Barrman
Well-known member
- 5,242
- 1,734
- 113
- Location
- Giddings, Texas
I used the M1009 to flat tow the M715 to my class today. We are going to throw a 6.2 in where the thrown rod big block is. While I had it in my class, I put it on the alignment machine to see how things looked.
The front was great. So was the rear. However, while looking at the numbers I remembered a thread from a week or so ago where somebody was asking if the rear tires should lean in any. So, I thought I would post up what my numbers where and try to explain them too.
Before a vehicle can be aligned, the thrust angle has to be figured out. Basically, you need to figure out if the rear axle is square with the frame and pushing the vehicle down the road straight. All of us with M1009's have been told our trucks are "dog tracking". People think that because the front axle is wider than the rear and if somebody is behind you, it looks like the truck is twisted over to one side. Most people never bother to pull over and look up the other side of the truck as well. If they do, they will see the same thing but backward on the other side. Just shake your head and say it is an optical illusion next time.
Or at least, I can say that for sure now. Toe is a measurement of the distance between the front and rear of the tires when looked at from the top. Put your feet flat on the floor and have your toes touch and your heals far apart. That is "Toe In" or positive toe. Toe Out is negative toe. My drivers rear tire is 0.33° toe and my passenger side rear is -0.26°. That means my passenger side rear of the axle is 0.30° behind the drivers side of the axle. My thrust angle is 0.30° There is no factory specification for thrust angle on this vehicle. A third of a degree is pretty close to square though and not something anybody can see with their eye or feel going down the road.
However, every alignment starts with that measurement because the front toe and steer ahead are based off of thrust angle. It is nice to see just to check though.
The factory does have a spec for front total toe. This is a direct tire wear angle. They figure anything within 0.24° of each other is good. The front total toe is supposed to be -0.12° to +0.12° I have a rear total toe of 0.07° No wonder I can't see any wear on my rear tires.
Then there is Camber. Camber is the inward or outwar lean of a tire when viewed from the front. Positive is top out and negative is top in. A vehicle will pull to the side with the most positive camber. Watch a NASCAR race and you can see this demostrated. They have gobs of positive camber on the drivers side and gobs of negative camber on the passenger side. They want the cars to turn left with minimal effort. Let go of the wheel and they are turned.
There is no factory spec for rear camber. It is just another angle to check, but do nothing about. Mine was -0.8° on the drivers side and -0.9° on the passenger side. So, my rear tires lean in just a hair at the tops.
The front camber has a factory spec, but can't be adjusted without special bushings which I don't have and probably won't get. The spec for the front camber is 1.5° with a range of 1.0°-2.0°. They got to that number by compromising handling, stability and tire life. The bigger the number, if even on both sides, the more stable the vehicle. Since camber is also a direct tire wear angle, the bigger the number, the faster the tires wear. Tire life wise, a tire perfectly flat will live the longest. It just won't track as straight or turn corners as fast.
The 1.5° factory spec means the front tires are leaned out just a bit. That is why our outside edges of the tires wear first. If you turn corners sharp and fast, yours will wear faster than others. But, it also means a rear camber angle within 2.0° degrees of verticle and even with the other rear tire will produce very little tire wear, not effect handling in a bad way and give you the most traction on flat ground you can get.
I just wanted to get these numbers posted in case somebody gets an alignment and wonders if their numbers are good, bad or meaningless. I used a Hunter Engineering optical aligner and it took me maybe 4 minutes from the time I turned the engine off until I had the readings. I was doing a 1985 K5 4x4 Blazer according to the machine. Just about any alignment shop should be able to give you the same readings.
The front was great. So was the rear. However, while looking at the numbers I remembered a thread from a week or so ago where somebody was asking if the rear tires should lean in any. So, I thought I would post up what my numbers where and try to explain them too.
Before a vehicle can be aligned, the thrust angle has to be figured out. Basically, you need to figure out if the rear axle is square with the frame and pushing the vehicle down the road straight. All of us with M1009's have been told our trucks are "dog tracking". People think that because the front axle is wider than the rear and if somebody is behind you, it looks like the truck is twisted over to one side. Most people never bother to pull over and look up the other side of the truck as well. If they do, they will see the same thing but backward on the other side. Just shake your head and say it is an optical illusion next time.
Or at least, I can say that for sure now. Toe is a measurement of the distance between the front and rear of the tires when looked at from the top. Put your feet flat on the floor and have your toes touch and your heals far apart. That is "Toe In" or positive toe. Toe Out is negative toe. My drivers rear tire is 0.33° toe and my passenger side rear is -0.26°. That means my passenger side rear of the axle is 0.30° behind the drivers side of the axle. My thrust angle is 0.30° There is no factory specification for thrust angle on this vehicle. A third of a degree is pretty close to square though and not something anybody can see with their eye or feel going down the road.
However, every alignment starts with that measurement because the front toe and steer ahead are based off of thrust angle. It is nice to see just to check though.
The factory does have a spec for front total toe. This is a direct tire wear angle. They figure anything within 0.24° of each other is good. The front total toe is supposed to be -0.12° to +0.12° I have a rear total toe of 0.07° No wonder I can't see any wear on my rear tires.
Then there is Camber. Camber is the inward or outwar lean of a tire when viewed from the front. Positive is top out and negative is top in. A vehicle will pull to the side with the most positive camber. Watch a NASCAR race and you can see this demostrated. They have gobs of positive camber on the drivers side and gobs of negative camber on the passenger side. They want the cars to turn left with minimal effort. Let go of the wheel and they are turned.
There is no factory spec for rear camber. It is just another angle to check, but do nothing about. Mine was -0.8° on the drivers side and -0.9° on the passenger side. So, my rear tires lean in just a hair at the tops.
The front camber has a factory spec, but can't be adjusted without special bushings which I don't have and probably won't get. The spec for the front camber is 1.5° with a range of 1.0°-2.0°. They got to that number by compromising handling, stability and tire life. The bigger the number, if even on both sides, the more stable the vehicle. Since camber is also a direct tire wear angle, the bigger the number, the faster the tires wear. Tire life wise, a tire perfectly flat will live the longest. It just won't track as straight or turn corners as fast.
The 1.5° factory spec means the front tires are leaned out just a bit. That is why our outside edges of the tires wear first. If you turn corners sharp and fast, yours will wear faster than others. But, it also means a rear camber angle within 2.0° degrees of verticle and even with the other rear tire will produce very little tire wear, not effect handling in a bad way and give you the most traction on flat ground you can get.
I just wanted to get these numbers posted in case somebody gets an alignment and wonders if their numbers are good, bad or meaningless. I used a Hunter Engineering optical aligner and it took me maybe 4 minutes from the time I turned the engine off until I had the readings. I was doing a 1985 K5 4x4 Blazer according to the machine. Just about any alignment shop should be able to give you the same readings.