Anyone ever 4 corner balance a 540i?

[topaz540i]

Im interested in what the ride height difference is between the front and rear to get near 50/50 balance.
the prob is that its not as simple as making the fender gap even front and back. With 50/50 balance the rear will actually appear to have less fender gap than the front.

[rf900rkw]

I've weighted a few cars over the years. You will not make any appreciable difference in the front-rear distribution by changing the rake a few mm. But it is very easy to dial in a ton of cross-weight and not know it.

[edjack]

Go to a public scale, and weigh each wheel separately. Slip the guy $20.

[topaz540i]

Road side weigh stations can do individual weights?

[JimLev]

Road side weigh stations can do individual weights?

Sure, just make sure you only have one wheel at a time on the scale.
Now seeing that your are in Jersey you may have a hard time finding a truck stop what has a scale that is free long enough for you to do all 4 wheels, add weight, and then re-measure the corners again.
Some junk yards also have scales.

[geargrinder]

Sure, just make sure you only have one wheel at a time on the scale.
Now seeing that your are in Jersey you may have a hard time finding a truck stop what has a scale that is free long enough for you to do all 4 wheels, add weight, and then re-measure the corners again.
Some junk yards also have scales.

metal dealers too. interested in this since I just did the CO's but we've not finished the ride height. FWIW the KW/ST kit rear links don't go that super low even wound all the way down. See the pics I posted on my other thread... I'll have to either do final adjust with software, or, mod the links, otherwise I'll have a lot of rake... actually seems like mebbe I've heard of that being an issue for some of the KW/ST guys...

BTW JimLev - would love to connect and see yer car some time when you're around.

[Justin517]

My buddy has corner weight scales for his hill climb car.

I decided that messing with them was more of a fiasco/headache than its worth. I ended up just lowering the car equally all around which should preserve the stock distribution.

[geargrinder]

I've been told for street cars that it's probably low value-add overkill but that it depends on the car and how much you lower it. If DIY'ing, you have to be careful with (or avoid using) fender-gap measurements based on body style - some cars are designed OEM to have bigger gaps in front than rear so if a DIY'er uses pure fender-gap for visuals (not saying you're doing this but lots of stancers do), he is likely actually weighting to the front.

[rf900rkw]

How can you say you are still on the factory weight distribution? What measuring method did you use to make sure the loaded length of your random adjustable aftermarket suspension unit is exactly the same the factory spring/shock/shim setup?

An experiment: Take your perfectly set up car, turn the RF and LR up two turns, and the LF and RR down two turns. These cars are stiff enough that your wheel arch measuring is gonna show pretty much the same as before. But you just jacked 100 pounds of cross weight into (or maybe out of) the car. the numbers given are educated guesses on the going spring rates and the course thread on the BCs. Those running 2x4 conversion springs will be even more sensitive.

As far as using a public scale, unless their platform and surrounding area is billardtable level, you'll just get random numbers. A 1/4" of run over the length of the car will change your numbers by over 100 pounds.

[Skwisgaar]

My indy offers that service (he's also a racing instructor). After he installed my coilovers he went ahead and corner weighted the car. Here's how it looked afterwards...

[Justin517]

I never said my car is perfectly set up. I just made what seems like a justifiable assumption that lowering the car equally front and rear should keep the weight distribution fairly close to stock, or at least more so than setting it based solely off of how nicely the tires sit in the wells/fender gap.

[Graham E39 528i]

I never said my car is perfectly set up. I just made what seems like a justifiable assumption that lowering the car equally front and rear should keep the weight distribution fairly close to stock, or at least more so than setting it based solely off of how nicely the tires sit in the wells/fender gap.

Justin, the force on the springs of your car changes all the time because of aerodynamics. The e39's front gets pushed down more than the rear.

Setting your car up for perfect weight distribution when static is a purely academic goal.

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[Justin517]

So that should mean that rake can possibly throw off distribution even further?

Shifting weight slightly forward AND angling the car down more in front I would think further increase front loading at speed. Akin to increasing the angle of a wing?

[Graham E39 528i]

So that should mean that rake can possibly throw off distribution even further?

Shifting weight slightly forward AND angling the car down more in front I would think further increase front loading at speed. Akin to increasing the angle of a wing?

Probably.

I just think aiming for some particular weight distribution when motionless is not likely to give you an advantage. The car's suspension is subject to a myriad of forces, most of it unquantifiable.

More important than weight distribution is polar moment of inertia. PMI concerns where the weight is with respect to the center of gravity, which can be spread out (bad) or close to the CoG (good).

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[topaz540i]

so what your suggesting is that instead of adjusting a static weight to 4 corner balance, you would rather see a system where the weight at each corner changes in real time? a fluid dynamic gravitas distribution and redistribution system for keeping the car's center of gravity at an optimal 90degree to the earth's gravitation pull?

heavey doc.jpg

[JimLev]

BTW JimLev - would love to connect and see yer car some time when you're around.

OK, not sure when I'll be up in the North Shore area again. Do you go to the BAV Show and Shine event?

[rf900rkw]

If you were to raise the back of the car 0.5 inches, how much weight will be moved to the front?

[topaz540i]

the math is really rather quite simple if you care to follow along

360 degrees divided by .5 inch equals 180 lbs
multiply 180 pounds by 4 tires then divided by 2 axles = 360lbs
360 lbs will be shifted from the rear to the front assuming that the car was referenced at a position level to the horizon and plumb to the earth's magnetic field.

this will of course only work with the saloon. the wagon will have a special version that costs extra.

[rf900rkw]

Nice try.


Compared to a 0.5" rise in the rear, you can shift more weight to the front by filling an empty washer bottle.

[geargrinder]

OK, not sure when I'll be up in the North Shore area again. Do you go to the BAV Show and Shine event?

I havent but i would if i wasnt out of town and had a good reason to - when is it?

[JimLev]

I havent but i would if i wasnt out of town and had a good reason to - when is it?

Its usually the first Sunday in October, i usually get there about 7am so I can get a spot in the front parking lot.

[Justin517]

Back from the dead...

I’m the service manager at a performance shop. I changed the BC springs for Hypercoils and set ride height where I thought the car looked right and put it on the scales.

I guess I got it pretty good.




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[geargrinder]

LOL back from the dead indeed. I woulda guessed you were out of the 540 long ago... Are you still rolling Audis too?

[Justin517]

LOL back from the dead indeed. I woulda guessed you were out of the 540 long ago... Are you still rolling Audis too?

I haven’t bought a car in 5 years.

Still have the 540 and 200 20v Avant. I drive new stuff every day and everything I’d buy is more than I want to spend right now and I just love what I have. Plus I’m closing on a house next month so I’m not buying anything right now.


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[geargrinder]

Still have the 540 and 200 20v Avant

That is so excellent, I was gonna ask. I fondly think of my Type 44 and C4 often. My C4 S6 is owned by my pro-tech buddy locally and hes made it way better and nicer (incl full repaint...) so I see it often (and of course lust for it but then again I didn't spend the months and months of labor and piles of dough on parts for all the stuff he's done to fix up the little bits since I sold it to him...). He's warming up to finally refreshing the motor - thing must have 200k on it now though and still running totally strong even w/ full RS2+ turbo/intercooler job and being driven hard including a few track days...

Re: new cars - yeah wife had a loaner A3 last few days (getting her Takata face-rippers replaced) with like 2k miles on it... its real nice.. in some ways... but somewhat personality-less... which is what we keep finding w/ new BMW's and Audis... gonna have to buy her a new car at some point tho'... I can keep driving my old rigs happily forever but she's "normal" and actually would like to have a new car once every 10yrs or so...