Suspension: Tie Rod Ends

epmedia  replies to a discussion about front suspension/alignment failure of a member's local alignment shop...apparently, trying to rip him off...

"It's really easy to test the tie rod joints (two each side, inner and outer).
Steer the wheel to the left abot 90%.
Raise the right front wheel off the ground.
Grab the tire at 3 and 9 o-clock.
Wiggle the wheel, feel and watch for looseness at the inner and outer tie rod joints (the inner joint is inside the bellow boot).
- Repeat on the left side with the wheel steered to the right about 90%.

The rack bushing test requires two people.
However, if the rack bushings are saturated with oil, they need to be replaced (unless they are urethane).
With all 4 wheels on the ground, Unlock the steering, have helper turn the steering wheel back and forth about 1/4 turn.
Observe for any movement of the rack. If you can see the rack move inside the mount (clamsheels), the rack bushings need replaced."

JDB continues the discussion: (Jeff BMW Tech)

"The guide bushings..
These have 2 "O" rings on each..total of 4.. that center them in the rack.
Part # 32 11 1 116 911

When worn they show as up and down play in the rack. They are avalible and pretty simple to install. Should be replaced with tie rod assembly for sure."

suspension rebuild parts

big difference in size

...compared differences between  77-79 and 80-82 front spindles...early styled suspensions means, larger wheel bearings...larger front sway bars...

 sway bars compared...rear stock - 16mm... ST rear - 19mm...'77 [9/76] front stock 23mm...ST front replacement 25.8mm...

coilovers suspension

BMW_E21_Gaz_GOLD_4caa381910363

Source - http://www.raceperformancemodified.com/BMW-E21-Shop/BMW-E21-Gaz-GOLD-Coilover-Kit

stance and suspension

over on the bf.com forums there was a discussion happening about how to lower an e21 without compromising the suspension geometry one of the member decided to separate the front subframe, adjust the lowering points and rewelding the separated pieces back together and boxing in and strengthening the support points...here are his comments...

''So I've got a little problem with my suspension in that I couldn't get it low enough to make my low profile 13" tires look right. As low as I dropped the coilovers, it didn't make a difference as the control arms bottomed out on the subframe. So I took an inch out of the subframe. This raises the control arm mounts and steering rack 1", while leaving the engine at OE height. This will help the make the suspension/steering better too. (I may need to put a half inch spacer on the motor mounts tho, as it doesn't touch the oil pain, but I might have issues when the engine torques.) I was originally concerned with the subframe being strong enough, but after taking it out of the car, and disassembling I have no worries, as it really is a pretty lightweight piece, and just spotwelded together. When I'm done it'll be fully welded and boxed in for more strength than stock.

Put bolts into the subframe mount holes and tighted them down and welded the bolt heads to the bench and then welded a couple other braces to the subframe to keep things square.''
 

Then I proceeded to cut an inch out of the subframe using a sawzall and air disc cutter.

I then used a spot weld drill and drilled out the remaining brackets and ground some rust off.

I then lined things back up and welded it back together. It's welded enough to hold things in place and square, but I'm dropping it off at a place to get sandblasted, and then I'll finish welding it, and then I'll drop it off at the powdercoaters (and I'll have better pics).

Mounted in the car, you can see it'll give more clearance. 2 of the bolts will still work fine but the two longer bolts needed to be an inch shorter so I went and bought a couple new bolts.

comments included...''epic win! This is why forums can be so valuable! This would give any of us who are lowered at all better suspension geometry. Even if you're not lowered an outrageous amount you will have a better roll center, less body roll and better handling. I spent a lot of time trying to figure out how to move the control arm pivot point upward an inch and decided it wasn't worth it if I couldn't move the steering rack as well since it would make bump steer much worse. I didn't think there was a good way to do it, you figured it out. I will absolutely be doing this sometime soon.

As for the steering shaft, I've heard of GM guys getting rid of the rubber flex disc and installing spring steel plates for a crisper steering feel. doing this would cut about 1/4" out of the length of the shaft. I'll see if I can drum up some pics. Also, I have almost 1/2 to 3/4" of splined shaft that's not being used, so you could probably just slip the coller down further over the splined input shaft on the rack.

