How much can you drop a McPherson strut without needing to adjust the roll center? Generally speaking.

And if you are going to get roll center adjusters, how thick of an adjuster should you get for a given amount of drop? Half as much? Or about the same amount?

 

generally? about an inch or two. the actual amount will vary. it depends on what angle the control arms were at to start with, and the amount of roll center change front to rear.

the amount of spacer you need i think would be the same amount as you lowered it, or until the control arm hits the wheel.

 

Here is a decent thread over on NRR:
Optimal front ball joint length for RC correction on S chassis - Nissan Road Racing Forums

my AWR RCAs are probably about 1"

but every car's stock geometry and lowering is going to be different. Do the measurements on your ride height and figure out what your spacing should be. There should be info on finding out where it is in here:
http://www.motoiq.com/magazine_artic...-your-car.aspx

You really should ask other MR2 guys if it's on your MR2 :P

 

An easy (general) way to tell, IMO, is if the lower control arm is horizontal at static ride height. If it's pointed up towards the wheel then your geometry is probably "in a bad place".

 

Check the heights of your control arm mounts in relation to your ball joints. That is one of the invisible lines that is used to figure out roll center height.

Generally you want the balljoint about 1/2-5/8 inch lower than your control arm pivot point. If you have big enough rims you can lower your car pretty far, then you end up hitting tires on the chassis on top. Much lower and you end up with jacking, much higher and your roll center gets too close to ground level.

Playing with roll centers can really unlock the chassis' potential or throw you so far off you end up with huge sway bars just to keep the car from falling over on its door handles.

 

The MR2 forums aren't super useful for advanced technical things like this.... RX7club has infinitely more knowledgeable members.

 

read XHead's posts.. dude's car is pretty dialed, he did win DP at Nationals once or twice.

 

gtfour77's SSM mr2 is also pretty ridiculous with custom control arms and such.

 

^ i've been looking for his build thread, got a link? can't find one.. that guy would be faster with a faster rack! oem manual rack ratios are garbage

/tangent

 

I'm pretty sure he has the OEM electro-hydraulic power steering rack (it's a 2nd gen). and he did replace it at one point, but I don't think the replacement rack wasn't that much faster.

He's semi-local so I've seen his car in person. From what I can tell he just puts all his updates into the mr2oc SM threads:
MR2 Owners Club Message Board