So I'm looking at getting as low as possible but keeping functional front suspension geometry. i.e. control arms droop down to lower ball joints, tie rod ends horizontal at static height.

I'm runing linear 60mmID springs front 500lbs/in on and 375lbs/in on LEDA coilovers. I have the alta PSRS and have it set at the 45deg setting for slight caster increase and decrease in bump steer (anti-lift).

have been using the helix camber plates but they have too much stack height for heavy springs(66mm). - I can't get lower than stock height with them. I'm getting K-Mac race CC plates. this will give me 2" less stack height above the spring.***Edit - the Kmac plates with coil perch (subsituting thinner clamp discs) are 46 mm stack so 20mm lower. k-mac qouted the stack height with the stock spring perch which is a lowering cup kit type. :(*****

This is an autocross setup. I run 9.5"x 23.5" race slicks on the front and 225/35/15 a6 hoosiers on the back.

right now I have 1.75" lateral droop in my control arms.

the possibilities:

I've seen the megan racing lower ball joint correctors. But I'd prefer to stay with the 15" forged wheels I have. the ball joint correctors are a great deal but I'd have to spend $2K to get a light wheel.

I can trim and remove whatever material i need from the wheel wells.
I could replace the strut towers with a tube frame but not that ambitious.

the lollipops (rear CA mounts) I can notch my floor in FPrepared, so I figure just shim the lollipos and Roll Bar mounts up 1/2-1".**Edit - I won't need to get that radical; I have Alta PSRS they are offset bushes. normally they move the pickup out and down. (which is how i installed them last year). Now I have caster plates so I don't need the change in caster from the PSRS. I can mount them with the offset up this will raise the mount point 1".

1) It looks like I can shim the inner ball joint brackets up with spacers bteween them and the subframe. The front bolt is under the inner CV boot. I can shim it only 1/2", the rear bolt has no clearance issues, so I can shim 1/2" or shim a little more (3/4") and rotate the axis of the ball joint slightly (faster wear). this would move the upper ball joint up either 1/2" or 5/8". And should be affordable.

**edit - measured today. the ball joint can shim up 12mm before it gets in range of the cv boot. To be safe I'd go with 10mm shim, 12mm ID. the 60mm long bolt under the CV boot just barely clears for installation. With the shim I need to get a 70 mm bolt in there, I would have to jack up the engine or dorp the subframe. the 4 bolts I need are M12x1.5 70mm 10.9(top half not threaded would be best).

What problems does anyone see with doing this.

2) the other thing is that the ball joint brackets bend down. 1/4 inch or so.
I'm assuming it will be an expensive PITA to modify them to be flat or bend up. I'll have to look at the old ones that are off the car this weekend. maybe another BMW bracket has the same overhead geometry and ball seat, but different topography.

3) flipping the ball joint brackets upside down and L-R. would put the ball joints at least 1" higher, may have to flip the CA's left and right upside down as well. Upside down the Rear CA bushes would work, havn't checked on the outer ball joints or Tie rod endlinks. I don't recall that the CA's have any vertical curve/bend to them. So upside down would just be a matter of fitting all the joints.

I'm pretty certain the inner ball joints would not be safe turned upside down. the weight of the chassis would be pulling them apart rather than pushing together.

also the bracket would likely bind with the CA before full droop.
and these are just the problems I can anticipate

4) does anyone know a source for solid metal ball joints/ spherical bearings that could provide a custom flat or elevated bracket, as opposed to the declined stock bracket.

5) custom tube control arms. and inner brackets. but the ball joints would be in the same position regardless of the control arm shape.

for now I'm planning to mess around with option #1 shimming the bolts 1/2". and go for a total of 1.5" of lowering but get for .75" of droop in the CA's. see how this messes up the drive shaft and tie rod angles. Then consider more aggressive options.

advice and opinions welcome.

thanks!

