The REAL Reason For Using Weights During Alignment (No, It's Not What You Think.)

Take a look at the first and second drawings.

That is what I mean by needing to bring the suspension to be parallel to the ground.

Drawing 1: Due to the pivotal point at the beginning of the control arm the wheels go 'in' when the car is high, go 'out' when the car is low, and Perpendicular to the ground when the arms are parallel to the ground.

It is when the arms are parallel (or more accurately when the line from the pivot point to the center of the wheel!), that you adjust your alignment angles. It is most obvious with the camber. You bring it to parallel pressing the car down using the weights, and then you adjust your camber to 2.0 degrees. You remove the weights, and the camber angle is now less than 2.0 degrees, as you can see from the drawings.

mw

Originally Posted by MatWiz

Take a look at the first and second drawings.

I agree with your basic argument about the camber changing as the suspension moves through its arc, but these illustrations exaggerate the effect because they show swing axles, like the old Corvair, VW, 356 Porsche, and early 1960's Mercedes axles, with universal joints only at the differential end of the axles. Modern independent suspensions have universal or constant velocity joints at the outer ends of the axles as well. The camber change in newer cars is less dramatic because the additional joint allows the wheel to remain more upright as it moves up and down. Your previous illustration was more accurate.

Originally Posted by bobdmac

I agree with your basic argument about the camber changing as the suspension moves through its arc, but these illustrations exaggerate the effect because they show swing axles, like the old Corvair, VW, 356 Porsche, and early 1960's Mercedes axles, with universal joints only at the differential end of the axles. Modern independent suspensions have universal or constant velocity joints at the outer ends of the axles as well. The camber change in newer cars is less dramatic because the additional joint allows the wheel to remain more upright as it moves up and down. Your previous illustration was more accurate.

Yes, of course, you are correct. I posted this one because of it's exaggerated drawing because I wanted to make the illustration (effect of height on camber) very easy to see.

Thinking that one will point it out, I wrote "or more accurately when the line from the pivot point to the center of the wheel!". Since we know that control arms connect to the lower part of the wheel hub. Therefore the parallel line is from the pivot points on the axle support (sub frame) points 12 and 6 on the parts diagram below, to the center of the wheel. Even when the line is parallel, the actual arms are slanted down.





Control arms connect to the bottom of the wheel hub, below the center of the wheel:



Now if you'll make the arms like this....

You could pretty much eliminate change of camber when the car is pressed down or moves up...



... But.... that's not in our price range...

And the E39 has basically one pivot point on the sub frame and one pivot point on the wheel hub, even tough we are using 2 control arms in a wishbone suspension.

In the above (yellow) suspension, one can argue that the wheels will not spread when the car is pressed down.

mw

Edit: someone is going to point out "but this is an inboard suspension!!!"...

That's all great, but I care more about how much the camber changes with the weights in the car--a half degree? a whole degree? a quarter of a degree? The front camber is not adjustable with the stock suspension, correct? What about the rear? Is it fixed as well, or is that one of the settings that's adjusted in aligning the E39's?

Does the weight in the car affect the geometry of any of the other adjustments besides camber?

In other words, I have to figure out some way to judge whether it's worth driving all over town, or even out of town, to have the alignment done with weights. If I have to drive an extra 20 miles and spend an extra $50 to gain a miniscule change in suspension geometry, it may not be worth my time and money.

Search the internet, especially roadfly E39 forum, you will see that for E39:

When comparing No weights (car with full gas tank and no weights) vs weights (3 x 68kg + 21 kg in the trunk thingy from BMW technical manual), the REAR camber goes from let's say -1.5 degrees to about -2.5 degrees.
Other alignments specs (Front toe-in, camber, caster) essentially unchanged by the weights.

The bottom line is the rear camber changes by 1 degree or so (on the negative side).

If you've ever built fences or patios, you'll find out pretty fast that even 1/8 inch or 0.5° can cause a lot of headache down the road...I'm gonna stick with the BMW recommendations.

