Caster angle?

[BoneSawTX]

What kinda a caster are you guys running? I was late jumping into FM4 and picked up a bunch in FM5, caster is one thing I'm not very sure what to do with.

 

[katpeeler]

Well, in FM5 I would bump the default caster from 5.0 to about 6.1. I did this in FM6 and while turning in a sharp corner the thing would fish tail. So I messed with some stuff and finding leaving it at 5.0 is ideal for all the cars I have messed with, unless you like drifting, I think if you bump it up will let you drift a lot better. I don't drift soooooo

 

[BoneSawTX]

No drifting here either. I've gone much lower in FM6 as well. Thanks!

 

[HBR-Roadhog]

I was playing around with it yesterday with a controller and the Indy cars and found that it was much smoother with the caster all the way down to 1, my lap times were faster and more consistent than at the default 5 or even 3

 

[Ridox2JZGTE]

This is useful infos on caster that I posted on Pcars forum :

Caster should be in the physics, when the front wheel is turned and positive caster, there should be camber gain and it affects the inner wheel as wheel as well outside wheel ( turn in, grip + load ) Road condition also will have great effect ( banked turn, dip in the apex, curb etc ) Cars with high caster would benefit from lower steering ratio ( faster turn lock to lock ) to make use the added stability ( centering more pronounced ), but this really depends on the driver too.

Past discussion about centering on the wheel and camber benefit in corners vs straight line might be largely affected by how caster is simulated Picture both axle camber has their own pros and cons, rear camber ( rear grip on corner vs straight line braking/accel, tire wear/even temp ) and front camber ( turn in, corner grip/contact patch, tire wear/temp, braking / corner entry )


This is a good read about caster, camber and toe Just basic easy to understand article :

http://www.aligncraft.com/terms/terms.html



Caster Definition
Caster can be defined as the forward or rearward tilt of the projected steering axis from true vertical, as viewed from the side. This line is formed by extending a line through the upper and lower steering knuckle pivot points. For vehicles with front control arms, visualize the line extending through the upper and lower ball joints. On strut equipped vehicles, the line extends through the lower ball joint to the center of the upper strut mount. Caster is always viewed from the side of the vehicle.When the upper pivot point is rearward of the lower pivot point, caster is positive. If the upper pivot is forward of the lower pivot point, caster is negative. When the two points are straight up and down from each other, the caster is zero. A maximum side to side variation of ±.5° is recommended on most vehicles. Caster is NOT a normal tire wearing angle and is used as a directional control for stability and steering returnability.

Front of Vehicle Caster Effect

Caster effect is necessary so that the load of the vehicle is "carried" through the steering axis line formed on the upper and lower pivot points. Positive caster gives a vehicle directional stability because the tire is being pulled along by the load which is projected in front of the center of the tire contact area. This causes a vehicle with positive caster (point of load ahead of the point of contact) to be harder to steer away from the straight ahead position. With Positive caster, road surface variations have a minimal effect on the tire, the tire will continue to go straight. When a tire has a Negative caster condition, where the projected steering axis point of load is behind the tire point of contact, a vehicle will have a tendency to be easier to steer but will lack directional stability. A vehicle with negative caster is affected by any road surface variation such as small road irregularities or bumps. With the point of load pushing the tire along (negative caster), any bumps or road irregularities which are encountered have a tendency to immediately affect directional stability and vehicle handling.


Front Caster Effects
Effects of Positive Caster
Vehicles usually have some positive caster specified since this promotes directional stability, however, excessive positive caster can cause two problems. The first is that excessive caster will cause a high level of road shock to be transmitted to the driver when the vehicle hits a bump, etc. The second problem is that a tire/wheel assembly with positive caster has a tendency to toe inward when the vehicle is being driven. If one side has more positive caster than the other, this causes it to toe inward with more force than the other side. This will cause a lead or pull to the side with least amount of positive caster.

Effects of Caster on Tire Wear
When set with a substantial amount of caster, the spindle travels in a vertical arc, causing it to move up and down and raise and lower the wheels as the steering wheel is turned. Because of this, camber changes occur. With a high amount of positive caster, the camber changes that occur, especially at low speeds in tight turns, cause the tires to show wear on their shoulders. In high speed cornering, the vehicle tends to continue straight ahead when the steering is initially turned. Due to this, and the amount of camber change that takes place when a spindle travels through its arc of travel, the shoulders of the tires on a vehicle may scrub and wear. When a left turn is made at a fairly high rate of speed with a vehicle which has positive caster, the caster of the left front wheel changes toward positive but the momentum of the vehicle is in a straight ahead direction. This causes the inside of the left front tire to scrub as it is turned. Just the opposite effect takes place on the right wheel as the vehicle is turned left at high speed. The right front wheel's camber will go negative but the outside edge of the tire is scrubbed because of the vehicle's momentum to go straight. On some vehicles setting caster more than +2.5° will cause scrub problems.

