ideal ride height for optimum performance?

[lagoon]

hi guys,

i would just like to know what the ideal ride height is for good/best handling performance? i bought my car with gc/koni's and would like to get it setup better. the car right now is pretty slammed, i love the look, and it does handle great, but between having the car slammed or having it perform better, i think i would prefer the latter. i'm not a professional driver, nor do i even attend the track often, but i do have adjustable suspension, so i might as well utilize it.

basically, at what point does lowering have negative effects? what height would be ideal to get good handling?

thanks.

[BeirBrennerE30]

well.... as you as you can go is the easy answer...

the hard answer is not so clear... the point of lowering your car is to lower the center of gravity which is good because it reduces weight transfer during cornering... and you want to do this because you want the weight of your car as evenly distributed as possible for maximum grip... so ideally you want your car as low as you can go without scraping bottom excessivly for a given track(or local streets)... then make small tweaks during corner balancing for as even as you can get weight on every tire.

here comes the problem... when you lower your car this much on coilovers and dont make any other modifications you completely screw up your suspensions geometry... your roll center plumets to teh ground and increases your roll couple(the distance between your center of gravity and yoru roll center in the vertical axis of yrou car) which causes yoru car to roll more and about a lower point... not so good... lowering your car this much can also cancel out any antidive built into the e30(none stock) and can cause teh car to go into prodive(never good) when applying brakes... in the rear it will cause excess tire ware from excessive toe in and very agressive camber that is only made worse when weight is transfered to the rear wheels(acceleration). The camber curves in the front will suffer also... sometimes to the point where you can gain camber( in the positive direction) in stead of lose it(becomes more negative) as the weight transfers to the front(braking)... there are other probelems too but these are the major ones..

so what to do about this? well in an ideal world when you lowered your car you would want to keep the same geometry as stock( kind of but close enough for this example) just lower the center of gravity... But this requires moving mounts and modifying struts... so if you are not willing to do that(few are) then lower your car just enough so that your front control arms and rear trailing arms dont invert( the side mounted to the car should be a little higher then the side attached to where the wheel is)... this is the best you can do for suspension without modifying other things and still being low(probably not as low as you are now if the coilovers were done for looks)...

you can actually calculate several of the suspension settings that were mentioned above and try to optimize them if you are feeling perticularly motivated... "how to make yoru car handle" is a good book with lots of info ... its a little dated info wise(doesnt cover the new bmw z-axel and stuff like that)... buts its find for the e30 since the e30 is a little dates aswell

[lagoon]

thanks very much for such a detailed and well written response. i guess for now, the best i can do it make sure the control arms are not inverted. does it matter how much they aren't inverted (if that makes any sense)?? does less inverted = better handling? i'm sure there are a number of differnent factors that come into play, but can that be used a general rule of thumb? or is the relationhip between good handling and positioning of the control arms not too linear? o god.. i hope at least some of that made sense..

eg. []\ _____ /[] or []--____--[]


the squares are the tires, the control arms being the lines that connect the tires to the middle.

thanks again.

[BeirBrennerE30]

looking from the front like you are isnt as big of a concern as looking from the side... perticularly for the rear.. but i would try not to go more than parallel with the road.. mroe like example 2 you showed than example 1

having a good handling car is in the eye in the driver... it depends on yoru drving style and whether you like having a car the oversteers, understeers or is neutral in the entry, apex or exit of a corner... if you dont mind tinkering i would say that you should try a couple of different setups and see what you like better and what feels better/faster(since you probably dont have datalogging capability to measure what really is faster)

[King Luis]

i just got my GC's and Koni's installed and i've gone by the rule below about the control arms.



here's a great article about lowering and its consequences.

http://e30m3performance.com/myths/Weight_Transfer/weight_transfer.htm

[IS]

That is irrelevant for our cars because you will run out of damper travel before having a larger couple on the lever becomes a big issue. Besides, it is completely alleviated by increasing spring rate!

For the e30 cars, you want to go as low as possible without running out of damper travel - simple as that.

[rwh11385]

my rear was low when i bought it and i rode on the bumpstops.

you can get away with a little more slammage if you have short struts and shocks and shortened housings, but having almost no suspension travel isn't a good thing in my book

I am going to take up the front of my car because the control arms are actually beyond parallel

[lagoon]

For the e30 cars, you want to go as low as possible without running out of damper travel - simple as that.

does it matter how much damper travel? sorry if these questions seem trivial, i'm just trying to learn.

i think i might take up the front and rear a little, because they are parallel or past. when changing ride heights, would it be necessary to get an allignment? or can i change the height say, 3-4 times, just to test different heights, then get an allignment done after i have the final height?

TIA

[rwh11385]

does it matter how much damper travel? sorry if these questions seem trivial, i'm just trying to learn.

i think i might take up the front and rear a little, because they are parallel or past. when changing ride heights, would it be necessary to get an allignment? or can i change the height say, 3-4 times, just to test different heights, then get an allignment done after i have the final height?

TIA

You can measure your fender heights, noting also your tire sizing and late/early model arches. Then compare to the suspension thread here and go for the ride height you want. http://www.r3vlimited.com/board/showthread.php?t=52154

Yes, that would work out okay. You may be away from ideal alignment, but you'll be fine for a short time. Better than racking up multiple alignments in a month.

FWIW, my front is 23.5" off the ground, and the control arms are below parallel. my rear was at 21.75 when i got it, and i had no travel with Koni SAs. (my old setup but NOT ideal...neither is the rake of current 23.5/23.75...)

IE Stage 3's are 24" in front (and control arms are good, and the 2004 K-Prepared champion was on H&R races, so it works well enough)

Sometime when I get all my adjustments done, I should be at 23.75-24" in front and 22.5-22.75" in the back. (all measurements with late model rear arches and factory sized 24" diameter tires)

HTH
not necessarily the definitive best suspension height, but good enough for IE3's and near what most GC's owners run.

[IS]

does it matter how much damper travel? sorry if these questions seem trivial, i'm just trying to learn.

i think i might take up the front and rear a little, because they are parallel or past. when changing ride heights, would it be necessary to get an allignment? or can i change the height say, 3-4 times, just to test different heights, then get an allignment done after i have the final height?

TIA

How much travel doesn't matter - what matters is that you don't run out of it and hit the bump stomps. This is a combination of damper length, spring rate, and ride height.

You do not need an alignment if you're simply adjusting ride height on a coilover suspension. The only thing alignable on our cars is front toe, and this isnt affected by this.

[rwh11385]

The only thing alignable on our cars is front toe

Maybe for you

I gots camber/toe adjustments both front and rear.

[IS]

You are just TOO cool. ;) I was referring to stock. Mine will be equipped shortly. Too much toe in and camber in the rear.

[lagoon]

Thanks guys, that really helps clear things up! I think I'm going to play around with the height sometime soon.

rwh11385, you had GC's and switched to IE3? just curious, why?

thanks again.

[rwh11385]

no, i was just referencing data from that thread, and from others.

but i am about to install H&R sports temporarily while welding on M3-style swaybar tabs and adjusting my heights!!

[BeirBrennerE30]

changing the height of an e30 just a lil will dramatically change roll couple... reguardless of what people on this thred say... just stay at parallel