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Old 11-16-2019, 12:40 PM   #1 (permalink)
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Camber/Caster alignment questions

Hello everyone.

Just had an alignment done and was wondering about the print out they gave me afterwards. Here are the before and after numbers.....

Toe in before: Left .71° Right .22°
Toe in after: Left .02° Right .00°


Camber before: Left -0.5° Right -0.6°
Camber after: Same Same

Caster before: Left 3.9° Right 4.4°
Caster after: Same Same


It looks as though they only adjusted the toe in and nothing else. So the questions are this........

1) Is the camber being that amount off bad? According to the little graph on the print out its almost perfectly centered in the green area. I'm assuming it's pretty close to perfect.

2) Is the caster being off nearly 4° bad? Technically it's still in the green area of the graph, but not even close to being centered. Is it enough to worry about or hurting my FE?

As a side question.......I don't think there is any adjustment for the rear on my Ranger, but I'm showing positive camber and caster on the left and negative camber and caster on the right and a thrust angle of .17°

I've never looked closely at these print outs before, but not knowing exactly what these numbers mean in terms of FE, I'm not sure how to interpret them anyhow. Just looking for some clarification, education, and advice.

Thanks

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Old 11-16-2019, 01:21 PM   #2 (permalink)
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I'm no expert on alignment, so take what I have to say with a grain of salt. Here's my understanding though:

You don't necessarily want zero camber or caster, and manufacturers often spec non-zero values for vehicles to change handling characteristics, stability or fuel economy.

My Insight calls for:

Front
Caster : 2° +/- 1°
Camber : 0° +/- 1°
Toe : 0mm +/- 2mm

Rear
Toe : in 3mm +/- 3mm
Camber : -1° +/- 1°
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Old 11-16-2019, 01:31 PM   #3 (permalink)
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Not everything is adjustable or as adjustable as it may need to. Caster makes the wheels want to naturally return to going straight. Camber is the tire leaning in or out, normally a little (or a lot) negative helps straighten the outside wheel with most of the weight when cornering, otherwise zero is better for tire wear. The toe you also want in a bit so it has a tendency to keep tracking straight, if it's toed out at all it will wander back and forth trying to figure out which front tire to follow.
I think your numbers look fine but I also am no expert.
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Old 11-16-2019, 07:07 PM   #4 (permalink)
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Quote:
Originally Posted by hat_man View Post
Hello everyone.

Just had an alignment done and was wondering about the print out they gave me afterwards. Here are the before and after numbers.....

Toe in before: Left .71° Right .22°
Toe in after: Left .02° Right .00°


Camber before: Left -0.5° Right -0.6°
Camber after: Same Same

Caster before: Left 3.9° Right 4.4°
Caster after: Same Same


It looks as though they only adjusted the toe in and nothing else. So the questions are this........

1) Is the camber being that amount off bad? According to the little graph on the print out its almost perfectly centered in the green area. I'm assuming it's pretty close to perfect. im assuming it’s pretty close to perfect too

2) Is the caster being off nearly 4° bad? Technically it's still in the green area of the graph, but not even close to being centered. Is it enough to worry about or hurting my FE? It’s not off by 4 degrees, the spec is not going to be 0. More caster might even help mileage by an insignificant amount. More caster improves directional stability, but this also increases steering effort. The actual measurement vs spec is not as critical as cross caster, which helps with road crown. A Harley with a stretched front end would be an example of positive caster, while that wobbly shaking wheel on the bad shopping cart shows off negative caster.

