Brian, Bryan, JimO, Pat, JimB, et al (the rest of you racer types), can

[frayed]

you guys tell me how important corner balancing is?

I understand the theory behind it, but in real life, I'm curious to know if there is a discernable difference in handling.

In my case, I lowered my car 1.25" all around from stock height. Whatever the original balance, it should be fairly well preserved in my current setup. I know lots of folks with c/o setups, but have not heard of these guys noticing any funky handling traits despite the fact they did not get corner balanced.

One accomplished racer told me that he was able to get the power down earlier after getting corner weighted. But, that's about the most I've hear regarding real-life affects.

I ask b/c it's quite costly in my neck of the woods. It seems that the only guy around here with scales and the know how want $400. If it's important, I may strike a deal with him. . . let me get on the scales, record weights, pay nominal fee, and go home to tinker. If I do that, it would also be good to know general rules of thumb on how cb'ing is affected by ride height changes.

Thanks!

[itsrotary]

Jeff,

I'll take a stab at this. Good balance is critical from a handling standpoint. Assuming you have lowered each corner the same amount then you would be right in assuming the balance has remained the same. However, how well balanced is the car from the factory and can you improve on that. You have not taken into account the effect that the drivers weight, amount of fuel, tire stagger, etc has on weight distribution and therefore balance.

Theres a couple weights that are important to optimize: Static weight (the amount sitting on each contact patch at rest), and cross-weight (more commonly a percentage that compares the diagonal weights, LF-RR, RF-LR, to the cars total weight). Static weight is more or less determined by design although removing things from the car, fuel & driver loads can affect this. Ideally, 50% side to side is the goal. Not too much you can do with this, the only way to change this is to physically move weight or ballast in the car.

Corner weighting - this is what you can change if you have coilovers or adjustable height suspension. Changing the ride height on any corner will change the cross percentage. If you raise the height on a given corner you will increase the weight on that corner and the diagonally opposite corner. You will lose weight at the other two corners.

Always record your cross weights and ride height in case you need to make changes.

As far as hooking up better, getting the power down is probably affected more by the rear weight percentage than corner weighting, which is a function of static weight and design.

Search out a race shop in your area. They'll be the most proficient (hopefully) at using the scales and making adjustments. I pay $70/hr up here for the service.

Will you notice a significant difference? Depends on how close to ideal you are before you start the exercise. A few percentage points will make a difference.

Steve

[frayed]

Hmm, interesting. Did you notice a difference when you had the car properly cornerweighted?

Another note, is that I thought Stock class cars, at least in BMW CCA racing, cannot use c/o's (adjustable height suspension). In addition, one pretty fast guy I know has never had his car cornerbalanced.

What I was trying to get a feel for, is, from factory weighting to more highly precise adjustments, are we talking a few tenths on the track? If so, I wouldn't do it. But, if it has a noticable impact on 'balance' of the car on the track, translating into predictability and driver confidence, I'd do it.

I suppose it all depends on how 'bad' or 'good' it is now. . .

[alexd]

When I lowered my old 1992 325is the guy I took it to is a real pro as far as setting cars up for racing. The first thing he did when I brought the car to him was put a computerized scale pad under each wheel, weigh the car by itself and then weigh it with me in it, he made a few notes and sent me on my way and I picked the car up the next day. Knowing him and his racing and race prep background I would say it is very important.

[itsrotary]

Can't speak to the BMWCCA class rules but in SCCA IT coilovers are allowed (as long as the shock body is not threaded). I use GC's "kit" on GAB race shocks.

Keep in mind my reference point is an IT racecar. Quite a bit of weight was removed, MOVED, and my fat a** added to the equation. Made a difference on my RX-7 that was noticeable. It also gives you a stable, defined platform to base other suspension adjustments off of. The car performs equally well in either direction (requires that you get the weight percentages within .5%, or so I was told). I had Archer Racing do my work.

Again, if you are starting with a well balanced car the gain may not justify the expense and work. As a minimum, and out of curiosity, I'd at least scale the car and find out where your at stock. Base your decision to proceed any further on that.

[frayed]

Steve,

I think I'll do that. Pay a few bucks to get it on the scales, and record the weights with ballast (ie me), 1/2 tank of gas, no spare. Then go from there.

Thanks,

[itsrotary]

Jeff,

Sounds like a good plan. Unless the car is off by a bit, and I would be surprised if it was, I predict you'll find the M3 is pretty close as is for your intended use.

For track days and DE's corner-weighting may not be a necessity. If you were going to race the car it would be one of the first things I'd do.

If you wouldn't mind sharing the info you get I'd like to see your numbers. You can PM me if you like.

Good luck,

Steve

[///Manuel]

Bimmerhaus just made a Koni c/o's install on some of my friend's car, they cornerweighted the car after that. I don't believe it to be critical or worth $400 for that matter, but it's nice to have it you are looking for a well balanced car after some weight reduction, that's for sure.

Jeff, I'm thinking about removing rear seats when going to the track from now on (~50lbs), plus you get to hear more noises (read information).

