How does caster affect handling? Is there any way to measure it without a machine? I'm experementing with adjustments to get best handling and need some advice. Have rear toe and camber eyeballed with strings and level. I will eventually take it to a shop, but I want to mess around with it before I pay for a pro. Thank You!

 

Unless you come across a rare old pro dont bother taking it anywhere. Those alignment machines are designed to get cars in and out fast within a wide but acceptable range. The biggest issue is that your suspension is disturbed from it's natural stance when loading it onto their alignment rack. Your home methods will get better results if you take your time. Do your settings on level ground with some garbage bags or plastic under each tire to allow for some movement when adjusting. For camber I cut down a level so that it fits on the rim, then use a .010 feeler gauge at the top of the level since I like a little negative camber. For toe, setup your strings off the center of the rims to get them parallel, then measure toe from convenient areas near the outside of the tires which will get you very accurate results. Many alignment machines use the rims but measuring at the outside of the tires is better. Caster is not that critical unless you are on the track, just get it in the range. Positive caster will better track going straight down the road, negative will make it feel more twitchy. If both front wheels dont have the same caster it will pull to one side.

To set Caster.. Use the level to measure camber. Write these numbers down. Negative camber is the tire/wheel tilting inward at the top. On our C3's I like slightly negative, .010 feeler guage. Then turn the wheel full lock to the left, and then measure the camber on both L and R wheels. Then turn the wheel full lock right and measure the camber again. Subtract the two left wheel camber numbers and that will be the left wheel castor setting, and the do the same for the right wheel. Toe must be re-measure/adjusted AFTER castor/camber is adjusted. Lars has a good paper on alignment with a table to convert the feeler guage to caster/camber angle.

 

So if I take all the shims out, that would be 0 caster? Then shim for camber from there? Will negative caster give quicker response with less stability and vice versa? Is bumpsteer caused by excessive neg caster? Sorry for so many questions, but just learning.

 

No and no

Castor needs to be positive, and within a half degree on each side. The car will pull to the side that has the least amount of Castor... This is the steering angle that cause the steering wheel to return to center after you make a turn. Just like a desk chair with casters on the bottom, when you push the chair forward the casters swing back. When you drive the car forward, the front wheels trail back just like your Castors On the bottom of the chair.

The best thing you can do right now, is to read up on front wheel alignment. Find out what all the angles do, and the problems they cause if they are set wrong.

 

when I was training alignment guys, I had a book at the Hunter machine that was written by the founder of Hunter engineering. I think it was called "wheel alignment equals motion balance" This is a good technical read for anybody interested in performing Front and alignments.

 

Thank you!