 

After reading your well thought out post, I'm really suprised that you didn't get any replies. I'm looking for an extra 1/2 " drop in the from as well. Have you tried to shim your inner ball joints yet? If so, how much did you shim and what were your results? It seems like a logical and safe solution. The inner cv joints have plenty of allowance, travel wise, to allow for the shims without any negative effects. Ease let me know if that worked.

Thanks,

Chad

 

The only negative I can see coming from shimming the inner ball joint is the added camber. Unless you have adjustable camber plates you're going to wear out the outside edge of your tires.

 

will be building this week.

Just got spherical Camber/Caster plates. modified some parts to get 45mm stack up height.

I have to extend the threads on the Leda strut shafts to fit the plates.

measure shims.
track down the hardware.
build
align

I'll post back results.

 

eatsleepautox,
My appologies for being a bit off topic...FP seems like it could be a good place for the MCS to run, so I like reading your posts! The 52mm inlet restrictor in the rule book for forced induction prepaired cars seems like a sure way to limit the fun- are you still able to produce fairly good power with that setup?

Jason

 

Have you tried trimming the bottom of the brake hose/ABS sensor wire bracket? I trimmed a 1/4" off the bottom so the strut sits deeper in the casting. This didn't create any issues and dropped my front end another 1/4". All of the welding on the bracket is way above the part you will be trimming so there is no weakening. I think I could get another 1/4" if I wanted to with a bit more trimming with a dremel but I achieved the height I was aiming for with 1/4" only.

 

Turbo XS Blow Off Valve Type H-RFL (BOV-RFL) With new and improved turbo xs rfl styling, the BOV-H-RFL remains true to it's roots - it's still really f'n loud!

 

jank are you running in FP. The r56 platform would be a better platform to develop for FP. Once i can drive with the 200whp from the SC ill look at loosing the SC for a turbo. Thinking BBR stage 3.
what a great idea. Even if i dont go lower i can get more strut travel before the bump stop. Too bad i didnt see your post before i did a string alignment.

So ill try to post some pics soon.
Heres what ive done:

drop subframe (new ktf ps fluid)
replace bent control arm
shimmed inner baljoint brackets up12mm above SFrame
check that lollipops are putting comtrol arms perfectly square
put front end back on
built string alignment jig
squared rear subframe to the inner control arm mount bolts
the ride height is set with 3.5" fr the ground to the Front sub frame
the rear has about 1/2" rake.
Alignment specs are
fcamber -2.6 fcaster is about 5, rcamber -1.7, 1/32 toe in on all 4 corners measured on15"wheel.
Stock front bar. Rear bar is hotchkiss comp bar soft setting
as stated before springs are 500 front and 375 rear.

On toyo tr1 street tires the car is insane on street drive. Race slicks on autox had to get rear struts tuned. 3 spins in first 2 runs. Then one good run but coned away.
My friend whose Evo just won SM at nats drove the car and was impressed with how well it settled into corners and how light the car feels.
So thats encouraging. Ill run it this sunday and hopefully get some good times.

i have alta psrs set at 45deg setting

 

The 52 mm restrictor shouldnt be much of an issue. I havnt built one yet as im not in a trophy spot to get protested. 2 ways to build it. Easy 1/2 alum plate place between compressor and plastic duct. This way is easy but would cause a sudden restriction and turbulence. Better way: Move the restrictor 4" up stream and intgrating it into the plastic duct pc would flow better as the duct has a tight turn about 6" from the sc. At the turn the cross section is a trapezoid with less area than a 52mm circle. So its not really a retrictor just a different shape then expands to the big square crossection that mates the SC.

Ill build it this winter.

 

good idea, but my Leda coilovers have a stop ring welded around the strut that sits on the knucle.

The car is handling very well. Almost no body roll and loaded wheels have good camber.
Here are some pix from the weekend
http://www.zodow.com/COAX/10COAX11/53_FP.php
http://www.zodow.com/COAX/10COAX11/53_W.php