When should I upgrade suspension components?

[NoSoup4U]

Let me be more clear (ala last thread where I didn't provide enough information for some people : ).

I currently drive a 1999 M3, OBD-I converted, stage II AA turbo, 8.5:1 CR. Lo-boost is 6.5 lbs that yields 322 rwhp and 297 ft*lbs of torque, SAE corrected on a LOAD dyno and not an inertial one. At hi-boost of 13 lbs, I do not use on the track, so I doubt this would have any effect on your answers below. I only use lo-boost on the track.

I have not touched the suspension other than rear bilstein shocks. I kept my front end stock boge. I am currently doing auto-x and HPDE's. I probably will end up completing around 7-8 HPDE's this year. I've already completed 3 so far this year. Auto-x ... well ... I am not as sold on it yet ... but, I plan on doing at least 5-7 auto-x events with 2 completed, another scheduled for tomorrow and the following weekend. So, this is a pretty good year for me as far as participation in events for a weekend warrior.

I have not added aftermarket springs or suspension components such as KA, PSS9, tckline, etc...etc... I've read most of the threads you guys post; but, it seems some are ripping incredible times on stock suspension ... so why do some of you guys upgrade the suspension???

A) Why would I want to use aftermarket springs??? What is the benefit of having the car lowered?? Does it give it a better center of gravity, help it turn in quicker, etc...??

B) Why would I want to use aftermarket shocks/struts?? Yes, Boge might not be the best ... but, it's hella cheaper than aftermarket PSS9's, etc... What benefit does it give me using aftermarket equipment??

C) Maybe this is a misconception on my part; but, I thought one of the more ideal modifications that I could do is purchasing rear camber adjusting arms or KMAC front camber plates . I thought the amount of toe/camber could greatly affect the car's ability to handle ... so why do some of you go after the suspension rather than alignment configurations??

It seems that many people throw on bilsteins/tckline/Koni's etc... but, don't touch alignment at all ... why is that???

I guess I don't want to throw money at something just because everyone else says I should do it. If I can't handle the car at 10/10th's in stock suspension format; why bother upgrading is my thoughts. Is this a wrong rationale that I am employing?? Should I upgrade???

I might need new Boge shocks soon, hence the barrage of questions .... Plus, please keep in mind my torque kick, with a stiffer suspension, I wonder if I am hurting myself over all ... isn't a softer suspension easier on the chassis/rear subframe, rear diff. bolt ... with the amount of power I'm putting down???

TIA!!

[zenon]

A bump for james

I have this book:
http://www.amazon.com/exec/obidos/tg...glance&s=books

I found it to be (a few years ago when I read it) a good general overview to give you a good understanding of the basics.



BTW Who's the guy that wrote all those grat suspension books? I thought it was Carroll Shelby but I can only see 2 titles by him @ amazon

[segal3]

Fred Puhn?

~Matt Segal

[zenon]

thanks matt


actually one of the book names came to me... race to win.
http://www.amazon.com/exec/obidos/se...889940-6532118

its Carroll Smith.

[simonh]

A) Why would I want to use aftermarket springs??? What is the benefit of having the car lowered?? Does it give it a better center of gravity, help it turn in quicker, etc...??

Exactly, the car will do all these things better with an aftermarket suspension, including better braking

B) Why would I want to use aftermarket shocks/struts?? Yes, Boge might not be the best ... but, it's hella cheaper than aftermarket PSS9's, etc... What benefit does it give me using aftermarket equipment??

Generally the aftermarket ones are going to be better but like you said you are going to pay for it

C) Maybe this is a misconception on my part; but, I thought one of the more ideal modifications that I could do is purchasing rear camber adjusting arms or KMAC front camber plates . I thought the amount of toe/camber could greatly affect the car's ability to handle ... so why do some of you go after the suspension rather than alignment configurations??

Good question, you should always get an alignment done after touching any suspension parts. Its also a cheap way to improve the cars handling, get rid of understeer etc. If I could only change one thing on the suspension it would be put in front camber plates and then get a good alignment Don't ask what settings I use though, I have no idea, I don't set the car up.

I guess I don't want to throw money at something just because everyone else says I should do it. If I can't handle the car at 10/10th's in stock suspension format; why bother upgrading is my thoughts. Is this a wrong rationale that I am employing?? Should I upgrade???

I think thats a good rationale, its upto you really, the car will handle better with the right aftermarket bits, but it is not going to make a hugh difference like some people believe. I guarantee you that a good driver can smoke someone in a stock car compared to one with a nice suspension. Gettting some camber in the front would be nice if for no other reason than to wear the front tires evenly and improve turn in, get rid of understeer etc. You'll be able to learn just as much on your stock suspension, you will have more body roll but I think you will still be surprized how fast you can go, you just have to wait a little longer to let the suspension take a set after that it will corner pretty damn fast.

I might need new Boge shocks soon, hence the barrage of questions .... Plus, please keep in mind my torque kick, with a stiffer suspension, I wonder if I am hurting myself over all ... isn't a softer suspension easier on the chassis/rear subframe, rear diff. bolt ... with the amount of power I'm putting down???

I would think the softer suspension might help some, especially having stock bushings. I'm just guessing here I have no idea really :12:

Anyway if you're concerned about money definitely leave the suspension alone maybe just replace the boge's with bilstein's to match the rears. Then add some washers to your lower strut to get some free camber. Its just like sway bars everybody buys them but I don't feel like they do much for you especially if you have a good shock/spring package. And then you have to reinforce the sway bar mounts because of the bigger bar. Anyway hope that helps some.

[zenon]

I've heard that the 5 small holes in BMW wheels are to mount the car to a laser alignment machine. If that's even true does this method net you much real precision?

[frayed]

The five holes are for the alignment heads on the factory alignment machine used by BMW for their cars: the Beisbarth machine. Not sure if they are laser or not (can't recall, as I've had two alignments done with that machine), but it's very accurate based on their calibration utilizing the hub as a reference point rather than the wheel.

In addition, perhaps more importantly, they don't rely on rotation of the wheels for calibration, but the static position of the hubs. This is significant b/c rotation of the wheels for calibration requires unloading of the wheels, which most often does not result in return to static ride height.

[zenon]

so the holes go right through then?

very cool, thanks jeff.

[NoSoup4U]

What is the maximum amount that I can affect in front camber without plates???

With washers what is the maximum amount?? How many washers do you guys use?

[BJO]

i've used 1 washer per bolt. it gave me around -.5 degrees negative camber at each corner.

[frayed]

zenon, yup holes all the way through.

Soup,

Alignment: all the camber/caster plates on the market have plusses and minuses. Mainly, no plate has the durability and NVH levels of stock. Problem is, of course, they ain't adjustable. So, I swapped them left right and got lots of camber. I further trim camber with washers.

The rear adjusters typically have enough to get what you need for the track. I can get anywhere from 1.5 to abotu 2.3 or so. Toe, of course, is factory adjustable.

Springs: Lower center of gravity, add roll stiffness to limit unwanted camber changes and limit bumpsteer, and improve transient response, as car doesn't take as long to 'take a set'.

Dampers: I'm not a big fan of Bilsteins. Too much compression damping. By going with them in the rear but not the front, I'd be concerned about oversteer issues caused by all the bump valving. Some people love them though, but I've not had great luck with them.