My E90 M3 Dedicated Track build (with pix!)

[derbo]

Originally Posted by SaNGRia

SYT_Shadow nailed it. The GTS i use comes straight from Bmw M GmbH . Appreciated my buddy SYT_Shadow and Thank you dogbone for the trust .

Did you flash the 442 to dogbone car or the 773?

[SaNGRia]

Originally Posted by derbo

Did you flash the 442 to dogbone car or the 773?

I had couple complaints on 442 before. i dont use that one anymore. 773 is Gold in my book.

[dogbone]

Originally Posted by ///Mobbin

dogbone Great update and I sincerely hope your problems are behind you! Also wanted to note that myself and many others have been running the original GTS DCT file with good success and I've even run it on two different cars now, think it should work well for you. Best of luck at your next event

Thanks! Yeah I'll need a bit of luck.

Originally Posted by StripclubDJ

By EAS he means me
And by Steve he means me


I'll see my way out.

hehe wait a minute----I do talk to Steve! What happens after that is the magic of EAS!

[StripclubDJ]

Originally Posted by dogbone

Thanks! Yeah I'll need a bit of luck.

hehe wait a minute----I do talk to Steve! What happens after that is the magic of EAS!

I look at the car, I tell Steve word for word what to text you, I fix the car, Steve collects 100% of the profit , then I go back to my single wide trailer and eat coup of noodles for dinner.

I live a positive life .

[dogbone]

Originally Posted by Redd

@dogbone, why are you against full spherical for the rear? Just curious. I for one think you will really benefit and appreciate the extra grip and feedback from sphericals, and now is the right time to do it since you're getting new arms.

A few reasons based on my experiences over the years.

1. Reliability. The stock arms may not be the lightest. They may not be the most adjustable. But they are 100% reliable. You virtually never hear of an OEM control arm failing [when torqued properly]. When I approached the idea of building this car, the top item on my list was reliability. I didn't want to be chasing stuff all the time. Some things high on the list were to leave the control arms stock and don't touch the wiring.

I know I've had a lot of trouble with my car this year, but prior to 2021, my car was SUPER reliable. I could go a whole season with just basic maintenance and replacing consumables. I truly believe the problems I've had this year are age related----meaning I've basically used up the effective lifespan of a lot of the parts on the car. Over the years, other fancy control arms seem to have more question marks surrounding them. I just didn't need that. Also, along my journey, I talked to a pro racer who had $300k into an E92 build. They still used stock control arms for the reliability.

2. Stress. Years ago, when I was very new to all this stuff, a very experienced tech and I stood under my car while on the lift. We were talking about the concepts behind making everything solid. Yes, putting solid stuff can make your settings more constant. Yes, there are some benefits to reducing flex/play in those joints. But, there's always another consideration on a production car. In this case, we were talking about the idea of----if you don't allow a part designed to absorb energy to do its job, where does the stress go? Obviously, there are very high stresses on the bottom side of the car. The rubber bushings are there to absorb those stresses. If you go solid in a certain spot, you are pushing the energy elsewhere. It's not a free lunch. The stress/energy has to go somewhere. And can the spot receiving the added stress take it? A good example of this kind of conversation would be the rear shock tower mounting point. When moving to true coilovers in the rear, the debate has raged on for years about whether or not you need to reinforce the top shock mount.

Now, you could argue that some of the rubber bushings in the control arms and sub-frame are simply for comfort since it started its life as a street car. Well, I don't design cars, so I don't know how strong they made all those contact points. But, after looking at it for some time years ago, I decided I was comfortable with solid aluminum subframe bushings because that area is beefy with big bolts, but that I'd leave most of the control arm joints stock. In essence, I took some of the flex/movement out of the system, but not all.

The other thing that doesn't appeal to me a whole lot is that the accepted solution for going more solid on the rear arms involves tack-welding sleeves into the OEM holes.....well, this feel a bit permanent to me. If I don't like it, it sounds like a pain in the ass to revert back.

