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      05-08-2013, 04:42 AM   #1
E92inSG
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too low affect handling?

1) can you lower your car too much such that it affects handling in a negative way on the track?

-assume that the shocks still have full travel ie. not hitting against the bump stops

-assume that the tires do not rub any part of the body or suspension

would you just want to set the car as low as possible to lower the center of gravity?

2) would the front need to be higher than the rear to provide for balance under hard braking?

3) I've read that the rear should be set stiffer than the front to increase front grip and reduce understeer.



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      05-08-2013, 07:22 AM   #2
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Quote:
Originally Posted by E92inSG View Post
1) can you lower your car too much such that it affects handling in a negative way on the track?

-assume that the shocks still have full travel ie. not hitting against the bump stops

-assume that the tires do not rub any part of the body or suspension

would you just want to set the car as low as possible to lower the center of gravity?

2) would the front need to be higher than the rear to provide for balance under hard braking?

3) I've read that the rear should be set stiffer than the front to increase front grip and reduce understeer.



background info: E92 M3 on Bilstein PSS10 and 18" TE37SL
In some countries like Australia you get pulled over by the cops if the car is deemed too low and is considered un-road worthy. There was a 3 series that was lowered too much and bottomed out and got airborne and crashing and killing three occupants.

I don't know why you want to drop too low. I don't think hiding the top of the tyre under the wheel arch is aesthetic at all. My 2c.
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      05-08-2013, 08:36 AM   #3
E92inSG
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thanks for the reply.

i'm asking purely from on track driving point of view.

i understand the downsides of being too low on the streets. However I was simply wondering rather theoretically if lowering the center of gravity will always have a positive effect on handling up to the point of the car body actually touching the ground.

nothing to do with aesthetics whatsoever
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      05-08-2013, 08:51 AM   #4
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yes it is possible to go to low, and this is determined by suspension geometry.

having the length of the strut / shock body match the spring length (or effective ride height) is critical. if the car is lowered too far, the strut will be losing out on a portion of its available travel, and will be in a constantly compressed state even at static height. this will cause the car to "bottom out" far more often which will upset the car and cause it to lose grip and thus handle worse.

you have to find that balance between low COG and appropriate suspension travel.
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      05-08-2013, 09:29 AM   #5
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Would you also be able to comment on the fronts being set higher for balance under hard braking?
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      05-08-2013, 11:24 AM   #6
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Quote:
Originally Posted by E92inSG View Post
Would you also be able to comment on the fronts being set higher for balance under hard braking?
Are you referring to a reverse rake...? I would think you use stiffer springs rather than making your front end higher (not 100% sure what you are referring to there).

Also note on how the whole suspension works, not just spring and damper (control arms, sway bar attachments, etc). bad geometry can cause your car to not handle optimally and also create longevity issues.

Back when I was in the subaru world, people would slam their STi (a rally car, never understood) and thought it would handle the best. In reality, they reversed the A-frame geometry and caused it to handle worse. There is definitely a balance of many variables that needs to be played with.

Last edited by happos2; 05-08-2013 at 12:29 PM.
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      05-08-2013, 11:29 AM   #7
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Quote:
Originally Posted by E92inSG View Post
Would you also be able to comment on the fronts being set higher for balance under hard braking?
generally speaking you need more travel up front under braking than you do at the rear for squat under acceleration to prevent bottoming at threshold. thus the front is usually set slightly higher than the rear. but as said above generalizing can get you in trouble as there are so many factors that come into play in various situations on the track. you can increase spring rates to minimize travel but that runs you into trouble of making the car over sprung and your always better with a suitable ride height and proper spring rate.
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