After a couple of weeks of agnoising over which springs & dampers or coilovers to get, I could really use a little education...

-What does rebound adjustment do and how important is it?
-What does compression adjustment do and how important is it?
-If I purchase a set of coilovers (say KW V2 or 3), can I adjust the spring rate or purchase new springs for them? For example, the megan coilovers seem to offer a lot of features for the momeny, but the 6/8kg spring rates put me off.

I've done a few searches on this and the MINI2 forum but haven't turned up anything usable so far.

As a further discussion point, which is likely to perform better - some good fixed dampers, or some rather more budget, but adjustable ones?

I'm sure I'm not the only one with these questions...

 

don't be afraid to run stiff springs. I have AST Coilovers with 6.1 kg/mm springs all round. Now, if i run them on full soft, they are just as compliant as stock. But if i run them on full stiff, they can break your back

A stiff spring can still ride well, as long as the matching of the spring and shock is done well

 

Thanks for the input etalj. 6.1kg is pretty hard though mate, not sure my shock towers would survive all that long on some of the black forest roads we drive on over here...

Any idea about the adjustable damping? Necessary? Gimmick? Do you ever use yours?

 

yeh for sure, i use it all the time, but i love modding the car. Full soft is great for long journeys, and also for wet days.

Also, depending on what sort of driving you're in the mood for, you can set the car up however you like. You can also dial in more stiffness front and/or rear, so you can make the car more or less tail happy.

Yeh, i'd also suggest getting some camber plates. Can't do without them. I'd probably say these are the first suspension mod i'd do along with the rear swaybar. The MINI's badly need some front camber.

 

so setting a softer compression and rebound setting has a noticable effect on ride and handling?

Surely the stiffness of the ride can't be much improved if you're still running the same springs?

I was always under the impression that the springs soak up the bumps and that the dampers are just there to dictate how quickly the process occurs, i.e. stiff damping means wheels react slowly to bumps and compressions, soft damping means they react more quickly. Is this not the case?

 

yes of course, damping force is velocity-sensitive.

My shocks are only single adjustable (which means that the compression and rebound setting are set in a ratio (probably 3:1 or something like that). A double adjustable shock is overkill for most drivers, but by all means that doesn't imply that no-one should own one. I just think one ought to be confident in what they are adjusting....

bump/compression stiffness is the damping while the wheel goes up and the body stays level (or body goes down and wheel stays level, same thing). This happens if you hit a bump, or under brakes (front wheels in compression). You want the compression stiffness relatively high. If it's too low, not much energy is absorbed and the wheel will bounce off the ground.

Rebound stiffness is the damping while wheel is on its way down (from say, a bump). You want rebound stiffness to be relatively low, because you want the spring to expand quickly enough to be able to keep up with the stiff downhill slope of a bump. if it's too high, the spring doesn't expand quickly enough to keep up with the slope and the wheel isn't touching the ground, (in an extreme case).


Think about it like this. You're driving over a series of very close and very small bumps. In a softly-damped car, after you hit one bump, the wheels is still rebounding and will probably finish its rebound stroke on the 2nd or third bump. It's as if you're ignoring every second or third bump. But on a stiffly damped car, the rebound stroke is much faster and thus will catch every bump. (Unless you stiffen up the compression stiffness so that one of the bump throws the wheel too high in the air to effectively miss a bump). :P

Anyways, a spring absorbs the bump temporarily, but (theoretically) loses no force. The damper absorbs some of this force, and allows the driver to control how quickly he or she wants the spring to bunch up or unwind. The stiffer the spring, the more force it takes to compress it the same distance, which means that some bumps won't be absorbed. Say for instance you hit a small bump with a soft spring. The body barely moves, as the spring is displaced a little bit, and the resulting force is also small. Now, if you hit the same bump with a very stiff spring, the tiny displacement of the spring results in a force 2 or 3 times larger than the soft spring.

 

crikey!

So in simple terms

- smooth roads = stiff damping
- bumpy roads = soft damping

That about right?

 

that's right.

If you don't understand anything from my long-winded previous post, just ask and i'll try and explain better

 

actually I think I just about got it (in the simplest terms possible).

I notice you're using Nolte camber plates up front - how are they working out for your? What's the range of adjustment and do they raise the front end like some do?

 

Fully Adjustable coilovers (IE: height, rebound, and compression all individually adjustable) are great for being able to dial in and fine tune the car's setup. However, if you don't like doing that and have no need to, then it would be a bit unecessary and costly to purchase a set like that.

If you are going to just be using the car for spirited street use/daily driving/occasional track, then your best bet might be to go with just some good height adjutsable coilovers. That way, you can just hop in and drive for the most part. But by all means, if you want to be able to really dial in and fine tune your setup, the options are out there, but they will cost a bit of $$$.

 

Good advice astro - I can't see myself messing about with the damping too much, and would probably only make things worse if I did!

Mainly I want them to allow me to get the right stance and to allow me to change the height as I add and remove bits n pieces on the car.

Thing is though, I gotta pay about 500 bucks fitting whatever I do so adjustables aren't that much more expensive in total, in the same way that coilovers aren't that much more expensive than plain old lowering springs.

Tough choices!

