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Re: rear end ratios to speedo

Posted: Wed Dec 28, 2011 4:38 pm
by mattcfish
It's been a long time since Jr. High Math.

Re: rear end ratios to speedo

Posted: Wed Dec 28, 2011 5:19 pm
by mattcfish
After being corrected on my ratio converting this is what you end up with.

32/10 = 3.20 ratio use 1.186 ratio speedo
33/11 = 3.00 ratio use 1.112 ratio speedo

A 33/11 with a 1.186 ratio speedo will be off by 6.65%
Every 100 miles you need to add 6.65 miles to your odometer reading.
At 60mph your actual speed is 63.99mph
at 70mph your actual speed is 74.66mph

I was pretty darn close. :)

Re: rear end ratios to speedo

Posted: Wed Dec 28, 2011 8:20 pm
by vanzen
I have used speeding tickets to quantify the degree of inaccuracy
of the always optimistic BMW speedometer.
Effective experimental procedure requires nothing more than a glance at the speedo
before the hand lets loose of the throttle
after seeing the blue flashing lights in the mirror.

'85 ? But officer, I distinctly saw an indicated 92 mph ...'

Re: rear end ratios to speedo

Posted: Wed Dec 28, 2011 8:33 pm
by robert
I usually say that at that speed I was too busy to look at the speedometer. I got out of at least 2 tickets with that explanation.

Re: rear end ratios to speedo

Posted: Thu Dec 29, 2011 1:27 pm
by Duane Ausherman
The ticket that I got for 125 mph was posted on my showroom wall. The officer told me that he ran out of power at 125 mph and I was still pulling away from him, so he could only use 125 mph.

I am not sure, as I too was not looking at the speedo. It was on a very fast R90S in 1974. After he discovered my dealer plate, he cooled down a lot and told me that he had been in my showroom several times. He was a rider too.

125 mph

Posted: Thu Dec 29, 2011 2:37 pm
by vanzen
Sunday afternoon,
heading out of Madison Wisconsin on the K1.
Triple digits, I was in a hurry.

Passed an unmarked cop car in the right lane.
The cop dropped in behind me to pace my speed.
He never turned on the radar, I would have known ...

4 or 5 miles down the road,
3 squad cars, lights a-flashing
blocked my path and flagged me down.

I never looked at the speedometer –
Wouldn't have mattered, it didn't work, anyway.

The cops laughed at my "cars SUCK" T-shirt
as I removed my helmet and coat

and then again when I asked,
'Why don't Wisconsin drivers move right ?'

I was told, 'Those drivers are from Illinois.'
as the speeding ticket was passed to my hand ...