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Das Beast: My E30 track / street build

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  • dvallis
    replied
    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.

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  • Digitalwave
    replied
    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.

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  • dvallis
    replied
    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?

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

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  • Digitalwave
    replied
    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.

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  • dvallis
    replied
    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?

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  • dvallis
    replied
    Definitely with you on that

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  • Digitalwave
    replied
    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*).

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  • citizen_insane
    replied
    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.
    Last edited by citizen_insane; 05-19-2020, 06:37 AM.

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  • dvallis
    replied
    ALWAYS taking advice. Thanks. :-) Will be scrutinizing the front shock tower plate later. Caster adjustment makes sense looking at this picture of the GC plate.



    Are you adjusting the rear toe and camber with eccentric bolts? I read so many horror stories about them or the IE kit coming loose we decided to go fixed and "run what we got" in the rear.

    I've still got this IE kit.

    Last edited by dvallis; 05-18-2020, 06:05 PM.

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  • Digitalwave
    replied
    Regarding the alignment (if you are seeking any advise that is), you'll probably just max out the camber and caster in the front. You don't have to take anything apart to adjust the caster. Just loosen the 3 top bolts that hold the plate to the shock tower and push them all the way to the back of the car.

    You'll probably want a little more than -2* rear camber; -2.5 to maybe -3 at the most. If you can get -1/8" rear toe that that would be a good number. Nobody runs front toe in on a track E30. Either 0 front toe or 1/16" toe out would be a good starting place.

    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.

    Leave a comment:


  • dvallis
    replied
    Thanks for the confirmation on setup numbers. Is the GC caster adjustable from underneath with the strut attached, or do I have to take the whole freaking strut off?

    We're running this custom built coil over based on reinforced stock struts with ground control adjustment plates.





    I haven't looked into roll center / bump steer correction yet, but it looks fairly simple on this car. Just a kit that adjustably lowers the tie rod ends. Any experience with the Garagistic or Ground Control kit? They look pretty solid.

    Leave a comment:


  • citizen_insane
    replied
    Those suspension settings look about right to me. I wasn't able to get more than -3.5° camber and 9° caster up front with my GC race adjustment plates, but I have stock shock towers, can't remember if yours are modified. Are you planning to use front roll center correction? I've got some extended ball joints I've been meaning to put in my car. My car isn't all that low, but the front end feels like it wants to give up a bit when I push it hard (unlike my other race car which is double unequal length A-arm up front).

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  • dvallis
    replied
    Suspension musings ....

    Could not find a decent write up of the math for string box alignment so here it is. There's a huge amount of confusion on the internet around using ASIN, ATAN or whatever to figure out toe per wheel, total toe, whatever. Instead of blindly relying on some internet calculator, or "I read that some guy said" here's the fundamental math.



    Negative toe is OUT
    Negative camber is IN
    Positive caster is wheel AHEAD of strut tower
    Front positive toe = better stability
    Front negative toe = faster turn in but less stability
    Rear positive toe adds under steer
    Rear negative toe adds over steer
    Adding camber also adds toe IN. Adjust camber first
    More caster keeps tire contact patch level when wheel turns
    Too much caster causes corner jacking (>10 deg on E30)
    More caster dynamically adds camber as the wheel turns

    May have to revisit the rear suspension depending on measurements. See this post for details and pics on adjustable rear suspension. Need to dig those IE parts out of the garage. Don't forget to add the Chrome photobucket fix from page #1 of the blog.

    Ground control caster adjustments
    Longacre Camber Caster gauge instructions (Caster part is funky. Still don't understand it)

    Some data for reference when we do the alignment.
    E30
    STOCK
    SPEC
    30
    DAS BEAST
    TARGETS
    Front caster (deg) 8.5 ±0.5 9.0 10
    Front camber (deg) -0.67 ±0.5 -3.5 -4.0
    Front toe (in) 1/8" ±1/32" -1/16" 0.0
    Front toe (deg) 0.3 ±0.08 -0.15 0.0
    Rear camber (deg) -2.0 ±0.5 -2.5 -2
    Rear toe (in) 1/8" ±1/16" 1/16" 1/8"
    Rear toe (deg) 0.3 ±0.12 0.15 0.3
    Thrust angle (deg) ±0.25 max 0.0 0.0
    Steer ahead (deg) 0 0.0 0

    E30 wheel base is 101.2"
    Last edited by dvallis; 05-18-2020, 10:28 AM.

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  • dvallis
    replied
    Onward with suspension setup. We want to be able to set up the car at a track if required, so "take it to a shop" is not on the agenda. There are a huge number professional and DIY alignment tools out there. No two of them alike apparently.

    To start with, we've got one of these. Nice Longacre camber/caster gauge. That's some of the problem solved.



    Next we'll make a ride height and toe alignment custom tool for the E30. Starting with 3 x 6' pieces of 1" x 1/8" angle iron. Make sure the inside radius between flanges has a lot of "meat" like this one. Means the stick will have a high "K factor" ensuring excellent rigidity and straightness. You can get them at Lowes for $15 each.



    We picked up this handy tool at a welding shop several months ago. I knew we'd need it some time. Lets you weld bar stock at perfect 90 degree angles.



    We cut 4 pieces, 13 inches long and notched them like this.



    Tool gives us a perfect join. Rob got out the MIG and went to work.



    Here's the end result. Two "C" shaped pieces each for the front and back. They will bolt directly onto the bumper supports like this. You can probably guess where this is going. Add some fishing line and we'll have a perfectly repeatable string box to measure toe and ride height.





    Must be wildlife weekend. On the way home we rescued a large turtle walking across a four lane road at Shoal Creek. Big guy tried to bite me once but settled down when he realized I wasn't trying to eat him. Swam away happily in the creek

    To be continued ...

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