3. Is everything locked down and solid really better? Ah, this one is tough. Some people will tell you that any play/movement in the system is bad----you need to go full stiff at every joint to get maximum grip. Others will tell you a little bit of compliance actually helps you. I think the answer lies in the tracks that you drive. I think if you run on super smooth perfect tracks, then yes, removing play in the joints would be good. But, I live in the USA. The reality is that most tracks in the USA are not smooth. Most of the time, the track surfaces are not super awesome. Buttonwillow, Willow Springs, Chuckwalla, Auto Club Speedway----these tracks have a lot of---ummm shall we say---"irregularities" in the pavement, not to mention tall berms you must attack for a fast lap time. The only track I've encountered that has super smooth perfect pavement all the way around the circuit is Watkins Glen (and Laguna Seca is pretty good, but the pavement is aging there and getting some waves in it in certain braking zones). So, I think a bit of absorption is not a bad thing.

fsmtnbiker has been going through this all year while setting up his car. While going through many spring changes and alignment settings and swapping suspensions, he has been saying over and over that he can't get on power the way he wants. He went full solid and started to wonder here on the forum if a mixture of solid and flexy might help in his answer. So, I think the answer to #3 is situational. If you live in Europe and see smooth tracks all the time, you can lock the car down more and remove compliance. But on a bumpy track, I think you could benefit from a bit of compliance.

Another example that comes to mind is a Porsche Cup Car. The accepted setup on an older Cup Car was 1500lbs springs on all four corners(!!!). Think about that for a second----a 2600lbs car with 1500lbs springs on each corner. Sounds like a nightmare to me. How the heck do you attack a berm with that setup? Ok, well think about where the Cup Car was setup----not in the USA. My friend has a 996 Cup Car and it came with that "stock" setup. He finally couldn't take it anymore and has had the spring rate dropped on the car. USA tracks just aren't as smooth. So, I think the answer lies in where you drive, and you could make good arguments for both something that's super stuff and locked down versus something that has some compliance in it.

Anyway, these are some of the ideas that have guided my actions over the years. Again, I'm not a race car designer, so I'm no expert here. But my car seems to move nicely over a variety of track surfaces and track features. Could it be better? I'm sure it can. I have REALLY been eager to put some hot laps at Buttonwillow to compare the MCS setup to the old JRZ setup, but my tech issues have prevented me from going for it. From what I've sensed so far in my warm up/practice laps, the car feels really good. In the future, I might do some experimenting by swapping rear bushings one pair at a time. But whoever does the work will have to assure me that I can revert to the old setup if I want.

[dogbone]

Originally Posted by Gmark958

What are the future plans for the car? Any new mods planned or is everything pretty much there and you're now just working on getting it all sorted out?

Unfortunately, sorting out the car has been the main task lately----in the last 13 months, the engine has been swapped, the suspension has been swapped (along with several rear spring swaps), the front and rear aero have been swapped, the transmission has been swapped (we tried swapping the clutches in the original trans), the steering wheel/paddles have been swapped, the power steering pump, steering rack, power steering reservoir and all the power steering lines have been swapped, the main radiator, oil cooler and power steering cooler have been swapped, all four hubs have been swapped, the control arms and some of the bushings have been swapped, several sensors have been swapped, the dual-mass flywheel has been swapped, the brake pedal assembly has been swapped---twice.....and I've been fighting weird grounding issues. And after all this, I still don't know if the car works.

But to answer your question, yes I have some things I'd like to do to the car if it stops breaking......

-rear plexiglass window to replace stock glass
-fire suppression system
-try to really solve the overheating issue with a boutique race shop. Have already started exploring the idea a bit. (expensive)
-there's other things, but I can't remember them right now because I'm so sad after typing that ridiculous list of swapped items.

[roastbeef]

gabe, you make a good case for leaving the arms alone.

as you probably know, i did everything except the rear trailing arms. next time we're at the same track day, you'll have to take my junk for a spin and see what you can discern. i'd trust you with it.

while i'm not any kind of an engineer either, i'd debate the amount of stress these arms increase on the car. i'd say the "weakest link" in the energy absorption between the car and the road is going to be the tires.
this is my thought process- imagine the car sitting still, but being pushed sideways by a tractor. a car on oem arms might have a little bit of compliance, but the tires are ultimately going to start slipping on the pavement as the car is pushed. a car with solid arms/bushings is going to take the same force to push sideways, its just going to happen sooner because there is no "give", its just more direct.
i could be wrong, but i just imagine the limiting factor being the friction between the ground and the tires.

[Redd]

Originally Posted by dogbone

But whoever does the work will have to assure me that I can revert to the old setup if I want.

Thanks for the detailed explanation, I see your logic. Converting the stock rear arms spherical using ball joints might be a good middle ground. And it's easily reversible - if you don't like the feeling then just press out the ball joint and press back in the stock rubber bush. You can do this easily for the guide rods and wishbones. Rear trailing arm is a bit more involved to get the stock rubber bushings out from the subframe and hub, but also reversible. Then if you like it, do the rear camber arm last (the one that requires tack welding).

