Hello all,

While there is generally ample data measuring the effects of power upgrades available to us (eventually!), suspension upgrades are different. Sure, we have some objective data, for example, springs that drop the car 1" or have an X% higher spring rate than stock, but in the end, we have precious little information available that lets us know the actual effects of a suspension upgrade, particularly before purchase, beyond the general "it handles like it's on rails" and the like.

Some of the gurus, including meb, Minihune, onasled, GoWest and others, have correctly warned that there is more to suspension upgrades than meets the eye. Seriously bad things can be done to our suspension geometry with many of the common upgrades available to us. Fortunately (or unfortunately!) our MINIs handle so well that a change in handling "character" at the expense of actual performance is often an acceptable choice to many because the modded MINI handles more to their liking and still handles pretty well, objectively speaking. That's perfectly fine, of course, but I want a suspension upgrade or suspension tweak to expand the performance envelope of the car first and offer a particular "feel" second.

How do we achieve this? Or, for than matter, how might we really understand what any suspension upgrade might offer in terms of performance and feel before buying? Kinematics should help. The more I think about this, the more I realize that we need access to kinematic analysis of our suspension. (links and info are provided at the end of the post)

"That's great, but so what?" you might ask. Well, to make any of the solutions presented at the end of the post useful, we need data regarding the location in 3D (i.e., X,Y and Z coordinates) of at least the following parameters:

FRONT SUSPENSION:

1. Ball joint pivot locations:
a. lower ball joint
b. steering ball joint
c. top strut mount pivot (since it's a Mac strut; allows us to define SAI)

2. Control arm
a. Rear pivot
b. Front pivot
c. Lower ball joint (same as above)

3. Other:
a. Wheel center


REAR SUSPENSION:

1. Control arms:
a. upper: inner pivot
b. upper: outer pivot
c. lower: inner pivot
d. lower: outer pivot

2. Trailing arm
a. front pivot (other pivots coincide with the above two outer pivots)

3. Other:
a. Wheel center

So, how do we get these data? We can rely on ourselves to actually measure the values, but...it occurs to me that auto body/frame shops need most all of this information to ensure a repaired MINI has its pick-up points in their proper locations. Everything we need is probably in tables in a reference manual. Does anyone on NAM own or work in such a facility or know someone who does?

Another option is the racers and serious autocrossers around here. Perhaps onasled or others have already done some or all of these measurements during the preparation of their race cars. If so, they may be willing to share.

I would assume that Nuzzo Motorsports has all of these data, but for reasons of competition, they may not wish to share. Further, they may not have stock, baseline measurements anyway, just their extensively modded values. Might not hurt to ask anyway.


The following values are also important to varying degrees:

• Ride height
• Sprung mass
• Weight distribution front/rear %
• Rear sprung mass
• Front sprung mass
• Total mass with driver
• Unsprung Mass
• Effective driven tire circumference
• Estimated average tire deflection
• Unloaded tire radius rear
• Tire width rear
• Unloaded tire radius front
• Tire width front
• Wheelbase
• Alignment specs given the above XYZ coordinates


With the stock geometries known, we can adjust the following parameters virtually and determine their effects:

• suspension travel
• spring rate
• compression damping
• rebound damping
• front/rear antiroll rates
• ride height
• etc.

Once stock geometries are known, we can also determine the effects of altering those geometries. For example (and this may be a poor example for a host of reasons), we may find that increasing negative camber may be best achieved, though not necessarily most easily achieved, by moving outward the lower control arm/upright attachment point rather then moving the top of the strut inward via camber plates.


There is likely to be omissions in what I have written, but I hope to start a discussion about this fascinating subject and provide a place for these values, once determined, to be "stored" for community use. Once myself or others obtain one of these programs and/or do a lot of Excel jockying, hopefully we can post results to hypothetical queries and offer some advice and direction based on the kinematics to help us all get the most out of our bitchen' little cars.

