HEY BOB, WHAT ARE YOU THINK'N, IT A NO BRAINER?? THE BIGGER THE TIRE THE
BIGGER THE DIAMETER, THUS THE MORE TIMES THE DRIVE SHAFT WILL TURN FOR EVERY
REVOLUTION OF THE TIRE.
From: Bob Tom [mailto:firstname.lastname@example.org]
Sent: Thursday, August 12, 1999 7:29 AM
Subject: Re: DML: RE: Ring Gear changes: 3.55 vs. 3.90
At 09:38 AM 8/12/99 -0500, you wrote:
>I've done the tire/rotation check more times than I care to count (from
>past shops and over the years) so I know what i'm doing. You don't have to
>turn it 10 times...three or four is more than sufficient. But what the
>heck, it all averages out the same.
Unless I am missing something in the interpretation, I will have to
respectfully disagree that jacking up the rear end, rotating the tire
(one which is a different diameter than stock) one complete revolution will
result in a change in the no. of revolutions of the driveshaft.
Visualize, if you will, for a minute. Gear ratio is 4.10:1 (for example
Put a straight line mark on outer edge of the stock tires sidewall. Place
ruler (whatever) on the marker and through the center of the axle shaft,
extend this marker
to the outer edge of the rim and draw another marker.
Rotate the tire one complete revolution. The driveshaft will have turned
the 4.10 revolutions. Note also that marker on the rim will have also have
one complete revolution, no more and no less. Therefore, a bare rim (i.e.
tire diameter of zero) with one complete turn will also give the same 4.10
revolutions of the driveshaft.
Now, imagine a larger (or smaller) diameter tire and put a marker on its
in the same way as above. How many times will the driveshaft rotate? 4.10
The only way to see a difference is to have the truck on the ground, put a
on the ground where the marker on the stock tire is, push the truck so that
rotates one complete rotation, put another marker on the ground where the
marker now is and measure. Now, repeat but with the tire swap and count
of driveshaft rotations. This is the 'effective gear ratio'.
Apologies to all concerned if this can be proven incorrect. Again, sorry
length, but when the industry refers to higher gears and, yet numberically,
is lower, it is against normal comprehension and is complex.
'97 CC Sport, 5.2L, 3.55, auto., 4x2, flame red
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