E12 Squatting Issue Fixed

fochmann · Post by **fochmann** » Mon Jan 30, 2012 10:09 am

I have a quite a few e12s and the number one thing I have always hated about them is there decisions to squat and take a shit when I floor it. I have tried everything as far as stock options are to go, they had a less tendency to squat with new aftermarket springs and some billy sports but it was still a problem.

Last week when I was in my 79 6er and floored it and ripped off my rear muffler I finally said I am through Im going to fix this stupid squatting issue. This weekend I spent all of my time trying to fix it and finally got it right.

For shock options on the e12 you have the billy sports that are sort of a coil over; they have the 6 positions about a half inch apart with the snap ring to hold the perch. IF anyone needs the part number I can get it for them. I had those on my car so it was more of a matter of finding a high enough rate spring to eliminate squatting. The spring size that is needed is 3 3/8 ID 4.5 OD and between 10 and 11 inches tall. It turns out that a Mercedes SL front spring from 72-89 is the right ID and OD but they are about 17 inches in length. You have two options as far as stiffness, 72-85 is the Mercedes 450sl and 380sl they have around a 250 rate spring stock. In 86 the 560sl came out and they have a 350ish rate spring stock. I used a 560 set as I had some lying around, I cut around 7 inches off of the springs from the top portion as the bottom portion of the spring is ground flat and so it sits perfectly flat on the lower perch of the bilstein. After my calculations the 560SL spring at 10.5 inches tall is a 625 rate spring and the car is quite stiff. The factory BMW e12 spring is around 180 rate and I believe the aftermarket springs I had in there were around a 250 rate. The SL spring sits very nicely in both perches up top I am using the Mercedes rubber spring insulator and on the perch I also have the Mercedes rubber insulator.

I cannot express in words how happy I was when I got in the car and drove it down the road. IT is extremely stiff back there but not to stiff still has excellent rebound but has eliminated the squatting issue I may have a half inch squat in the back end when I floor it, if event that. It corners better and gets better traction from the get go. As far as wet road traction I will update when we get some weather here next but I suspect that it might be abit worse. I do not drive like a buffoon when it is wet so im not to concerned about it. If you do not like stiff cars do not attempt this I can feel every little fracture in the pavement with 35 profile tires.

I know I could have bought a set of ground controls and it wouldn't have any issues but after getting ground controls set up right 2 grand is out the window. The Billys are $300 for the set and you can obtain the Mercedes springs for around $100.

I will update my experiences and post some pics of the car. I have it sitting quite low at the moment.

Eddie in TO · Post by **Eddie in TO** » Mon Jan 30, 2012 12:11 pm

WOW. This certainly looks very interesting. I'm having some serious squatting issues as well.
600+lbs springs on the rear sound very, very stiff but keep in mind that I'm just starting to get familiar with spring rates.

I'm looking forward to hearing back on the rest of your driving experience.

Mike W. · Post by **Mike W.** » Tue Jan 31, 2012 12:53 pm

625 on the street? Wow that's stiff. Reminds me of a street legal 2002 race car I ran across one time. Pushing on the fender the body flexed more than the suspension compressed.

fochmann · Post by **fochmann** » Tue Jan 31, 2012 2:06 pm

Yes 625 on the street, We have had dry weather here the past few days so I have had the chance to toy around with it. Cornering is a huge improvement, from a dead stop It seems like it has abit more traction and doesn't squat more than a half inch. If it did I would hear my tires rubbing.

This is flooring it in a 400hp e24 if the spring shock combo can handle that much force it can handle anything. For a stock e12 most people are probably going to want to use the 450-380 springs from the earlier sl. As far as being downtown and going over bumps a gazillian times in arow my back started to hurt. It is extremely stiff to say the least.

tschultz · Post by **tschultz** » Tue Jan 31, 2012 5:17 pm

So basically the way to compensate is for very stiff springs?

Would Stiff shocks also do the trick? It seems like that may be too stiff for my liking. But at least with the squat, people know when you really get on it

fochmann · Post by **fochmann** » Tue Jan 31, 2012 8:49 pm

Its not so much compensating its more correcting. BMW did not put near stiff enough springs in these cars in my opinion. For the average driver they are ok and for the time they were being produced I am sure they were considered a very good handling car. I don't really car about what people see my car doing its more the fact that scraping the diff, exhaust, and tons of other things on the asphalt and then watching sparks fly in the rear view mirror. Not trying to be a butt to your comment but its the truth. On my non lowered e12 I havent ever had it squat so bad that it scrapes things but the e24 did.

Stiff shocks I do not think would do the trick as they are designed to help the spring rebound not control the stiffness or the ride height.

There is no point in having a powerful car if it cannot handle the power.

tschultz · Post by **tschultz** » Tue Jan 31, 2012 8:58 pm

Sure, that makes sense. I just was curious on your thought.

I haven't had an issue with scraping, but I do enjoy the handling benefits of a stiffer setup.

fochmann · Post by **fochmann** » Wed Feb 01, 2012 8:12 am

Drive it in a rain shower to work, Wet traction is about the same. It hasn't gotten worse but I cannot say that it has improved.

Tomslide · Post by **Tomslide** » Thu Feb 02, 2012 11:44 pm

swapping to an e28 rear subframe also helps with squat as well as dive, due to revised control arm mount locations. surely not as much as such a large spring rate increase, but obviously without any of the same drawbacks.

fochmann · Post by **fochmann** » Fri Feb 03, 2012 11:20 am

I thought about doing the e28 rearend swap as I have one but it would be a ton more work in my opinion.

Tomslide · Post by **Tomslide** » Fri Feb 03, 2012 12:05 pm

absolutely fochman. don't get me wrong- I AM going to the junkyard today or tomorrow to pull springs out of an SL haha.

Odometergears · Post by **Odometergears** » Fri Feb 03, 2012 3:15 pm

Running 386 foot Lbs at the rear wheels and 450lbs rear springs with coil overs. No issues and lots of grip.

wkohler · Post by **wkohler** » Fri Feb 03, 2012 11:52 pm

Dinan found the E28 handled better with a higher rear spring rate. I can't say 625 lbs is what they were thinking, not to mention the stress being applied to the body with those rates.

The real problem with the car is the Bilstein sports. Whatever is being sold as E12 Bilstein Sports is completely wrong. The compression is way too soft.

fochmann · Post by **fochmann** » Mon Feb 06, 2012 9:04 am

For now it works when something breaks ill fix it, that's my approach. I get grip and no squat so im fine with it. If I need to reinforce the rear strut towers i will do it.

Removing sl front springs without the proper klein tool compressor is almost deadly. Those springs in an sl front control arm is like a hand grenade ready to explode.

Even if the shocks are to soft, and I put in a stiffer shock its not going to fix the squatting issue. IF you think it will please enlighten me.

tschultz · Post by **tschultz** » Mon Feb 06, 2012 1:35 pm

fochmann wrote:For now it works when something breaks ill fix it, that's my approach. I get grip and no squat so im fine with it. If I need to reinforce the rear strut towers i will do it.

Removing sl front springs without the proper klein tool compressor is almost deadly. Those springs in an sl front control arm is like a hand grenade ready to explode.

Even if the shocks are to soft, and I put in a stiffer shock its not going to fix the squatting issue. IF you think it will please enlighten me.

Well just from the aspect of a shock function, it tends to dampen the oscillation, so in theory a stiffer shock may help if the goal is to reduce the oscillation in the spring.

But as long as it works, I'm sure there are many ways to approach it.