Ride height for street & track?

I'm dropping my EDC car with a spring/sleeve kit (it works with the GC camber plates I already have and was cheap; if unsatisfactory, I'll go coilovers, but brakes killed my mod budget for this year).

Anyway, I've had some trouble finding posts on a good ride height for a tracked, mostly street car. Here's what someone posted for the factory setup on a 2012 M3 E92 ZCP, which seems like a good starting point:

-F 14.2"
-R 14.0"

(I got that from this post: http://www.m3post.com/forums/showpost.php?p=12870480&postcount=7 but now I wonder if I'm reading it correctly... it seems like he means those are stock and then goes on to say how he modified it. So, when he says a R 0.25" rake, does he mean the rear is 0.25" higher than front?)


As for my goals, I know I don't need to lower it, but I have coilovers on my A4. It's not slammed, but dropped a little below the factory S4 ride height. I have grown to love its firm ride and the connected feeling of driving it. I've never liked the M3's ride as much, on any EDC setting. I'm hoping the stiffer springs and a slight drop will help.

BTW, both cars have 18" wheels with 35-aspect tires. It seems like a good track setup, and the streets around here would not be kind to 19" wheels.


Thoughts?

BTW, I have a non-ZCP car, so that's why I'm looking to ZCP as a step in the right direction, but still street-friendly.

Well, can anyone at least advise on what amount of rake to use? Do I want higher in the rear? Is 0.25" good?

I noticed this thread, which lists the factory ride height:
I went with a 0.5" drop, in front, which is ~13 mm. So, just a tiny bit lower than ZCP. I'm using a 0.5" rake, so the rear is adjusted accordingly (I'll post that number if I find it). Seems planted on the track, and I really like the way it handles on the street.

I upgraded the front & rear springs to Ground Control's EDC-compatible coilover conversion kit. I think the front spring rate is now 440 pounds (the invoice says something about that). I don't know the rate of the new rear springs. It adds firmness and really helps in corners, but EDC comfort mode is still very compliant (if a bit bouncy).

I'm finally rather pleased with the way my car rides, both street & track (previously, I was not very happy with either). It's still not optimal, but my current thinking is that I'll probably upgrade the rear subframe bushings before doing anything more with springs/dampers/coilovers, if ever.

GTS specs:

32 00 Wheel Alignment E92 / M3 GTS
Observe test conditions

FRONT AXLE:
Total toe-in 0° 10± 8'
Adjustment total toe-in* 0° 10± 6
Toe difference** single wheel between left/ right max. 12'
Camber (difference between left/right max. 30') -1° 10 ± 20
Adjustment camber* -1° 10 ± 10
Toe difference angle (difference between left/right max. 30')
- with inner cornering wheel at 20° steering angle -2° 02 30'
Castor angle (difference between left/right max. 30')
Front wheel offset 0° ± 15'
Maximum steering angle
- Inner cornering wheel approx. °
- Outer cornering wheel approx. °
REAR AXLE:
Total toe-in 0° 10 ± 6
Adjustment total toe-in* 0° 10 ± 6
Camber (difference between left/right max. 30') -2°00 ± 15
Adjustment camber* -2° 00' ± 10'
Geometrical driving axis 0° ± 12'
*Note: To minimise adjusting errors (measuring inaccuracies), use a narrower tolerance for adjusting toe/camber.
*Note: Toe difference front axle = criterion for steering wheel inclination

31 00 Front axle - ride height E92 / M3 GTS
Ride height in normal position (DIN empty)

Attach tape measure to bottom middle of rim flange and measure to lower edge of wheel arch


Tolerance ride height in
-Normal position +/- 3mm
SERIES
19" wheel rim mm 613


33 00 Rear axle - ride height E92 / M3 GTS
Ride height in normal position (DIN empty)

(attach tape measure to bottom middle of rim flange and measure to lower edge of wheel arch)


Tolerance ride height in
Normal position +/- 3 mm
Difference ride height between left/right in
Normal position +/- 3 mm
Series
19" wheel rim mm 597


31 00 ...
Notes on threaded chassis M3 GTS

The BMW M3 GTS features a threaded chassis with the following range of adjustments:
- Vehicle height
- Camber on front axle
- Rebound/compression stage, shock absorber

This can be used to adjust the chassis to different road profiles and driving styles.
The chassis has two preset setups:
- Road setup = factory setting for operation in traffic
- Racetrack setup = setting for operation on a racetrack only
Important!
For operation in traffic, the factory settings (road setup) must be used!



