I was inspired by tristancliffe's post in the General Discussion section to open a technical discussion on dampers. I'll begin with how I think about dampers.

The way I think of it, compression dampers act very similarly to anti-roll bars, but only at the transient parts of a corner (entry, exit, etc.). So, for example, if you're oversteering on corner entry, more compression damping in the front will result in more roll resistance at the front of the car, and thus less oversteer. Similarly, if you're oversteering at the exit, less compression damping in the rear may help to alleviate it.

Rebound dampers are very usefull for keeping the car planted over crests. For example, in the OWRL's MRT season, there was a race at AS1R. I was on Server 1 with the top drivers in the league, yet I led almost the entire race because I tweaked my rebound dampers in such a way that I could take the "Eau Rouge" turn flat out if I hit it just right. Other times I'd have to lift only slightly. With too much rebound damping, the wheels would simply lift off the ground. Too little, and the car would become very bouncy, possibly launching itself even higher. It also meant that I didn't lose much grip on the bump in the tight right hander at the end of the straight.

More recently, I used rebound damping to great effect while hotlapping in the FO8 at KY2. At the exit of the double right-hander after the first chicane, there is a slight crest. I found that I had trouble getting the power down on the exit, so I reduced the rebound damping a bit. The result was much more rear end grip and more confidence to get on the gas sooner.

What have your experiences with dampers been like? Have you found my examples helpful? Do you think I'm completely wrong in my way of thinking? Let the discussion begin.

an easy way for people to think of it is this:
nose down = weight over front end = oversteer bias
nose up = weight over rear end = understeer bias

bump damping affects the suspension on the way down
rebound damping affects on the way up

so for more understeer bias under acceleration, you would reduce front rebound and rear bump.

for more oversteer bias while braking, reduce front bump and rear rebound.


All that said, the main point I am yet to really 'work out' is a good starting range. A lot of the time it seems that most traction under brakes and acceleration can be found with low damper settings. I've been running comparably stiff springs and quite low dampers for best times - this runs completely against any of the 'frequency' style of tuning that some have suggested in the past. On south city particularly, tuning for bump compliance gives much better cornering than tuning for outright peak traction.

Getting a handle on the dampers made heaps of difference to my ability to set up a car to suit me. Being able to adjust turn in under brakes, and behaviour under acceleration, mostly independant of each other is great. (Yes, this can also be done with the clutch pack dif)

My best example was in the old S1 South City Classic. In the chicane there was the tram line and the big step in the road at each side. Hitting this would case the car to jump a bit (a lot) and I found that gradually lower the rebound damping would keep the tyres in contact with the road a bit more and allow a faster exit.

Because the rest of the track was quite 'flat' there were very few side effects as far as I could tell, although it did encourage a bit more oversteer in the last, quick corner. Maybe this was a good thing as the oversteer could be balanced by entry speed and lock, so the corner became 'faster' too (but with a bit more risk).

Quote from Forbin :

I was inspired by tristancliffe's post in the General Discussion section to open a technical discussion on dampers. I'll begin with how I think about dampers.

The way I think of it, compression dampers act very similarly to anti-roll bars, but only at the transient parts of a corner (entry, exit, etc.). So, for example, if you're oversteering on corner entry, more compression damping in the front will result in more roll resistance at the front of the car, and thus less oversteer. Similarly, if you're oversteering at the exit, less compression damping in the rear may help to alleviate it.

Rebound dampers are very usefull for keeping the car planted over crests. For example, in the OWRL's MRT season, there was a race at AS1R. I was on Server 1 with the top drivers in the league, yet I led almost the entire race because I tweaked my rebound dampers in such a way that I could take the "Eau Rouge" turn flat out if I hit it just right. Other times I'd have to lift only slightly. With too much rebound damping, the wheels would simply lift off the ground. Too little, and the car would become very bouncy, possibly launching itself even higher. It also meant that I didn't lose much grip on the bump in the tight right hander at the end of the straight.

More recently, I used rebound damping to great effect while hotlapping in the FO8 at KY2. At the exit of the double right-hander after the first chicane, there is a slight crest. I found that I had trouble getting the power down on the exit, so I reduced the rebound damping a bit. The result was much more rear end grip and more confidence to get on the gas sooner.

