hopefully this isnt something that is often suggested but i think it would be really nice to have a roll center point and CG point in the suspension diagram in the garage view.
i think it would really help with tuning and tweaking the suspension for specific uses, rather than the trial and error method i currently use.
bobs VHPA helps a lot in this aspect, but still, more info is needed, at LEAST on the gtr cars.
hopefully this isnt something that is too hard to accomplish
I agree this would be nice, although I think for now you can approximate the roll centre height by extending a line perpendicular to the wheel travel direction line, and seeing where this would cross the centre line of the car.
HAH!
i was right about those green lines then.
the thing is, for a strut suspension, the roll center is actually a very important part of the tuning, more so than a SLA or double wishbone type suspension.
not having upper arms, the roll center on a strut suspension needs to be controlled with huge bars or you end up with funny handling...
of course most cars that have front strut suspension also have live rear axles, not strut rear as well...
in a car with struts on both ends, its not as big a deal, but especially when you have a torque arm rear suspension where the roll center is FIXED at the midpoint of the panhard rod (usually 13-16" off the ground), combined with a strut front where the roll center is usually 1-2" from the ground, you can get some really wacky handling characteristics.
with a SLA or simple wishbone suspension you can put the roll center nearly anywhere you want it so the car will handle however you want. if you have the ability to adjust the spindles, this becomes even more true
[rant]
one thing LFS needs IMO is the ability to do some suspension modifications.
changing the spring rates is all fine and dandy, and the fact that we have weight jackers at each corner is great as well, but in any racing catalog you pick up, there are all kinds of spindles you can choose from to get whatever balljoint height you want. this in turn lets you pick your ride height and roll center height independently.
currently, if the RC is at a reasonable level, the cars look like 4X4's, and if the cars look like they are at a good height, the RC is 2 feet underground, requiring massive roll bars to compensate.
in a real street car, the roll bars are very very flimsy but there is still not much body roll due to having properly engineered suspensions.
LFS is a great physics engine and amazing game, but its still got a long way to go before its a great simulator, and thats why people are always asking for more cars IMO, because the cars we have dont handle right.
[/rant]
i will say that my favorite car to drive in LFS is the XRG
its got enough power to be fun and is light enough to be nimble.
i have the suspension almost perfected, but the car needs bars that are way too big to be realistic.
if it were real life, i'd put 2" drop spindles on it front and rear, then use longer springs to bring the ride height up 1.75" so i would end up with a 0.25" drop
this would put the RC much closer to where it should be, and mean that i could use smaller bars for more grip and a better ride.
it would also give a better camber curve, but lets not get in to that
oh, and to answer your question in fewer words,
in a strut suspension the roll center is mainly dependent on the lower a-arm angle.
the strut inclination angle and steering axis angle also come in to effect, but the major player is the lower a-arm.
if the a-arm is horizontal, the roll center is way underground. the problem is that putting the arms horizontal gives the correct ride height, so you end up with a connundrum
I've seen several websites show a diagram for locating the roll centre of a MacPherson strut like the one I've attached. I have no idea how accurate in terms of scale the garage suspension view is (but if the RC really is well below the ground, it must be off by quite a lot), but when I applied the method I found that the roll centre was above ground. The suspension frequency is ~2.7Hz and ride height reduction is 0.088m.
you make a valid point.
in that case, the roll center is just about at ground level.
however the CG is approximately at the midpoint of the body, slightly lower.
this gives you a HUGE roll moment, or, the distance between the CG and the RC.
the bigger this is, the more the car rolls over in turns.
if the RC was say, at the midpoint of the front tires, the moment would be reduced by half.
the only way to accomplish this is to raise the suspension.
this however also raises the CG and you end up with a circle.
granted the RC goes up faster than the CG, but you also get to a point of diminishing returns, not to mention that it just looks plain ODD to have a 4X4 stance in a car meant for racing.
i never actually did the calcs to figure out where the RC was in the game, i guess i mis-judged based on the calcs i have done before.
as you can see, the angle of the a-arms has a profound effect on the roll center.
in a strut suspension, you only get camber gain when the arms are pointed down.
when the arms are level, the outer one moves upwards as the car rolls over onto it.
however to get the car to sit right in the game, the arms are usually angled upwards slightly