Originally Posted by bobdmac

That's all great, but I care more about how much the camber changes with the weights in the car--a half degree? a whole degree? a quarter of a degree? The front camber is not adjustable with the stock suspension, correct? What about the rear? Is it fixed as well, or is that one of the settings that's adjusted in aligning the E39's?

Does the weight in the car affect the geometry of any of the other adjustments besides camber?

In other words, I have to figure out some way to judge whether it's worth driving all over town, or even out of town, to have the alignment done with weights. If I have to drive an extra 20 miles and spend an extra $50 to gain a miniscule change in suspension geometry, it may not be worth my time and money.

Yes the rear camber is adjustable and is part of the alignment.

Yes it is worth it. Read my first and #16 post.

mw

Originally Posted by bobdmac

That's all great, but I care more about how much the camber changes with the weights in the car--a half degree? a whole degree? a quarter of a degree? The front camber is not adjustable with the stock suspension, correct? What about the rear? Is it fixed as well, or is that one of the settings that's adjusted in aligning the E39's?

Does the weight in the car affect the geometry of any of the other adjustments besides camber?

In other words, I have to figure out some way to judge whether it's worth driving all over town, or even out of town, to have the alignment done with weights. If I have to drive an extra 20 miles and spend an extra $50 to gain a miniscule change in suspension geometry, it may not be worth my time and money.

Yes the rear camber is adjustable and is part of the alignment.

Yes it is worth it. Read my first and #15 post.

mw

On the subject of down force and alignment. 5 years ago I had the opportunity to run 42 laps at California Raceway in Fontana in a Richard Petty Car. Coming out of the pits and going up through the gears the car turned so hard LEFT that you had to turn hard RIGHT to make it go straight. I entered my first corner in this car at about 100 mph and had a small slip in the back end. Loss of traction. This scared me so I went back into the pits to tell them something was wrong. They explained downforce, how the tires were still running in the middle of the tire and had not flattened on the track and the suspension was not loaded yet. They advised me to take it up to 120 - 150MPH and I would love it. This took a leap of faith since I had never experienced this before and I was afraid to enter a corner at 150 when I know for sure the car slid at 100. Well, they were right. At 150 the steering was perfect and light to the touch as opposed to a wrestling match at 100 mph. The grip felt awsome and was very confidence inspireing. At the end of 42 laps I was so stoked I was jacked up for several hours. I had even begun flooring it at midpoint of the corner trying for best lap times. I did nothing inspiring, my best time was a full 20 mph slower than the Real drivers but it was amazing how much the car changed with downforce. At 100 mph I wanted out of the car, at 150 I wanted 200. The highlight though, I got to do this only 3 or 4 times, coming out of the pits and needing to accelerate up to track speed. Taking a 2000 pound car with 650HP and a 4 speed and flooring it as you go through the gears is just AMAZING. I really crushes you into the seat with power. This car was a detuned version of the real race cars. Only 650 HP while the real cars are approaching 850 HP. I had to share, your thoughts on downforce brought back a great memory.

Originally Posted by MatWiz

Yes it is worth it. Read my first and #15 post.

Okay, at the risk of belaboring what probably seems to many like an already exhausted topic, I dug out a copy of an alignment printout, done on my car by the previous owner, about 40,000 miles ago. I think I have a more recent one, but this was handy. It shows the specified camber range as -2.0-2.2 degrees, and the "actual" was set at -2.1. It's not clear whether this was done with weights or not, but if not, and if I drove much of the time loaded down with occupants and luggage, I understand I'd likely see excessive tire wear and below optimum ride quality. However, let's assume for the moment that it was done with weights. Unless my situation changes, most of my miles will be with me as the sole occupant, with little luggage. Given what people have said about the camber change with the additional weight, it seems as if in that case much of my drive time would be spent with the rear wheels at less than factory-specified negative camber.

On the other hand, while cornering ability (rear-wheel grip) in that case might suffer, it seems that with the wheels closer to perpendicular, my tire wear should improve, because the tire/road contact would be distributed over a greater width of the tread. So then it becomes a trade-off, of handling vs. tire wear, and I have to take into account how I plan to drive this thing. I also know that negative camber can improve resistance to cross-winds, by the way.

