New Dinan Tech Article About Suspension Travel and the M3

[rzm3]

Originally Posted by lucid

If I do end up going for the Dinan setup, and you end up going for the H&R setup, I'd be happy to meet and exchange cars for a comparitive experience. I don't do street racing if that's what you mean though.

Of course not. Street racing is for uneducated folks.

Keep me posted, perhaps a track event?

I already installed the H&R today. Still trying to evaluate the impact. Will post later.

[lucid]

Originally Posted by rldzhao

Keep me posted, perhaps a track event?

I already installed the H&R today. Still trying to evaluate the impact. Will post later.

Not sure how we'd go about objectively assessing the differences on the track as I'm not letting someone else drive my car on the track.

But we could definitely hook up in a BMW CCA track event in the region next season and compare observations though.

Keep us posted about the H&Rs.

[rzm3]

Originally Posted by lucid

Not sure how we'd go about objectively assessing the differences on the track as I'm not letting someone else drive my car on the track.

But we could definitely hook up in a BMW CCA track event in the region next season and compare observations though.

Keep us posted about the H&Rs.

I probably wouldn't let you drive either, but hey, the passenger seat is there for a reason .

[lucid]

Originally Posted by rldzhao

Yeah of course, if you cut a spring in half, both halves will have the same k.

Actually, that is incorrect. The cut halves will each have twice the stiffness of the uncut spring.

[lucid]

Originally Posted by rldzhao

I probably wouldn't let you drive either, but hey, the passenger seat is there for a reason .

I don't know about other BMW chapters, but mine won't let non-instructors ride shotgun in a car driven by a non-instructor. I am not an instructor.

[rzm3]

Originally Posted by lucid

Actually, that is incorrect. The cut halves will each have twice the stiffness of the uncut spring.

You are right... what was I thinking?! Earthworms?

Originally Posted by lucid

I don't know about other BMW chapters, but mine won't let non-instructors ride shotgun in a car driven by a non-instructor. I am not an instructor.

I am sure we can figure something out. Keep us posted on whether you get the Dinan package.

[spyderco10]

Sure is interesting to say the least to watch two Mechanical Engineeners? debate!
Everything past post #1 is over my head. To be honest, more than anything, I think the ride height of the H&Rs look pefect. It's just right, not too high, not too low.

[MysticBlue]

8.9 labor hours. I assume that means if you have your dealer do it, installation will more or less double your cost?

[Gearhead999s]

Just to bring some of my experiance with using bump stops as a tuning tool.When I was racing Solo ! & 2 in the 80's in the class that chose to run,the springs had to be 100% stock but the shocks were free.So the trick was to pack the shock shafts with bump rubbers to limit the travel to increase the wheel rate and by playing with the shock only it was 100% class legal.The nice thing is that using this setup is that you had very easy adjustability for track conditions or balance as needed.It was a terrible steet setup but for the track or Autocross it worked so well that I won 2 National class championships and a regional Solo 1 championship and this was in 5.0l fox bodied Mustang.

[lucid]

Originally Posted by rldzhao

Keep us posted on whether you get the Dinan package.

If I go for it, I will let everyone know. (I am seriously considering leaving this car alone and picking up an early E46 M3 and stripping/messing with that for the track. The mod your street car path is beginning to look very deep and troublesome as I get more and more hooked to track events). Regardles, if do get the Dinan setup, I will also take compression vs force data on the spring that would be going in, the stock spring, and if I can get my hands on one, the bump stop.

[lucid]

Originally Posted by Gearhead999s

Just to bring some of my experiance with using bump stops as a tuning tool.When I was racing Solo ! & 2 in the 80's in the class that chose to run,the springs had to be 100% stock but the shocks were free.So the trick was to pack the shock shafts with bump rubbers to limit the travel to increase the wheel rate and by playing with the shock only it was 100% class legal.The nice thing is that using this setup is that you had very easy adjustability for track conditions or balance as needed.It was a terrible steet setup but for the track or Autocross it worked so well that I won 2 National class championships and a regional Solo 1 championship and this was in 5.0l fox bodied Mustang.

You were effectively retuning not just the spring rate but also the damping then, which makes sense. I doubt that you'd want to stiffen things significantly without modifying damping on the race track either, which is the focus of the discussion. Anyway, I'd be interested in hearing your opionion on any of the aftermarket suspension mods for the M3 if you get a chance to drive a modified car since you seem to be qualified to make a much more accurate real world assessment then I can as a driver. Same request applies to a few other folks on the forum who have significant racing and tuning experience...

[e46e92love]

Originally Posted by lucid

BMW picks the parameters of the suspension system for a general audience, who mainly drive on the street. If one is interested in a more aggressive setup, which won't be optimal for street driving, there is always room for imporvement. However, as you are saying, it is not as simple as dropping some aftermarket springs into the stock setup. If you change one parameter, the others are now out of line, and need to be re-considered and manipulated. Dinan is doing exactly that. Most folks don't get this though. Morever, certain parameters like suspension geometry are difficult to alter without making significant modifications.

This is the one thing no one takes into account. In fact the only after market to even mention this is Dinan. Just makes me nervous to mess with a very well balanced suspension setup without having a suspension expert and more preferably a BMW //M suspension expert having spent a ton of R&D on it; and that means I have to be willing to drop a lot more than a few hundred dollars for springs because extensive and proper R&D costs $$$.

[e46e92love]

Originally Posted by rldzhao

I remember this because spring-mass-dashpot system is one of the most taught topics for a Mechanical Engineer: once in Differential Equations, once in Physics, once in System Dynamics, plus some other labs.

My heads hurt just reading this........

[Gearhead999s]

Originally Posted by lucid

You were effectively retuning not just the spring rate but also the damping then, which makes sense. I doubt that you'd want to stiffen things significantly without modifying damping on the race track either, which is the focus of the discussion. Anyway, I'd be interested in hearing your opionion on any of the aftermarket suspension mods for the M3 if you get a chance to drive a modified car since you seem to be qualified to make a much more accurate real world assessment then I can as a driver. Same request applies to a few other folks on the forum who have significant racing and tuning experience...

Yes we did play with the shocks quite a bit to make it work.To the best of my recollection I had a set of specially valved Koni's on that car.My point is that to properly tune a car the Dampers,bump rubbers & spring all have to be a balanced package in order to properly work.I think that Dinan would be the only way to go if you want a suspension system that works properly.A non-street driven race car is another matter and what works there does not nessarily transfer to a sophisticated performance street car.