In article <3.0.1.32.20011215081618.013a32f0@mailhub.exis.net>, John T.
Blair <jblair@exis.net> writes
>At 10:59 AM 12/15/01 +0000, Michael Hargreave Mawson wrote:
>
>>
>>Having recently replaced the gearbox and speedo cable in my non O/D
>>1500, I have noticed that the readings I am getting on the speedo are
>>lower for a given engine speed than hitherto.....
>
>>Now, it would be rather handy to know whether I am doing 46 mph, 51 mph
>>or 54 mph at 3000 rpm (or rather, to know by what percentage my speedo
>>is reading low at a given speed). Does anyone have a formula to
>>convert rpm into road speed for a UK-spec 1500?
>
>Michael,
>
>Measure the height of the tire - the diameter from the ground to the top.
>The circumferance is: C= pi * D, where pi = 3.14....
I'm using the standard 155R13s, so I hope that my answer would be the
same as that for anyone with standard tyres.
>
>Do you know the final gear ratio?
1.0:1, according to the handbook.
>
>Distance = RPM * final ration * C.
I presume that "C" in this instance doesn't stand for the speed of
light, but the circumference of the tyres? :-)
>
>But the easiest way is to find a spot on a road where it is marked off
>in 1/4 mi., 1/2 mi etc. Some fixed distance. If you don't have anything
>like that, measure off a distance on your own, with a ruler.
<boggle>
> Now travel
>that distance at a fixed speed in 4th gear and measure the time it takes
>to cover that distance. The longer the distance the more accurate your
>results will be. V = D/ T where V = velosity (mph), D = distance in
>miles, and T = time in hours.
Yes, this would work, but I was hoping that someone might have a
formula, which not only took into account the diameter of the tyres, but
also frictional losses, air resistance and so on. I'm sure that there
must be such data already calculated, probably by Triumph.
>
>>A corollary to the above question is, "Is there anything I can do to
>>calibrate my speedo?"
>
>In many towns there are shops that will calibrate your speedo for you,
>or at least give you true readings for specific guage readings. Look in
>your local phone book.
There doesn't seem to be anyone in the Yellow Pages who offers this
service - and, to be honest, I'd rather do it myself if I could.
ATB
--
Mike
Michael Hargreave Mawson, author of "Eyewitness in the Crimea"
http://www.greenhillbooks.com/booksheets/eyewitness_in_the_crimea.html
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