Effect of very soft springs with very hard dampers
Hi there
This is more a real life than a LFS question, however I thought the "car setups" forum would be the place to post this.
What would be the effect of a combination of very soft springs and very hard dampers (or "too" instead of "very"). And what would happen if you choose hard springs and soft dampers?
I think Colin Chapman tended to go for soft springs and more damping. You end up with the car softly sprung (which tends to give more grip), and the high damping keeps the movement in check, and stops it from wallowing around.
Hard springs and soft dampers would lead to poor wheel control, as the springs wouldn't be sufficiently damped.
Generally try and run a car as soft as you can get away with, and add damping to keep the wheels in check, and ARB to keep camber control.
That's my basic understanding of it. If I was doing this in real life (which I am, sort of) then I'd do more more detailed research.
"as soft as possible, as hard as necessary" - I've known this.
if the the springs are too soft, wouldn't it take the damper a looooong time to return to its initial point - which would be bad for the next bump or turn?
Yes, if you use too much damping, the suspension will not recover (either at all or before the next bump), so you don't just use 'max' damping But you tend to use a bit more.
If you hit a bump before the wheel has recovered, the car can jack itself down, until you bottom out and nasty things happen. In which case you have too much rebound damping (I think).
I get out of my depth very quickly with dampers, so hopefully someone clever will come and take over from me now
If you are setting up a road car, the dampers are often very soft anyway, so a lot harder wouldn't necessarily be any harder than what a race car used anyway. I'm not sure if going over critical damping would be well advised but if the fast bump/rebound are set a lot lower then the suspension should still do something over bumps (important if you don't want to bounce over the small bumps - not ideal for traction). Sadly in LFS we don't have such adjustable dampers but, even if dampers are not 4-way adjustable, it's usual for the fast settings to be proportionatly lower than the slow settings.
Another consideration is the amount of work the dampers will have to do.
If they are used with very soft springs they won't last as long. Rebound on dampers tends to reduce over time quite a bit until eventually you need to get them re-conditioned.
if you take a roadcar (production car) with a sporty stock suspension and...
A) lower it by just replacing springs (which are usually harder and shorter), you will have all the benefits of a lower center of gravity (which doesn't really affect grip, does it?), a bit more negative camber, but on the expense of damper lifespan (obvious) and the ride will get bouncy and therefore you will possibly have less grip / traction.
B) mount dampers that are harder (and mostly shorter) than the stock dampers (although I don't know why one would do this - maybe because their "better"), you wouldn't have any real benefits, would you?
a) Lowering it lowers the CoG, which reduces load transfer, which generates more grip due to load sensitivity. Lowering the CoG is ALWAYS a good thing! Bit more negative camber could be too much for a road car, as you don't want to replace tyres every 1000km! If possible you could adjust the camber on the top mounts (by replacing them with adjustable ones if necessary). Damper lifespan won't be seriously reduced, but you will have incorrect damping, which will probably be too soft - you probably WILL get less grip/traction, unless you change dampers. What you change them to is a different matter - manufacturers spend thousands of miles testing damper setups to find the right one, so I very much doubt you'll get anywhere near 'correct' in your first half dozen purchases. This is why I dislike ricing (modifying road cars), as you will very very VERY rarely improve on the standard car overall...
b) Improving the damping would be necessary with the higher wheel frequencies. You can do a theoretical calculation for steady state critical damping, but that's only the first 2% on the road to making the car better.
You might just be able to get away with slightly shorter springs of the same rate, then readjusting your camber to suit. Same wheel frequency, lower CoG = damping still about right (maybe a touch soft for racing, but fine for the road 99% of the time) = better, quicker car that won't annoy you when you're not driving like a lunatic (which will be 99% of the time).
In reference to your point A - lowering the car by reducing the length of springs will also effect the suspension geometry which will lead to changes in the Steering Axis Inclination and scrub radius. This can cause all sorts of problems with steering but also roll centres. I lowered a Golf Mk2 with a set of coilovers and initially had major understeer until I raised the front back up again by quite a bit. The problems with steering sensitivity remain owing to the fact the wheels on there have a different offset which also effects scrub radius.
In reference to both your points - you ask what the benefits are when changing to harder springs and dampers. The answer is none, unless you are going to use the vehicle on a nice flat surface like a race track. On the road the extra stiffness results in less tyre contact with the road because of all the bumps you get on typical (uk at least) roads.
Can you explain this in simple terms? I only BELIEVE but don't understand it -
sure. that's why I like those lowering springs that fit every version of your car so much.
Yep. That basically matches my experience. And the twistiest roads are more often than not the bumpiest (which is cool because it feels faster ).
After years I've come to the conslusion: If you want to improve your roadcar's road holding without side effects, invest in good tyres.
But still (I'm not asking this because I want to alter my suspension) I wonder about benefits / drawbacks of "overdamping" (that's having too hard dampers for a given set of springs, right?). Any additional thoughts on this?
I think, in general at least, the best way to improve a road cars handling is simply to increase the rear ARB rate. Most road cars have massive amounts of understeer dialed in because most people don't know what to do in an oversteer situation. This means statistically understeer is safer.
But if you are experienced at driving quickly and can cope with a bit of oversteer, a bit more rear roll bar, especially on FWD cars can result in a big improvement in balance without wrecking the smooth ride road setups give.
Also, a brand new rear anti rollbar can be got for as little as £100 for some cars. Pretty easy to fit too. Worth adding some poly bushes while you are there aswell. Compare this to the cost of coilovers or dampers and you see where I'm coming from.
