You can use your old springs and simply just purchase new shocks/struts. These items are something you don't (in my opinion) want to skimp out on, as quality is something to keep key. I would also replace the rear shock mounts while your doing the job.
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didnt want to start a new thread on this so, what would be some recomended suspension brands. i was looking at blistein sport shocks with H&R springs or Vogtland springs. thanks for any help. i have a 1986 325.
Back in the good old days (some time in the last couple weeks) I saw a post somewhere about someone who changed out his springs and was experimenting with different spring stiffnesses in the front and rear. He started out with something fairly even and ended up with 700# in the rear and 400# in the front (not sure if the nomenclature is correct). On a '91 325i Cabriolet, what should the spring stiffness be for good handling and a ride that is not overly harsh? Should the rears be that much stiffer than the front?
Just for comparison, what is the spring stiffness of the H&R sets (the ones that lower the car 1.25") sold with Bilstein Sport shocks on many web sites? Are these a good choice or should I go with something more custom?
The spring that I have are sport springs so the handling was drstically increased over stock, but they aren't soo stiff that they ruin the ride. My wheels fit fine with these springs. All in all, it is much better than the stock "four wheel drive kit" that BMW put on their early 318's.
My friend adjusted the camber for me so I am not sure where exactly it is set right now. My friend and I did all the work. The difference in camber on the rear wheels was not to the point that I would spend money to correct it. It was a very minimal change in camber.
I installed Bilstein HD struts and Shocks using the stronger 325ic convertible rear shock mounts on my 89 325i 3dr sedan. I used H&R OE Sport springs which lower the car only 1 in instead of the more drastic lowering. These are progressive wound springs and run just over $200 a set new. E30 M3 springs I've also seen used which lower the car even less. Be aware though, Bilstein HDs tend to raise the car slightly with stock springs. If you use the Sport springs you MUST use the shorter Bistein sport shocks NOT the HDs. I also used Eibach Sway Bars which are 20 mm front & 16 mm rear and are adjustible. I find the ride firm but fine for an everyday driver and occasional driving school. My wife uses the car as well so it mustn't be too bad.
With only a 1 inch drop the camber change is a non-issue. Tire wear is normal and the slight change in negative camber is desireable. It's when you go to more drastic lowering that camber plates are desireable. When modifying the suspension I also used the M3 offset control arm bushings instead stock for improved high speed handling and is a worthwhile upgrade on all E30s. I did mine before I did any suspension upgrades and did it when the ball joints began to show wear so both were done ar the same time thus only 1 alignment charge. This change was done a year before the suspension upgrade mentioned previously. Incidently Bilstein HD struts and shocks can be used with stock springs but do change the rear shock mounts to the 325ic mounts. They are only $5 more than stock 325i mounts and well worth the money. You can also get the billet mounts for about a $100 more but unless you are doing some serious track time its overkill. You may also want to consider an Eibach or another brand of strut tower brace. It reduces body flex and can help eliminate the cracking of the welds where the strur towers and the body meet especially on the passenger side where the 84-85 318i had its battery.
The picture of the GC caster plate shows a shock tower brace that looks like the one Ireland Engineering sells. Does it require two holes to be drilled into the car (for bolts, I assume) and are they on the side of the tower where we can't see them? It looks like a good brace.