Das Beast: My E30 track / street build

[citizen_insane]

Agree with Digitalwave on the front alignment, you basically just get what you get until you're hitting the inside of shock tower as you push the shock back and to the inside. You will probably not be able to adjust camber with the struts installed, so I left my camber adjustment bolts loose, pushed everything to the max, tightened one bolt and then unbolted the top hat from the shock tower so I could get to the top again to tighten all the adjustment bolts. For the rear adjustment, I think the Posi-Lock style is a good idea. I cam cam bolts on my car and they've moved once before.

The problem with most of the roll center correction kits is that they also have steering quickener and additional angle built in to please the drift crowd. I got lucky and MRT had some extra extended front ball joints that they sold me separate. I'm really impressed with the build quality, very nice hardened pin and 12-point ARP nut. They weren't that expensive and I could't find anyone else who had drop in front ball joints. If you go to custom LCAs you can use circle track ball joints which would be much more economical.

[Digitalwave]

I do not run any adjustment in the rear. I watch the Spec E30 guys fixing their loose trailing arms every damn day. I don't want to deal with it. I have a little more rear toe in than I'd like, but the camber is good (about -2.75*).

[dvallis]

Definitely with you on that

[dvallis]

Digitalwave said: Check out MRT Engineering, they have the nicest E30 bump steer kit I have seen, with real engineering behind it. Second choice would probably be SLR Racing here in Florida. I wouldn't buy anything from Garagistic; they just copy other's designs and sell them for bottom dollar. They typically get a lot of complaints for poor fit and finish.

I talked to the MRT guy on eBay, His kit fits stock struts with the Z3 rack. Also found this thread that shows the MRT kit installed. It puts the knuckle really close to the Stoptech rotors he's using. My rotors are also way thicker than stock.(11.75" x 1.25" Hawk DTC) Not feeling grinding the knuckle for clearance. Any comments?

[Digitalwave]

I don't have any direct experience. I run E30 M3 struts and knuckles where the steering arm is separate from the strut tube, so I just have a block of aluminum between the two pieces that helps correct the roll center.



My spacers are only 13m thick; they still work with 16" wheels. Usually you can run up to 25mm/1" thick if you are only going to use 17" wheels.

I have seen guys with BBK's even with stock roll centers on E30 M3s grind down the tip of the control arm for clearance against the rotor. However, I don't think you can really tell anything about the clearance from the angle of that photo unfortunately. It might be plenty, or it might take some creative grinding.

[dvallis]

That is some good suspension porn. Didn't realize E30 M3 struts were an option. Hmmmmm .......

[dvallis]

Revisiting the spring rates while doing alignment research. Back in 2018, Spec30 adopted a Ground Control kit with 535 lb/in front and 700 lb/in rear. We're currently running 400 lb/in front, 650 lb/in rear. Slightly softer but we did a lot of weight reduction. They might be right for this car.

Spec30 fronts are maked with a custom "Ground Control part number. GC150.64.92

My stock Eibachs are marked as "0600.250.0400" ( 6" length, 2.5" ID, 400 lb/in)

Any racers care to comment on spring rates for an M20 powered E30?

[Digitalwave]

I would not worry about spring rates and such until after you have a bit of seat time in the car. Then adjust as needed.

That is a street setup for the most part, but it shouldn't hold you back for a while.

[dvallis]

Finished our ride height and toe tools today. Top string is on the frame attached to the car. Bottom string is on jack stands, checking the floor with an attached level.



Surprisingly, our floor is completely level, front to back and left to right. Now we know for setup the string attached to the frame will give us accurate ride heights for corner balancing.

[MrScuba]

I have an e30 track car, with the Spec e30 suspension. It was a huge improvement in responsiveness over the mutt track/street suspension that was on it. The only criticism I am aware of is from a friend who has a problem with the car hitting the bump stops. I think his car is too low.

[dvallis]

Thanks for the feedback. My rates & height are close to Spec30 so we should be good for now. Getting more into setup.

Working on building a set of 3500 lb digital corner weight scales for $100 next. Proper scales, not bathroom scale ghetto lever hack. Requires some electronics knowledge, coding skill and a bit of soldering.

Stay tuned.

[dvallis]

This thing is a $9 load cell. It's a piece of steel with a full bridge strain gauge laminated to a location that bends .. slightly. I used similar strain gauges in the Navy to measure deflection of F18 wing beams under a 10,000 lb computer controlled hydraulic press. THAT was fun to write code for. :-) This one happens to be rated for 220 lbs. Put 4 under a metal pate with associated electronics and you've got an 880 lb scale. One of those under each wheel and we're done.



IT'S ALIVE. Volt meter sees 1.2 mV out of the load cell as I lean on it with my thumb. Using a 24 bit ADC we can resolve ~0.6 uV per count over a 5V range. That 1.2 mV would look like 2000 ADC counts. No problem.



Now I know that works, we'll design the scale plate.

[citizen_insane]

This is VERY relevant to my interests. I've thought about doing the same a few times, but never bothered to actually look up where to get the hardware. Where are you sourcing your load cells?

[dvallis]

I found this one on Amazon. You could check eBay too. Most important thing is load rating. They need to be at least 100 kg (220 lb) rated so four under a plate will have enough capacity. Most you'll find are only rated for 50 kg.

You can also just buy full bridge strain gauges from Omega and laminate them to your own metal load cells. Probably better quality but you need to know how much strain your cell will experience under load.

[citizen_insane]

I found this one on Amazon. You could check eBay too. Most important thing is load rating. They need to be at least 100 kg (220 lb) rated so four under a plate will have enough capacity. Most you'll find are only rated for 50 kg.

You can also just buy full bridge strain gauges from Omega and laminate them to your own metal load cells. Probably better quality but you need to know how much strain your cell will experience under load.

Awesome, thanks. I haven't put on strain gauges since college, not sure I fully trust myself to do it if there are relatively cheap off the shelf options.