333pg333

^ Yes, good point about the brake mounting tabs!! Mo30 is no good if you want to mount Cup type calipers.

rbuit

This way with the adapters it is more universal so you can use any brakes you want.
With the adapters it is easy to position the calipers in the right position.
You only need to make custom adapters.
I use AP brakes with 343mm rotors and have to make some new adapters because the ears are 6mm thicker for strength.

333pg333

What suspension do you run Richard and what is your rear setup? Are you allowed to change to a twin arm style?

Van

Very nice work. Did you consider (or perhaps it's done) moving the strut mounting position lower so you don't end up compromising the shorted stroke of the strut on a lowered car?

rbuit

i have send you a mail patrick

Van, i did not consider what you suggest because the shafts would be more complex to fabricate and on the track i don't need more stroke.

TurboTommy

Van;
I read your piece on roll centers and understand what your saying.
But, just for clarification, I gotta ask:
The CG has a greater "leverage" on the roll center when the roll center is possibly somewhere below the surface of the pavement, but wouldn't the "degrees" of rotation be alot less severe? Possibly a good trade-off resulting in less camber change?
Another-words, higher roll centers would result in much more "degrees" of body rotation, because the imaginary circle is smaller (radius length from CG to roll center is much, much shorter)
Probably bad choice of words, and probably not seeing something right.
Thoughts?

robstah

Dubai944

No. Seems like you are imagining that the arc distance is fixed by the amount of weight transfer and therefore the same distance around a smaller circle is actually a higher number of degrees. Higher roll centres result in less roll as long as you are moving towards the CoG. In theory if the roll centre and the CoG coincide you get no roll at all.

Van

Dubai is right. To imagine the other extreme, if the roll center is above the CG, then it would be like a pendulum swinging out, and the outside wheel would increase its negative camber under cornering.

A motorcycle doesn't have a lateral plane roll center like a car because it has only 2 wheels - but envision how that "leans into the turns" and creates more negative camber as cornering force increase. How ideal would that be if a car could tilt all its wheels to minimize sidewall deflection and maximize contact patch and weight transfer!

TurboTommy

Yes, that's how I'm thinking it.
What am I not seeing right?

Dubai944

No idea...

Simplistically you should try and picture the weight transfer from one side of the car to the other as being a horizontal sideways force, it's not a turning force. You will only get rotation if you apply a sideways force to something that is attached to a lever point that is not at the same point as where you are pushing.

The same amount of weight transfer causes less and less rotation (which is caused by the vertical component of the weight transfer vector compressing one side of the suspension) the shorter the lever gets. Eventually there is no lever at all when the roll centre and CoG coincide, and there is no vertical component at all to compress one side of the suspension . The weight transfer is the same, but now it's all sideways force acting laterally on the tire contact patch but not compressing the suspension. If you have enough weight transfer to exceed the tire grip the car will just slide sideways without rolling at that point.

Roll is not necessarily a bad thing and neither is a low roll centre. You can control the amount of body roll with suspension stiffness. In reality the roll centres are not fixed points and move around all over the place as the suspension moves, and the relationship between front and rear roll centres makes the whole equation far more complicated than this simplistic view of physics.

Van

Under heavy braking (leading into turn in) the front roll center gets lower and the rear roll center gets higher. This, in turn, can let the lateral force have more of a moment at the front than the rear, and this will result in a twisting chassis. Street cars can typically see as much as 2 degrees of torsional twist.

TurboTommy

Dubai;
ah yes,
It didn't occur to me that as the body rolls, the "imaginary radius lever arm length" from the roll center to the CG constantly changes and the centrifugal load acts on the sprung weight in a lateral direction only (never "around" the roll center).
I think that's what you're saying.