As for motor clearance, can you fill your engine mounts with poly? I need to do this as well, the stockers are too soft and the motor rocks way too much.''

the fabricator responds...''This might seem complicated, but in actuality, I've only got like 2 hours of time into it so far, so it really isn't that complex of a thing. Just a matter of angleing the sawzall just right with long sawzall blades. And of course welding / bracketing the subframe to the bench ahead of time so you don't lose the proper alignment.

I'm using that sway bar link upgrade from the FAQ's, and I do have poly in my motor mounts, although it didn't really stay very good. I might try to get some more poly today and redo them as much as possible. (I think I pulled my "mold" tape off too soon and didn't let the poly harden up enough).

Although the steering rack has moved vertically up 1", the steering shaft is at an angle so the length that that changes is less than an inch. I haven't figured out exactly how much that is, and planned to just tackle it when I got to it.

When I was doing my brake master replacement work, I buggered up my steering shaft a bit, so it is less than pretty, so I wouldn't mind getting another one.

another member responded...However, if getting the car to sit a bit lower was the intended result, I think you may end up dissapointed on that front. The ride height shouldn't be affected by relocating the subframe, it will however greatly improve your roll center on a lowered car.

other members continued the conversation with...''This is such an improvement for suspension geometry in every way. My car isn't even super agressively low, but I'm sure I've bottomed out the control arms and the control arms are parallel with the ground. This means camber decrease (very slightly) as suspension compresses, poor roll center which means more body roll, etc.

raising the control arm pivot point restores geometry to offer camber gain as suspension compresses, better roll center, and it even changes the angle of the sway bar (ie double acting as a radius rod or tension rod for us) to improve brake dive.''

above..is an example of how body roll can flex the suspension or when a car is extensively lowered or lowered and driven aggressively this is where a bottomed out control arm hits the subframe...

 this is the result of the raised subframe allowing the control arm greater swing...

a member objected to the design with these comments...''DISCLAIMER: I may not be getting what's going on, but I did some math and drafting so I'm looking for criticism, or anyone who can clear up my possible misunderstanding.

I don't think this will lower your car, nor do I think it will lower your roll center. In fact it should leave your car at the same height, and raise your roll center.

Point 1. In a car with MacPherson Struts the car is "suspended" on the damper/spring system. The lower control arm has nothing to do with supporting the car, only locating the wheel during bump and droop.

Point 2. Therefore when you cut your subframe 1" you are moving the lower control arm chassis mount up 1" in relationship to the tire contact patch at the road surface.

The following is a drafting of the MacPherson Strut Roll Center calculation where you raise the control arm chassis mount 2" (to show exagerated effect). Not only does the roll center go up but because the length of the controll arm is static you have now tucked your front wheels into positive camber (you can't really see this in the resolution of the drafting but if you look at the two large circles at the top you get the point that if the lower arm chassis point moves up it must cause the whole upright system to rotate around the axis of the upper MacPherson strut mount and therefore move in towards the center of the chassis).

 The dark dot is the Roll Center

I highly recomend reading Allan Staniforth's book "Competition Car Suspension" before doing any major suspension work on any car. Even if you don't follow the axiom that Roll Center location is the be all end all of suspension design, he still gives you a number of methods for desigining suspensions and modeling them.''



it continued with...''I think the problem with e21's is that that control arm on lowered cars sits about parallel to the ground. When the car corners, the outside wheel will rise in relation to the body causing the control arm to move beyond parallel (higher on the strut side than the chassis-mount side). All kinds of funk is supposed to happen when the control arm gets like that. This mod would eliminate that and bring the control arm movement closer in line with that of a stock e21. Well, that's how I understand it anyway.''

 the poster replied...''That's an interesting point Adam. It can certainly cause a problem in a double wishbone system if during bump or droop you get to a point where the control arms don't actually converge in the imaginary "vanishing point".

I'll measure where the chassis pickups and strut mount actually are, then do some variations for lowered/raised, and introduced negative camber and see what happens. I should have some draftings up later this week if I can get measurements off my 320i.

Anyone want to give me a balpark lowest lowered position with coilovers? I am going to have to make an arm that locates to the strut mount so that I can get a vertical measurement off of it (like a giant caliper) but I'd be interested in how much the car can be lowered. I'll then draft in increments that make sense.

