10mm out, 1/2" down....what happened?

[StereoInstaller1]

So yesterday I put the pair of 10mm H&R spacers I had sitting around on the rear of my car.

I also pulled out the spring pads.

For some reason, the car feels quite a bit different. It feeels much more stable in a straight line, feels more "planted" cornering, too.

Can anyone explain the geometry changes here? I am really not into the whole 'race car" thing, but I am really curious how 20mm wider or 1/2" lower can change the feel so radically.

Thanks!
Luke

[Jonsku]

Center of gravity went lower and track width increased, both make the car handle better. Plain physics.

[StereoInstaller1]

Center of gravity went lower and track width increased, both make the car handle better. Plain physics.

Yeah, that part is obvious...but I want to learn some terminology to explain what feels so different on my car.

[golde30]

Luke, down'n'out baby, down'n'out!

[ditchdigger]

I also pulled out the spring pads.

For some reason, the car feels quite a bit different. It feeels much more stable in a straight line, feels more "planted" cornering, too.

Aside from the lower center of gravity and wider track you also changed some other stuff.

By removing the rear spring pads you shifted the center of gravity towards the back of the car giving a different front/rear weight distribution.


Also when you dropped the rear of the car you added a little bit more caster to the front.

[StereoInstaller1]

Also when you dropped the rear of the car you added a little bit more caster to the front.

I bet that explains the increase in straight line stability.

[JGood]

I bet that explains the increase in straight line stability.

I don't think the amount of caster gained will have that big of an effect, considering there is, what, 8 degrees or so stock?

Maybe placebo effect?

With the spring pads removed, your car technically gains more body roll now since the CG dropped and your spring rate hasn't changed. But again, it's such a small difference you shouldn't notice it.

I'd say the spacers most likely made the biggest difference, but even that shouldn't be very noticeable on a street car.

[StereoInstaller1]

I was thinking placebo too, except that I didn't expect the car to feel any different at all.

It really does, though.

And, if 20mm of rear track width makes that big of a difference, I wonder why BMW didn't so it in the first place?

[z31maniac]

It's all in your head, what you really need to do is buy 15mm spacers, and send those 10mm jobs to me.

It's really in everyones best interest.

[Hick]

change in rear toe by dropping the back end.

I removed my front spring pads just recently, and it has chaged how the car acts. That only effected the front toe [have camber plates]

[Aptyp]

+1 Placebo

You made your rear toe in slightly bigger with spacers, so you be feeling better grip as car is turning rear wheels against each other a little. Weight distribution blah blah blah, with H&R's you should have been evenly planted to begin with, but with removed pads you may have put a little bit more tension on your sway bar, so it pushes back.

All theories, impossible to "feel" from inside the car unless you are defying gravity sideways.

[nando]

+1 Placebo

You made your rear toe in slightly bigger with spacers, so you be feeling better grip as car is turning rear wheels against each other a little. Weight distribution blah blah blah, with H&R's you should have been evenly planted to begin with, but with removed pads you may have put a little bit more tension on your sway bar, so it pushes back.

All theories, impossible to "feel" from inside the car unless you are defying gravity sideways.

how the hell do spacers affect rear toe?

I think you need to see what an E30 rear supension looks like. Also, lowering your car doesn't put more tension on the swaybar - which is called preload BTW, and you don't want any. It does affect the geometry of the sway though and make it less optimal, unless you get adjustable links. ;)

[StereoInstaller1]

Yeah, I have been considering going to some kind of adjustable link.

[VacMan]

how the hell do spacers affect rear toe?

Spacers wouldn't, but removing the spring pads would. If he took out all 4 that's another 1/2" or more drop.

[Jand3rson]

I was thinking placebo too, except that I didn't expect the car to feel any different at all.

Have Andy take the spacers off and put the spring pads back in without your knowledge, and see if you notice a difference back the other way. :D