raised rear subframe?

[kman_e30]

im trying to figure out how the raised rear subframe works to get more positive camber. ive searched, but i cant seem to find very much on the subject. so first off how does it work? im thinking that by raising the rear subframe closer to the car, but you keep your coilovers at the same height, this will make keep the rear camber the same but the wheels will be even closer to the car(making the back of the car even lower), then you raise the coilovers up so the car will sit where you had it before, but camber will go closer to the stock setting? am i close or does this sound like a bunch of crap? my next question, can i adapted this idea to an e24/28 chassis, considering that our rear subframes are similar?

thanks guys

[SkinnyVT]

your ride height remains the same (close to it), by raising the subframe you restore some of the stock geometry into the trailing arms, the closer to horizontal your arms are, the more negative camber you get. When you raise the subframe it increases the angle of your trailing arms therefore reducing the negative camber.

Never saw a e24/28 rear suspension setup but if it is similar to an e30 then yes.

[nando]

it doesn't change ride height at all. it reduces camber and toe, that's it.

[shiboujin]

I should draw diagrams but alas, I am lazy.

It's the same idea behind adjustable sway bar links. your sway bars need to be parallel to the ground when the car is sitting to avoid preload and bind. It just makes the sway bar more useable.

When you raise the rear subframe, everything gets closer to it's factory location. After all, when you lower a car, you lower the car, not the wheels. Therefore, the mounting points are also lowered. E30s gain negative camber and positive toe on compression. You're essentially pre compressing it.

[shiboujin]

it doesn't change ride height at all. it reduces camber and toe, that's it.

Should raise the car an unnoticeable amount. Remember the spring is on a lever on our cars.

[nando]

it doesn't move the spring. you're adjusting the subframe, the trailing arm only rotates a small amount..

[shiboujin]

Yea, it doesn't move the spring. And yes, the trailing arm will move a veeery tiny amount. But it will raise your ride height a tiiiiny tiny amount. Think like a sea saw. You're pushing down on one side, the spring is your fulcrum, and the other side will go up.

[SkinnyVT]

Yea, it doesn't move the spring. And yes, the trailing arm will move a veeery tiny amount. But it will raise your ride height a tiiiiny tiny amount. Think like a sea saw. You're pushing down on one side, the spring is your fulcrum, and the other side will go up.

bingo

[nando]

.000001" isn't worth arguing over. :p

[shiboujin]

well. assuming the spacers raise the car 10mm, your rear end will raise by 10mm (very generic math here). I doubt anyone will notice but it is def worth noting.

[nando]

you meant raise the subframe?

the springs are much closer to the center of the wheels than the subframe. Whatever leverage exists is very small.

[shiboujin]

yea raise. Shh I'm actually working and slacking at the same time.

The springs are about 54% down the trailing arm. I use 50% as a rule of thumb. IE a spring rate of 500# is effectively 250# at the wheel. This is why most multi link and solid axle cars have stiffer springs in the front while E30s have stiffer in the rear.

[nando]

that's the wheel rate between the wheel and the spring.. what we're talking about is the leverage from the point where the subframe connects to the trailing arm to the spring, and then to the wheel. opposite direction. :)

[shiboujin]

The distance from the trailing arm pivot to the center of the spring is 15 inches. From the center of the spring to the wheel hub is 11 inches. By moving the trailing arm mounting point up 10mm, you lower the wheel (raise the car) 7.3mm. Roughly anyhow.

[shiboujin]

<_< I don't see how you got that.