Camber + Caster VS its affects when steering

[Bugzilla]

I will start off by saying I am no pro when it comes to this stuff but I have tried my best to understand it. I have read up the great write up that Ron did (and I have to say thank you for all the info you have shared) and I get most of it. So I went out to the garage last night and took some measurements and think I came up with some odd number. My measuring wasn't 100% accurate but was pretty close. So here is what I have.

Miata spindles measured at 8° KPI
Caster is set to -8°
Camber is at -1.5°
Toe is at 0°
Unsure of max steering angle in both directions but its more then normal cars

So here is the thing, after reading the write up Ron did, it seems like having the same degree caster and KPI should keep camber the same as the wheels are turning (correct me if I am wrong). So if I start at -1.5° camber and turn the wheel all the way to the right (using passengers side wheel for example), I now have +3° camber. Turning the wheel all the way to the left, I get -3°. Does this seem normal? I understand if I remove some caster then I will move those angle around and say end up at 0° to the right and -6° to the left. But if I remove caster, then caster is less then KPI which is not good? So I guess my main question is, starting at -1.5° camber, am I ending up at good camber when turning? Is there a set value (camber) to start with when the wheels are fully turned? Meaning I should shoot for something like +2° when locked out to the right and -2° to the left? Or is this something that will be based off roll center being specific to my car? Any input from others would be great.

[GrabberGT]

You are not factoring in the cars roll as its banked in a turn. The inside tire will lose camber.

[Bugzilla]

I understand that the inside tire will drop and loose camber through a turn as well as the body rolling to one side, but are my static measurements a good starting point? Do static measurements even mean anything since the car will always be leaning through a turn? Would a better comparison be if I take measurements with one wheel an inch above ride height and the other an inch below to simulate the roll? If so, at that point, should I have one wheel end up at +3° and the other at -3°? Would that mean that if the car is rolling 6° that the tires will be flat on the ground?

Also, keep in mind, all my measurements are at full steering lock. I doubt on the track it will ever see full lock. Should I measure at say a half turn on the wheel instead?

Sorry for all the little questions. This is the last step I do before finalizing the front suspension setup and I would prefer to get it right the first time.

[Rod]

Would that mean that if the car is rolling 6° that the tires will be flat on the ground?



there is no absolute!! your measurement is good at that exact turn rate and at that exact speed.... set up is dynamic and dependent on Roll Center, Anti-dive, Moment Center, Wheel Jacking, ride height, tire width, spring rates, weight transfer......its all tuning...you have a general static setup but it will change to fit the designed parameters of the car

[Bugzilla]

Rod - Thanks for the reply. So you think I am at a good starting point then? I guess that is all I am shooting for. I know I will have to make adjustments down the road, just want to be in the ballpark to start with. I am going to wait for more people to chime in though.

[Rod]

Miata spindles measured at 8° KPI
Caster is set to -8°
Camber is at -1.5°
Toe is at 0°


sounds like a good start

[David Pozzi]

Your caster setting should be +8, not -8 as you listed in your first post. Otherwise, I think you are pretty close to good settings.
Ron's using dynamic caster in his recommendations for static caster settings, so on the outside loaded tire: you usually gain caster in dive due to anti-squat geometry (angle of the upper A arms). You lose some caster due to front squat: chassis angle. Camber is lost due to roll angle, but offset by camber gain due to geometry. It takes software to look accurately at all these factors.

In addition to all this, you need to be looking at the roll center location and movement, & how much front dive you will be having.
I highly recommend you have Ron do an analysis and point you in the right direction.

[Bugzilla]

David - Sorry about the caster typo. I always thought the way it is slanted was negative. But either way, the top of the spindle is slanted to the rear of the car, correct?

I would love to talk to Ron about all of this. He is a man that knows his stuff! I am kind of scared that he would say, sorry but you need to start over.

This is my first ever suspension design and I have learned a lot from the time I started. Lets just say I am on my second set of arms (front and rear) and third set of mounting positions (front and rear as well). I also had to redo the rear portion of the frame to get the mounts in the correct spot. For me, it was all trial and error. Got to start somewhere in order to learn...