Metric Chassis Roll Centers

[vl racing]

On the metric chassis the roll centers, from what I understand are mainly influenced by ride height, because we can’t change control arms ect. My question is, is there a generalized starting point for front and rear ride heights that will get the roll centers close without have some fancy program to figure it out, and what are they? Thanks in advance for any knowledgeable responses.

[NickHolt]

A bit more information is needed to answer your question with any degree of accuracy.

 

1) Do you have to run the stock springs in terms of wire diameter, inside (or outside) diameter and free spring height?

 

2) Are you permitted to use screw in ball joints?

 

3) Are you permitted to change the ball joints from stock?

 

4) Do the a-arms have to remain in their stock locations?

 

5) Are you permitted to change the angle of the top a-arms?

 

6) Are you permitted to change the ride height? If yes, what are you permitted to do to change the ride height?

 

As a general rule, most asphalt stock cars run around 3.5 to 4.0 front roll center height, although many run lower roll centers than they would like simply because the stock location is very low and they're not allowed to change it.

 

And if you can tell me what the rear roll center height is on a stock metric four link I'd appreciate it. You're pretty much stuck with what you get, which isn't all that bad really.

 

Nick

[Wayne Walker]

Nick, answers to questions 1-5:

7. FRONT SUSPENSION: All components must be steel, unaltered OEM, in OEM location, and match frame. No jack bolts allowed. Adjustable spring buckets are allowed. Must use OEM upper and lower A-frames and mounts. OEM upper A-frame may be replaced using aftermarket upper A-frame (STEEL only), must display “IMCA approved” decal. Upper A-frame mounts may be modified and moved for caster and camber adjustment, but must remain OEM material. Lower A-frame mounts and bolt holes on frame must be in OEM location, mount may be notched for clearance. All A-frame bushings may be aftermarket, but no bearing/heim type. OEM style ball joints only, may be tacked in. Sway bars(optional) and brackets must remain OEM.

 

#6:

11. REAR SUSPENSION: All control arms and mounts must be steel, unaltered OEM, in OEM location, and match frame. No jack bolts allowed. Adjustable spring buckets allowed, may be dropped as long as they remain in OEM location. If upper spring cup uses all thread, it must be securely welded to chassis. Lower spring cups must be centered on housing. Control arms may be reinforced, but cannot be shortened or lengthened, must remain OEM length. All control arm bushings may be aftermarket, but no bearing/heim type. Bushings cannot be drilled. No suspension parts may be altered or lightened. No aluminum parts allowed, other than bushings.

 

This is from the IMCA web page for Southern Sport Mods.