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How Low Is Too Low


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#1
CSPCRX

So I have been doing a lot of suspension work on the CRX. Put ITR Koni racing shocks on the rear using my ground control sleeves. Problem is they are at the bottom of the treads and still the rear sits higher than it did with the tokico shocks and same sleeves. Clips are on the lowest setting and sleeves are orientated correctly.

This got me thinking do I have the car setup too low. I remember long ago a trusted 1st gen racer saying something about the perfect height being when either the control arm or torsion bar arm was sitting level.

Any of you know or recall which it is?


Victor
86 K24 Powered CRX SI (SMF Solo2, HPDE-4 NASA & TA-A Time Attack

85 CRX DX totally original
07 Harley FXST Softail

2021 Tacoma Tow/Daily


#2
gtpilot

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We ran the arm level.

 

Also consider what happens to bump steer - keeping the arm (or lower inner pickup to outer lower pickup) horizontal at rest allows the lower outer pickup to travel in roughly the same arc in bump/rebound. If the arm is below/above horizontal at rest, as the body rolls in a turn the wheels are steering differently as the respective arms are going through different portions of the arc (one knuckle could be pushed outwards and one being pulled inwards) and bump steer changes radically. 

 

As well, when you start lowering the car enough that the arm is pointing upwards the roll center moves all over the place very quickly.

 

Read this thread



#3
CSPCRX

Thanks so control arms are what we are looking at than. I need to get under there and see how the car sits at rest. As I look at the design the torsion bar arm attaches to the control are but which is actually dictating the arc? Both? I have to imaging they have to be in the same plane or they would be fighting each other.

Thanks for the help.


Victor
86 K24 Powered CRX SI (SMF Solo2, HPDE-4 NASA & TA-A Time Attack

85 CRX DX totally original
07 Harley FXST Softail

2021 Tacoma Tow/Daily


#4
gtpilot

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The Torsion Bar is inline with the center of the arm as it is rotating. e.g. the center line axis of the Torsion bar is what it is pivoting around.



#5
CSPCRX

Thanks GT.

Victor
86 K24 Powered CRX SI (SMF Solo2, HPDE-4 NASA & TA-A Time Attack

85 CRX DX totally original
07 Harley FXST Softail

2021 Tacoma Tow/Daily


#6
Andy69

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So I have been doing a lot of suspension work on the CRX. Put ITR Koni racing shocks on the rear using my ground control sleeves. Problem is they are at the bottom of the treads and still the rear sits higher than it did with the tokico shocks and same sleeves. Clips are on the lowest setting and sleeves are orientated correctly.

This got me thinking do I have the car setup too low. I remember long ago a trusted 1st gen racer saying something about the perfect height being when either the control arm or torsion bar arm was sitting level.

Any of you know or recall which it is?

I’ve been working on modeling the suspension.  I used Racing Aspirations to model the front.  From what I’ve been able to tell, you can go to an angle of -3 degrees on the front LCA before you start running into problems with bump steer and excessive body roll due to CoG and roll center separation.  Set the rear about 1/8” lower than the front.