I have a '82 300D Turbo Diesel. The outside edges of the left and right
front tires are wearing out much faster then the inside edges. The tires'
centre treads wear eveningly. What causes these? Thanks.
Fast cornering will skuff the outside tread away - do you let a 16 year
old drive it?
Each front wheel should be almost perpendicular to the roadway -
something like 00 or + 1/6 of 1 degree. That's called the "camber angle"
and is adjustable. You can check that by parking on a level surface -
check that first and drive the car onto shims that will make it so - and
hold a bubble level against the alloy wheel, not the tire. Vertical
bubble should be approximately level.
The other thing that you can check (and adjust) is the wheels' "toe-in".
The front wheels should be virtually parallel to each other except for a
1/8 inch "toe-in" whereby the front edge of the alloy wheel is closer to
the car's center than the rear edge of the same wheel. Drive the car to
a halt with the steering wheel absolutely centered, use the parking
brake to stop. Don't touch the steering wheel as you exit. I hold a
bubble level against each alloy wheel - as an accurate 2" shim - and
sight down the "shim" to the rear wheel - the visual "target" there is
about 2 1/2" outside the rear wheel.
The steering wheel is centered, so should each front wheel be; this
check will tell you if it is. If not you can adjust the toe-in by
loosening the tie rod clamps on the offending side and turning the
adjusting sleeve to reposition its wheel IN or OUT. Note the position of
the clamps before and try to achieve same afterward.
The last check is correct tire inflation, under inflated tires wear on
both outer edges.
You simply have too much toe-in. Believe it or not you can probably correct
this yourself if you have a little bit of mechanical knowledge. If not skip
the rest of this reply and take your car to an alignment shop. Incidentally,
you will either have to replace the front tires or switch them with your
rear tires before most shops will even bother with a toe-in alignment with
tires that have been excessively scrubbed.
Now, on to the "easy" way to correct toe-in/toe-out.
Drive your car onto a flat, smooth surface, probably your garage.....if you
have one. Take two long, straight sticks like a 1 x 2 or 2 x 2 at least 8
feet long. Place the ends of each on stands or supports of some sort which
are approximately the same height as the center of your front tires. Place
the rear portion of the first stick against the outside of the tire so that
it rests against both the front and rear outside edge of the tire itself.
The remaining portion of the stick is forward of the car with about 5 feet
in front of your front bumper. Measure the distance between the points where
the stick actually touches the sides of your tire. Take this measurement to
the forward end of the stick and make two marks corresponding with this
dimension. For example, if you measured 26 inches between the two points
where the stick makes contact with the tire, make two marks toward the far
forward end of the stick, also 26 inches apart, front to rear. Do the same
on the other side of the car.
You then measure the distance across the width of your car between the
forward marks on the sticks. Mark it down, and do the same on the rear two
marks. The difference between these two dimensions is your approximate
toe-in (or toe-out should that be the case).
Your objective is to get the two dimensions between the sticks the same or
with the front measurement no more than 1/16th inch less than the rear. This
will give you a straight ahead alignment or a very slight toe-in. I prefer a
slight toe in as this tends to keep the front end from wandering while
trying to drive straight down the road.
Now to the harder part. Locate the "adjusting sleeves" on your tie-rods, one
on the right and one on the left, each toward the rear of the tires. These
are about 7-inches long with a tightening bolt on each end. If your steering
wheel points directly ahead when driving straight you will need to turn
these sleeves equal turns in order to maintain the same steering wheel
alignment when you're finished.
Turning these sleeves one direction or the other will either get you more
toe-in, or less. Experiment until you find out which direction decreases
toe-in (forcing the two sticks further apart at the forward end). IMPORTANT:
Keep track of just how much you turn each of these sleeves. If you're trying
to find out which direction decreases toe-in make sure you keep track of how
many turns it took you on the first side to find this out, and then return
it to its original position before adjusting further.
Once you've determined which direction to turn the sleeves in order to
achieve correction, turn each sleeve one full turn to correct approximately
each 1/8-inch of excess toe in. Once you've made your adjustments tighten
the sleeve bolts and drive the car at least 50 feet or so. This can be
simply backing up into your drive and then back into your garage. Check the
toe-in and make any other adjustments necessary. Repeat this procedure until
your satisfied the toe-in is either neutral (straight ahead, parallel) or
with slight toe-in.
Incidentally, now that you have the preceeding mastered you can correct
steering wheel alignment if it doesn't align properly. Do this by simply
turning the adjusting sleeves in opposite directions. This is a trial and
error method but works. Turn the driver's side sleeve in a top-forward
direction while turning the passenger side in a top-rear direction an equal
number of turns (or partial turns). Drive your car in a straight line. If
the wheel has gone further out of alignment you're going in the wrong
direction. Do this until you have the wheel where you want it. This is
important since many power steering units want to return to a "neutral"
position and can force the driver to put constant effort in one direction or
the other to keep the vehicle in a straight line. When you release the wheel
while driving straight your car should continue going straight. If not this
could be the problem. However, be aware there may be other reasons you
vehicle doesn't continue to track straight when the wheel is released. If
you need a diagram of this let me know and I'll try and get one to you.
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