As a side question.......I don't think there is any adjustment for the rear on my Ranger, but I'm showing positive camber and caster on the left and negative camber and caster on the right and a thrust angle of .17° There wouldn’t be caster on a non steering axle. The camber should theoretically be 0 with a solid axle, but there’s margin of error of the machine, some tolerance of the axle being manufactured, tire pressure, and how level the alignment rack is. If the thrust angle was out it could be a worn out bushing, of something bent that could adjusted with a frame puller, sledgehammer, torch, welder... I wouldn’t worry about .17 though

I've never looked closely at these print outs before, but not knowing exactly what these numbers mean in terms of FE, I'm not sure how to interpret them anyhow. Just looking for some clarification, education, and advice.
In general, the manufacturers specs (middle of the green) will get you the best fuel economy. Toe being the most critical, then camber, and I think caster would have a bigger indirect effect on driver fatigue than direct effect. Some could argue for different specs, but I’m not sure I could reliably test to see the difference. At the same time it might show in tire wear. So if theres a forum for you vehicle and everyone says make some small change for even tire wear, I wouldn’t be scared of that either
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Old 11-17-2019, 11:24 AM   #5 (permalink)
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Thank you all for the the information. They did tell me that the caster could be adjusted by removing some pins, making the adjustments, and replacing the pins, but it was going to cost almost as much as another alignment. Funny that they call it a "front end alignment" when it's really nothing more than a "toe in reset".

As for the rear, the only way I can see these being off (according to the print out) would be if the axle wasn't square to the frame in at least two axes. Something like this would account for the thrust angle being off. I suppose I could use some string and a marker and measure the center to center on the wheel hubs on each side, but like 2000mc said, it's probably not enough to worry about. Not sure how I could measure the center to center in the vertical axis. Theoretically it should be the same because the truck sits on the tires and they sit on the road. As long as the tires have the same diameter and sidewall height all things should be equal.
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Old 11-17-2019, 11:50 AM   #6 (permalink)
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The thrust alignment being off just makes the truck "crab walk" a bit down the road. Still the tires track straight but the body is a bit off. If it's way off the rear tires won't follow the same track as the front. I dont think .17 is bad. There is an accuracy of analysis in play with all of this stuff, not the range of acceptable specs but the difference in readings you would get if you measured it over and over without changing anything. They used to do alignments with strings all the time but I believe even the best lazer systems even when brand new might be variable to .05 degrees. Plus set whatever specs, drive the car around the block and numbers that precise will be changed already.
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Old 11-18-2019, 07:47 AM   #7 (permalink)
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I thought thrust angle was the angle perpendicular to the rear axle? I still agree that .17 is not enough to worry about. Now I'm just trying to learn.

If the thrust angle is the angle perpendicular to the rear axle, then the only way to change it is to move one wheel forward, causing the opposite wheel to move rearwards. This would cause the vehicle to want to travel "crooked" and have to be corrected by turning the steering wheels "counter thrust" to compensate.

I thought "crab walking" was when the rear wheels were offset to the front wheels but still tracking in the same angle. Theoretically both at 0° but one axle being more outboard of the other.
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Old 11-18-2019, 08:44 AM   #8 (permalink)
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I would imagine a driver would automatically correct if the rear axle were off by only a few degrees, and may not even notice.


I've certainly seen a few vehicles driving down the road like this:
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Old 11-18-2019, 10:12 AM   #9 (permalink)
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The reason they're charging extra for camber and caster adjustment is because the have to mess with shims which can be extremely time consuming. Generally speaking your typical alignment will include toe at all four corners, and camber/caster anywhere that doesn't require extra parts/disassembly, i.e., if there are eccentrics or threaded adjusters.

Based on where your alignment is, I wouldn't even worry about it, camber is probably where it's supposed to be, and caster is only off half a degree side-to-side, which might cause a very slight drift left on a very flat road, but would probably drive straight on most crowned roads. Caster is also not a wear angle, so as long as it drives properly I wouldn't give it a second glance
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Old 11-18-2019, 02:12 PM   #10 (permalink)
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Crab walking, dog walking, I think are all the same terms, the rear axle will align itself straight down the road no matter what on a solid axle. So a .17 degree thrust will require a .17 degree steering input to keep it straight.
That picture above is an extreme example I would say more like a 15.00 degree thrust or almost 1000 times worse than what you have.

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