So while I appreciate your endorsement of the use of weights for the alignment (and yes, I had already read your previous posts), I still question whether it presents the same value proposition for all drivers, and I wonder whether the same weights should be used for all driving situations.

Originally Posted by bobdmac

Okay, at the risk of belaboring what probably seems to many like an already exhausted topic, I dug out a copy of an alignment printout, done on my car by the previous owner, about 40,000 miles ago. I think I have a more recent one, but this was handy. It shows the specified camber range as -2.0-2.2 degrees, and the "actual" was set at -2.1. It's not clear whether this was done with weights or not, but if not, and if I drove much of the time loaded down with occupants and luggage, I understand I'd likely see excessive tire wear and below optimum ride quality. However, let's assume for the moment that it was done with weights. Unless my situation changes, most of my miles will be with me as the sole occupant, with little luggage. Given what people have said about the camber change with the additional weight, it seems as if in that case much of my drive time would be spent with the rear wheels at less than factory-specified negative camber.

On the other hand, while cornering ability (rear-wheel grip) in that case might suffer, it seems that with the wheels closer to perpendicular, my tire wear should improve, because the tire/road contact would be distributed over a greater width of the tread. So then it becomes a trade-off, of handling vs. tire wear, and I have to take into account how I plan to drive this thing. I also know that negative camber can improve resistance to cross-winds, by the way.

So while I appreciate your endorsement of the use of weights for the alignment (and yes, I had already read your previous posts), I still question whether it presents the same value proposition for all drivers, and I wonder whether the same weights should be used for all driving situations.

Go outside and look at cars driving by.

Count the number of cars and the number of occupants in the car.

Guess what the number will be.

Do you think BMW thinks that the car has more then 1 occupant most of the time? It's one occupant. Sometimes 2. Very rarely more than 2. Those who take the whole family usually have a minivan.

C'mon. It's all nonsense. Weights is not to simulate a full family in a luxury sports sedan. BMW does not set their specs to the weekend when you take your wife and your kids to see grandma.

But really. Do what you want. This thread is getting a little off topic. It is not to convince people who want to make their own alignment specs because they know better than the BMW engineering team. After all, what does BMW know about alignment and handing, right?

mw

You're all missing the point: the TIS alignment specs require that the car is laden as specified. This allows for a "reference" starting point. Otherwise, the alignment will be incorrect.

Originally Posted by edjack

You're all missing the point: the TIS alignment specs require that the car is laden as specified. This allows for a "reference" starting point. Otherwise, the alignment will be incorrect.

Exactly.

mw

So how does one get a BMW aligned with lowering springs? For instance, with H&R sport springs, we're getting somewhere around 1-2" of decreased ride hide depending on which e39 is fitted. Does H&R provide details as to how much the springs compress under a 150lbs load? What if different shocks are used, many have experienced different ride heights with the Bilstein HD's compared to some other shocks. I'm about to fit bilstein sport shocks to my H&R sport spring setup and it sounds like it will be nearly impossible to get a proper alignment afterwards.

Also, from what I understand it's not just camber that changes under load, the front tires toe-out and the rears toe-in under load.

I'd honestly be shocked if the e39 produced any significant downforce at highway speeds.

Originally Posted by tomjrau

So how does one get a BMW aligned with lowering springs? For instance, with H&R sport springs, we're getting somewhere around 1-2" of decreased ride hide depending on which e39 is fitted. Does H&R provide details as to how much the springs compress under a 150lbs load? What if different shocks are used, many have experienced different ride heights with the Bilstein HD's compared to some other shocks. I'm about to fit bilstein sport shocks to my H&R sport spring setup and it sounds like it will be nearly impossible to get a proper alignment afterwards.

Also, from what I understand it's not just camber that changes under load, the front tires toe-out and the rears toe-in under load.

I'd honestly be shocked if the e39 produced any significant downforce at highway speeds.

No problem.

Set the alignment machine's computer to a E39 with Sports Suspension (it's right there on the alignment menu). It accounts for lower ride.