And caster + camber use in stock car :

http://www.joesracing.com/rt-4189-caster-creativity.html

• Caster is measured in degrees
  Caster is measured in degrees. When a line is extended from the top ball joint through the bottom ball joint the caster line is created. Zero caste would be when the upper and lower ball joints create a line that is perfectly vertical. Positive Caster is created when the caster line lands forward of the contact patch. Caster and Caster split can be adjusted to find more speed and stability. A common example of caster is a shopping cart. As the shopping cart is pushed forward the front wheels spin back and trail behind the caster line.
  
  Caster creates stability as the geometry created forces the wheels back to straight. The front wheels are “encouraged” to stay straight as turning them involves lifting the car weight. Expensive street cars often have high amounts of positive caster providing them with a superior and stable feel. The drawback comes in the form of added steering effort. The invention of power steering has allowed for more caster to be added. When power steering fails it is easy to see the negative effects. As soon as the dripping wet driver gets out of the car and asks for help opening a beer due to his arms being worn out it becomes clear how power steering has allowed higher amounts of caster.
  
  In stock cars, we can use caster to help our cars going beyond simple directional stability. Caster split is often used as a chassis adjustment. Running more positive caster on the right than on the left is common. The question is how much split and how much positive caster should you run?
  
  Caster split and the appropriate amount chosen is one of those chassis adjustments where there is not a magic amount or a right or wrong answer. If you understand the effects of caster split you can make your own decisions based on your track, driver and goals. Commonly crew chiefs run 3 degrees positive on the right side and 1 degree positive on the left side. At times it may pay to run 4 or 5 degrees on the right and .5 degrees positive on the left. It all depends on what you are hoping to accomplish for your specific chassis needs.
  
  An often overlooked element relating to stock car caster is that the more positive caster you run the more “beneficial” camber gain you will get. As the car rolls you will see more negative camber gain on the right side and more positive camber gain on the left in lock step with running additional caster. Camber gain through travel is typically a good thing but like all adjustments you want to avoid going too far. If you are aggressive with A-Arm lengths that create high amounts of camber gain you want to be careful that you do not get to aggressive with caster. As always balance applies.
  
  
• 
  Speed Secrets
  You can find a "speed secret" by understanding that more caster beneficially adds to negative camber gain on the right front and more positive camber gain on the left front. You can check this effect by measuring your camber gain at your current setting and recording the numbers. Next - add caster and check your camber gain again and you will see the benefits visually right in the shop. With the knowledge you can tailor your set up package to overcome obstacles presented by your car, track and driver.
  
  To visualize the benefit of the caster induced camber gain it pays to think in extremes. If you are running 3 degrees of positive caster on the right this would be in the normal range. For our visualization, picture adding caster until the caster line is adjusted an exaggerated amount until it becomes completely horizontal. At this hypothetical and exaggerated point, the result would be pure camber change instead of directional change. The benefit is that with more static caster, the right front wheel would gain more negative camber as steering input is increased. The left front wheel gains more positive camber as the wheel is turned. Cool, we get more camber gain when we need it most by running more caster through a left hand turn! Even experienced crew chiefs can be unaware of the relation to caster and beneficial camber gain in left hand turns. Personally, I find understanding the camber gain from caster to be a true “speed secret”.
  
  Running more caster on the right side verses the left is an adjustment tool that can help cars turn left. The amount of caster split can create benefits as the wheels are turned. More split will “de-wedge” the car at maximum steering input helping the car to turn in the middle. As the steering wheel is un-wound - wedge is added back helping the car to hook up better on exit. Wedge is added back as the wheels return to straight or even back through to the right. You can easily see this change when you have the car on scales. The next time you weigh your car and you have recorded your race ready numbers simply turn the steering wheel 10 degrees left and you will see your scale numbers display less wedge when the wheels are turned left.

Most of Pcars default setup has high caster around 6 - 7 degrees.

 

[ImaRobot]

I was playing around with it yesterday with a controller and the Indy cars and found that it was much smoother with the caster all the way down to 1, my lap times were faster and more consistent than at the default 5 or even 3

Really now? I always stood away from doing that cus I thought it would be too extreme. I'll be trying that out today.

