Can we talk about caster?

About caster, do fwd double wishbone cars not need as much as a mac strut car?

They don't need as much in many cases because you can build a double wishbone setup to gain negative camber during compression travel just by changing the length and static angle of the arms whereas to gain camber during compression with mac strut cars you have to incline the struts inward and mcstrut cars are almost always transverse-engine FWD trying to fit the whole drivetrain lengthwise between the strut towers and don't have enough room to allow that intrusion of the strut towers. Also they're built for drivers who don't care in the majority of cases.

Trackmouse wrote: Note- too much caster, and your steering wheel won't return to center. It may not even move. Which means manually steering it 24/7. I slammed my ae86 once, while the gain was awesome, I wasn't able to do no handed drifting because the wheel wouldn't return to zero. I used to make money from my friends doing stunts like no handed drifting.

Hmm,as a guy that spent 9 yrs with a race only AE86 this makes no sense to me.Lower it all you want and castor isn't changing enough to notice and even if it did change enough to notice it would be the complete opposite effect.I assume you didn't only slam the rear.

I think you had something binding independent of any castor effect.

My dad has a 1937 Toro tractor that had some extreme wear on the buggy-sprung front pivot-axle. It caused the kingpins to tilt forward about 15°. It was very interesting on a side hill, because it always wanted to turn itself uphill. If you tried to run it at top speed, however, it wanted to go every direction other than straight, and the death wobble was intense.

In reply to kevlarcorolla:

It was back in a time when I had shops do things. They put slings in and then said "we also have to do an alignment. I don't know what they did. But it was not effective and that's why I sold it.

snailmont5oh wrote: My dad has a 1937 Toro tractor that had some extreme wear on the buggy-sprung front pivot-axle. It caused the kingpins to tilt forward about 15°. It was very interesting on a side hill, because it always wanted to turn itself uphill. If you tried to run it at top speed, however, it wanted to go every direction other than straight, and the death wobble was intense.

I really enjoy the fact that a 1937 Toro tractor with a worn suspension is a legit part of this discussion

Back to the mention of the Jeep CJ earlier, that issue want caster. It was the front location of the spring shackles on the front leaf springs. It really lets the front end wander back and forth. The taller the shackle, or softer the shackle bushing, the worse it gets. Leaf spring shackles should always be on the back side of the spring.

If you ever get a chance have somebody saw the steering wheel back and forth, and watch the chassis swing a few inches left and right while the wheels just turn in place. Then imagine that on the highway at speed. There's a reason companies still make shackle reversal kits for CJ's/YJ's.

You can talk about caster without talking about KPI, but you probably shouldn't.

Slotting strut tower for more caster on a track only car a reasonable thing to do?

If resting distance from center of wheel to top of strut tower is roughly 21 inches, and I'm looking for a 2 degree change in angle. How far would I need to slot the strut tower back towards the firewall?

Or if you could post what the equation is that would be helpful as well. Otherwise I'll be taping sheets of computer paper together in order to draw it out and measure it. :P

On my ZX2SR I installed offset LCA bushings to increase the caster. It really improved the handling of the car.

On CJ's, I vaguely remember there was a time when the front springs had the shackle on the rear of the spring.

Slotting strut tower for more caster on a track only car a reasonable thing to do?

Reasonable as in no downsides? Sure. But unless you convert to a coilover and different 'top hat' there usually isn't much space to slot a stock strut inward before part of it starts contacting the strut tower. Convert to coilover and camber plates and you might have a solid inch or two on top of the adjustment in the plate. If you have setup like that, or further, a setup where you can adjust camber at the top AND at the strut yoke, you would want to max out the inward inclination of the strut as your first adjustment because it will give you a small dynamic camber gain while the adjustment at the strut yoke just gives you static camber.

iceracer wrote: On my ZX2SR I installed offset LCA bushings to increase the caster. It really improved the handling of the car. On CJ's, I vaguely remember there was a time when the front springs had the shackle on the rear of the spring.

Would you mind elaborating on what you did with the bushings? I have a 3rd Gen sedan and I'm looking for options to maximize the caster to get more dynamic negative camber.

Vigo wrote: They don't need as much in many cases because you can build a double wishbone setup to gain negative camber during compression travel just by changing the length and static angle of the arms whereas to gain camber during compression with mac strut cars you have to incline the struts inward and mcstrut cars are almost always transverse-engine FWD trying to fit the whole drivetrain lengthwise between the strut towers and don't have enough room to allow that intrusion of the strut towers.

Actually the incline of the strut has very little effect on the shape of the camber curve, it changes static camber. To change the camber curve of a macstrut car you need to change the angle of the LCA at rest, which means massive ride height changes or drop/lift spindles.

The STOCK incline of the strut has little effect. Imagine the strut being inclined at something like a 45* angle and you will see it starts to act like an upper control arm that gets shorter as the suspension compresses. Admittedly the gain you could get within the confines of a stock strut tower are small, but some people care about small gains. Look at what miata people do to get 2hp!

You can use a ball joint spacer to improve the camber gain you can get by changing the LCA angle, but at least on my cars i am limited on the ball joint spacer by wheel diameter. Only my cars with 17s&18s seem to have enough room for it to be worth it, which is sad because my cars that are slammed on 15s need it the worst.

In reply to Fr3AkAzOiD:

Assuming you're just adjusting it in 2D space, you would use basic right triangle trig functions. The caster angle would represent Theta (Θ) and the adjacent and hypotenuse legs would represent your spindle-tower vertical height and strut length respectively.

sobe_death wrote:

In reply to Fr3AkAzOiD:

Assuming you're just adjusting it in 2D space, you would use basic right triangle trig functions. The caster angle would represent Theta (Θ) and the adjacent and hypotenuse legs would represent your spindle-tower vertical height and strut length respectively.

I would assume this is some form of math? :/

Fr3AkAzOiD wrote:

sobe_death wrote: In reply to Fr3AkAzOiD: Assuming you're just adjusting it in 2D space, you would use basic right triangle trig functions. The caster angle would represent Theta (Θ) and the adjacent and hypotenuse legs would represent your spindle-tower vertical height and strut length respectively.

I would assume this is some form of math? :/

Thank you sobe_death for pointing me in the right direction.

Thank you Google for helping me avoid the math. http://www.mathwarehouse.com/triangle-calculator/online.php

Haha no worries. Most of us don't carry that math with us past high school; I know I tried hard to forget it once I graduated college.

All hail our savior, Google!