[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: best tyres up front or in the rear? (was '89 200q ?s)

Sarge sez:

>>>>>It is my understanding that you should *always* run the tires with the
greatest tread depth on the rear. If you put the worn down ones on the rear
(where there's less weight) the car will hydroplane on the rears much more
easily. This becomes even worse on braking, which of course transfers more
wieght to the front, allowing the rears to hydroplane much sooner than the
fronts. Hence that squirrely feeling that becomes even more pronounced in the

Well, at the tender age of 18 I've learned an easy lesson not to to put my
best tyres on the rear (although I drove RWD cars in my rather snowy neck of
the woods at that time). Once I saw how a neighbour slooowly drifted on
mirror-sleek ice under a standing truck @5km/h with all his weight on the
brakes and the eyes sized like silver half dollars. He, naturally, had better
tyres in the back for better pulling snow traction and they were_rolling,
unaffected by brakes(!) while the bold front tyres were the only ones that
did the braking, but they were helplessly sliding in a lock-up. That incident
cost him a hood and a windshield.

Can you say *proportioning valve*? On an empty car (any empty car for that
matter) this valve sends a far greater braking pressure to the front wheels
than to the rears in order to prevent a car's spin-off. Does anyone enjoy
doing "giro" U-turns in snow by pulling up the e-brake while spinning the
steering wheel and depressing the clutch? Same principle: you lock up the
rear wheels while allowing the fronts to keep on rolling.

Even the standard rear brake service procedure (Bentley) calls for a 6mm
drill bit to be inserted under the spring of the proportioning valve in order
to check the rear brake operation. This simple measure fools the valve into
thinking that the car is loaded and, therefore, is sitting lower.

Fellows, pleeeeze, do yourself a favor: always put your best tyres in the
front! If you don't believe me just watch any empty, non-ABS car braking on
ice and you'll see how the front tyres lock up while the rears keep on
rolling, not participating in the braking chores.

Igor Kessel
'89 200TQ