After reading many posts complaining about front tires skidding rather
than turning, I found I should throw in my 2 cents.
When I rode my Sears garden tractor (those have lower-profile tires)
for the first time, it felt like go-karting on an abandoned log road.
It turns out that there was 17psi in all 4 tires, while the markings
specified 10 and 12 psi. The tires were sitting on the pavement
perfectly round, and the contact patch must have been about 3" by 3".
On relatively hard surfaces like mature lawn, the grip is directly
related to the contact patch. After I dropped the pressure to 8 psi (I
like a comfy ride but not a flat beer) the contact patch looked like
it more than doubled. Although I did not have grip problems, that
would certainly have helped.
In another post I described the excessive toe-in my front wheels
showed when I got the tractor. We're talking 3.2 degrees. You need to
hit an SUV with your car to get that kind of toe-in on it. Although
there are opinions that toe-in helps steering response in turns, I
doubt it is intentional because of the cost in straight line
stability. If toe-in really helped, the technique would be used in car
racing (although they do use skewed camber and caster adjustments).
The wheel spindles geometry already takes care of turning the inside
wheel by a greater angle than the outside wheel, so each gets its own
turning radius for maximum grip. These angles are carefully calculated
based on parallel position at 0 degrees and are a function of the
track and wheelbase. Any toe-in or out throws off the two turning
circles for less optimal grip.
On 9/27/2007 9:38 AM, firstname.lastname@example.org wrote:
Toe in will tend to keep a vehicle going in a straight line, helping
high speed stability. Excessive toe in will make a vehicle (lawn
tractor in this case) hard to turn, with the front wheels trying their
best to stay centered with respect to the rear. I imagine that 0 degree
toe in would help turning at the expense of a sight tendency to wander
whilst going straight.
Before he passed away, my uncle owned an automotive garage. My dad and my
uncle had a conversation about front end alignment. Evidently, whether the
driver is in the car can play into that. How much is this reflects on a
riding mower's toe-in, I'm guessing much more. So, put a few of bags of
sand on the driver's seat before checking toe. Put that in your pipe and
smoke it. Rest of the clowns too.
You're absolutely right Dave! On a vehicle with independent suspension
like most cars and trucks, the toe is affected by the vertical
position of the wheel by virtue of the geometry of the suspension.
I've always been sceptic about the method of aligning an empty car.
When the heck is a car empty while it moves??? I'm having no more of
that. My crown vic had its first alignment at 70k and showed a slight
more wear toward the inside. After the "aligner" told me he did not
need to touch my toe, I told him to please pardon me for asking him
for removing 0.1 deg to the toe. He asked why, then told him that you
can't tell people to get their car aligned so their tires last longer,
and at the same time completely ignore wear on the tires when the car
is aligned "right"! He reluctantly removed the .1 deg, and now my
tires wear evenly. Your Uncle knew that.
A garden tractor is has no suspension Dave, hence toe is unaffected by
This clown rests its case.
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