DMS Recommended Ride Heights & Alignment

[Dean]

Straight from the DMS 50 Manual:
For Subaru Impreza -WRX (GD)

Heights in mm from axle center to fender edges via plumb line.
      Rally Dirt AutoX Street Tarmac
Front 395   395  355   355    355
Rear  385   385  360   360    360

For reference: 
355mm = 13.9764in 13+31/32in
360mm = 14.1732in 14+3/16in
385mm = 15.1575in 15+5/32in
395mm = 15.5512in 15+9/16in

Toe for all conditions
Front 0-1.5mm in 0-1/16in
Rear  0-3°mm in 0-1/8in

Camber
      Rally   Dirt  AutoX Street Tarmac
Front -1.5-2° -2°   -2.5° -1.5°  -2.5° 
Rear  -1.5°   -1.5° -1.5° -1.5°  -1.5°

By the way, changing camber by 1° changes total toe by 3/8°

Cool home alignment site:

http://www.pelicanparts.com/techarti...ome_toe_in.htm

[MattR]

So, this info is likely universal for most coilover/ camber adjustment applications? I would assume so. Good info.

[Dean]

Originally Posted by MattR

So, this info is likely universal for most coilover/ camber adjustment applications? I would assume so. Good info.

Yes, at least through '04. I have a whole bunch of other alignment info from other sources, but this is the only ride height info I've seen.

Scott needs this since his tranny is heavy, so I posted it for everyone's consumption...

I am making the assumption that these ride heights minimize camber going positive as the A arms go past horizontal. They may not "look" the way you want, but are handling not looks oriented. I may post assumed spring rates for each surface as well.

[sperry]

I'm not so sure about the whole STi tranny is a lot heavier theory... my car weighed 3089 last night, which is only 9 lbs heavier than stock WRX curb weight! 'Course that was with only 1/4 tank of gas, but I don't see 12 gallons of gas weighing 200 lbs, which is the number that's always thrown around.

But before I could get to work balancing the car, I accidentally rolled it off the scales and into the closed garage door. I'm a fucking idiot... doesn't look like there's any real damage to the door, but one of the hinges put the hurt on my rear bumper. No e-brake in the corner pocket! That's when I decided I was too tired to try to get the suspension aligned. Hopefully I'll be able to get out of work early enough to get it done before driving out to Lovelock. At least I've got the garage leveled, which took about an hour.

Anywho... I think I'm looking at about 3300 lbs at race-weight (1/4 tank of gas + driver). Not bad for what's supposedly a much heavier transmission. I'm shooting for 1000 lbs per tire in the front and 650 per tire in the rear, which is right around 60/40. Of course the more weight I can get in the back to balance things out, the better, but I'm not so sure there's much I can do w/o getting way too jiggy w/ the ride heights.

[AtomicLabMonkey]

Gas weighs about 6lbs per gallon.

[Dean]

Originally Posted by sperry

Anywho... I think I'm looking at about 3300 lbs at race-weight (1/4 tank of gas + driver). Not bad for what's supposedly a much heavier transmission. I'm shooting for 1000 lbs per tire in the front and 650 per tire in the rear, which is right around 60/40. Of course the more weight I can get in the back to balance things out, the better, but I'm not so sure there's much I can do w/o getting way too jiggy w/ the ride heights.

Ack, standard misconception above.... Cornerweighting is not about front-rear or left-right, the primary purpose is about cross corners....

Your objective is to have LF + RR = RF + LR with driver in the seat and approriate fuel load. This will make the car handle mostly evenly in left and right corners. Think of it as leveling a 4 legged table or stool. If one leg is short, it will pivot/rock on the two diagonal corners next to that corner.

Get within 40lb, and you are golden.

To adjust left-right, or front/rear, you have to actually move weight. Cross corners can be done with strut length.

The key is that you must do all the prep to be accurate.

SCALES MUST BE PERFECTLY LEVEL Think within 1/32nd of an inch or less.

Driver or equivelent weight in the driver's seat.

Disconnect sway bars.

If you can, disconnect the shock tops

Tire pressures to EXACTLY what you expect your hot pressures to be...

If you are working in the sun, or the temperature is changing, check pressures often.

...

Here is an OK resource for Cornerweighting process.

http://www.racepal.com/web-content/G...nerweight.html

[sperry]

Thanks for the info Dean.

I understand the purpose of crossweight... the numbers I posted are ideal, since the crossweight would be 50%, in addition to left/right and front/rear balanced.

Unfortunately I didn't check the crossweight, or write down the static corner weights before I crashed the car into the garage door, or I'd have some idea of where to go w/ the adjustments already.

[Dean]

Originally Posted by sperry

Thanks for the info Dean.

I understand the purpose of crossweight... the numbers I posted are ideal, since the crossweight would be 50%, in addition to left/right and front/rear balanced.

Unfortunately I didn't check the crossweight, or write down the static corner weights before I crashed the car into the garage door, or I'd have some idea of where to go w/ the adjustments already.

Ah, OK... You were just talking F/R so I didn't know. It's just really hard to do front/rear and left/right in a street car since your butt is left shifted, and there just isn't enough stuff to move to balance it out without adding to the overall weight.

All these people who add 10lb or more of wire to move their battery to the trunk for example are not buying themselves anything.

