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View Full Version : Just installed Ground Control RSM's


thinair
03-22-2003, 09:45 PM
Well I finally got around to installing the Ground Control rear shock mounts I had here.

Aside from the time consuming part of ripping apart the truck, the install was very straight forward. The bushings material is incredibally stiff compared to the stock bushing. With the stock rsm you can jam a screw driver into it and move the center everywhere, but they hadn't started to tear out yet.

The Ground Control units look very well made, the bushings have two ways of installing them, a street and a race position (I chose street for now). I also installed the rsm the right way (the bushing bulge on top), but if I notice any issues with the rear wheels coming off the ground getting into driveways, I may install them upside down to increase the wheel droop. That probably won't be necessary until I get sway bars though.

I put everything back together and lowered the car to the ground. When I put weight on the rear of the car, I don't notice the bushings flex at all!. The car barely moves with me trying to bounce the rear end, only the tires flex a bit.

Unfortunatly I won't know for a couple weeks how it drives, but I'll post info once I get the car out....

The whole install can be complete in about an hour, but it took me longer because I decided it'd be a good idea to detail the rear shocks and spare tire well for no reason.

Maybe Tuesday I'll install the UUC tranny mounts.....:rolleyes:

Autotechnica
03-23-2003, 01:30 PM
Glad to hear you like it!

When I first installed mine I noitced the same thing you did. However, it doesn't feel like it actually improves the hanlding of the car at all. I thought maybe a stiffer rear end would give my car more oversteer.

Anyways, I was hoping you would try the "track" setting since the last time I installed it I used "street" as well. If you ever decide to try using the "track" setting let me know how it goes. I always love a stiffer suspension setup.

Thanks,

Bry

ROB89M3
03-23-2003, 02:18 PM
I have these as well. It did make a lil noticeable improvement in rear-end cornering stability. The main reason to install these is to prevent rear shock mount failure,typical for lowered BMW's.

qwk325
03-23-2003, 03:28 PM
where did u purchase them.

thinair
03-23-2003, 05:06 PM
Originally posted by qwk325
where did u purchase them.

Bimmerworld on a group buy, I paid like $150CDN after taxes/duty/shipping.

M52_Alpina
03-24-2003, 09:52 PM
i got mine from the Bimmerworld GB as well.

I am running the street setup too, however, will it cause any damage if i run the race setup on the street?

Do i reverse fit (ie: with the step inserted into the RSM) both bushings for the race setup or just the one in the fender well??



Originally posted by Autotechnica
Glad to hear you like it!

When I first installed mine I noitced the same thing you did. However, it doesn't feel like it actually improves the hanlding of the car at all. I thought maybe a stiffer rear end would give my car more oversteer.

Anyways, I was hoping you would try the "track" setting since the last time I installed it I used "street" as well. If you ever decide to try using the "track" setting let me know how it goes. I always love a stiffer suspension setup.

Thanks,

Bry

thinair
03-24-2003, 10:11 PM
Originally posted by M52_Alpina
i got mine from the Bimmerworld GB as well.

I am running the street setup too, however, will it cause any damage if i run the race setup on the street?

Do i reverse fit (ie: with the step inserted into the RSM) both bushings for the race setup or just the one in the fender well??

I dunno, I want to see how they feel in the street position before flipping both steps inward for the race setting. It shouldn't be a huge difference, but I wanted to start softer first....it's not like they're solid steel race RSM's or anything.

So yeah, both lips in is the race setting. I'm really considering installing the RSMs upside-down though.

M52_Alpina
03-25-2003, 12:58 AM
let me know if you are installing the RSMs upside down. I was unable to reinstall my rear strut brace with the GC RSMs. Let me know how it goes.

Originally posted by thinair
I dunno, I want to see how they feel in the street position before flipping both steps inward for the race setting. It shouldn't be a huge difference, but I wanted to start softer first....it's not like they're solid steel race RSM's or anything.

So yeah, both lips in is the race setting. I'm really considering installing the RSMs upside-down though.

thinair
03-25-2003, 04:47 AM
Originally posted by M52_Alpina
let me know if you are installing the RSMs upside down. I was unable to reinstall my rear strut brace with the GC RSMs. Let me know how it goes.

Which strut brace do you have? The older style GC RSM's had a horseshoe style upper mount, maybe you could cut the upper mount to fit (leaving at least half of the "O" together) and use a z3 RSM reinforcement between the chassis and the strut brace.

http://www.rose-hulman.edu/~smithm3/mods/GC_RSM/GC_RSM_1.htm

M52_Alpina
03-25-2003, 05:00 AM
Originally posted by thinair
Which strut brace do you have? The older style GC RSM's had a horseshoe style upper mount, maybe you could cut the upper mount to fit (leaving at least half of the "O" together) and use a z3 RSM reinforcement between the chassis and the strut brace.

http://www.rose-hulman.edu/~smithm3/mods/GC_RSM/GC_RSM_1.htm

I have the racing dynamics rear strut brace. Mine looks different compare to the picture, mine is a full oval shaped upper mount, not sure if you know what i mean though. It complete cover the top part of the shock tower. I might be able to fit the brace if i install the RSM upside down, but not sure if it would work though..

thinair
03-25-2003, 05:40 AM
Originally posted by M52_Alpina
I have the racing dynamics rear strut brace. Mine looks different compare to the picture, mine is a full oval shaped upper mount, not sure if you know what i mean though. It complete cover the top part of the shock tower. I might be able to fit the brace if i install the RSM upside down, but not sure if it would work though..