 

Keep in mind, that those fancy dual adjustable coilovers and such are really meant for racing use. It is total overkill for street use. There is a school of thought that says the more adjustment you have the more ways you have to screw things up if you don't have the knowledge about how to set it up.

Racing teams have race engineers and enthusiasts have many hours spent in educating themselves on how this stuff works so they can be competitive in a race situation. Really no point in all that for street use.

That being said, some nice adjustable Koni shocks are cool b/c you have a little bit of adjustment that you can use to tailor the suspension to your tastes. If you plan on doing a track day, stiffen them up. If you are just crusing on the street, soften them up a bit. If you know you are going to go to an area with lots of bad roads, run them full soft.

There are some good books on the subject of suspension tuning that you should read if you want to go that route. Searching forums for posts from people who might not necessarily know what they are talking about, isn't the most winning strategy. I could be a kid who has only been driving for 2 years or I could be a racer who has been racing for 20 years. How do you determine quality of the post and whether any of the info the person posting is correct?

 

right you are PG3, gotta be a bit careful what you believe on a forum, but on the whole it's a pretty great place to start.

What are the titles of these suspension books then, I'd love to school up about it.

 

I'm a kid that's only been driving for 2 years, so maybe you shouldn't listen to me

The Noltec i bought off a guy who only used them for a week before selling his MINI, and they've been quite good to me. So far i haven't been able to tell what the range of adjustment is as the adjuster **** on my coilovers is hitting the edge of the strut tower. I'm going to trim that today and see if i can get the 2.5 i want. At the moment i have -2 deg up front, and when i had stock shocks and springs, i had -1.5 up front.

My plates were obviously thicker than OEM, so i'd say it probably raised it, though not enough that i'd actually notice it with my eyes

 

http://www.amazon.com/review/product...owViewpoints=1

I linked to the reviews for this book, "Race Car Vehicle Dynamics." Read a couple of reviews before looking at the price.

I've been told it's THE book to read regadring vehicle handling. A good friend of mine who is a Ride Control Engineer for a large Automotive supplier won't shut up about it.

 

Here are 2 good choices from H&R.

RSS Club Sport
http://www.outmotoring.com/mini-coop...ni_cooper.html

Standard Coilovers
http://www.outmotoring.com/mini-coop...coilovers.html

The RSS system is a bit more agressive and allows lowering from 1"-2" all around.

The Standard version is a bit softer, more designed for the street and allows lowering from 1"-1.5" in front, and 0.6"-1.5" in the rear.

Both are fixed as far as rebound and compression go, all you can do is adjust the height. However, you can always swap out the springs down the line if you want a different rate.

They are very easy to install. 3 bolts hold the entire coilover assembly in place, so you just have compress the springs, and then you are all set.

 

Here is the how-to for a spring install. It is essentially the same thing for coilovers.

https://www.northamericanmotoring.co...ad.php?t=30575

 

If you are still looking, Megan Coilovers are a good bang for your buck. Your average moron (me) can install them. And they have camber platers, damper adjustment, and ride hieght adjustment. Dustin at AutoXCooper.com (AutoXCooper here on NAM) can give you some insight more ont he technical side than I can if you want.

 

Rebound should be somewhere about 1/2 to 2/3 stiffer than bound - very generally.

Spring and tires are the shock absorbers. What we call the shock is more appropriately called a damper because its function is to dampen the oscillation of the spring and tire - the tire being an uncontrolled spring at some level.

I don't think there is any absolute criteria for matching springs and dampers, but there are plenty of bad 'criteria' in use.

Koni yellows, for example, reach their limit - so I'm told and have found thru experience - with 400# springs. This is infor from Koni and TrueChoice. Heavier springs ask the damper to work beyond its design to control the spring's oscillations; the oil may not have the correct viscosity for a higher rate spring and may therefore break down quickly since it may over-heat. Some of the internal components may not be designed for heavy springs. And so, it is also true that dampers designed to work with 1,000# springs will not work well with 400# springs.

Each damper has a limitation, a range if you will, designed for a specific purpose/application/market.

Also in general, a damper that is too strong for a given spring will cause the car to feel a little lazy since the spring is being controlled too well. The opposite is also true. On the other hand, some dampers have such a huge range, they can cause incredible nervousness if set at high settings. And the adjustment ranges are not necessarily linear; a setting half way between full hard and full soft may in fact represent a damping force/curve that is 1/4 of the damper's high setting. And the ratio of bound to rebound adjustment in single adjustable rebound dampers should be known.

Damping curve and damping force are two criteria that determine how a damper will feel; you can have two dampers with indentical damping force yet, with completely different damping curves. Each will feel very different.


You really have to decide where you want to drive and then pick a system that works with that venue. If you buy a spring from one manufacturer, you should be inquisitive about about the damper's ability to work with that spring. If you buy a spring/damping system from one manufacturer, you should at some level getting an engineered system...not always true, unfortunately. You can always have your dampers tested and the results will give you some information to work with.

My adivice is to keep it simple on the street. A street/track compromise is about the worst place to end up...but that's where we all go...at least once. 400# plus springs are pretty stiff on North Eastern roads...

I know nothing about progressive rate springs...very hard animals to follow.