lost interest in the matter by the time the 427 Cobra was in
production.

Roland

<Prev in Thread] Current Thread [Next in Thread>