Can someone measure the natural length of some e30 springs?

[Jafxod]

Use 6" coilover springs, maybe 5" in the back if you wanna go real low. But i run 6" rear springs with no adjuster and i tuck tire on 205 50 15

[acolella76]

I don't get why people constantly try to re-engineer E30 suspension setups. There are numerous threads on what works and what doesn't.

Use 6" coilover springs, maybe 5" in the back if you wanna go real low. But i run 6" rear springs with no adjuster and i tuck tire on 205 50 15

Crazy, and those are undersized too! I was going to go 5" but seems 6" would be better... and easier to find no less

[taiden]

I don't get why people constantly try to re-engineer E30 suspension setups.

It probably has something to do with the fact that I'm a mechanical engineering student on winter break and need something to work on or else I'll go marginally insane. :p

[petrolhead]

The free length of stock e30 springs has no bearing on the height of a stiffer coil over spring. They are hella compressed (preloaded) on a stock car.



For example, H&R Race springs in the front are like 5 inches shorter than the stock spring but only lower the car 2 inches or so.


.

What this gentleman said. Plus changing to a coilover setup in the rear will change the leverage (that a word?) ratio.

[taiden]

What this gentleman said. Plus changing to a coilover setup in the rear will change the leverage (that a word?) ratio.

And how does it do that?

Line of action is colinear in both cases

Motion ratio is the same at a consistent ride height

Off the top of my head I can't see how this is possible

[nrubenstein]

It probably has something to do with the fact that I'm a mechanical engineering student on winter break and need something to work on or else I'll go marginally insane. :p

So, why can't you explain what the use of the stock spring length is to you?

[petrolhead]

And how does it do that?

Line of action is colinear in both cases

Motion ratio is the same at a consistent ride height

Off the top of my head I can't see how this is possible

I mean when you move the rear spring from its original location , to sit around the shocks. In original location the spring is closer to the "pivot" of th semi trailing arm and further away from the wheel. Spring rate x kg/mm doesn't give you x kg / mm wheel rate. Wheel rate is dependent of spring rate and "leverage ratio".

And pardon my english , I hope I wrote this understandably..

[taiden]

Saying 'coilovers' for the rear is a bit of a misnomer, but I have no plans on running a coil over shock setup in the back. Yes, if you did this, your motion ratio at the spring would change. You are absolutely correct. But this is not what I plan on doing. And your technical english was very good.

If one knows the natural length and the spring rate of the original spring, and the compressed length at full droop, they can find preload. If you then know the corner weights you can calculate compression at static equilibrium and then confirm on the car.

With this information it is much easier to make an accurate decision about what new spring rates and lengths you want to run.

Spring rates can be tested with cinder blocks , a bathroom scale, and a ruler

[petrolhead]

I don't get why people constantly try to re-engineer E30 suspension setups. There are numerous threads on what works and what doesn't.

..because the suspension was designed for 1980's tires and to be driven like a responsible adult , and to have safe and predictable handling (=understeer+ moar understeer) ? Whereas I intend to put on semi slicks and drive it like a stolen rental. Takes some reconfiguring..

[taiden]

..because the suspension was designed for 1980's tires and to be driven like a responsible adult , and to have safe and predictable handling (=understeer+ moar understeer) ? Whereas I intend to put on semi slicks and drive it like I stolen rental. Takes some reconfiguring..

Could not have said it better myself

Also, off the shelf stuff is made for the masses. I am not the masses

[LJ851]

It probably has something to do with the fact that I'm a mechanical engineering student...

Aha, this explains everything! Have fun re-inventing the wheel.

[Kvasi]

Dats the essence of r3v, and most forums. Lets attack the poor bastard and tell him hes fucked up wrong and dont have a cloue..
Remember when u got ur first car and didnt know how to change out that broken headlight? Didnt think so..

[taiden]

I think it's funny that the person who helped me the most is also the one talking the most trash. :)

[taiden]

Does anyone know the length of a front H&R sport? If my quick math is right, it should be ~10.5" tall

[acolella76]

Ah, I know the feeling. I am an ME student as well. what I was sort of getting at is that the area on E30 suspension that needs improvement is the rear. So get crackin!