Note the following procedures for setting the various setups:
• Ride height
• Rebound and compression stage setting

Recommended adjustment values:
Road setup Rebound stage Compression stage Ride level
Front Axle 8 clicks open 5 clicks open 613
Rear axle 9 clicks open 4 clicks open 597
Racetrack setup
Front Axle 8 clicks open 3 clicks open 597
Rear axle 9 clicks open 2 clicks open 585

wish someone had a GTS on these boards and would post some actual yumminess.

I would stay stock until full suspension upgrade.

I just posted the exact setup for the GTS dude.

spr wrote  

I just posted the exact setup for the GTS dude.

Talking about some real pics of their own gts. Not a spec sheet.

pkim1079 wrote

wish someone had a GTS on these boards and would post some actual yumminess.

I would stay stock until full suspension upgrade.

GTS = KW Clubsports with custom valving:

http://www.m3post.com/forums/showthread.php?t=385970

i was under the impression that for track use a slightly raised front compared to the rear was needed. need more front travel under braking than rear.

1MOREMOD wrote  

i was under the impression that for track use a slightly raised front compared to the rear was needed. need more front travel under braking than rear.

Isnt the stock setting like that too? My front sits higher than rears but theres still some rake.

pkim1079 wrote

I would stay stock until full suspension upgrade.

Well, I had stock EDC and really wasn't happy with it on the track. After installing the GC spring & sleeve kit + camber plates, with the ride height and camber settings I mentioned above, I'm very pleased with it on the track, yet it's very usable on the street. Until the EDC dampers need replacement, I don't see any reason for furher upgrades. Even then, there's a 50/50 chance I'll keep the same setup and just buy another set of EDC dampers.

Drifty// wrote

Well, I had stock EDC and really wasn't happy with it on the track. After installing the GC spring & sleeve kit + camber plates, with the ride height and camber settings I mentioned above, I'm very pleased with it on the track, yet it's very usable on the street. Until the EDC dampers need replacement, I don't see any reason for furher upgrades. Even then, there's a 50/50 chance I'll keep the same setup and just buy another set of EDC dampers.

stock set up is not nearly firm and precise enough once you get to intermediate. once your that quick the car feels slow and wallowy. i was waiting around for the car to settle into the entry phase of the corner.

1MOREMOD wrote

stock set up is not nearly firm and precise enough once you get to intermediate. once your that quick the car feels slow and wallowy. i was waiting around for the car to settle into the entry phase of the corner.

What springs were you running? The front springs in my GC kit are 440 pounds/inch. Do you remember what ride height you used?

I'm not claiming this is the ultimate track setup. Just that suspension no longer feels like a glaring weakness. So far, I'm very satisfied with how it feels on the track, and it's still very street-friendly.

Drifty// wrote

What springs were you running? The front springs in my GC kit are 440 pounds/inch. Do you remember what ride height you used?

I'm not claiming this is the ultimate track setup. Just that suspension no longer feels like a glaring weakness. So far, I'm very satisfied with how it feels on the track, and it's still very street-friendly.

sorry stock springs and stock edc suspension. so changing to higher rate like that may help for the time being. stock set up is a glaring weakness once you go a little faster. now i am on 700 front and 800 rear.

pkim1079 wrote

Isnt the stock setting like that too? My front sits higher than rears but theres still some rake.

yes stock is like that and rake is due to the taller rear tire compared to the front

conceptually the front needing to be a bit higher than the rear makes sense to me.

KennyPowers wrote

conceptually the front needing to be a bit higher than the rear makes sense to me.

On the track? Seriously?

All three shops I've been to since installing these springs have experience in preparing cars for the track, and two of them have their own race teams. They all agreed with the idea of a forward rake (not sure if that's the right term, but I mean the rear of the chassis sitting higher off the ground than the front). The rationale for this is to create more aerodynamic downforce. And note that this is measured between the chassis and ground - not at the fenders.