[leftfootbr8king]

Originally Posted by Redd

Thanks for the detailed explanation, I see your logic. Converting the stock rear arms spherical using ball joints might be a good middle ground. And it's easily reversible - if you don't like the feeling then just press out the ball joint and press back in the stock rubber bush. You can do this easily for the guide rods and wishbones. Rear trailing arm is a bit more involved to get the stock rubber bushings out from the subframe and hub, but also reversible. Then if you like it, do the rear camber arm last (the one that requires tack welding).

Millway subframe side camber arm bushing doesn't need to be welded in.

Throw an eccentric bushing in knuckle side of the camber arm because roll center correction is nice if you can get it.

[derbo]

Originally Posted by leftfootbr8king

Millway subframe side camber arm bushing doesn't need to be welded in.

Throw an eccentric bushing in knuckle side of the camber arm because roll center correction is nice if you can get it.

You would probably need to do the all inboard (including camber/trailing arm) or all outboard (including trailing/camber arm) or all 8.

[leftfootbr8king]

Originally Posted by derbo

You would probably need to do the all inboard (including camber/trailing arm) or all outboard (including trailing/camber arm) or all 8.

Correct. But It's 6 per side.

[leftfootbr8king]

Upper arms are already spherical on inboard side.

[derbo]

Originally Posted by leftfootbr8king

Correct. But It's 6 per side.

Sorry, I meant all 4 bottom ones each side on the virtual A-arm if you are aiming for roll center correction.

[leftfootbr8king]

Trailing arm eccentrics correct bumpsteer. Depending on rear ride height theres roll center correction to be had with eccentric on just the knuckle side.

[derbo]

Originally Posted by leftfootbr8king

Trailing arm eccentrics correct bumpsteer. Depending on rear ride height theres roll center correction to be had with eccentric on just the knuckle side.

I agree, I'm just not agreeing on 6 per side.

Either you can do eccentric outboard trailing and Camber arm, inboard camber and trailing arm, or both. That's a total of 4 bearings per side? The upper arm bearings replacement wouldn't need eccentric for roll center correction.

I think we are all on the same page

[leftfootbr8king]

Originally Posted by derbo

I agree, I'm just not agreeing on 6 per side.

Either you can do eccentric outboard trailing and Camber arm, inboard camber and trailing arm, or both. That's a total of 4 bearings per side? The upper arm bearings replacement wouldn't need eccentric for roll center correction.

My 6 per side comment was in regard to number of spherical/solid suspension arm bushings per side that can be changed (eccentric or not, upper and lower) vs oem

I have done them all, with eccentrics in knuckle side lower arms plus SPL toe links.

[derbo]

Originally Posted by leftfootbr8king

My 6 per side comment was in regard to number of spherical/solid suspension arm bushings per side that can be changed (eccentric or not, upper and lower) vs oem

I have done them all, with eccentrics in knuckle side lower arms plus SPL toe links.

Yea thats what I was thinking. I was like we have to be on the same page.

[Redd]

Originally Posted by leftfootbr8king

My 6 per side comment was in regard to number of spherical/solid suspension arm bushings per side that can be changed (eccentric or not, upper and lower) vs oem

I have done them all, with eccentrics in knuckle side lower arms plus SPL toe links.

Guide rod - 1
Wishbone - 1
Trailing arm - 2
Camber/spring arm - 1

Total 5 per side. How did you get 6?

[derbo]

Originally Posted by Redd

Guide rod - 1
Wishbone - 1
Trailing arm - 2
Camber/spring arm - 1

Total 5 per side. How did you get 6?

If we were doing eccentric , it would be 1 or 2 on camber arm, 1 or 2 on trailing arm eccentric.

[leftfootbr8king]

Originally Posted by Redd

Guide rod - 1
Wishbone - 1
Trailing arm - 2
Camber/spring arm - 1

Total 5 per side. How did you get 6?

2 on trailing arm (in/out) 1 each on both upper arms (outboard side) and 2 on lower camber arm(in/out).

6.

[leftfootbr8king]

Originally Posted by Redd

Guide rod - 1
Wishbone - 1
Trailing arm - 2
Camber/spring arm - 1

Total 5 per side. How did you get 6?

Camber arm has a soft inboard/subframe mounted bushing that can be swapped for solid or solid eccentric. You know this.

[Redd]

Originally Posted by leftfootbr8king

Camber arm has a soft inboard/subframe mounted bushing that can be swapped for solid or solid eccentric. You know this.

Yeah I counted the rubber inboard camber arm bushing. The outboard is already ball joint, so I counted only 1 for camber arm.