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Discussion Starter #1
i'm finally going to pull the trigger on suspension this week but i'm still a tad on the fence between ground control and bilsteins. what i'd like to hear from are ground control owners. i've found a ton of threads on the pss9's but very little usable info on the ground control stuff.

price is pretty much a wash - 1899 vs. 1999.

components - not sure who has the edge here. i'm thinking GC just based on what i've read but again that's minimal.

install - GC hands down. they come pre-assembled and can just be installed. the bilsteins require either purchasing all new hardware to do the same thing or disassembling the current stuff and swapping parts. this is a huge one for me because i HATE screwing with spring compressors.

ride/handling - again, i've heard good things about the pss9's but nothing really about the GC stuff. not sure here.

my end result i'd like to acheive is to tighten up the 'floppiness' of the car and obviously improve overall handling. i autocross but i'm also realistic that i'm not going to get a 2 ton m5 to handle like a lister. i'd like to drop the car a little but by no means want to slam it like a 16 year old with a civic.

i also am concerned about fitment issues in the front with the GC stuff... i have 19's - 8.5 up front and 10 in the rear. i don't want fitment/rubbing issues.

thoughts from GC owners? or anyone else? :haha:
 

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i'm finally going to pull the trigger on suspension this week but i'm still a tad on the fence between ground control and bilsteins. what i'd like to hear from are ground control owners. i've found a ton of threads on the pss9's but very little usable info on the ground control stuff.

price is pretty much a wash - 1899 vs. 1999.

components - not sure who has the edge here. i'm thinking GC just based on what i've read but again that's minimal.

install - GC hands down. they come pre-assembled and can just be installed. the bilsteins require either purchasing all new hardware to do the same thing or disassembling the current stuff and swapping parts. this is a huge one for me because i HATE screwing with spring compressors.

ride/handling - again, i've heard good things about the pss9's but nothing really about the GC stuff. not sure here.

my end result i'd like to acheive is to tighten up the 'floppiness' of the car and obviously improve overall handling. i autocross but i'm also realistic that i'm not going to get a 2 ton m5 to handle like a lister. i'd like to drop the car a little but by no means want to slam it like a 16 year old with a civic.

i also am concerned about fitment issues in the front with the GC stuff... i have 19's - 8.5 up front and 10 in the rear. i don't want fitment/rubbing issues.

thoughts from GC owners? or anyone else? :haha:
I've got a GC suspension and for the track it's wonderful. I don't know anything about the Bilstein except what I've read.

The GC suspension kit is built for you based on what you want to do - call GC and talk to them and they'll give you springs that are tuned for your needs. Bilstein doesn't do that.

As for clearance in the front, NOTHING has as much tire clearance as GC. You can run 9.5" wide rear rims in the front without spacers on the newest GC setup. You have to be careful on spring choices if you want to drop the car - the lower perch has to sit above the tire. I'm not sure the Bilsteins will clear your rims (they might) because they have a tender spring that comes down into the tire clearance zone of the damper.
 

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Discussion Starter #3
thanks. what spring rate did you go in for? track, i'm assuming? does your car see much street driving? i'm curious as to the ride during everyday driving.

i did call GC and talked with someone(forget who) and they said the majority of people seem to go for the track spring rates... the others who have gone for street seem to regret it and end up swapping for the higher rate springs.

thanks for the comments.
 

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thanks. what spring rate did you go in for? track, i'm assuming? does your car see much street driving? i'm curious as to the ride during everyday driving.

i did call GC and talked with someone(forget who) and they said the majority of people seem to go for the track spring rates... the others who have gone for street seem to regret it and end up swapping for the higher rate springs.

thanks for the comments.
I got 430#/inch front, 380#/inch rear springs - the track package, but not the "race" package.

It's a firm ride, magic on the track, and manageable on the street. I don't know about auto-x though - it might be too soft.
 

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i did call GC and talked with someone(forget who) and they said the majority of people seem to go for the track spring rates... the others who have gone for street seem to regret it and end up swapping for the higher rate springs.

thanks for the comments.
You should make sure you talk to Jay. There have been reports of less that concise telephone support at GC by others. Jay is the master of suspensions.

Good luck- good choice

A
 

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I got 430#/inch front, 380#/inch rear springs - the track package, but not the "race" package.

It's a firm ride, magic on the track, and manageable on the street. I don't know about auto-x though - it might be too soft.
-Interesting. I am running 500/600 f/r springs on my Z4 MC, which is a much lighter car than the M5, and it's ok for street use if you don't mind a firm ride. I would think similar spring rates would have a good ride in a 700lb heavier car. But I admit this is just hypothesizing on my part.
 

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-Interesting. I am running 500/600 f/r springs on my Z4 MC, which is a much lighter car than the M5, and it's ok for street use if you don't mind a firm ride. I would think similar spring rates would have a good ride in a 700lb heavier car. But I admit this is just hypothesizing on my part.
You can't just go by spring rates when comparing two different cars. You must compare the effective wheel spring rate (taking into account the leverage ratios). I think jaj has the leverage ratios for the M5 fwiw.
 

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You can't just go by spring rates when comparing two different cars. You must compare the effective wheel spring rate (taking into account the leverage ratios). I think jaj has the leverage ratios for the M5 fwiw.
It's good to search back on the board for posts by member "stever" because he had the GC "race" setup with 550F/425R springs. He said much the same thing as Palantirion - firm but nice, handles like its on rails. From memory, the Bilstein PSS9 springs are around 500F/400R (you'll have to search) putting them about half-way between the two GC setups.

The correct lever ratios for the M5 are 1:1 at both front and rear so the wheel rate is the same as the spring rate. The E36, 46 and 9x chassis have a less-than-one lever in the rear suspension so the wheel rate is lower than the spring rate. The front of all these vehicles is a McPherson strut, so it's 1:1.

According to posts by Lscman and confirmed by my own experience, on an E39 chassis the front spring rate and damping has less effect on the perceived "ride quality" than the rear rate and damping. At various times I was partway through an install and I had to put the car on the road for a day or two so I ran the GC fronts with stock rears (on the street...) and it rode like stock. The car only rode stiff after the stiffer GC rear springs and dampers were installed.
 

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You can't just go by spring rates when comparing two different cars. You must compare the effective wheel spring rate (taking into account the leverage ratios). I think jaj has the leverage ratios for the M5 fwiw.
-Very good point. I knew I was missing something.
 

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Discussion Starter #10
thanks for the input guys. i've decided on ground control and i'm going to order tomorrow.

i'll take pics of the install, etc.
 

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thanks for the input guys. i've decided on ground control and i'm going to order tomorrow.

i'll take pics of the install, etc.
Make sure you call them to get the setup you want. If you want the new front design like jaj has (i.e. red tubes with clearance for OE rears up front with no spacers), you'll likely need to talk to them directly about that.
 

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Make sure you call them to get the setup you want. If you want the new front design like jaj has (i.e. red tubes with clearance for OE rears up front with no spacers), you'll likely need to talk to them directly about that.
Absolutely call. Don't use the website. Try and get Jay on the phone, more care may be applied to your order!

A
 
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