And I honestly don't see why you'd need or want more suspension travel for braking. I can't see when brake dive is ever a good thing. Maybe in the snow or rain, but not in typical track conditions.

1MOREMOD wrote

sorry stock springs and stock edc suspension. so changing to higher rate like that may help for the time being.

Okay, so that's where I started, and I can tell you that just installing the Ground Control kit and the ride height adjustment helped immensely. It also included replacement swaybar end links and I think replacement bump stops.

I actually installed the camber plates before the first time on track, so I'm just comparing stock springs/height to the GC springs w/ 0.5" drop.

Drifty// wrote

And I honestly don't see why you'd need or want more suspension travel for braking. I can't see when brake dive is ever a good thing. Maybe in the snow or rain, but not in typical track conditions.

brake dive isnt a good thing but when you slow down a 3000lb mass weigh will shift forward. its just physics. much of that is reduced with stiffer fronts but it still happens, and once you increase a cars grip with better tires you begin seeing increased braking and more weight shift again.

Drifty// wrote

On the track? Seriously?

All three shops I've been to since installing these springs have experience in preparing cars for the track, and two of them have their own race teams. They all agreed with the idea of a forward rake (not sure if that's the right term, but I mean the rear of the chassis sitting higher off the ground than the front). The rationale for this is to create more aerodynamic downforce. And note that this is measured between the chassis and ground - not at the fenders.

And I honestly don't see why you'd need or want more suspension travel for braking. I can't see when brake dive is ever a good thing. Maybe in the snow or rain, but not in typical track conditions.

You want more suspension travel on the track, period. Running out of suspension travel means you are beyond the capabilities of the suspension to control the car. BMWs are front end heavy (like almost every other front engine sedan) so you need as much travel in the front suspension as possible.

You will find the car will rotate under all conditions much better by keeping the car pretty close to level.

My E46 M3 is pretty close to level and it rotates very well.

Drifty// wrote

On the track? Seriously?

All three shops I've been to since installing these springs have experience in preparing cars for the track, and two of them have their own race teams. They all agreed with the idea of a forward rake (not sure if that's the right term, but I mean the rear of the chassis sitting higher off the ground than the front). The rationale for this is to create more aerodynamic downforce. And note that this is measured between the chassis and ground - not at the fenders.

And I honestly don't see why you'd need or want more suspension travel for braking. I can't see when brake dive is ever a good thing. Maybe in the snow or rain, but not in typical track conditions.

over-react much?

FYI I said the suspension travel / wheel gap conceptually makes sense to be more in the front than the back. most cars run taller tires in the back vs the front, so the rake is natural. never claimed to be a pro driver or race car specialist.

brake dive isn't a good thing, but it happens on any car.

FWIW:

For my 2009 E90 with 19" wheels:

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
245/35-19 3.4in 12.9in 25.8in 80.9in 783 0.0%
265/35-19 3.7in 13.2in 26.3in 82.6in 767 2.1%

= The rear tire is 0.5" larger in diameter than the front (0.25" higher rear ride height due to the larger radius).

I measured my E90 M3 at:

Front Fender (ground to lip): 26 5/8" = 26.625"
Rear Fender (ground to lip): 26 7/16" = 26.438"

Front Framerail (at jack point): 6 3/8" = 6.375"
Rear Framerail (at jack point): 7" = 7"

Thus: The front fender sits a bit higher than the rear (~0.187") while the radius of the front tire is 0.25" less. This visually should look like almost 0.5" (~0.437") of a gap more in the front between the lip of the wheel and the fender than the rear.


Rake:

Measured at the frame rail at the jacking points, the rake is 0.625" with the front of the car lower than the rear. Rake is somewhat arbitrary and what only matters is using the same point when measuring from Car A to Car B, or from setup A to setup B. You can use the fenders as a baseline for rake, but in racing they can be moved and bent so it's not the best place to measure from. At the end of the day, the chassis is nose-down while the fenders are almost even if not slightly nose-up.


I wouldn't call the M3 as "nose-heavy" since its pretty much 50/50 weight distribution. Due to the anti-dive in its suspension geometry, the front does not travel much during braking, especially when you use high spring rates. As long as the front suspension dosn't bottom-out, the front ride height or spring rate of the car does not need to be excessively high.


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