I’ve started tuning a couple years ago (Think I first started tuning in FM6 and have done a lot of it since then) and I think I have a pretty good handle on just about everything… Apart from adjusting caster and tire pressure.
Tire pressure, from what I’ve seen so far on the forums, ranges from “leave it be” to "adjust depending on weight, add this much depending on the car, should be equal on both sides, etc.). Caster is still a complete mystery to me. I know what it is, I know what it does in principle (something something increasing caster creates a heavier steering feel something something, I’m on a controller), but most of the time I don’t touch that either.
It doesn’t help that the default tire pressure settings in FH5 raise more questions from me. In previous Forzas usually you’d aim for a specific tire pressure for every car (i.e. 31 psi when hot all around), but now different cars have different tire pressures by default (think lighter cars have lower tire pressures standard, heaver cars have higher psi).
So I wanted to pose a couple questions to anybody willing to give an answer
- What works for you when adjusting tire pressure? Do you adjust it at all or leave it be?
- Should a car’s weight be considered when adjusting tire pressure in FH5?
- Do you adjust caster? What do you feel for handling-wise when adjusting caster?
Ok, lets get this out of the way.
IRL:
Caster increases the amount of camber as you turn the wheel. It allows you to set a lower base camber and have it increase as the amount of steering input increases. 0 caster has the spindle and suspension in a “vertical” position, as you increase caster the pivot point is pushed forward so the suspension and steering are (from the bottom) pushed forward. Think of it as a pendulum.
That something, something stuff was going to drive me nuts
When it comes to tire pressure, I’ve heard all kinds of stuff. Personally I run 26 front and rear. But I’ve heard of some dropping it to just about bottom without issues. Staggering front to rear can help with a car that is understeery/oversteery, but only a little.
That something, something stuff was going to drive me nuts
Sorry about that, thanks for providing the IRL explanation. 
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I’m maybe mistaken here but doesn’t the caster (angle) simply defines if a wheel gets pushed (neg) or pulled (pos)? It presumably can or does effect camber to a certain degree but I’d say that’s rather neglectable and other effects like for example higher forces (steering thrust) needed with a positive angle or inferior steering return with a negative one and things like this are what this is actually about.
@Godhydra: I never messed with the pressure except for some rare cases with offroad tires. I think you’ll only really notice an effect here if you’ve turned on damage which seems to bring temperatures and wear into play. But that’s just an assumption. I never tested it. I never adjusted caster in this game so far.
When you take the bottom of the suspension (front) and move it’s connection point to the frame forward, it changes the camber when the steering is turned. If done to an extreme amount it can actually turn camber into toe, but that is an extreme case. Caster can affect a number of things including effort (force required to turn), stability, and cornering effectiveness.
This article gives a decent explanation of each steering adjustment (toe, camber, caster).
At the end of the day, how effective it is in FH 5? Meh, effort is not shown unless you’re using a wheel in game. Stability does seem to increase mildly. But it doesn’t really relate all that much in the cornering department.
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As far as tire pressure is concerned, when I’m tuning a road racer I just start with the stock tire pressure since I’ve never seen any measurable effect from fiddling with it. And I’ve never seen any useful effect for varying front and rear for under/oversteer.
Then when I’m tuning camber, using the telemetry heat page, I keep an eye out on the tire footprint’s graphical image for noticeably different heat between the center and the outer edges of the tire, and I’ll adjust up or down a trifle if I’m seeing any.
Caster I just leave alone; nothing I’ve ever done with it has had any useful effect.
Tire pressure makes a difference for me, mainly in the rear.
Sometimes, I want a bit more give in the rear end to maybe get a little bit better slip angle into a turn.
Having the tire pressure increased with the right balance of slip and grip produces that little extra kick out while still in control I am looking for.
Front Camber settings also are something I play with a lot.
When setting the camber, I go to the roundabout at the end of the freeway, and go around it in 1st or second gear, and use the telemetry that has the tire pressure and the camber readings - 4th screen.
The goal is - get the camber as close to 0.00 on the slight negative side - so around - neg -0.24 or so.
With the setting as close to negative -0.00 as possible, that provides the greatest amount of tire contact on the road while in a turn.
If I got it right, I can look at the tire temp telemetry screen and my outside and inside tire temps shouldn’t vary between the two readings more than 10-15 degrees. IOW full tire contact evenly dispersed.
The rear camber usually starts at the standard -0.5 and play with it from there with the goal of slightly loose - just my preference.
Caster - I find that + 0.01 in the front turns the car a hair better, but can make it a bit squirrely sometimes.