Tony Posted November 18, 2007 Report Share Posted November 18, 2007 We know actual dampening is a matter of taste..... But for the novice who has just installed his 30 (theoretical) way adjustable dampers, how would you advise him to set them? To refine the opinions lets say this car is a domestic RWD with no track intentions. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 19, 2007 Report Share Posted November 19, 2007 Ok this is a massive subject, in the Motorsport and OEM world right now damper development is an absolute hot bed of innovation and development. To answer the question simply, if you've got no information to work yet with just place all the adjusters in the middle and hope like hell the damper manufacturer new what they were doing when they developed these things, that is of course assuming the company involved did any development To explain why I give such a lame answer..... The biggest problem that most novices face when trying to understand dampers (shock absorbers) is that there are very few hard and fast rules and even fewer accurate mathematical formula. All we can say for sure about any given damper is that it'll give you some forces at some speeds (thats shaft speeds, not road speed) The force inside a damper is re-active, that is to say to acts against an opposing force, normally the force is generated by using oil or gas trapped in a chamber and slowing allowing it to bleed away. These systems are sensitive to two main variables Shaft speed Tempreture Most dampers have a fixed relationship between compression and re-bound damping and all that is really adjustable by the end user is volume of the overall damping. I personally prefer these dampers for after market use but only as long as the compression/rebound damping relationship is correct out of the box and that is all down to the manufacturer carrying out sufficient pre-production development. Some dampers have separate adjustment for compression and rebound allowing you as the end user to define the relationship between the two damper modes. Think very carefully before using this type of damper. Are you qualified to adjust this damper? do you have the foggiest what your doing?... Manufacturers love supplying this type of damper because it means they don't have to develop the unit, so in reality that means DON'T USE THE MIDDLE OF THE DIAL THEORY! There are also 3 and 4ways dampers now available on the market, it will take me pages to explain these properly but suffice to say once set up they are excellent, and the main difference from a normal damper is that you have split damping rates for low and high shaft speeds. Like I said at the top this subject is huge and is changing everyday, everyone in the industry seems to have there own idea's as to how damping should be done. hope this helps a bit at least Quote Link to comment Share on other sites More sharing options...
Tony Posted November 19, 2007 Author Report Share Posted November 19, 2007 I am sure those in the position to set the damper ratios will welcome your input Sam.... I do agree with you that the "out of the box" damper-coil option is preferred.... But this leaves a void for the modified car or indeed a car intended for the track. I suppose the best form of attack is natural, then front-rear bias then diagonal bias.... Then test, test and test again Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 20, 2007 Report Share Posted November 20, 2007 Well if we ignore that there is no easy way of quantifying actual damping forces for the moment and just look at the basic principals... The main aim of a vehicle suspension is to eliminate vertical force variations, unfortunately because we live in the real world all we can really do is limit the load force variations. Another main role of the suspension system is to communicate forces from the road wheel to the chassis these include the obvious and desirable tractive forces, lateral acceleration forces and braking forces... often other less desirable forces are accidentally transmitted like acoustic harmonics for instance. These two base roles are contradictory in their demands because for us to eliminate vertical force variations it must be possible for the road wheel to retreat away from any surface deformation with zero resistance. But this would mean having zero wheel inertia, zero spring rate, zero damping and infinite suspension travel. On the other hand for the job of transmitting forces from the wheel to the chassis we ideally want our suspension to be absolutely rigid and inflexible. It is this basic and fundamental contradiction that underlays all vehicle suspension development during which we try to find a "perfect" middle ground of suspension compliance and suspension rigidity... Damping is a significant part of this compromise. Quote Link to comment Share on other sites More sharing options...
Tony Posted November 21, 2007 Author Report Share Posted November 21, 2007 Dampening is a can-O-worms topic i know but here we go anyway......Someone reading this thread may wonder this? Since "out of the box" dampers are subject to testing (normally) so considered a favorable option to adjustable dampers that historically are not subject to prolific testing due to their dampening options, then why isn't adjustable dampers preferred since the owner has the option to address the variables. Wouldn't the chance to perfect the dampening balance fall into the realm of adjustable dampers, rather than fixed "out of the box" units. Quote Link to comment Share on other sites More sharing options...