What have your experiences with dampers been like? Have you found my examples helpful? Do you think I'm completely wrong in my way of thinking? Let the discussion begin.

I agree with everything in here. Ofcourse IRL top quality dampers have separate adjustment for fast and slow bump. Not in LFS yet though and to be honest I think it might just confuse people.

Quote from Forbin :

I found that I had trouble getting the power down on the exit, so I reduced the rebound damping a bit. The result was much more rear end grip and more confidence to get on the gas sooner.

I reduced the downforce on a FOX (at aston) to 15degrees, and i was spinning on the exit and the entry. Then, i reduced the rear rebound damping, and it worked! BUt I still spin on the entry, so i guess i will increase the front compression dampening.

Quote from wheel4hummer :

I reduced the downforce on a FOX (at aston) to 15degrees, and i was spinning on the exit and the entry. Then, i reduced the rear rebound damping, and it worked! BUt I still spin on the entry, so i guess i will increase the front compression dampening.

Front bump is the place to start but if one or two clicks don't have the desired affect then a click of spring rate or bar can help. If the springs or bars are too soft it doesn't matter how much bump you add.

Most sets I've seen are generally very over-damped. So I'm not surprised softening the damping helps putting the power down.

This is a great discussion, we need more of these!

Quote from Bob Smith :

Most sets I've seen are generally very over-damped. So I'm not surprised softening the damping helps putting the power down.

Would you say a lot of road car setups are too stiff on the springs too? I know I'm guilty of thinking that stiffer and lower will always be quicker, but then I end up making the car awfully hard to handle over curbs and bumps. I used one of my fairly stiff aston setups at blackwood in the LX6 and had to soften it up quite a lot to deal with the bumps.

I often try stiff springs to get a bit of response out of the slower road cars, but it never seems to help, or hinder, much. Stiff springs and soft dampers usually provide quite predictable response over curbs for me - soft springs can sometimes wallow around too much, providing more traction but less directional stability...

Quote from Blowtus :

I often try stiff springs to get a bit of response out of the slower road cars, but it never seems to help, or hinder, much. Stiff springs and soft dampers usually provide quite predictable response over curbs for me - soft springs can sometimes wallow around too much, providing more traction but less directional stability...

I'll go with that.

Michael - definately some road car setups are too stiff but the biggest problem in my experience is people dropping their cars too low and screwing up the roll centres.

Quote from Blowtus :

an easy way for people to think of it is this:
nose down = weight over front end = oversteer bias
nose up = weight over rear end = understeer bias

bump damping affects the suspension on the way down
rebound damping affects on the way up

so for more understeer bias under acceleration, you would reduce front rebound and rear bump.

for more oversteer bias while braking, reduce front bump and rear rebound.

If it really is this simple (the basics) I think I may have a chance. (nothing to add, I even understood very little )

Quote from Michael Denham :

This is a great discussion, we need more of these!


Would you say a lot of road car setups are too stiff on the springs too? I know I'm guilty of thinking that stiffer and lower will always be quicker, but then I end up making the car awfully hard to handle over curbs and bumps. I used one of my fairly stiff aston setups at blackwood in the LX6 and had to soften it up quite a lot to deal with the bumps.

Yes, most road cars that are lowered and stiffened end up MASSIVELY overdamped. Then they fit lighter wheels, and make it even worse. People don't seem to realise that the manufacturers spend millions on suspension choices - it's not the work of a quick afternoon. So why should it be possible to improve it with an off the shelf kit using random wheel for £200 by flicking through a glossy magazine? People just don't know, and think that as it's for sale and has a nice sticker on it it must be good. They forget that the people who 'designed' the kit might not even know what they are talking about.

Edit: Gentlefoots comments about the roll centers is also exceptionally valid.

Quote from Gentlefoot :

I'll go with that.

Michael - definately some road car setups are too stiff but the biggest problem in my experience is people dropping their cars too low and screwing up the roll centres.

Would this be a bad place to start a bit of a discussion about roll centres (something else I know little about!) or should we start a new thread in here on suspension tuning?

Quote from tristancliffe :

Yes, most road cars that are lowered and stiffened end up MASSIVELY overdamped. Then they fit lighter wheels, and make it even worse. People don't seem to realise that the manufacturers spend millions on suspension choices - it's not the work of a quick afternoon. So why should it be possible to improve it with an off the shelf kit using random wheel for £200 by flicking through a glossy magazine? People just don't know, and think that as it's for sale and has a nice sticker on it it must be good. They forget that the people who 'designed' the kit might not even know what they are talking about.