 

[BoneSawTX]

im finding 6.0 to work with some of my tunes. Some of the cars in lower classes I've been around 5.2 or 5.3.

 

[HBR-Roadhog]

I find that when using a non FFB wheel I can tell very little difference between 1 and 6 on the caster setting on most cars. With the controler I can tell a bit of difference as the steering seems less sensitive at lower settings. With a FFB wheel you may feel more depending on if FM6 got it right or not. I know in 4 and those before it never worked the way it should. I did not even realize this until i started tuning for PCars where it is easy to feel even a small change in the caster. A high caster setting makes it much harder to physically turn the wheel and a low setting makes it easier. So with high caster you get a heavy wheel and low caster a light wheel in PCars but I had never felt any noticeable difference in the feel of the wheel weight in Forza 2-4. Some cars do tend to drive better at lower or higher settings depending on the track and the amount of camber being used.

Does this setting make the wheel heavier in FM6 or is it pretty much the same as the older Forza titles?

 

[Motor City Hami]

I spent a lot of time playing with suspensions and caster specifically when I raced remote controlled cars. In that racing, adding castor added faster turn in. With a car that you can pick up with your hands, move the suspension and see every movement, it was easy to see why this worked. The outside front wheel spindle would allow the suspension on that side of the car to move closer to the tarmac and the inside wheel would do the opposite and push the inside wheel down/suspension up. You could easily see the chassis on the inside lift in ride height and the chassis on the outside drop. The more caster added, the quicker it forced the weight shift across the chassis.

For off-road dirt racing, the more we could get, the better because grip on the front was an issue. Get the chassis to move dramatically just by turning the wheel and you could break the rear loose a bit and get right back to power out of the corner. We ran 25 to 30 degrees of caster on dirt.

For banked oval tracks, again, lots of caster on an oval car was 10 vs. 2 degrees for flatter tracks.

I also experimented with caster gain and caster split for oval racing. On flat tracks, I built in caster gain on the outside tire and caster loss on the inside tire and the entire front of the chassis would drop in ride height simply by turning the wheel. I won a ton of oval races with that set up and most people didn't notice the caster split/gain trick. I only shared it with a couple of teammates and we usually finished one, two, three.

As for Forza 6, I am very early into testing, but I did try lowering caster on a loose on entry car and it seemed to help. I only did a few tests and didn't dip below 3. Hoping that the physics remain as real worldish as they seem to feel, this early into the game.

 

[EddyMaroon]

I spent a lot of time playing with suspensions and caster specifically when I raced remote controlled cars. In that racing, adding castor added faster turn in. With a car that you can pick up with your hands, move the suspension and see every movement, it was easy to see why this worked. The outside front wheel spindle would allow the suspension on that side of the car to move closer to the tarmac and the inside wheel would do the opposite and push the inside wheel down/suspension up. You could easily see the chassis on the inside lift in ride height and the chassis on the outside drop. The more caster added, the quicker it forced the weight shift across the chassis.

For off-road dirt racing, the more we could get, the better because grip on the front was an issue. Get the chassis to move dramatically just by turning the wheel and you could break the rear loose a bit and get right back to power out of the corner. We ran 25 to 30 degrees of caster on dirt.

For banked oval tracks, again, lots of caster on an oval car was 10 vs. 2 degrees for flatter tracks.

I also experimented with caster gain and caster split for oval racing. On flat tracks, I built in caster gain on the outside tire and caster loss on the inside tire and the entire front of the chassis would drop in ride height simply by turning the wheel. I won a ton of oval races with that set up and most people didn't notice the caster split/gain trick. I only shared it with a couple of teammates and we usually finished one, two, three.

As for Forza 6, I am very early into testing, but I did try lowering caster on a loose on entry car and it seemed to help. I only did a few tests and didn't dip below 3. Hoping that the physics remain as real worldish as they seem to feel, this early into the game.

Cool. Oval racing setups really are fascinating. I usually increase my caster setting slightly to get a sweet turn-in response.

 

[Motor City Hami]

Cool. Oval racing setups really are fascinating. I usually increase my caster setting slightly to get a sweet turn-in response.

I was in Kevin Harvick's car hauler at MIS a couple of years back. His car tech showed me their tray of shocks. He pulled out a front shock for Bristol and put it on the floor, collapsing the shock all the way in. When he picked up the shock, the shock shaft stayed all the way in and he said it would take a whole day to push itself all the way back out. It was to keep the nose of the car planted on the surface and fight against throttle application on the way out of the corner.