Opinions on Toe/Tire pull etcetera.

[theKbStockpiler]

I would like to include actual experience along with theory with this subject.

The individuals that write tech books state that toe will not create a pull but it seems obvious to me that which ever side of the car is loaded more in the front is going to direct the car in the direction that ,that particular tire is pointing. A tire with toe is pointing in two directions. Camber thrust is a proven aspect with pull but I can't see how caster in a straight line will cause pull at all. If two motorcycles with a different rake were bolted together and in motion down a road there is no force that would move this contraption off of a straight line.
Am I missing something?

[Ol'fogasaurus]

Do a search on the subject of toe-in and toe-out then look into Ackerman Geometry.

Here is a URL for general research on Ackerman: https://www.bing.com/search?q=ackerman+ ... =QBRE&sp=2

I hope this helps.

Lee

[saltracer]

if the caster angles of the front wheels differ side to side you will absolutely have a pull if the split is too much or too little. Most vehicles actually have more caster on the right hand side than the left by about half a degree to take the crown of the road into account. If the caster is the same a car will "fall" off the road.

Toe in is fairly stable, you can have far to much toe in and the car will travel down the road straight as an arrow, you will however destroy tires in rapid order. Too much toe out however will cause the car to wander and dart, especially on a loose surface. The tires are fighting to pull the car one side to the other and if one hits a patch of dirt or ice the other side will pull the car to that side.

[theKbStockpiler]

This guide is the most comprehensive that I could find and it still does not state how the forward motion of a car is traduced to a motion to the left or the right by a difference of caster.http://www.agcoauto.com/content/news/p2_articleid/176

It mentions " as the wheel is turned" but this would not happen in a straight line. If a car veers after the wheel is turned I would deduct it was because of the wheel being turned.

[wreck]

A long time ago I used to do a lot of wheel alignments , In Australia we drive on the correct side of the road,as the old romans intended . most cars were set up with 1/2 degree difference with the higher setting on the curb side ( as Saltracer stated ) to counter the angle of the road , I also off set the camber 1/4 degree as well for better tyre wear.

Mercedes run a lot of caster ,around 9 degrees , I was off setting them by up to 1/2 degree camber and 2 degrees caster to get them to drive straight .

[theKbStockpiler]

Thanks for the responses!

Does anyone know if the weight distribution from front to rear makes a vehicle pull more or pull less? I'll have to look as some rear engined alignment specs.

I wonder if the weight of the vehicle is making the tread bend over and making the heavy end of a car 'shuffle' down the crown.

[Ol'fogasaurus]

Thanks for the responses!

Does anyone know if the weight distribution from front to rear makes a vehicle pull more or pull less? I'll have to look as some rear engined alignment specs.

I wonder if the weight of the vehicle is making the tread bend over and making the heavy end of a car 'shuffle' down the crown.

Something to think about: if you take a tire off the car the air pressure in it kind of makes the tread rounded add to that, when mounted on a car with little weight on them the sidewalls don't have to work much. The sidewall debate was one of the big discussions when bias ply tires were being replaced by radials, either fabric radials or steel radials and their differences were a big discussion too. If you do a search there should be some video of the way the sidewalls work. There is a couple of discussions about sidewalls and makeup on the web.

On a rail or a buggy even there is not much weight up front then there is most of the weight in the rear and with tire pressures down pretty low (5#s in my rear tires, 25#s in my "steering" style of front tires both for the sand) the sidewalls can move around a bit more than normal.

Lee

[theKbStockpiler]

On new years eve I don't have much better to do than make a post on this thread.Lol. If you're interested in this subject that fact works out for you. Lol. I have done a extensive search on why a car pulls on a crowned road and how caster effects this. Most sources of info state that having cross caster will not alter pull from a flat road to a crowned road but most do. It does not matter much what the article says because most of them are just repeating words from other ambiguous sources of information. One article I found said that cross caster would pull to the left on a un crowned road.
I actually did find one single article that states more than 'vehicle pull on a crowned road is caused by not enough cross caster'. According to them it was just a element of camber that caster created. That's my own paraphrasing and I will post the link if I can find it again.

This all got me thinking. Prior to reading this article I as approaching the cause as the terrain was causing the vehicle to veer because of the skid steer effect with distance travelled by the 2 different front wheels. I don't think this theory would cause force to be placed on the steering wheel though. That would leave force acting on the wheels which in turn ,moved the steering wheel.

Now we have to get a foundation for steering geometry as it is in actual practice and not just words that are repeated in a guide that only plagiarizes previous guides that contain information that can not actually be observed in real life.

SAI or Steering Axis Inclination ; I will presume when defined, is the inclining of the axis of steering or the inclining of the rotation points of where the suspension pivots up and down. More simply put , if a straight line is drawn through the upper to the lower ball joint ,the line is not parallel to the wheel. When the wheels only path can go from perfectly right to perfectly left and vise versa, the wheels move into the ground raising the body of the car. So when it' stated that the weight of the car causes the steering wheel to go straight if turned ,this is completely true. This also adds stability because anything that causes the wheels to move from interaction with the road also has to lift the car as well.

lets add caster to this. For what I present here ,I'm only going to use the definition that caster adds camber on turns and that is it.Comparing a shopping cart wheel to a automobile wheel has so many differences that they are hardly analogies at all. The front of a shopping cart is steered by moving the body of the cart to move the wheel and not the wheel moving the body of the cart , the cart's wheel swivels perfectly vertically and the shopping cart
s wheel tracks the opposite way as well. Caster is defined as adding stability to a car like SAI by making the car body raise in the air. The problem with this definition is that one side of the car will go up while the other goes down and caster does not have a centering effect when the car is still with a tendency that I don't think can be explained with friction. This would imply that motion also caused the centering effect of caster.

As this post is long I'm going to leave it at that for now.Maybe I'll be able define why caster cancels out road crown later or maybe this post will help a reader to do it for me. :

[theKbStockpiler]

I made sort of a model of a front suspension with caster. If you lay it on a surface and then tilt the surface, the wheel will move to point down. If you move the surface back to flat it will straighten out. It works like a camera tripod with swivel feet. Besides for maybe tracking changes with additional caster, I have not figured out why it would lessen pull on a crowned road. It looks like caster to begin with is what causes it.

[FJCamper]

Excellent subject.

My general advice is pay less attention to the technical tomes and more to your actual experience. Before I was ever introduced to pro racing I saw the wheel balancer's and optical alignment racks all advertised like aspects of NASA science, and at my first 24 hour at Daytona watched the Goodyear tire truck crew bubble balancing tires, quick and dirty, that were going on cars that spent more time over 160mph than below it.

Wheel alignments were being improvised in the paddocks with string and bubble indicators.

The confusion comes when an intelligent person reads an intelligent tech piece about alignments and presumes it applies to the specific car and road they have in mind. Think of these tech articles like most Supreme Court rulings. Isolated clarifications for very, very specific circumstances.

FJC

[theKbStockpiler]

If the established beliefs on a subject don't add up you have to build a test model to sort it out.

Any thoughts on SAI? it adds camber on turns and lifts the wheels similar to caster.