[AtomicLabMonkey]

Originally Posted by Dean

SCALES MUST BE PERFECTLY LEVEL Think within 1/32nd of an inch or less.

Good luck with that. We use ~1/16" shims.

Originally Posted by Dean

All these people who add 10lb or more of wire to move their battery to the trunk for example are not buying themselves anything.

I gladly took the extra ~5-6lbs hit from wiring to relocate my battery from the LF to the RR in my car. It was well worth it, because it mostly evened out the corner weight imbalance, as well as shifting the static weight balance about 1% towards the rear. I could just set up the ride heights I wanted at the suspension pivots and it took almost no spring perch jacking to even out the diagonals.

[sperry]

Austin... don't forget:

Subaru Battery:
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Mustang Battery:
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[Dean]

Some of the hard core Solo2 Subaru guys are down to this for a battery...

______
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Tiny Motorcycle SLAs

[sperry]

Originally Posted by Dean

Some of the hard core Solo2 Subaru guys are down to this for a battery...

______
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|____|

Tiny Motorcycle SLAs

With the amount of stalling I do w/ my car, I'm gonna keep my heavy-ass optima.

[Dean]

Originally Posted by sperry

With the amount of stalling I do w/ my car, I'm gonna keep my heavy-ass optima.

Please refer to this thread for assistance with your stalling issues... http://www.seccs.org/forums/showthread.php?t=3274

[AtomicLabMonkey]

Originally Posted by sperry

With the amount of stalling I do w/ my car, I'm gonna keep my heavy-ass optima.

If you've got a standard Optima red-top, it's the same as what's in my car.

[sperry]

Originally Posted by AtomicLabMonkey

If you've got a standard Optima red-top, it's the same as what's in my car.

I've got the standard one for the WRX. The "standard" one for the Mustang is larger, unless you got the smallest Optima since you've got a relocated setup.

[MattR]

Bump so I can find it easier...

[Dean]

Just a bump for season prep and some new info...

No warrenties or responsibility expressed or implied. Modify your car setup at your own risk.

If you don't understand all the implications of making changes to your alignment and other setup settings, do the research and make changes in small increments with testing at each stage in a safe controlled environment...
----------------------------

The latest manual for the '04 STI DMS 50s show the same info as teh first post, so no substantial changes, but...

After talking to the technical guy at DMS North America, he had some additional suggestions.

Tarmac / Autocross: Rear suspension can be lowered an additional 10mm to 350mm without significant geometry impact. May reduce downforce at higher speeds though compared to 360mm.

Front Alignment:

Camber -2.75 may be more appropriate for high lateral loads.

Front toe of 1/32" OUT per side 1/16" total toe OUT will substantially help turn in.

Rear toe of 1/32" IN per side 1/16" total toe IN appears to have the best results for road course performance especially at corner exit.

A very small amount of Rear toe OUT (1/32"-1/16" total toe OUT)will substantially assist entry and mid corner rotation, but adversely affect corner exit speeds. This is probably only appropriate for tight autocross courses on cars with stock or similar understeering suspension setups and lower torque.

[MikeK]

Recommended rear camber? Same as the first post?

[Dean]

Originally Posted by MikeK

Recommended rear camber? Same as the first post?

Yep. Apparently, much over 1.5 doesn't aid overall corner speed and decreases acceleration at corner exit.

Now be aware that this guy is not a hard core autocrosser, and primarily these recommendations are for road course configurations as STARTING POINTS! Optimizing settings for individual cars, driver styles and course conditions will require energy and effort...

[sperry]

IMO, all that data is bunk w/o indication of tire size and make.

I can guarantee -2.5deg front camber on Proxy RA1s means corded tires on the outside edge after a weekend at the track, for example. I'm running -3.5deg and I'd run more if I could get it easily.

[Dean]

Originally Posted by sperry

IMO, all that data is bunk w/o indication of tire size and make.

As I said, these are starting points... You gotta start somewhere... Even different drivers of the same car can have different wear and handling results do to the way they handle the car.

YMMV

[sperry]

Originally Posted by Dean

As I said, these are starting points... You gotta start somewhere... Even different drivers of the same car can have different wear and handling results do to the way they handle the car.

YMMV

My point was that even as a starting point, these numbers don't take into account that most R-compound tires like tons of neg. camber. i.e. DMS should indicate these numbers are start for street tires, or people following these numbers (like me) are going to tear up a set of $1000 tires in a weekend.

Start at the -3 to -4 deg that Toyo recommends when running RA1s for example. I had a good 50% tread left on the inside edge of my RA1s when the outside shoulders corded. And I didn't even realize how close to cording they were because I'd never used them before and didn't know how beefy the shoulders aren't.

[Dean]

If your tire manufacturer gives recommendations, then I would agree that you should use them. I don't believe most manufacturers do... I don't recall any from Khumo or Hankooks, but that doesn't mean there aren't any.

[NevadaSTi]

I read this whole thread, and I am not sure where I should have my car setup at / with. I know I want to play with the alignments to back my car steer better with its new FSB. So, some help would be greatly appreciated. Thanks.

[Kevin M]

Your alignment is simple. All the camber you can get front and rear, which is still not enough, and a little toe out front and maybe a litle toe in rear.