ryanrlamothe
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Calculating Caster Angle and other Suspension Geometry - 2006/04/04 15:25
So, Matt calls me and asks "I'm moving my strut towers xxxx mm, how will that change my caster angle". Well, caster is extremely difficult to calculate directly. From what I know, and to quote a little bit from some sources, caster is the angle of the kingpin in relation to the vertical plane, when looked at from the side of the car. As an example, 0° of caster puts the kingpin in a vertical line. Positive caster means the kingpin leans rearward at the top. Increasing the positive caster on your car will slightly increase the steering turning into a corner and slightly decrease steering coming out of the corner. Reducing the positive caster will decrease the amount of steering you have going into a corner and increase the amount of steering you have in the middle of the corner and exiting the same corner.
So, I went about looking for some good explanations in an easy and understandable manner.
Here are some of the results of that search:
www.onlineshowoff.com
Look at Step Eight
--I will post more information later
Post edited by: ryanrlamothe, at: 2006/04/04 21:12
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 16:05
Since that website appears to be borked every couple of times you click on the link, I made an Adobe PDF of the entire thread including all relevant pictures and have uploaded it to Paladin Rally instead 
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 16:18
Also, there is a fairly inexpensive tool I am considering purchasing myself that can help to measure camber and caster. It is the SmartCamber tool.
Here are the links of interest, and you can do these measurements without the tool, just use the template and a calculator:
SmartCamber Owners Manual
See: Page 8
Template
For use with Page 8
Post edited by: ryanrlamothe, at: 2006/04/04 21:13
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 16:23
Owners Manual upload
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 16:36
Template Upload
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 16:40
I also found this article to be of interest as well:
DIY Alignment
The important formula to use from this link is:
Caster (deg) = (180 / 3.1415) * [(camber1 - camber2) / (turnangle1 - turnangle2)]
Which is what is essentially used in the links above as well.
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Matt
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 18:10
Wow Ryan, that is awsome! 
I was sorry to have disturbed you late at night in my frenzy how to determine caster angle, but seeing the wealth of info youve turned up, I'm not sorry anymore. 
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 20:51
Oh, no problem, you are welcome to call at any time. Unfortunately, one of the few times I was not available was the other night, but it was not any fault of yours when you called.
The first article I linked to was originally from SportCompactCar but it does not have nearly as much information as the link I posted above. It appears that the author of the link I posted above added a lot more additional interesting and useful information.
And there are other gems there as well, like this article written with the help of Adam Levy GC8 to GDB WRX Engine Swap
Post edited by: ryanrlamothe, at: 2006/04/04 21:08
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ryanrlamothe
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 21:21
Also, another way to get some useful information is if you have a TiresPlus in your area. The reason I say TirePlus is because, at least where I live in Wisconsin, they have an "Unlimited Lifetime Alignments" package for about $115. You can get as many four wheel computer alignments as you like with them for the entire time you own your car.
And they do custom alignments as well. Some of the Rally and Club Racing guys go to the TiresPlus's around the area to get their racing alignments done. Plus, it is all computerized, so you can see your alignment settings in real-time and everything is printed out for you to take a look at later if you want to make any changes.
Are there any places like that near Paladin Rally? If I end up moving from here, that will be one of the things I miss the most.
EDIT: Bummer, the nearest TiresPlus to you are all in PA. Maybe there is another great tires place near Westmoreland, NH?
Post edited by: ryanrlamothe, at: 2006/04/04 21:24
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Matt
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Re:Calculating Caster Angle and other Suspension Geometry - 2006/04/04 21:35
I've always gotten along with the guys from the local Sullivan Tire. They have a machine that can mount and dismount rally tires without tearing the bead. Lifetime allignments would be awsome, hopefully a TiresPlus chain will open around here.
From everyone I've talked to, and from my own expierence, it seems that atleast in rally, turn in is King. Most of what we do is geared twards gettin the car to start turning, consistently, and accuratly. Everything else, tire wear, stability, oversteer, takes a back seat.
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