Put enough weights to bring the car to the specific ride height as specified in the documentation or the TIS for sports suspension. You see, the beauty of doing the alignment based on measuring the car height is that it makes sure that your suspension is parallel to the ground before you start your alignment, and it will account for different springs and shocks.

mw

Originally Posted by tomjrau

So how does one get a BMW aligned with lowering springs? For instance, with H&R sport springs, we're getting somewhere around 1-2" of decreased ride hide depending on which e39 is fitted. Does H&R provide details as to how much the springs compress under a 150lbs load? What if different shocks are used, many have experienced different ride heights with the Bilstein HD's compared to some other shocks. I'm about to fit bilstein sport shocks to my H&R sport spring setup and it sounds like it will be nearly impossible to get a proper alignment afterwards.

Also, from what I understand it's not just camber that changes under load, the front tires toe-out and the rears toe-in under load.

I have Eibach springs and bars and Bilstein Sports and 275/35-18s all around and I get very even wear on them. Maybe the indy I have it aligned at knows how to compensate. I don't know. I'm surprised my Direzzas are doing so well, wearing so nice and slowly. Great tires.

Originally Posted by QSilver7

Just an FYI for those that didn't know about wheel alignment and the recommended weight BMW suggests:

It appears the specs were the same from my e34 Bentley Service Manual:

NOTE: M3 Sport suspension requires no weights. What is not shown is additional text that describes what the ride height measurements must meet.

Originally Posted by QSilver7

Just an FYI for those that didn't know about wheel alignment and the recommended weight BMW suggests:

It appears the specs were the same from my e34 Bentley Service Manual:

NOTE: M3 Sport suspension requires no weights. What is not shown is additional text that describes what the ride height measurements must meet. As stated elsewhere, you add weight to bring ride height within +/- 1mm of spec, then do the alignment.

All the alignment specs you wanted to know and didn't know how to ask.

Ride heights, tire size, angles, tolerances, terminology explanations, trouble shooting.

Official BMW RA document

Enjoy, my geeky friends.

Bluebee!!! A treasure chest for you!

mw

Wooow, that specs .pdf is awesome!

sent from the EVO baby!

Originally Posted by MatWiz

All the alignment specs you wanted to know and didn't know how to ask

Very nice. So nice, that I will take the liberty of pointing to your post in a variety of places, not the least of which are the E38 and E36 forums but also, of course, the E39 bestlinks.

I also renamed it so that the title was more indicative of the contents.

Originally Posted by MatWiz

All the alignment specs you wanted to know and didn't know how to ask.

Ride heights, tire size, angles, tolerances, terminology explanations, trouble shooting.
Official BMW RA document
Enjoy, my geeky friends.

Wow, what a great resource! Do you have any other goodies like that up your sleeve? After reading it over and seeing all the measurements and procedures involved, I know that my next alignment will be at a shop that specializes in BMW's, just so I know what it should feel like with everything at factory specs.

Just as a footnote to this whole discussion, it still bothers me that I was so obtuse about the whole thing, but when I saw the specification for ride height in combination with the camber, for some reason it all clicked, and I thought, "No, duh!" Of course you need to get the ride height to a certain spec in order for the camber settings to be appropriate. Anyway, thanks, MatWiz, for finally getting through to me.

Originally Posted by bobdmac

Of course you need to get the ride height to a certain spec in order for the camber settings to be appropriate

Since I don't mess with the ride height, nor the wheel offset, nor anything else, the BMW specs are fine by me.

But, this would appear to mean that it behooves the 'modder' to actually know what they are doing when 'they' modify such things.

Do they take all this into account when they mod the ride height, for example? Dunno. I hope they do.

And, what about the alignment shop. Do THEY take into account pertinent user modifications when they adjust the alignment?

What's the list of pertinent user modifications that will force a deviation from stock alignment specs anyway?

• ride height?
• camber plates?
• wheel offset?
• coilover springs?
• tire size?
• aerodynamic wings?
• ? what ?

