Caster change through travel

[LEE1969GB]

Is it the norm to have caster change through the travel on the front, If so how much? I assume this would be done by not mounting the top and bottom wishbone pivots paralel (where is the spell check?) to each other, and how would this help.

[yoshi]

Originally Posted by LEE1969GB

Is it the norm to have caster change through the travel on the front, If so how much? I assume this would be done by not mounting the top and bottom wishbone pivots paralel (where is the spell check?) to each other, and how would this help.

Some vehicles with front brakes rake the upper a-arm more than the lower to help with anti-dive, as the rotation of the top of the spindle backward (from raking the upper arm more) is to help cancel out the forward rotation caused when the caliper grabs the rotor and tries to rotate the spindle forward (which causes the front end to dive). The downside to antidive is it take the weight off the front end, and can also lift the suspension so you don't have as much dampening ability when you hit bumps. It was created for street cars because the motor is in the front, and the car would slam down to the ground under braking. I think it has more drawbacks in an offroad situation with a loose surface, but that's just my opinion......

[bdkw1]

Originally Posted by yoshi

The downside to antidive is it take the weight off the front end, and can also lift the suspension so you don't have as much dampening ability when you hit bumps. It was created for street cars because the motor is in the front, and the car would slam down to the ground under braking. I think it has more drawbacks in an offroad situation with a loose surface, but that's just my opinion......

Bzzzzzz. To have the front lift you would have to have stupid amounts of anti-dive. You still get weight transfer, you just don't have the front slamming into the bump stops on hard braking. It also makes the car more stable under braking as you maintain constant castor.

Look at it this way, if your chassis has 6* of pitch when you stomp on the binders and you are running 6* of static castor, you will have 0* castor with full brakes. Anybody wanna guess how this will steer?

As stated before, I don't like the standard method of achieving anti-dive that auto makers use. It has it's own drawbacks on long travel suspension. Instead of angeling the top mount relative to the bottom mount, you angle the top mounts towards each
other in the front. Viewed from the top, they would look like this.
front
/__\ . This will give you castor gain in bump and droop where as the other method will only gain in bump and loose it in droop.

[masterfabr]

Originally Posted by bdkw1

Bzzzzzz. To have the front lift you would have to have stupid amounts of anti-dive. You still get weight transfer, you just don't have the front slamming into the bump stops on hard braking. It also makes the car more stable under braking as you maintain constant castor.

Look at it this way, if your chassis has 6* of pitch when you stomp on the binders and you are running 6* of static castor, you will have 0* castor with full brakes. Anybody wanna guess how this will steer?

As stated before, I don't like the standard method of achieving anti-dive that auto makers use. It has it's own drawbacks on long travel suspension. Instead of angeling the top mount relative to the bottom mount, you angle the top mounts towards each
other in the front. Viewed from the top, they would look like this.
front
/__\ . This will give you castor gain in bump and droop where as the other method will only gain in bump and loose it in droop.

How much of that would be needed approximately to keep relatively constant caster over 18" or so of traval?

[bdkw1]

Originally Posted by masterfabr

How much of that would be needed approximately to keep relatively constant caster over 18" or so of traval?

There isn't a set answer, every car will be different as it depends on a lot of factors. How high and how far back is the CG? How much rake? How much rear travel? How much does the car weigh? Bias? Is the suspension going to be set up with 50% up travel? 60%?

Without a lot of CAD work, this is kind of a guessing game. The more you have built, the better guesser you are. This is the first buggy I have built with anti-dive, since it is a lot lighter in the front I'm going with less anti-dive than I would for a truck. Since I have trucks fairly well dialed in and I know roughly what the differences in the specs are between the buggy and the truck it should be close. If not, thats where some tricky shock valving some into play.