Yeah, mine is full oval too, I meant if that you could cut half the mount so it looks like a horseshoe (like in the pic) if that gives you more clearance for the strut bar. As long as the two bolts are still held together as one unit, but that's your call if you want to butcher up a brand new part.

The RSM can be mounted upside down, I'm just not sure if I have enough clearance with my shocks and bump stop to run it like that. Maybe you have more clearance, I guess it depends on your shocks and how much drop you have.

GR8 Ride
03-25-2003, 10:59 AM
And I'm still wondering why you would want to install your rear shock mounts upside down???

Pat

thinair
03-25-2003, 04:19 PM
Originally posted by GR8 Ride
And I'm still wondering why you would want to install your rear shock mounts upside down???

Pat

To increase the droop/negative travel. When I lift my car with a jack, the rear wheels don't go down all that much. When getting into driveways at an angle the shocks can top out and lift the inside rear wheel. This hasn't happened to me yet because I haven't driven my car since installing them (actualy I haven't driven it much since I got it). The GC RSM's can be installed upside down without issues, many people do.

GR8 Ride
03-25-2003, 08:19 PM
Actually, there IS a reason against installing them upside down, which is that the E36 rear shock towers are notoriously weak.

Putting the RSM's on upside down should cause some additional stress on those shock towers, as the bulk of the RSM was designed to sit UNDER the shock tower, not above it.

And I'm still wondering how installing them upside down gives you more negative suspension travel? Visually it still doesn't seem to make any sense...

If anything, you're moving your entire shock travel DOWN, which would have the effect of raising the rear suspension on your car....

Also, I have about the stiffest suspension on here, and I have no issues with lifting inside rear wheels when pulling into a driveway....

Sounds like this is a solution to a problem that doesn't exist.


Pat

thinair
03-25-2003, 09:55 PM
Originally posted by GR8 Ride
Actually, there IS a reason against installing them upside down, which is that the E36 rear shock towers are notoriously weak.

Putting the RSM's on upside down should cause some additional stress on those shock towers, as the bulk of the RSM was designed to sit UNDER the shock tower, not above it.

And I'm still wondering how installing them upside down gives you more negative suspension travel? Visually it still doesn't seem to make any sense...

If anything, you're moving your entire shock travel DOWN, which would have the effect of raising the rear suspension on your car....

Also, I have about the stiffest suspension on here, and I have no issues with lifting inside rear wheels when pulling into a driveway....

Sounds like this is a solution to a problem that doesn't exist.


Pat

The GC RSM is weird, if the RSM is positioned upside down, the RSM is still under the shock tower. It wouldn't even sit properly on the of the shock tower (theres a lip there), and if I did, it wouldn't put the bushing any lower the fit it was mounted properly. This RSM doesn't have the threaded studs as part of the RSM unit, it's part of a circular metal piece that goes on top of the shock tower. The RSM nuts are in the wheel well, not the trunk.

The newer RSM's have a full oval on top, not a horseshoe like in this pic below.
http://www.rose-hulman.edu/~smithm3/mods/GC_RSM/GC_RSM_11.htm

Unsidedown mounted GC RSM
http://www.rose-hulman.edu/~smithm3/mods/GC_RSM/GC_RSM_12.htm

Apperently people who have the Bilstein PSS/9 shocks have issues with rear wheel lift on cars that aren't lowered all that much (my car is only 1" below stock) because the shock travel is decreased. So the shock tops out when entering driveways. Like I said, I haven't encountered this first hand yet.

GR8 Ride
03-25-2003, 10:44 PM
Ok, I see what you're talking about now. I run the GC RSMs in my car, and I've never seen any issue with too little shock travel.

However, I still fail to see you could get that much flex in the chassis to have the rear wheel max out shock travel, particularly when turning onto a driveway.

That strikes me as being an issue of the wrong sized shock for the car, not being a RSM issue.

The reason I suggest this is because of the nature of shocks. The opposite of not enough negative travel is too much positive travel; ie, the shock can then bottom out when the suspension on that side is fully loaded. This has two problems associated with it. One, your spring rate becomes infinite, which can lead to nasty over-steer situations. Two, it tends to wear out the shock prematurely, because your car is then using the shock to suspend the vehicle, instead of the spring.

Remember, the ONLY time your shock should have any effect on your car's handling is when the spring is in motion. The shock itself should not be supporting any portion of the vehicles weight.


Pat