Edit: Gentlefoots comments about the roll centers is also exceptionally valid.

Yeah, I know so many people who do stuff with the suspension on their Miatas, but I'm quite happy leaving mine stock, I'm sure the engineers know what they're doing! In autocross I'm often near the top of CSP guys (the class with Miata's with modded suspension) despite being in the stock category...

Quote from tristancliffe :

Yes, most road cars that are lowered and stiffened end up MASSIVELY overdamped. Then they fit lighter wheels, and make it even worse. People don't seem to realise that the manufacturers spend millions on suspension choices - it's not the work of a quick afternoon. So why should it be possible to improve it with an off the shelf kit using random wheel for £200 by flicking through a glossy magazine?

Manufacturers trying to sell a car to the masses often operate with a different set of parameters to Johnny Corneringfreak though
My own car for instance, although designed to be a highly capable sportscar for it's time, is quite limited in it's ability to put any power down under high cornering loads, with the *cheap* open dif that's in it. It wasn't the dynamics guys who put that there, it was the accountants

Indeed that is the case Blowtus, but my point is that buying one from VauxhallPerformance.co.uk (or whatever, I made that url up) could quite easy be a big pile of crap. Chances are they just bought any old diff, welded on the correct flanges and let it be (ok, so maybe a diff is a poor example). Manufacturers go to extreme lengths to get what they put on the car right - they don't decide the car isn't sporty enough and bolt on some stiffer springs and be done with it. Which is what Johnny Corneringfreak will do - the chances of it being an actual improvement are slim to none.

Quote from Bob Smith :

Most sets I've seen are generally very over-damped. So I'm not surprised softening the damping helps putting the power down.

Sometimes my first racing setup advice that is . . . soften your springs.

Maybe alright for an alien on hotlapping duty but for Joe Bloggs having the car stiffer than a vicar in an all girls convent just doesn't help.

IT's all about wieght transfer. Too much understeer? Too much wieght staying on the rear. Too much over steer? Too much weight transfering to the front. But is it under braking, cornering or accelerating. Change a damper setting for braking balance and you upset the exit. Oh, what to do, what to do.

Don't forget though, you don't just have bump settings, you also have rebound settings. I raced the FZR predominatly and that responded very well to adjusting the rebound dampers as much if not more than the bump dampers. The FZR needs a setup that can keep that big arse in a straight line and I found under braking having a high rebound damper setting on the rear allowed the rear to balance against the need for the front to 'duck' to allow effective braking.

Learn to fell your motor vehicle. Whilst testing allow the car to repond to your inputs without you correcting as you would in a race, then you can adjust any 'bad' traits out and balance your car correctly.

It does strike me sometimes that when racing the WR sets you are constantly fighting the car for control. While racing, especially longer distances, requires sets that almost allow the car to drive itself. You need to look after it and for that you need setup sympathies otherwise you will always find yourself outclassed.

It doesn't take long to learn how to setup. So I wold reccomend anyone to give it a try and learn.

Quote from Michael Denham :

Would this be a bad place to start a bit of a discussion about roll centres (something else I know little about!) or should we start a new thread in here on suspension tuning?

It might be an interesting discussion for those that know a bit about it but TBH without diagrams, the discussion would be useless for anyone trying to understand roll centres for the first time. You can't really explain it textually but with a diagram it's easy. For example I could say "The roll centres are calculated by taking a line inboard, at 90 degress from the top of the Steering Axis Inclination. Extend the line of the lower arm inboard and where the two lines cross is your roll centre." Now I know what I mean but I bet no one else does.

Quote from Gentlefoot :

It might be an interesting discussion for those that know a bit about it but TBH without diagrams, the discussion would be useless for anyone trying to understand roll centres for the first time. You can't really explain it textually but with a diagram it's easy. For example I could say "The roll centres are calculated by taking a line inboard, at 90 degress from the top of the Steering Axis Inclination. Extend the line of the lower arm inboard and where the two lines cross is your roll centre." Now I know what I mean but I bet no one else does.