If anyone uses AutoCAD or the like I can post dwg or dxf files when I am done so you can run different suspension options through and see where you end up.

This might seem complicated, but in actuality, I've only got like 2 hours of time into it so far, so it really isn't that complex of a thing. Just a matter of angleing the sawzall just right with long sawzall blades. And of course welding / bracketing the subframe to the bench ahead of time so you don't lose the proper alignment.

I'm using that sway bar link upgrade from the FAQ's, and I do have poly in my motor mounts, although it didn't really stay very good. I might try to get some more poly today and redo them as much as possible. (I think I pulled my "mold" tape off too soon and didn't let the poly harden up enough).

Although the steering rack has moved vertically up 1", the steering shaft is at an angle so the length that that changes is less than an inch. I haven't figured out exactly how much that is, and planned to just tackle it when I got to it.

When I was doing my brake master replacement work, I buggered up my steering shaft a bit, so it is less than pretty, so I wouldn't mind getting another one.

Charbel, how much for yours?

Quote:

Originally Posted by jrcook320 As for the steering shaft, I've heard of GM guys getting rid of the rubber flex disc and installing spring steel plates for a crisper steering feel. doing this would cut about 1/4" out of the length of the shaft. I'll see if I can drum up some pics. Also, I have almost 1/2 to 3/4" of splined shaft that's not being used, so you could probably just slip the coller down further over the splined input shaft on the rack.

Another option is one of these like from Afco or another company. I've also got one from a VW lying out back in my shop. They use a U-Joint as well.





Source -  http://forums.bimmerforums.com/forum/showthread.php?t=1253615

ireland engineering - toe and camber

in discussions with ireland engineering over the years, i know that when jeff is explaining the nunances of their eccentric toe and camber adjustments he discusses the possibility of 'tac' welding them in place so that movement stops...this is obviously in part due to customer feedback....this is what ireland has modified their toe and camber adjustments to  look like...clearly, this would stop the gradual movement after the item is installed...

front axle support

http://www.realoem.com/bmw/showparts.do?model=2933&mospid=47175&btnr=31_0009&hg=31&fg=05

Coil Springs

Lowering e21's has become a fad within the tuner community...this is not without unanticipated effects...while lowering the mass will certainly have the aftereffect of less body roll, lowering a mcpherson strut can actually have the opposite affect. this occurs because the geometry of the strut when lowered will also lower the 'Roll Center'. think of it as a lever. if the pivot point (roll center) of the lever was about the top of the trans tunnel, the the lever to the roof is short, but if you lower the car and by doing so lower the roll center to the road surface the the lever becomes quite a bit longer and has a greater mechanical advantage. the added mechanical advantage will cause the car to roll more not less. this is an exaggeration of course to make the point.

Cutting off coils can only lower the car. Progressive coil - cutting some off will have less effect on height but more on stiffening. Non progressive - cutting some off will have more effect on height and less or none on stiffening.

Road & Track said that the E21’s ultimate cornering speed was limited by its predilection for lifting the inside rear wheel, and that aggressive drivers would be well served by specifying the optional limited slip differential. The press was not alone in experiencing this characteristic, which was blamed for the car’s tendency to suddenly oversteer and quickly became a known quirk of the 1977 320i. BMW’s chassis engineers responded by stiffening the front springs on all E21s for 1978, while U.S.-market cars also received a smaller front anti-roll bar and the total deletion of the rear anti-roll bar. The fix seemed to work, as Road & Track’s re-test of the 320i in 1978 found it to be “a very balanced and forgiving car to drive.”

 Coil Springs

Springs are wound with the same wire diameter wire from start to finish. Spring rate is defined as follows:

k= (Gd^4)/(8nD^3)

G=modulus of rigidity of spring material
d=spring wire diameter
n=number of active coils
D=mean coil diameter

As you can see, as you reduce the number of active coils, spring rate will go up. Progressive rate springs act on this principle. A certain number of the total coils are wound closer together. As the spring compresses, all coils will compress equally but the closely spaced coils will bottom out and become inactive. In the case of the e21, the rear springs have about 8 active coils, 4 are wound very close. Once those 4 bottom out, the active coils are cut in half and spring goes from somewhere around 90 to about 180 lbs-in.

