240sx Suspension Update

So after months of driving around with 7 degrees of camber (according to the angle finder) in the rear of the car, and recently experiencing basically no traction at 7psi with my turbo, I felt that it was time to rectify the situation.

On Wednesday evening, after work, I decided that it was time to shorten the rear lower control arms (RLCA) and get that camber in check.  Also had to dial the toe arms back since the RLCAs were extended an inch or so.

As I shortened the RLCAs’ adjusters, the adjusters started off from being kinda hard to turn, to fully relaxed by the time I got the adjuster fully bottomed out.  I guess the suspension was actually binding at that point.

In any case, I didn’t have time to mess with ride height or wheel fitment or anything of the sort.  I literally shortened the RLCA adjusters, got the toe to be within the ball park by performing the “rolling test” and that was it.  My “rolling test” consist of rolling the car back like 10 feet or so, then pushing it back forward another 10 feet or so.  Not only will that help your wheels/suspension get into place after an adjustment, it also can tell you if your toe is way off, or at least close enough to not cause the tires to be working against each other with toe in or toe out.

Resulting drive afterwards yielded a much more compliant rear suspension on the bigger bumps, but the smaller bumps and slight waves in the road still yielded a quite bouncing ride from the car.

Oh, after fixing the rear suspension bits, I did take a couple minutes to push my front struts mounts all the way inward on the camber plates.  I have been meaning to fix this for a long time, but since I was already working on the car last night, I felt that an extra couple minutes couldn’t hurt.  Basically, I had to do this because my SAI from before was causing very heavy steering, most likely due to my very large positive scrub radius.

For those who don’t know, let me try to explain real quick.  There is an imaginary line that starts from the top strut mount point that intersects the center of the ball joint on the front lower control arm (on a MacPhereson Strut suspension)  and continue to point downward, and if this line lands inside the center line of the contact patch on your front tire, it is said to have positive scrub radius.  If the line lands on the outside of the center line of the contact patch, then it is said to have negative scrub radius.

As my wheels got wider and the offset lower, the center line of the tires’ contact patches moved outward, thus the need to move the top of the strut mount points inward had to be done to keep the scrub radius in check.

Anyway, the results of the change was that, steering efforts was lessened (steering wheel easier to turn), steering wheel self centering was a little easier/smoother, and small bumps/dips/waves on the road don’t jerk the steering wheel as much.  Also, bumps don’t cause the steering to jerk either, even though it wasn’t doing it before from bumpsteer correction.

All in all, good changes, and hopefully this weekend I will have more time to dial in the fine details.


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