During last weekend's BMW CCA Car Control Clinic, I realized that the BMW tuned the E46 M3 for understeer. I think their intention was safety -- with so much power available, it's all to easy for a beligerent, leadfooted driver to spin the car exiting a corner. By making the front tires lose traction first, I think BMW was trying to avoid the M3 having a reputation as a car that is hard to control.
Plowing around the different exercises at the Car Control Clinic wasn't as fun this time as last year in my old E36 M3 with H&R Coilovers and 17x9 BBS RGR wheels all around. The E36 was dialed in -- beautiful neutral handling; the E46 was not. Around the skidpad, I had the E36 dancing around the cones with the throttle connected magically to the turning radius. The E46 just plowed around no matter what I would do.
Driving home from the CCC, I decided this must change. The car's soul is just to good to cripple it with so much understeer.
After doing lots of research online, I learned that three important things need to be changed about the E46 M3 to make it handle better. First, the front end needs more negative camber. The stock suspension allows for maybe one degree of negative camber, not enough to keep the outside front tire planted on the ground in hard cornering. Instead, it rolls onto the outer edge of the tire and loses traction (hence, understeer). Second, the front bumpstops are too long. When the outside front suspension is loaded up going around a corner, the soft springs allow the shock to compress the bump stop too easily. The result of this is the "effective" spring rate (or "wheel rate") goes to infinity. A high front wheel rate relative to the rear means the front loses traction (hence, understeer). Third, the springs and shocks are not matched very well. The springs are very soft, and the shocks don't seem to be well matched to them. The car rolls a lot, and thus exaserbates the first two problems (hence, understeer).
I knew I needed camber plates to address the lack of negative camber, different bump stops, and different springs and shocks. I looked at many different options, and decided that <a href="http://www.ground-control.com/">Ground Control</a> was the way to go.
The Ground Control Street/Track kit (the "1849 Kit" in their nomenclature) addresses all of these problems deftly. It has their race camber plates, with calibrations etched onto the plate face. They work with the stock strut tower brace, so that's an extra bonus. When you order a suspension kit from GC, they basically interview you to determine what spring rate will bring the most satisfaction. My priorities were: decrease understeer, preserve most of the good ride of the stock M3, reduce some body roll (within reason). Jay at GC recommended 440 lb/in fronts and 550 lb/in rears. "You can take this to the track, but not get bitched at when you go places with your wife" was how he explained the kit. Fantastic! So I placed the order on Monday.
The kit arrived Friday. Arti called me at work at 2pm when she got home, "There's a big box outside the front door. It's too heavy for my to bring in, so I'll leave it out there for you." Nothing at work can be as important as a new suspension, so home I came!
The components were absolutely beautiful. GC's custom threaded spring perch collars were anodized red, with anodized gold perches. The camber plates are anodized black. The yellow Koni shocks (top adjustable all around is standard with the 1849 kit) are nice pieces too. It was almost a shame to put the kit on the car where it would get all kinds of grit, grease, and grime on the components. But better handling awaits! The front struts (strut, bump stop, camber plate) and rear shocks (shock, GC rear shock mount [RSM]) were completely assembled. They have a shock dyno, so the Koni shocks are precisely adjusted to your chosen spring rate. Excellent!!!
I got started about about 5pm. The rear was straightforward. Move the carpeting in the sides of the trunk out of the way to get at the RSM nuts before you get greasy. Put the rear of the car on jackstands, remove the wheels, remove the shocks, pull out the springs. Don't forget to release the e-brake, otherwise you won't be able to get the springs out. The new rear springs have adjustable spring perches to adjust ride-height. These must be attached to the upper control arms. Easy. I put the collar right in the middle of the adjuster, and the ride height ended up just right -- 13" from center of wheel to fender lip. Put in the new springs, bolt in the shocks, check the torque of the 3 bolts per side. Put the wheels on, put car on ground, torque log nuts. Total time for the rears: 1.5 hours.
Time for dinner. Total time: 30 mins. Total tastiness: off the charts.
Now for the front. Drive the car up on Rhino Ramps to get access to the front jack puck in the center of the front of the car. Jack up car, put on jack stands. Remove wheels. Remove the four nuts that hold the factory strut tower brace onto the strut towers. Remove brace.
E46 M3's with xenon headlights have a sensor that's connected to the front lower A-arm to keep the headlights level when the car goes over bumps. This sensor must be relocated with the GC kit. It comes with instructions and some hardware to do this. Pretty easy, but it was difficult to drill the one hole that was necessary to mount the sensor. Having a short-profile right angle drill would make working in the confined space a lot easier.
The E46 M3's front struts are different than the E36 in that the bottom of the strut on the E46 slides into a "pinch collar" on the steering knuckle. The E36 just bolts on to the steering knuckle. The Bentley manual specifies that the lower A-arm must be removed in order to get the strut out, but Jay gave me a little hint to getting the strut out without having to take more things apart. It took more than his hint. Here's what to do:
<ul> <li>When working on the passenger side, turn the steering wheel all the way to the left. (this was Jay's hint) <li>Remove the two 19mm bolts holding the brake caliper on, remove the caliper, and put it somewhere so that the brake hose is not strained. <li>Remove the bolt holding the swaybar connector to the strut <li>Loosen the three nuts on the strut tower as much as possible without taking them off, or remove them then put them back on one full thread <li>Remove the 19mm bolt that "pinches" the steering knuckle around the strut <li>Jimmy the strut around so that the steering knuckle drops down as much as possible. It will seem impossible to get the strut the rest of the way out (but it's not!) <li>Now go back up top and tighten the three strut tower nuts (this is the secret step!) <li>You can then go back down to the steering knuckle and jimmy the strut the rest of the way out. It <b>will</b> come out! <li>Remove the three strut tower nuts, and you can remove the strut. </ul> Installation, as they say, is the reverse of removal. Getting the old strut out is the hardest part. The new struts are shorter than the originals, so they go in very easily. Button up the struts, torque the pinch bolt to 81 ft-lbs, and tighten the strut tower nuts. I set the camber plates to an indicated -2.0 degrees. It's a good place to start -- I'll let a pro align and corner-balance the car "for real".
I originally set the height-adjusters to halfway between highest and lowest, but the car sat a bit high, so I lowered it three full turns from that midway point. That pretty much nailed the recommended 13.5" from center of wheel to fender. Put the wheels on, put the car back on the ramps, torque the lug nuts, and back off the ramps. Reinstall the factory strut tower brace, and take it for a ride. Total time for fronts: about 2.5 hours
My first impression? "YEEE HAW!!!" This is WAAAY better than I expected. The ride is both a bit firmer than stock, and at the same time more comfortable. Body roll is cut in half, and the car seems VERY eager to enter and carve through turns. It still has that wonderful "planted on the pavement" feeling at 80-100mph that the car came with from the factory.
Arti and I went for a drive both last night (pre-suspension) and tonight (post-suspension). She feels the car is more comfortable now, and I feel it handles 100% better. Win, win! I love it!
As I said, the ride height is just about 13.5" front, 13.0" rear. I did a poor-man's camber measurement and came up with -2.25 degrees rear, -3.0 degrees front. I'm not sure how accurate my method is, but it doesn't matter so much. I have an appointment at <a href="http://www.tcdesignfab.com/">TC Design</a> in Milpitas to get the car aligned and corner-balanced. It looks good, drives good, and handles good. I'm a very happy customer. Big ups to the guys at GC for engineering such a awesome product!