When I used to run rallyes in my 1962 +4, we always had about a 12%
difference at the odometer check.
Smoke Signals
Robert W. Perry
rperry@stny.lrun.com
131 E High St
Painted Post, NY
14870-1305
-----Original Message-----
From: HOOGLY@aol.com <HOOGLY@aol.com>
To: morgans@autox.team.net <morgans@autox.team.net>
Date: Sunday, July 19, 1998 6:13 PM
Subject: Speedometer calibration
>My neighbour and I were exercising our Morgans on the highway last week at
>what seemed to me to be a legitimate speed when we came upon a gendarme
parked
>on the median. My friend slowed dramatically. Afterwards I asked why he
had
>slowed when we were doing only 65. "We were going close to 80" he replied.
>I had always thought my speedo was reasonably accurate. I also know that
65
>just seems like 80 in a Morgan. Also, knowing that British motorcars from
>the 60's are geared on the low side compared to modern American automobiles
I
>had never attempted to equate revs to mph.
>So, I went home and pulled out Fred Sisson's "Bedside Reader" and found
that
>on a 1965 +4, 3000 rpm = 60 mph. I measured the circumference of my wheel,
>multiplied by the 3.73 rear end ratio and divided into 5280 ft per mile and
Lo
>and behold the answer was 3000 rpm.
>I then took the car out and matched the speedo to the tach. Guess what? I
>found that at 40 the speedo read 35, at 60 = 52 and 60 = 70.
>If my car has a 3.73 rear end then my speedometer is about 14% slow.
>I then looked at the speedometer face. It reads to 120mph. I then dug out
my
>immense collection of photos of other people's Morgans and found that most
>(but not all) Morgans of that era have speedos that read to 140mph.
>If you look at Fred's book p148/149 you will see that he had a similiar
>experience so I can only conclude that a previous owner replaced the
original
>with a TR3 speedometer without having it recalibrated. It has taken me the
>nine months I have owned the car to notice this, perhaps because the speedo
>had been refinished to match the appearance of the other instruments.
>So, for me to solve this mystery and try to put it right, is there anyone
out
>there who would know:
>1. Did all 1965 Morgan +4's have a 3.73 rear axle or was there a lower
ratio?
>2. Did all 1965 Morgan +4's have 140mph speedometers because I have seen
>one other 120mph
>3. Is there a vendor out there who could put a 140mph face on a 120
>instrument. Calibration would then be unnecessary.
>4. Is there a vendor in the US (Mid West) who could recalibrate a Smiths
>instrument.
>Of course, I could do nothing. A speedometer on this car seems to be
>positioned for the benefit of the passenger....and having it read slow
maybe
>is not a bad idea.
>Fred solved his problem by installing an overdrive to correct the ratio but
>that solution is too elaborate for me.
>
>Anyway, any response would be wecome
>Thanks,
>John Rogers
>65 +4
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