Something like this?
http://e30m3performance.com/my ... _Transfer/roll_center.jpg

/mike

Quote from mike20002 :

Something like this?
http://e30m3performance.com/my ... _Transfer/roll_center.jpg

/mike

Spot on! That illustrates my point perfectly.

Quote from Gentlefoot :

Spot on! That illustrates my point perfectly.

Great ,
Question:
How do I know if my roll center is too low or high?


/mike

Quote from mike20002 :

Great ,
Question:
How do I know if my roll center is too low or high?


/mike

It's not so much where the roll centre is as how much it moves in bump and droop. I told you its complicated.

I read in The Race and Rally Sourcebook - Staniforth that the roll centres are the point around which the cars pivot. You obviously have one front and one rear.

Imagine this, take and empty box of matches and a skewer. Make a hole in the middle at the front and one at the back of the box and push the skewer through. The matchbox represents the car obviously and the skewer represents the point around which the car rotates. The holes represent front and rear roll centres.

Rotate the skewer and see the effect on the matchbox. Then, take another matchbox and make the hole at the front near the top and the hole at the back near the bottom. This simulates having a higher front roll centre than rear. Now rotate the skewer and see how the rotation of the matchbox/car is influenced by the change in position of the holes.

This is the beginning of the stuff you have to think about when considering roll centres.

A general rule is that the lower, softer end of the car should have the lowest roll centre. But as I said before, it's more about where the roll centres move to in bump and droop. Although I read that rule and it didn't make much sense to me as you could have the softer end of the car being the higher end.

I really am no expert in this area and have found it really difficult to find anyone who is. Hopefully someone who knows a bit more about it will turn up. I reckon Tristan might know a bit more than me.

Nope, you're pretty much at my limit (I learnt a lot from Staniforth too ). And as you say the softer end of the car should try to have a lower static roll center. But the instantaneous roll center can move, not just up and down, but also left and right. A Formula one car might have an instantaneous roll center below ground level several tens of yards to one side of the car at one moment, and only a few yards long and 6" from the ground a few seconds later.

Gentlefoot - do you get Racecar Engineering? A couple of issues a go there was a good article on roll centers (and mainly how they apply to solid-rear-axle cars). I haven't actually read it myself yet, but my Dad has recommended that I do.

One day I'd love to be able to understand everything about suspension analysis, but right now I'm still at the level you are - pretty good, but not 100%

Quote from tristancliffe :

Nope, you're pretty much at my limit (I learnt a lot from Staniforth too ). And as you say the softer end of the car should try to have a lower static roll center. But the instantaneous roll center can move, not just up and down, but also left and right. A Formula one car might have an instantaneous roll center below ground level several tens of yards to one side of the car at one moment, and only a few yards long and 6" from the ground a few seconds later.

Gentlefoot - do you get Racecar Engineering? A couple of issues a go there was a good article on roll centers (and mainly how they apply to solid-rear-axle cars). I haven't actually read it myself yet, but my Dad has recommended that I do.

One day I'd love to be able to understand everything about suspension analysis, but right now I'm still at the level you are - pretty good, but not 100%

Staniforth eluded to your point about rollcentres being 10s of metres to one side of the car. He didn't really expand though which I found rather annoying. He just kinda dropped it in to tease us.

No I haven't seen that publication you mentioned but it's sounds like just what I should be reading. Solid rear axle cars - perfect for my Golf setup. I'll try and get hold of a copy.

Never really got a response to the query of 'where do you start, how do you get in the ballpark' etc, for damping. Anyone got any suggestions? I have good feel for tweaking transition balance with the dampers, but in general I just seem to like quite fast (low damping) weight transfer, so start with lowish settings (rebound slightly more damped than bump, this is normal yeah?) and go from there. Suspension frequency and notions of 'under or overdamped' never really seemed to work for me when I tried in the past.

To get a general starting point for the rebound dampers, this is what I do:

-go in the garage, hit "drop"
-note the car's movement when it settles
-does the car settle really slowly? less rebound damping
-does the car move up very fast and overshoot the settling point? more rebound damping
-does the car come up nice and fast and not overshoot? perfect

For compression damping, I usually just stick with the Race_S defaults and go from there, though I do usually end up softening them quite a bit in the end. On super bumpy tracks like SO, FE, and AS1R, I'll use the least possible compression damping.