For the cross linked record, since this thread by MatWiz is the canonical thread on why add weights when aligning ... this was posted today:
> E39 (1997 - 2003) > Using weights to preload suspension: no exception for E39 Sport Package

Originally Posted by jpseagle

The BMW TIS has a table--explained here http://www.bmwmotorsports.org/BMW_docs/x5align.pdf
--that provides stock ride heights. According to Jim Cash, "measurement is to be done with car in normal loaded condition." In other words, ride height is measured in what the TIS calls "normal position," with weights added to the seats and trunk.
http://www.bimmerfest.com/forums/sho...5&postcount=14
The exceptions to the rule of using weights mentioned in TIS and BMW alignment documents are M-cars, i.e. the e39 M3 in this: 32 00 Wheel Alignment - Normal Position / Inspection Conditions E36 / E38 / E39 http://ebookbrowse.com/td-wheel-alig...pdf-d291668225
Nonetheless, there is a broader claim, heard occasionally on e39 forums, that all sport models are an exception to the rule for using weights to pre-load suspensions.
http://forums.bimmerforums.com/forum...5&postcount=61
This appears to be a misinterpretation of the table in the BMW TIS that classifies suspension types.
http://www.bimmerfest.com/forums/sho...7&postcount=15
32 00 Wheel Alignment - Normal Position / Inspection Conditions E36 / E38 / E39
• Low Slung Sports Suspension - This is used on vehicle with Sports Package Option.
• M Sports Package - Used on Motorsport vehicles or those with M Package Option.
This table creates confusion by mishandling the exception to the pattern, the 2003 540 Sport. The Low Slung Sports suspension is indeed for all sport package e39s, but not that one. The M-sport suspension type is for all M-model cars; however, "or M-sport suspension" pertains *only* to the 2003 540. This is confusing for owners of e39s with M-sport package and/or M-sport suspension. Worse, the 2003 540 Sport, commonly designated M-Sport II to distinguish it from the preceding M-Sport e39s, belongs to the suspension class M-Sport.
This agrees with evidence from owners: 2003 540 owners note that their struts have an M on them, which is the way this suspension type is identified. The M5 ride height is known to be higher than for the 540, which agrees with the table. E39 M5 owners do not use weights: M5board gurus agree that the instruction, "tighten in normal position," refers not to weights but to having the car on the ground, or the suspension otherwise compressed.
Like many, I hesitate to use weights, given the time and effort involved with ten 50lb sandbags. But weights are called for when torque data say, "tighten in normal position" for replacing control arms, thrust arms, and sway bar brackets. The main reason for weights is that the alignment specs are not correct otherwise: http://www.bimmerfest.com/forums/sho...5&postcount=37
Another reason: weights are needed to do the ride height specs by the book. Why lower accuracy when the ride height tolerance for a 540 is only +/- 10mm? Especially given the numerous sources of error: settling of a new suspension, thicker new mounts; level ground; measurement methods--a carpenter's square (cn90 front suspension) vs. a tape measure along a non-perpendicular line to the wheel edge (BeisianSystems); when using the alternate method to normal position–-jacking up the hub to the known, measured, height-you must apply a lot of force, not all of it vertical, to a floppy object; or, as the BeisianSystems Thrust Arm procedure puts it, "Optimal placement of lift at wheel carrier is unclear."
This post is more of a clarification than a question._a_

See also:
- Which of the dozen alignment specs are adjustable on the BMW E39 (1) (pdf) & cn90's front (1) (2) and rear (1) wheel alignment DIYs & how to keep the steering wheel (SW) straight during home alignment (1) (2) & what tools measure rear camber at home (1) (2) and what tools measure front/rear toe at home (1) & what tools lock the steering wheel & brake pedal at home (1) & the theory of alignment with weights (1) or without adding weight (1) (2) (3) & philosophically why most people prefer to let a professional alignment shop align their suspension (1) & what expensive equipment is used at the stealer to align your suspension (1) (pdf) & Internet references for how to DIY caster, camber & toe at home (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31) (32) (33) (34) (35) (36) (37) (38) (39)