Thanks,
Jeff


= = = = = = = = = = = = = =

Here are some of the better known, reasonably priced software offerings:

www.performancetrends.com/SuspAnzr.htm
www.mitchellsoftware.com/prod01.htm
www.bevenyoung.com.au/suswin.htm

From what I gather from the the SCCA forums and elsewhere, Warren Rowley's "An Introduction to Race Car Engineering" is a fantastic book that includes a suite of highly developed Excel spreadsheets for kinematic analyses as well.

www.rowleyrace.com/publications.php

Here is another resource (not MINI specific, and not modifiable) that offers a glimpse of what's possible with just Excel:

forum.rscnet.org/showthread.php?t=157180

and here:
http://www.mae.cornell.edu/moonbuggy...uspension.html
http://www.mae.cornell.edu/moonbuggy...ensionizer.xls


For other-worldly coolness, as well as expense, check out Lotus' tools:
www.lesoft.co.uk/

 

Jeff,

A wonderful question! I've looked at a couple of programs...and everything you wrote, in my opinion, requires an answer if suspension tuning is how one's living is made; I am a very curious fellow and my curiosity leads me down paths that are at times successful, but most of the time not. If I had the answers to your questions, would I be more successful? Depends upon my goals. I have so little time these days and sometimes I simply stick my thumb in the air and make an educated guess. Time is a huge factor here for me, not money - well unless you ask my wife.

On the other hand, your thread is one of those gentle reminders that we all need to grow and growing can be painful, read time consuming.

Perhaps, and I think you suggested this so I'll apologize in advance, we should divide and conquer. Tell me what info you want me to provide and it what time frame, and I'll let you know what I can do.

I would also keep this thought in mind; there are several folks within the Mini community - not necessarily contributors to NAM - who thru extensive past racing experience - have setup their Minis successfully. I know a few who turn some sobering times at a few tracks. finding the answers to the questions above for these folks might be enlightening at best. In other words, they may have arrived at the best setup without the info. The buried question in my last sentence is, what you gonna do with the info when you get it? Knowing what pieces are more important than others is extremly important when working with a given, the Mini's basic form is a given. I'm experimenting with big wheel spacers currently. I would like to know how these change the Mini's motion ratios for example, so I can determine how much effectivness the springs and dampers have lost. But, I'm not an accomplished race car driver; I wouldn't know if increasing the spring rate by X would yield a faster car...perhaps it would be slower. Seat time and development are still part of the equation.

Again, I think your question is timely, and of incredible interest to me personally. No doubt, the information would become a handbook useful to many. The process would indeed be rewarding as well.

In a related story...I work with counter top folk who produce granite BBQ counter tops for some of our more elaborate projects. One of these guys uses an on-site plotter to get the shape exact. He sets up three receivers around the basic BBQ and then triggers the plotter as often as the shape requires to get it right.. I've been thinking about asking him if I could borrow this $40,000 devise to plot the location of some of the Mini's suspension pieces. I imagine that once the Mini is on perfectly level ground, the rest would be easy. His info is downloaded to a CNC machine, but I have no idea how to turn this info into a 3D model...but of the points are accurate and relative, these can be incorporated into a kinematics program. I'll ask...

Michael

 

This is all fine and dandy to think a group approach will yield appropriate data but the reality is measurements taken on one MINI don’t necessarily transfer accurately to another. Some examples: The attitude of front control arms can vary, the support brackets can be moved a good quarter inch in almost any direction (except up and down) before being secured; that’s why there’s a bevel in the piece which attaches to the body to give flexibility. The rear frame rails can vary as much as an inch between vehicles; although they don’t hold suspension components they are indicative of the differences in builds. My car has numerous differences between left and right bolt placements. A group install of motor dampers reviled a disparity in engine locations. It seems the human element had a major impact in regards to manufacturing the MINI. How could a standard baseline be established with so many build variables? I’m not trying to dissuade a group gathering of data; I’m suggesting that it would only be representative in general terms.

