Proper alignment specs with new suspension set up

[dcaron9999]

Originally Posted by E82MSport

I had a discussion recently with Ground Control in regards to their Street plates with use of the race perch. When I mentioned the measured stack-up height as compared to the OE top mount they were slightly confused that it was shorter. I'm not stating it's a bad thing because without that height difference my ride height would have been roughly 20mm higher that it is now and I had actually taken that difference into consideration.

My problem is similar to yours and I also need to raise the front by ~5-8mm but also reduce my spring preload by roughly the same amount. With my current lower perch height within 3 threads of highest setting (i.e no more adjustment to raise the vehicle) I found the engagement of the internal bump stop was happening more often under very hard compression loads on the track. The only way I found to both increase ride height and reduce spring preload was a two step approach. First I needed to raise the damper in the spindle by way of a spacer and the second was a smaller spacer on top of the camber plate. Because of the additional spacer on top of the camber plate I needed the corresponding length (like you mentioned) of the studs in the attachment girdle. Ground control was able to install longer studs into two new girdles for this purpose based on my specs.

Like you I also had help from a very knowledgeable forum member that I'm very thankful of.

I'm glad you sorted out your issues, I enjoy reading your posts.

Glad that Ground Control was able to customize the top mounting plates for you.

I find it odd that Ground Control has not planned ahead for differences in total stack height though. Based on type of application, they should offer the following;

1. When customer is using stock or aftermarket spring + damper combo, GC street camber plate stack height should mimick BMW OE top hat stack height.
2. When customer has a coilover setup, GC street camber plate stack height should approach BMW OE top hat stack height, or offer different stack height options.

My setup is different than yours, so no spring perch or pre-load issue to deal with, makes things simpler. For my lowered/stiffer Spec-R spring + Bilstein B8 damper combo, the techs I spoke with, suggested that the damper would not sit as snuggly into the hub knucle if I was to raise it from the bottom of the damper, because some of the damper designs are slightly tapered in that area and thus, would not be pinched/secured sufficiently.

It seems as if the preferred approach to address rake issues for spring/damper setups, is to use the appropriate spacer above your camber plate...

[dtla1]

Originally Posted by dcaron9999

Gentlemen, thanks for the amazing input as always. I'm sitting at an alignment shop now, and the senior tech found a loose bolt on the rear toe arm, and toe was massively out of wack. Camber in front had moved a half degree apart. This is four days after I got my toe arms installed, camber plates spacers installed, and alignment done!

The senior tech verified all front+rear camber and toe bolts for proper torque tightness.

After a quick discussion with him, I opted for - 3.0* & 0 toe Front, - 2.2* & 1/8" total toe Rear. This is from -3.2* & 0 toe (front) and -2.2*& 1/4" total toe (rear).

For what it's worth, a very reputable race prep alignment shop nearby recently set me up with a "semi race" alignment setup at -2.4* camber front, 0 toe and -2.2* camber rear with 3/32 total toe in. Seems to ride quite nice so far but haven't been able to really test her out quite yet.

[dcaron9999]

Originally Posted by dtla1

For what it's worth, a very reputable race prep alignment shop nearby recently set me up with a "semi race" alignment setup at -2.4* camber front, 0 toe and -2.2* camber rear with 3/32 total toe in. Seems to ride quite nice so far but haven't been able to really test her out quite yet.

Pretty close to my specs in the rear. In fact, I have -2.2* camber and 1/8" total toe (1/32" more than you).
In the front, I run 0 toe, and -3.0* camber, but might increase camber a little more, or install a stiffer way bar this summer ....

Love my alignment specs for both track and street.

[dtla1]

Originally Posted by dcaron9999

Pretty close to my specs in the rear. In fact, I have -2.2* camber and 1/8" total toe (1/32" more than you).
In the front, I run 0 toe, and -3.0* camber, but might increase camber a little more, or install a stiffer way bar this summer ....

Love my alignment specs for both track and street.

I notice you also were running b8's so we are kinda close in that regard, although I'm using Eibach pro-kit springs not swifts. The alignment tech noted that I could get to -3.0* camber in the front with my M3-TRW front arms and Dinan fixed camber plates, and could get more than -2.2* in the rear but opted to keep it mildly tame since I indicated I also drive spiritedly in the canyons which he knows are unforgiving to any mistakes. Oversteer in canyon driving is not good, since lanes are tight and staying in your lane is not only a rule but a mandate in the canyons, lest you go in the opposing lane and at the least you get a ticket from the police from crossing the double yellow, but even worse you could hit another car, bicyclist, or motorcyclist in the oncoming lane.

[dcaron9999]

Originally Posted by dtla1

I notice you also were running b8's so we are kinda close in that regard, although I'm using Eibach pro-kit springs not swifts. The alignment tech noted that I could get to -3.0* camber in the front with my M3-TRW front arms and Dinan fixed camber plates, and could get more than -2.2* in the rear but opted to keep it mildly tame since I indicated I also drive spiritedly in the canyons which he knows are unforgiving to any mistakes. Oversteer in canyon driving is not good, since lanes are tight and staying in your lane is not only a rule but a mandate in the canyons, lest you go in the opposing lane and at the least you get a ticket from the police from crossing the double yellow, but even worse you could hit another car, bicyclist, or motorcyclist in the oncoming lane.

I think your mechanic made a wise decision to not max out your front camber as it is safer for a street car to maintain a slight understeer behavior.

[dtla1]

Originally Posted by dcaron9999

I think your mechanic made a wise decision to not max out your front camber as it is safer for a street car to maintain a slight understeer behavior.

Exactly, and since they do alignments the old school way with bubble angle gauges and straight rods with viewers for measuring toe, and due to their reputation I have a good level of trust with them.