Quote:
Originally posted by LarryIII
Cigarjohnny,
The driveshafts of AWD cars with different size tires (front to rear) must turn at different rpms not the same rpm.
The distance that circumference of the small tire must travel per unit time must equal the distance that the cirumference that the larger tire must travel in the same time.
The difference in rpms is the ratio of the diameters of the front & rear tires. The smaller tire must turn faster than the larger tire.
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Actually Larry, I said the drive shafts must turn at equal speeds, not the axles. The different ratios for those cars with different sized tires is made up in the front and rear differentials. That is how they allow the smaller fron tires to turn faster than the larger rear tires.
For example, the front diff, with a smaller tire, might be geared with 4.11 gears, while the rear diff, with larger diameter tires might be geared with 3.57 gears. This allows the drive shafts from the center diferential, or transfer case to turn at the same rpm, thereby eliminating wear on the clutch in the center differential.
It's when the drive shafts turn at different rpms, that you end up breaking things, so I stand by my original post.