 

For me, the goal of my query is two-fold: one is to really understand suspension design in general and the other is to obtain practical information for the MINI. In the abstract, the first goal is possible by simply reading Race Car Vehicle Dynamics or Warren Rowley's book (at least if you want the math – other books avoid it like the plague!). However, combined with some MINI-specific data, the abstract understanding of goal 1 can be directly applied to our cars and enable goal 2 to be accomplished.

Like you, time is a very important and scarce commodity for me, and the $120 cost of “An Introduction to Race Car Engineering” is a no-brainer given that it would take me more than 120 hours to put together spreadsheets even remotely like those (that I’ve read) come with the book. No matter how much I’d like to do it myself, my time’s worth more than $1/hour -- at least I’d like to think so! Same thing for the software packages. I’ll probably spend the $300-$500 on one of them, because they’ll help me accomplish both goals, and do so in far less time than if I were doing it all on my own.

And I do think that goal 2, if accomplished, will offer a lot of value to the NAM community. For example, those who have coilovers could find out whether changing a spring rate by +/- 75 lbs/in, 50 lbs/in or 25 lbs/in would be more likely to offer the effect they’re looking for (or, for that matter, assess what effect such changes would cause). Anti-roll bar shoppers may realize that the three-hole bar they’re looking at doesn’t offer as suitable range of adjustment as a competitor’s adjustable bar. Usually they’d just buy the first and hope it’s what they were looking for. In reality it’s probably fine, but why settle for fine when we might be able to have the product that is great for our particular circumstances? This project will hopefully result in fewer purchase mistakes and wasted money.

Your point about racers is spot on. Knowledge, experience, budget, and time can yield a darn fast result. I always wonder, however, whether any particular fast setup simply reflects a “local minimum,” and whether starting from scratch (keeping in mind the “given” parameters you mention) can yield an even faster setup. A crude analogy would be Japanese tuners (as in, those who live in Japan with their smooth roads) utilizing very small anti-roll bars (or none at all) and very high spring rates to control body movement compared to others who rely primarily on anti-roll bars to accomplish roll control combined with lower spring rates. Generally this has to do with surface conditions, etc., but you get the idea -- there are certainly different means to a fast end, but one may really be better for the conditions a person experiences in their own driving. It’s conceivable that we could pursue answers to those questions with kinematics. Who knows, for sure, but it’d be great to give it a go!

Am I a racer? Well, not yet! Do I really need all the information that will be available to us (via the programs and spreadsheets) if we end up obtaining all the data listed above? No. I’m not planning on applying to join an F1 team anytime soon, but I love the pursuit of something so multifaceted and complex as this, and all the more so when it can actually influence my purchase decisions.

As for a division of labor in determining these values, thank you! However, first I’m really curious to see whether anyone knows of a repository of existing data. It’s got to be out there already. The body shop example is enticing to me, but I may be out to lunch on that one. If nobody chimes in, we can certainly discuss the best, most consistent way to make these measurements.

As to k-huevo's excellent real-world point, it won't be perfect, but I would certainly think that either factory specs, as they must exist in some available table out there somewhere, or averaged values will still yield valuable insight. I would hope to do this with a stock car so that a true baseline can be generated.

Jeff

 

dang... lots of reading and not much playing.

i would choose 2 of the most popular setups mentioned in this section
and try it out yourself. from there, your car will tell you what it needs
to meet your specific needs. if you can't tell wat it's saying then more reading
and studying is needed.

 

You guys are way over-thinking this. Forget the street because who cares -- the stock setup is fine. But the track...
There is no perfect setup. Venues change, track conditions change, and on it goes. Take NASCAR racing for example; during practice teams try to pick the right spring/damper combination. But they hedge their bets for the race by tie wrapping rubbers to the springs. They put them in and take them out as needed. They also make tire pressure adjustments as well as adjustments to the track bar all race long.
Just buy products from a company that actually has race experience like H&R, Bilstein, or KW and call it a day. You'll then have time to focus on your driving skill.