pbsdesign Posted November 22, 2007 Report Share Posted November 22, 2007 Dampening is a can-O-worms topic i know but here we go anyway......Someone reading this thread may wonder this?... Wouldn't the chance to perfect the dampening balance fall into the realm of adjustable dampers, rather than fixed "out of the box" units. Hi Tony & All, my first post here... I have Koni "yellow" adjustable dampers on the front of my bmw, and Bilstein Sports on the rear, so I might be entitled to an opinion on this one. The Konis are great, and I run them on just a hair (16th of a turn) more than full soft for daily driving. They are still very firm and much harder than stock, but not uncomfortable. The Bilsteins are harder still, actually a bit too stiff for the roads, but do their job well. I chose the koni/bilstein combination with the theory that you want stiffer in the rear so as not to introduce understeer in what was a perfectly neutral handling car, and then could balance it by adjusting the fronts. I'm hoping to buy myself some adjustable rear konis for xmas... So if I were to go on a track day, or to the Nurburgring maybe, one of these days when the car and me are ready (I don't want to trash it yet), I can crank up those konis and have all of the benefit of sport dampers, but still be able to live with it day to day. Adjustable is good I would agree with tdi's remark that I am probably not qualified for any more than a "soft to firm" kind of setting, and given the chance and a perfect bit of tarmac would probably run full firm in the rear and softer in the front. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 22, 2007 Report Share Posted November 22, 2007 Dampening is a can-O-worms topic i know but here we go anyway......Someone reading this thread may wonder this?... Wouldn't the chance to perfect the dampening balance fall into the realm of adjustable dampers, rather than fixed "out of the box" units. Hi Tony & All, my first post here... I have Koni "yellow" adjustable dampers on the front of my bmw, and Bilstein Sports on the rear, so I might be entitled to an opinion on this one. The Konis are great, and I run them on just a hair (16th of a turn) more than full soft for daily driving. They are still very firm and much harder than stock, but not uncomfortable. The Bilsteins are harder still, actually a bit too stiff for the roads, but do their job well. I chose the koni/bilstein combination with the theory that you want stiffer in the rear so as not to introduce understeer in what was a perfectly neutral handling car, and then could balance it by adjusting the fronts. I'm hoping to buy myself some adjustable rear konis for xmas... So if I were to go on a track day, or to the Nurburgring maybe, one of these days when the car and me are ready (I don't want to trash it yet), I can crank up those konis and have all of the benefit of sport dampers, but still be able to live with it day to day. Adjustable is good I would agree with tdi's remark that I am probably not qualified for any more than a "soft to firm" kind of setting, and given the chance and a perfect bit of tarmac would probably run full firm in the rear and softer in the front. Hi, interesting that you've found running the rear harder reduces push. Thats a pretty graphic illustration of how the true mechanisms behind chassis dynamics can be quite unintuitive and how tricky it can be to remain un-subjective as a driver. pbsdesign I can guarantee you that at the grip limit the stiffer of the two axles will saturate it's tires, drop grip and slide first. But right up until that point the stiffer axle will be the more responsive. Everything gets reversed at the grip limit. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 22, 2007 Report Share Posted November 22, 2007 Dampening is a can-O-worms topic i know but here we go anyway......Someone reading this thread may wonder this? Since "out of the box" dampers are subject to testing (normally) so considered a favorable option to adjustable dampers that historically are not subject to prolific testing due to their dampening options, then why isn't adjustable dampers preferred since the owner has the option to address the variables. Wouldn't the chance to perfect the dampening balance fall into the realm of adjustable dampers, rather than fixed "out of the box" units. The answer to this is a resounding yes, but do bare in mind that even a set of adjustable dampers for an EVO for instance will need different damping response curves and different damping rate ranges to an adjustable damper designed for an M5 Quote Link to comment Share on other sites More sharing options...
boo50 Posted November 22, 2007 Report Share Posted November 22, 2007 at the moment i'm be concerned with the same question. my new KW Variant 3 must be delivered in a few days (wating them already over 2 months... ohhh my fastest dealer ), but i don't know nothing about their adjustment. but one good news for me is what KW have recommended settings in the manual for the most users, so i'll try them first. Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 22, 2007 Report Share Posted November 22, 2007 Yep I would advise you do just that, KW are a good company and their kits are properly researched, the advised settings will most likely be a great starting point. Quote Link to comment Share on other sites More sharing options...
yemgi Posted November 22, 2007 Report Share Posted November 22, 2007 I have Variant 3 on mine, brilliant piece of kit I set the damping a bit stiffer than recommended by KW as I like it hard Just modified the rebound after 3000 miles as I found the car too bumpy I have had them on the car for about 30000miles now and they are still in great working order Quote Link to comment Share on other sites More sharing options...
pbsdesign Posted November 23, 2007 Report Share Posted November 23, 2007 Sam@TDi: "pbsdesign I can guarantee you that at the grip limit the stiffer of the two axles will saturate it's tires, drop grip and slide first. But right up until that point the stiffer axle will be the more responsive. Everything gets reversed at the grip limit." Well, it's all about being 'on the limit' isn't it? I mean 95% of the time my car has way more grip than I have balls, and it's just those "on the limit" moments that make you want to mess with the suspension anyway... also I suppose my experience is subjective to the modifications I've made to this car (having always had classics/bangers before): When I first got the car (with factory Msport suspension) I took a roundabout a lot faster than I should have and was treated to a small, but very definite 4-wheel drift, ie neutral handling. I did this a couple of times before I realised that I really needed more grip. So I installed Eibach springs, M3 spec antiroll bars, and the aforementioned adjustable Konis on tthe front, but left the softer BMW dampers on the rear. The result was loads more grip all round, but when I was really pushing, the front would break loose first and give me that dreaded understeer feeling. I think because at this point the whole car was stiffly sprung all round, and that extra bit of compliance at the rear stopped it from getting unstuck. So then I put the Bilstein Sports on the rear (much stiffer than the konis), again I had a bit more grip all round, but now when I'm really pushing or come into a corner too fast, the front sticks and I can feel the rear end just start to creep out, giving me that lovely controlled oversteer feeling that we all crave (or at least I do). That's why I said I would run stiff rear/ soft front. Again, my experience is limited to real world driving on really crap UK roads, so on a track or in ideal conditions the setup might need to be very different to produce the same balance. Cheers, Paul Quote Link to comment Share on other sites More sharing options...
Sam@TDi Posted November 23, 2007 Report Share Posted November 23, 2007 Yep we're actually agreeing here I think, you say that your saturating the rear axle first.... which is the stiffer on your car by the sounds of it. Quote Link to comment Share on other sites More sharing options...
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