XP Autocross E36 LS3

**Zlalomz** · 01-08-2018, 05:38 PM

I purchased an XP car from forum member XPbimmer here in the Sacramento Region SCCA. From my experience in FP with a Datsun 240Z I want to take the current soft spring, big front bar setup to a much stiffer setup. The best info I have on this is from the Vorshlag Alpha One e36 that I think was running 800f and 900r rates with a 28mm front bar. I will be using radial Hoosier slicks 12 inches wide and 23.5 diameter on 16x12 wheels. The car has the Moton Sport double adjustable shocks. The car is track only with a full cage, fiberglass and Lexan. Anyone's input is welcome as I am new to BMW suspension. If Fair is still on the forum, I would love his input as he seemed to be wanting an even stiffer setup, I thought I read. This should be a fun and wild ride after I get it dialed in.
21752305_10214717622842140_7170259254351198197_n.jpg

**modernbeat** · 01-10-2018, 12:33 PM

With stiffer front rates there are issues with the tire becoming the (undamped) spring. I think that is about as stiff as we could go with a real tire and autocross aero.

Also, everything in the suspension should be spherical with those forces. I assume it's already that way, but you know about assumptions...

**Zlalomz** · 01-10-2018, 06:42 PM

Thanks. Digging into it now and making lists of little and big surprises. Hopefully spherical bearings, but if not, Ground Control is just up the hill from me. So far the camber is set up for radials but he was running bias ply slicks, The car did an off course (not disclosed to me) that crunched the driverside floorpan right under the seat. Lucky he wasn't paralyzed. This took out the rear brakeline, photos to follow. He was running 300 lb front springs with the largest GC sway bar on full stiff. I assume the shocks were helping on that soft of a setup. Don't know the rear rates yet. Does anyone have experience with bumpsteer correction and 16 inch wheels? Is there room for spacers at the tie rod ends? The big plus for me is the rollcage was built for someone my exact height 6'4"and inseam but I carry a hundred lbs more than him. This is the first caged car I really fit in.

**NotoriousJJE** · 01-10-2018, 06:45 PM

Originally Posted by Zlalomz

I purchased an XP car from forum member XPbimmer here in the Sacramento Region SCCA. From my experience in FP with a Datsun 240Z I want to take the current soft spring, big front bar setup to a much stiffer setup. The best info I have on this is from the Vorshlag Alpha One e36 that I think was running 800f and 900r rates with a 28mm front bar. I will be using radial Hoosier slicks 12 inches wide and 23.5 diameter on 16x12 wheels. The car has the Moton Sport double adjustable shocks. The car is track only with a full cage, fiberglass and Lexan. Anyone's input is welcome as I am new to BMW suspension. If Fair is still on the forum, I would love his input as he seemed to be wanting an even stiffer setup, I thought I read. This should be a fun and wild ride after I get it dialed in.
21752305_10214717622842140_7170259254351198197_n.jpg

The 800F 900R setup is what I run on my roadrace car with very limited aero and 245 R Comps. Home track is Sebring (bumpy as hell) and the car is not oversprung.

I would think an AX car with 12" wide radial slicks could handle those rates all day.

**Zlalomz** · 01-10-2018, 07:52 PM

Looks like those rates could be a good starting point. Thanks for the information.

**jakermac** · 01-11-2018, 03:13 AM

Judging from the quality of that build, I'd be very surprised if those front springs were actually 300lb. Are there part number on the springs that you could take a pic of?

**Zlalomz** · 01-11-2018, 10:49 AM

300lb.jpg
There you go. I googled the Ground Control number to find the rate. There's is a lot of good and a lot of WTF on this car. The giant rear wing was held onto the trunk with little machine screws and fender washers through one layer of sheet metal. I will build mounts up from the frame. The wiring and plumbing is also scary, messy. It has been around awhile with 3 owners and I think 4 different power train combos, including a Volvo turbo motor I believe. Did I mention a 2 speed powerglide auto trans? I will hold my reservations until I have tested it. They ran it in second always because the 430 whp LS just spun the wheels no matter what speed, up through 70mph.

**Zlalomz** · 01-11-2018, 10:55 AM

IMG_2854.jpg
25x13 Goodyears given to me by a fellow XP Turbo RX7 competitor. A definite nope.
The original owner in the Bay Area.
eriks+car_small.JPG

**jakermac** · 01-11-2018, 03:29 PM

Well! I guess someone was trying something radical. Not sure how successful that would have been.

Oh, and if you're interested in trying the small GC front bar, I'd love to try the large one. We could do a straight swap. Just the actual bar itself, none of the mounting hardware, etc... They're plug and play!

**Zlalomz** · 01-11-2018, 03:51 PM

I'll keep that offer in mind! Isn't there some crazy tax crossing the border ?

Bath Day.jpg IMG_0549.JPG Here is my FP autocrosser with 16x12 Panasports and where I gained a little knowledge about MacPherson struts, geometry and spring rates. The weight of the Z and the Bimmer are almost identical...weird.

**jakermac** · 01-11-2018, 08:17 PM

Originally Posted by Zlalomz

I'll keep that offer in mind! Isn't there some crazy tax crossing the border ?

Not an issue for you, as I do all my shipping to and from Blaine, Wa. And the canadian border guards (notice I didn't say tax collectors) are very relaxed about that kind of stuff these days.

BTW, love the 240!!

**Zlalomz** · 01-31-2018, 02:49 PM

Edgeworks My BMW.jpg I found another pic of my car in a former life. I guess 25 inch tires might work. I will mount one up and check clearances through full suspension movements.

**mslevin** · 02-02-2018, 05:56 PM

Originally Posted by Zlalomz

Edgeworks My BMW.jpg I found another pic of my car in a former life. I guess 25 inch tires might work. I will mount one up and check clearances through full suspension movements.

Now THAT is some nice tire fitment right there.