 

Kenchan and Don have always told me to keep it simple. I didn't listen...I'm not happy.

I have Race Car Vehicle Dynamics - quite a read.

Let me throw this out there...Don and I have talked about this. A few years ago a spoke with a suspension engineer about damping rates. He showed me 10 dampers with 10 identical damping rates. All 10 however, possesed vastly different damping curves. These curves have the potential to influence ride and roll rates way more than spring selection. The relationship between components is so vital to proper performance. Objective data is also a great thing. But it's those little things between things that are often missed, perhaps not quantifiable, but very important nonetheless.

Don's last sentence is great advise, in my opinion.

 

I disagree. We have a setup that never changes really changes. All we do is minor adjustments (tire pressure, toe, camber, and shocks) Once you get the spring rates and sway bars dialed in, the rest can be easily tuned at the track and there is enough tunabilty to cover most any track condition.

 

What can I say? You are the only person I have ever heard of who holds the view that there is a perfect setup. What are you really trying to say? By the way, those are not minor adjustments that you listed!
Springs are first, dampers second. Sway bars on further down the tunability list.

 

Nice to read someone else believes in this philosophy too...I've written the same thing here a dozen times or so.

Collin Chapamn, by the way, did not believe in rear sway bars. Now, he had an advantage that we do not; he designed the car from the ground up. But we have'm and they are a fine tuning mechanism.

 

yes, it's to pause for a second and think about wat you're doing
before executing it.

 

Ahhh, yes. That would be one of those.

 

pushing cows over will be next....

 

Well, a cow with a very high center of gravity is easy to push over so long as its roll center is very low - there's a bit of education in that response

 

very nice. we need to get him a lowering kit.

better yet, wrap some swaybars on the cow! push push push....
BOING!! NY cow typeJDM.

 

Whaaaaaat?

 

meb:

The plotter idea is terrific -- I've never heard of such an apparatus. If, by some miracle, they let you carry out the project, hallelujah! While we could extrapolate from your measurements and figure things out without it, do you know anyone nearby you who still has a stock S that could be measured as well?

Your damper comment is illuminating and makes me want to send my (eventual replacement) dampers out for some work including damper dyno printouts! Again, is this necessary? Of course not, but if you’re jumping through all the mental hoops to arrive at your well reasoned setup, might as well have the hardware hold up its end of the deal.

dmh:

Regarding driver skill…I am certainly doing my part. Though I get to attend fewer driving events than I’d like, I still try to get to several each year. Living in CA helps as they’re available year round.

Kenchan:

Just make sure you don’t increase the cow’s roll couple too much by lowering him -- it’ll make it even easier for us to tip him!

mini552

What’s your question in particular about that long, long post? Obviously, I’m more than happy to spew forth with my thoughts!

Jeff

 

Don would be the better person to speak with about testing dampers. But unless you are setting up a race car, I believe his suggestion is the best one...unless you are just curious - not a bad thing.

Michael

 

Don,

I forgot to comment on your reply: it is my impression from reading all the coilover threads on NAM that H&R, Bilstein and KW all give a fairly sizeable minimum drop (> or = 1") even when set at their highest setting. I seem to recall that one of them [KW variant 2s?] was well more than 1" minimum). That the Megans allow for stock height is one of the things drawing me to them. If it turns out that a modest drop's roll couple effects take a back seat to the advantages of a lower CG, then the other coilovers may be great for me as well.

To your knowledge, is my impression regarding H&R, Bilstein and KW drop incorrect? I'd certainly give the others some consideration if so.

Thanks,
Jeff

 

What is your goal or intended use with coilovers?

 

Don,

There are two answers to that question, both of which are important to me.

