Jim Grant's Tech Tips
'97 Ford F150, Tire Cupping
'97 Ford F150 extended cab with 97k miles is on its second set of tires.
The second set of tires began cupping about 20k miles ago. A four wheel
alignment was done with the new tires @ 60k miles. Tires are rotated faithfully
every 6000-8000 miles. Could my shocks (original) be the problem? How
do you know when your shocks are shot?
the tires are correctly balanced and the steering and suspension components
are tight then it is very possible that the shocks on your vehicle need
replacing. Shocks or struts for that matter do not have to be leaking
to be bad. They can even pass the bounce test and still be bad. The valving,
piston and cylinder inside a shock works hard. This hard work causes heat
and the heat causes the oil in the shock to break down. This results in
scarring of the cylinder and piston which causes a reduction in the absorbing
abilities of the shock/strut. The valving and piston can be damaged from
the vehicle's suspension bottoming out, like hitting a pot hole. The internal
damage can never be seen. But when the shock/strut is working the hardest
it can no longer perform. The result can be tire cupping problems. If
all else is right install new shocks on all 4 corners of your vehicle.
After 90+k your truck deserves it. I'll bet a coffee you'll feel the difference.