[frayed]

Just a little more background...

The reason I was asking, is b/c I was contemplating going to a longer length rear spring, killing the rear adjusters, and gaining travel. But, if I do that, I kill my ability to cornerweight, which I have never done. So, I was trying to get a feel for how important this is.

I'm presently getting b/t 2.5" to 2.75" of rear wheel travel, and I may be able to get another 1/4" to 1/2" of travel. More travel = good.

A little while ago, I spoke with a local pro racer, who I've talked to in the past. A great guy, and apparently a helluva tech and hotshoe driver:

http://www.moorespeed.com/about/moore/index.html

David had an E36 M3, and is presently setting up an E46 M3 for hard track use. In connection with the E36 he said two items made a huge difference for the track:

1. solid monoball rear t/a bushings. At the time, there was no aftermarket solution, so machined his own. Other racers have also pointed to the importance of solid t/a bushings.

2. cornerbalancing.

He considered both night and day differences.

BTW, he remains impressed by the E46, stating that from the factory, the balance is better than the E36, and beyond his expectations for a production car.

FWIW. . . .

[///Manuel]

Well if the cornerbalancing happened after everything was stripped out, you betcha it made a huge difference. For a near stock car ... I don't know, I guess it depends on factory settings.
I think it's time for me to update my bushings.
Cool info on the E46.

[frayed]

The cornerbalancing info came from David on his personal street/track car, not a full blown race car.

I gotz some new bushings on the way.

[Scho]

Jeff,

I talked to Autoscope here in town and they quoted me $240 for cornerbalancing and $110 for alignment. I know you get alignments cheaper, but i thought the cornerweight pric was decent. The owner of the shop has a yellow S/C E36 M3 with JRZ suspension. He is a club racer and I am sure you have seen him at Motorsport Ranch.

[Jim O.]

Corner balancing is generally a good idea. However, how you achieve the balancing is important. If you move around things inside your car, like your battery, to even out the weights, it's a good thing. If all you have are the height adjusters, then it can be a bad thing. If you radically change the ride heights on each corner, then you can end up with your suspension pre-loaded, which will make (in my opinion) more of a difference in handling than having uneven cross weights.

With a full-out race car, you can ballast or move stuff around to get equal corner weights, with the same ride height at each corner. You can't really do this with a street car. So, I would suggest that you first get your car on a level pad (set up for whatever your normal use is, with the driver seat weighted, etc.), and set the ride heights equal side-to-side. Then, get your car on a set of scales to see how close it is. If you can get it corner balanced with minimal changes in ride height (like maybe 1/8" max), then corner balance it. Otherwise, I'd just leave it alone...

BTW, 400 bucks seems really excessive. The most I've ever paid for corner balancing was something like 150 bucks, but average was about 75 bucks. Doesn't take a whole lot of specialized BMW knowledge to do, since you have height adjusters in each corner. Since you have tracks in town (or nearby...), I'd guess that you have race prep shops around, or more people with scales who can do the work. I'd talk to some of the real racers, or the SCCA or NASA guys to find out where they have their work done.

Jim

[itsrotary]

Jeff,

I think the benefits of CW'ing can be had in any car. You may not see as great an improvement or it may be less obvious in a street car where other components and set-up are compromised vs a racecar where everything is optimized, or at least less compromised. Besides it can't be too far off stock or the thing would be a ill-handling POS.

CW'ing will eliminate one variable and give you a known quantity and good solid base to work from when making other suspension adjustments. IOW, you won't have to use your adjustments to filter out or compensate for poor chassis balance, they can do what they're intended to do.

Will it give you tenths of a second per lap? I don't know, but I think I'm safe in saying it won't give you as much time as making fewer mistakes will.

If your getting rid of your coilovers then its a moot point. If your keeping them then you might as well take advantage of them and get it done. It can't hurt you (except maybe in the wallet)!

As always, just one man's opinion........

Steve

[frayed]

Thanks guys. I'm full circle on this. Must get on a set of scales to get it checked, then take it from there. I'll be sure to start with precise L - R ride heights before I do.

[GR8 Ride]

Jeff,

I'm going to agree with Jim on this one as well. One of the concerns with corner-balancing a car which is still primarily street driven is that you corner balance it based on adjusting ride height, and not actual weight movement.

As Jim says, you can end up with too much / too little travel in certain corners, and also a *really funky look*, should one corner require massive adjustments. Remember, adjusting ride height in various corners ALSO adjusts your aerodynamics; changes in one factor of performance affect several others. So while you may get your car corner balanced, you can also upset the aerodynamic balance of your car, and theoretically make it worse to drive.

Another thing to keep in mind. If you're not planning on Club Racing your car, and generally you like the *feel* the car gives you, corner-balancing it won't make a significant difference. If you do plan on taking in racing eventually, and you're looking for every 10th you need, then it's a more persuasive argument.

Pat

[hccyong]

Here are the before and after specs for my 318is with about 2/3 fuel in the trunk.

[hccyong]

Sorry, that didn't work for some reason. Let me try again.