(1) real world: I commute in the car and attend as many track events as I can. Realistically, I can see that meaning a dozen per year, maximum, but it's meant far less than that frequency so far. Darn newborns! Roads are pretty decent where I drive, so having a available selection spring rates would be nice -- that is, I may be able to "comfortably" deal with spring rates higher than those that come with the coilovers assuming that's what the calcs and my butt suggest. 2.5" diameter springs would be nice for reasons of clearance for negative camber.

(2) in the spirit of this thread: I want adjustability. Walk where others have trod, K.I.S.S., and all that. That's great, but I really want the coilovers to have the ability to do (within reason) whatever I ask of them, be it ride height, spring rate, custom valving, etc. I don't want to be forced into a 2" drop; rather, I'd like to arrive there if my tuning takes me there. An anti-roll bar analogy: I'm drawn to the Webb anti-roll bar, which adjusts from less than stock rates to quite a bit stiffer than stock rates. Other bars go stiffer, but what if I end up wanting to go with stiffer springs for primary roll control at the expense of anti-roll bars? Most of the other bars on the market won't allow me to go softer than stock as well as significantly stiffer than stock, particularly with the granularity of the Webb bar. Any one of these changes, be it anti-roll bar changes or changes in ride height, coilover spring rate, valving, etc., may only be something I experiment with and quickly discard, but I want to be able to do it myself.

In the end, I had been thinking that something along the lines of tein, KW v.2, or Megan would address my needs, but it seemed that only the Megans allowed me the ride height latitude I was looking for. I'd be happy to be wrong!

Thanks,
Jeff

 

if you're thinking about TEIN's superstreet coilovers (i think that's wat
they're called) the spring rates are too high.

you'll be back with mushroom problems all over the car.

 

Of course nothing is perfect, I can't think of anything that is.

What I am saying is that mechanical parts such as springs, bars, and shocks should not need to be changed for each track. There should be enough adjustability in the chassis to cater to whatever track condition you encounter (assuming only road courses).

Those tuning measures that I mentioned (camber, toe, shock tuning, and tire pressures) are things that I consider minor, they can be changed between sessions, at the track, and quickly. They also have a very strong effect on altering the handling dynamics of a car if the right adjustments are applied.

I can come off the track with an idea of how my car is handling and then use those adjustments to get it right.

In summary, I know a great setup (springs, shock model (adjustable), and bars) can be found and then other methods can be used to dial those in.

 

ive yet to master the 4 wheel string alignment technique...

 

Jeff and the rest of the gang,

Jeff, in his original post raised some top flight questions on a number of levels:

1) What are the facts about MINI's suspension geometry? Where are the typical roll centers, CG, scrub radius, anti-dive,............characteristics?

2) With enough knowledge, can we calculate a killer setup, or some version of that statement.

3) (implied) Are there pitfalls to avoid or predictable coupled series of suspension mods that we can agree are useful?

The discussion boiled down to the fact that there is no ideal setup and that "killer" setups are perfected on the track thru a trial and error process. The initial setup, however, does require at least approximate knowledge of the suspension geometry so that logical development is possible. Also, certain suspension elements have a vastly greater impact on track performance than others, and hence have a much greater priority in the development process. So much of the rest of possible tuning changes is of little value.

I think that Jeff's questions are still relevant if put a little differently. I'd like a group of knowledgable track oriented people to discuss, agree, and publish what they think are the important suspension characteristics of MINI. Agree on which characteristics are the desired variables to tune. What are the high priority items? Are there linked modifications (e.g. lowering the car and resetting the roll center), etc? So much of this information is buried in bits and pieces in the NAM Forums and simply not readily accessable. This information is also buried in the minds of those responding to this thread and should see the light of day.

The bottom line is that we at least need to consolidate what we do know about the MINI suspension and outline a logical tuning pathway for improved track performance.

Regards,
John Petrich in Seattle