Lateral Load transfer is a function of CoG height, vehicle track, and lateral acceleration. And I think that's it (there might be one more thing, but I can't think what it is). Changing springs won't change the load transfer, dampers merely change the time taken for the load to transfer, but not the amount etc etc etc.
But the CoG height defines the moment arm causing load transfer. Lowering the CoG will reduce this moment arm, reducing load transfer.
Because a tyre doesn't gain grip linearly with load, they exhibit load sensitivity. Therefore two tyres with equal load (say 500kgf) on each will give more grip than one tyre with 999kgf and the other with 1kgf. This demonstrates that load transfer is a bad thing, and should be reduced - either by increasing the track (or wheelbase if you are looking at longitudinal accelerations), lowering the CoG, or simply driving slower round the bends (which racers don't tend to approve of).
Of course, sometimes tyre load sensitivity can be the lesser of two evils. If you have a car with no anti-roll bars, it will have some load transfer and camber change = x grip. Adding an anti-roll bar will cause more load transfer (takes load from inside and puts it on the outside), which is bad, but helps with camber control which might be double plus good. Net result is more grip, even though the tyre load bit gives you less.
If that makes sense I'll eat... a Twix
Edit: Thus, if your car has good camber control (relative to the road, not to the chassis, like in sliding pillar cars) and sufficient suspension travel (particularly in droop on the outside rear) then you barely need to run any anti-roll bars at all, because the improved grip from load sensitivity reduction more than makes up for it. Might feel a bit weird for the driver though, so confidence inspiring ARBs could be added to make the driver feel more confident.
I know that whichever end of the car has the greater roll stiffness will have more load transfer, so stiffening the rear anti-roll bar will cause more weight transfer at that end (and thus less grip and less understeer/more oversteer), but didn't think the total weight transfer was affected. So stiffening front and rear in proprtion yields the same net weight transfer, but less body roll, so likely more grip from better camber control.
it isnt ... well at least not until you factor in all the differences in camber etc caued by less roll which might lead to a change in overal centripetal force and thus weight transfer
but as far as the simple mechanics go at the same cornering speed the car can be as rigid or soft as youd like it will always transfer the same total amount of load (discounting cog movement due to body roll)
But doesn’t it effect the total rolling resistance? (in benefit of total camber control)
e.g we have a typical understeery setup with higher rolling resistance at the front than at the back.
Not using numbers, just hypotheticaly a clear example. If we put a proper rear antiroll bar so as a result we have same rolling resistance at the back as in the front.
That won’t effect the total rolling resistance?
I think that it would and that’s what I have seen irl… In a friend’s Rover 416GSi model 90’s it’s stock rear antiroll bar was silly soft and the car rolled quite a lot in the corners. We knew that the “better” vertion of the same car, the 416 GTi had nothing more than a harder rear antiroll bar…
We did replase the GSi’s antiroll with the GTi’s and the roll did decrease dramatically. Isn't that normal?
Yes a stiffer rear antiroll bar decreases the grip at the rear but it doesn’t simultaneously increases the front grip? At a turn, because of the increased total roll resistance without hardening the front ARB, the front inside suspention arm, more independently, pushes the inside tire against the road instead of transferring thru the ARB more force to the outside tire. At least that’s the way I understand it.
Anyway in an already netural setup I agree that hardening ARB in both ends gives more roll resistance - better camber control, for the less weight transfer than in any other unbalanced situation.
But in my opinion hardening the antiroll bar in one end of the car, not only decreases traction at that end but also increases traction at the other end.
At the thread's main topic now, too soft springs with too hard dampers, sound to me like a description of an overdamped suspension. I doubt that this could benefit grip in comparison with a normaly damped suspention... unless we are talking about a glass-like flat road with no bumps whatsoever.
But anyway i don't think that any selfrespected damper manufacturer will provide you a product like that.
Yes, as their name implies, anti-roll bars reduce roll. Not weight transfer. It's just the force gets to the outer tyre using the anti-roll bars, rather than using the springs, hence less roll.
I'd agree, although the effect is identical in any case, it's just the magnitudes that differ.
Plus one minor correction - the term is roll stiffness, not rolling resistance (that's for tyres).
a car with too stiff springs and too soft dampers will bounce around like a coked out whore, but a car with too soft springs and too stiff dampers will feel about as lively as a college girl passed out from beer and ruffies.
I am ok with that and thanks for correcting me about the rolling resistance term, this mistake has to do mainly with my bad English
I already agree with that but about what I have experienced irl, yes it is normal or yes it isn’t?
And I completely loose you here.
I can’t figure out how hardening the ARB in one end of the car, doesn’t effect total roll resistance.
Unless you got what I was saying wrong cause of my wrong usage of the term “rolling resistance” so its all my fault.
Anyway I am not asking you to explain it further because it is off the main topic and it may be better to spend your time in something more interesting.
I will figure it out myself. There is plenty of info to search.
wouldnt it still affect the total weight transfer by loweing the overall available grip thus loweing the amount of centripetal force the car can generate ?
Possibly, yes, but I was ignoring weight transfer by body roll and tyre load sensitivity there. Anti-roll bars only affect grip during single wheel bump situations and only then because of the affect on camber. On a perfectly flat track (e.g. autocross arena) you could have infinitely stiff ARBs without negative effects.
But you tend to use a bit more.
-