Changes in coil diameter also will affect spring rate (such as a bee hive shape), but this does not make a spring progressive as there is no change in rate as a spring compresses. It just means the active coils with a smaller coil diameter will be stiffer and compress less than the larger diameter coils, having the same affect on mean coil diameter through out the entire compression range.

To put it simply: cutting coils in a manner to reduce the number of active coils will both shorten the free length of the spring (which will lower the car) and increase the spring rate. To fully reduce the number of active coils, you have to re-close the end of the spring.

Removing one of the coils on the tight end of a progressive rate spring will reduce free length, and change the total number of active coils (changing both spring rates), and change the point at which the spring changes from one rate to the other.

 

Spring rate: refers to the amount of weight needed to compress a spring an inch (Example: 500 lb. per inch) To understand and properly check a spring for rate you need to know the factors that determine the rate of the spring. Fortunately, there are only three things that affect spring rate. 

 

1. Wire diameter - effects rate, the greater the wire diameter the stronger the spring, the lesser the diameter wire the softer the spring. Therefore, as wire diameter is increased, spring rate increases.

 

2. Mean diameter of spring - Mean spring diameter is the overall diameter of the outside of a spring, then subtract the wire diameter. As the mean diameter of a spring increases, the spring rate decreases.

 

3. Active coils - Count the total coils, then subtract 2 for springs with both ends closed. Count the total coils then subtract one for springs with one end closed and one end open. Bottom Line: as the number of active coils increases, the spring rate decreases.

If a spring's rate is linear (i.e. racing springs have linear rates) then its rate is not affected by the load put onto the spring. For example, a linear rate spring rated at 500 lb. per inch will compress 1" when a 500 lb. weight is placed onto the spring. If another 500 lb. weight is put onto the spring the spring will compress another inch. At this point the load on the spring has increased to 1000 pounds. The rate of the spring, however, remains constant at 500 lb. per inch.

If the load put onto a spring increases the rate of the spring, the spring is said to have a progressive rate. Progressive rate springs are sometimes used on torque arms to absorb engine torque. Keep in mind that the load (or preload) put onto a progressive rate spring can greatly increase the rate of the spring.

Progressive rate springs are made by varying the spacing between the springs' active coils. During compression the close coils bottom out and deaden. This reduces the amount of active coils and spring rate increases as a result.

Springs that are designed to include coils of different diameter or are wound using a tapered wire will also produce a progressive rate. 

how low can you go?

this blog is only a place where i have chosen to store pics, and information related to the restoration of my own 1977 e21. The restoration to stock is pretty straight forward and between the repair manual and the bimmerfourms there are plenty of helpful resources...however, the changes, upgrades, and customizations are what require research...this is an example of just that...this e21 has undergone what i assume was extensive suspension work...part of that included the lowering...i can't know what exactly took place BUT...for me, its just to low and i suspect this is what many describe as so low that it is performance effecting...

Source: http://a4.sphotos.ak.fbcdn.net/hphotos-ak-snc7/299854_2337306426464_1063958279_32430172_1668798842_n.jpg

Source: http://imageshack.us/photo/my-images/257/img0311zw.jpg/

this is vic's car...vic is from russia and frequents this website...today, vic responded to this post by directing me to his e21...as you can see, there is a significant difference between a standard 'stock' stance e21 (above) and a lowered e21 (top)..there are a lot of considerations i am thinking about in regard to lowering my 320i...the condition of the roads is probably THE most important consideration, the overall geomotry of the suspension is another obvious consideration...(are adjustments possible?) those are the things i am considering and i'm sure you are too, good luck!...nice car vic!

rear ground control

jr z rs front struts

jr z rs

new rear sway bar

stance

Cutting Stock Springs for a lower ride

this is an example of 2.5 coils cut in the front and 3.5 cut in the rear:

don't use an OXY welder to cut the springs, use a 1mm cut off wheel on an angle grinder, if you want a 2" drop cut about 1 coil off your spring...notice the effect of wheel size on the overall stance and profile...13" vs. 16" wheels..