Caster / Camber

[StephenB]

This is the first year ever that my brother and I will have the ability to do Camber and CASTER adjustments on our ITB Audi's! We are very excited but we are scared as well... :wacko: We have never had the ability to change the Caster although we undertand the principle and why it is good to have at least some positive Caster (In the past we have always ahd negative caster...) we still don't know what a good goal to have is and or the best most effective way to measure it is. I have installed plates that will allow me to go back to my "old" car set up that I liked, but it also allows me to gain the most caster possible legally in IT. I want an easy foolproof way to measure it and I really don't mind spending money on a gauge if it will make it easier. I am not looking for a cheap way to fake it but rather some advice on how to do it correctly and accuratly so I can benifit from this new adjustment! I know seem to have all these possible adjustments but no clue how I should be making them :unsure:


I am positive that I can learn a lot from some of you here so fire away your thaughts and feel free to argue I like to hear both sides of the story!
:cavallo:
Stephen


What do you use to do your measurments?


How do you do them?

[JohnRW]

You can measure caster with a camber gauge. I'm still using the cheap $39 bubble-type camber gauge that I bought 15 years ago - I think Racer Wholesale still sells them.

Caster = 1.4 x 'camber change' for +/- 20 deg. steering angle

So...crank the front wheels ('wheels', not 'steering wheel') 20 degrees to one side, then measure camber. Crank the wheels back straight, then 20 deg. to the other side (40 deg. total) and measure camber again. Then just do the math - multiply the total change in one wheel's camber by 1.4.

It helps to have some 'slip plates' under the tires to do this. I use two ~1/8" aluminum plates under each tire, about 12" x 12". Smear'em with grease, or thick oil. I use a cheap protractor at the edge of the plates, so I know when I've gotten to 20 deg. of wheel angle.

More caster, in theory, gives you better loading of the inside tire when turning. In practice, it makes you look like 'Popeye' if you don't have power steering, or the steering wheel isn't big enough. Start eating spinach.

[RSTPerformance]

You can measure caster with a camber gauge. I'm still using the cheap $39 bubble-type camber gauge that I bought 15 years ago - I think Racer Wholesale still sells them.

Caster = 1.4 x 'camber change' for +/- 20 deg. steering angle

So...crank the front wheels ('wheels', not 'steering wheel') 20 degrees to one side, then measure camber. Crank the wheels back straight, then 20 deg. to the other side (40 deg. total) and measure camber again. Then just do the math - multiply the total change in one wheel's camber by 1.4.

It helps to have some 'slip plates' under the tires to do this. I use two ~1/8" aluminum plates under each tire, about 12" x 12". Smear'em with grease, or thick oil. I use a cheap protractor at the edge of the plates, so I know when I've gotten to 20 deg. of wheel angle.

More caster, in theory, gives you better loading of the inside tire when turning. In practice, it makes you look like 'Popeye' if you don't have power steering, or the steering wheel isn't big enough. Start eating spinach.
[/b]


Thanks John,

I have started eating spinach :)
I guess this must be the secret stuff that noone wants to share except us java script:emoticon(':o', 'smid_22')
:o

Stephen

[mowog]

Caster: plain language on some benefits, quick and easy way to measure

Caster, in very simple terms, is how much camber your wheels have when you turn the steering wheel. Therefore you measure camber, and after applying an equation, you can determine how much caster you have. It affects how easy it is to turn the steering wheel and how quickly the steering will "center" after you turn. Yes, there are other things involved, but this is meant to be a simple explaination. To better understand, look at wheels on many office chairs. They are often angled. This is caster. If your two front wheels have different caster, you may have brake problems you don't understand (don't ask how I know!).

You want the top of the wheel to be angled toward the rear of the car. On cars with kingpins, that means the top is more rearward than the bottom. If you have upper and lower balljoints, look at the position and angles.

Simple measurements:
You need a camber gauge of some sort. Set your camber as you normally would, with the car on the ground (roll the car around a little to eliminate any friction that will give you false readings). Turn the steering wheel some known amount - I always use 3/4 rotation from center (the bottom spoke is now at 9:00 or 3:00), and measure both wheels. Turn it the opposite way 3/4 rotation from center, measure again. Keeping it simple, you want both wheels to change the same amount.

I don't have the formula handy, if no one prints it here, you can google it. If you want to set to a known value, but don't know what that value should be, I've heard every number between 3 and 4.5 quoted at some time on some forum. The correct number is the one you prefer for your driving style and car. I think 3 is a bit light on the centering (the steering doesn't return to center quickly enough for my taste), but the overall steering effort is OK. I think 4+ is too much on the steering effort. If I get somewhere around 3.5 to 4, and both sides are equal, I quite messing with it.

Last note, I really like the Smart-Level camber gauges, but they are rather pricey.

[Festus E. Simkins]

On the 1st Gen Rx-7 I get 5 degrees + Caster. Equal on both sides. Car is pretty light I never had problems with steering effort. No power steering. Car does not have rack and pinion steering.

[RSTPerformance]

I never thought about how important it is to get the same caster for each wheel.... is there anything good about having more caster on one side VS. the other at a track like LRP? (all rights except 1 turn) thanks for the advice! that is something I never even thought of...

Stephen

[Dyno]

I once read that Indy Car drivers set up their cars with differential caster in order to create a slight pull to the right. This way, all of the slack in the steering system is already taken up when they nudge the car into the turns. Clever.

[Blix]

Since some of the NE spec miata guys read this I will tell you "No, there is absolutely positively NO advantage to having differential caster at a track that is predominantly 'one handed'. NONE!"
:unsure:

Seriously, tho...get a caster setting that you like...then start shifting one side a bit and see how it feels. You might like what you find.

Or get a data acq system and figure out what your steering angle is at certian key areas on the track, and then model your suspension in a program like Bill Mitchell's WinGeo programs...figure out what camber you want at a certian steering angle and then set the camber to allow that...