Jump to content
SAU Community

Recommended Posts

  • 2 weeks later...

sorry inbox full. didnt realise.

thought it was weird that i had no PM's.

Sorry matt .

tried to call u wekks ago.

if u still have it im keen.

Had internet dramas aswell.

sskyline....please re send PM's.

someone asked me what they do and how can they benefit from them....

well heres an explantion.

(stolen from wikipedia)

Suspension Tuning

Caster

Caster is the angle between the steering axis and the vertical axis as viewed from the side of the car. Caster affects straight-line stability and "camber gain". Positive caster is when the top of the steering axis is tilted back (steering axis intersects the ground in front of the tire contact patch). Negative caster is when the top of the steering axis is tilted forward (steering axis intersects the ground behind the tire contact patch). I have never seen negative caster used, and I do not believe it is beneficial in automobile suspension geometry. Therefore, for the rest of this section, when I refer to caster, I am talking about positive caster.

To visualize caster, think about the wheels of a shopping cart. The steering axis of the wheel intersects the ground far ahead of where the wheel touches the ground. As a result, the wheel is essentially dragged behind the steering axis. This keeps the wheel moving straight. If the steering axis intersected the ground at the same spot that the wheel touched the ground, then there would be no caster effect. The wheel would be free to spin around the steering axis as long as it was not held in place by some other force.

Unlike in a shopping cart, the steering axis on a car is placed close to the hub of the wheel. Therefore, the only way to make the steering axis intersect the ground ahead of the tire contact patch is to tilt the steering axis. The more the axis is tilted (in the positive caster direction), the greater the caster effect.

Example of Positive Caster (Side View)

Enlarge

Large caster settings increase the tendency of the front wheels to center themselves. This tendency is mainly due to the camber gain that occurs when the steering axis is tilted and the wheels are turned. Camber gain involved with caster is not easy to visualize. Think about the extreme case where the steering axis is tilted to the point where it is horizontal. When you turn the steering wheel, the front wheels would stand up on their edges. If you turn left, the left tire will stand on its outer edge, and the right tire will stand on its inner edge. If you turn right, the left tire will stand on its inner edge the right on its outer edge. The same type of camber gain, only on a smaller scale, takes place with less caster. This camber gain is exactly what you want in a corner. Read the previous section on camber to see what it is and why it’s beneficial.

When the tires stand up on their edges, the front of the car is actually raised up. This is why the wheels "center themselves" when you let go of the steering wheel. The weight of the car pushes the wheels flat on the ground, which resets the steering. This improves high-speed stability because it keeps the steering firmly in the center position. However, it is difficult to turn a car with a large caster setting because, while turning, you are actually lifting the front of the car with the steering. This effect is most visible in luxury sedans, where high-speed stability is important and sophisticated power steering makes up for the extra steering effort. If you watch one of these cars as the wheels turn to full lock (maximum steering angle), you will see the front end of the car rise slightly.

Increased caster is advantageous for racing and, in some cases, street driving. The only disadvantage is the added steering effort. While camber gain due to caster is generally good for increasing the grip of the front tires in a corner, too much camber gain will cause the tires to heat up, lose grip, and wear out prematurely. Therefore, do not use more than a few degrees of caster. If your car uses a MacPherson Strut suspension, it may be necessary to modify or install new strut tower mounts to be able to adjust caster.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • So..... it's going to be a heater hose or other coolant hose at the rear of the head/plenum. Or it's going to be one of the welch plugs on the back of the motor, which is a motor out thing to fix.
    • The oil pressure sensor for logging, does it happen to be the one that was slowly breaking out of the oil block? If it is,I would be ignoring your logs. You had a leak at the sensor which would mean it can't read accurately. It's a small hole at the sensor, and you had a small hole just before it, meaning you could have lost significant pressure reading.   As for brakes, if it's just fluid getting old, you won't necessarily end up with air sitting in the line. Bleed a shit tonne of fluid through so you effectively replace it and go again. Oh and, pay close attention to the pressure gauge while on track!
    • I don't know it is due to that. It could just be due to load on track being more than a dyno. But it would be nice to rule it out. We're talking a fraction of a second of pulling ~1 degree of timing. So it's not a lot, but I'd rather it be 0... Thicker oil isn't really a "bandaid" if it's oil that is going to run at 125C, is it? It will be thicker at 100 and thus at 125, where the 40 weight may not be as thick as one may like for that use. I already have a big pump that has been ported. They (They in this instance being the guy that built my heads) port them so they flow more at lower RPM but have a bypass spring that I believe is ~70psi. I have seen 70psi of oil pressure up top in the past, before I knew I had this leak. I have a 25 row oil cooler that takes up all the space in the driver side guard. It is interesting that GM themselves recommend 0-30 oil for their Vette applications. Unless you take it to the track where the official word is to put 20-50w oil in there, then take that back out after your track day is done and return to 0-30.
    • Nice, looks great. Nice work getting the factory parts also. Never know when you'll need them.
    • Thanks @jtha7 I will have a look around tomorrow but it is a prick of a spot. These are some photos i tried taking 
×
×
  • Create New...