Guess my camber and toe in (rear)

[datonyb]

i cant see why lowering would induce so much change to the toe in settings myself

unless it was taking it far beyond its design amount of travel

just a query though clarky


on progressive springs i thought it was the looser wound coils that were the softer/progressive bit

as the tight wound coils are already at there design tension?

[superclarkey]

If the spring is all the same.. ie. same windings then when the springs is compressed they all move by the same amount... agreed.

With the tightly wound coils... you'll notice that if you ever take a spring off the car the tightly wound ones are always worn between coils, and normaly the paint has cracked off.... this is because the spring binds into itself nad locks out...... so these coils are progressive in the sence they are only used for "part" of the travel at which point they lock out (press into each other, as no further travel) and the spring rate changes instantly, causing the spring to get stiffer, as the number of coils "active" denotes the spring rate.

By removing these tightly wound coils, the spring rate stays constant and does not bind out, nor does it compress quickly so give you a stiffer ride with more control.

Most springs are wound in a way to give ride confort at the same time as handling, differnt pitchs of the springs react differentyl and differet bumps, the responce of the srping is everything, but if like me you don't want the car pitching and diving about over the smallest of bumps, you remove these coils and the spring takes up the bump quicker and harder.

The bmw, with stock suspension run what is called "Zero Preload", ie you lift the car up, the suspension sags to the very lowest postion and the spring comes loose and moves about.

On coilovers you have preload to which you can set a weight on the spring before its compressed, so if you set 100kilos preload... the suspension wouldn't move until 100kilos was reached.. then it would relact. not so good for bumpy roads or fast driving...

each to there own, i've learnt what i've learnt from many track days and working within the motorsport world for many years.

clarke.y

[Andyboy]

The bmw, with stock suspension run what is called "Zero Preload", ie you lift the car up, the suspension sags to the very lowest postion and the spring comes loose and moves about.

Rubbish!!

If that were the case, why do you need spring compressors when taking the standard springs off the struts? Zero preload only comes with cheap rubbishy lowering springs fitted to standard struts with damper rods that are too long for the springs.
Zero preloading on the springs results in a soft bouncy ride where the poor dampers are working their nuts off. The whole idea of coil springs as opposed to torsion bars or leaf springs is that a coil spring gets stiffer the more you compress it. That's why a proper set up has coils under partial compression - pretty elementary really.
That's why E36 cars for example with M Technic suspension use a strut with a shorter damper rod as well as a shorter bump stops. Consider that an E36 standard front strut has 110 mm of travel with the suspension on full drop. Lower the car down and that becomes a little over 60mm. Fit 50-60mm springs and you have a car on its bump stops with springs that are not giving the correct springing rate. Notice how all these cheap shit springs are wound from steel wire that's the same diameter as a standard spring. To make it work you'd need substantially thicker wire to restore the springing rate, or much shorter damper rods which you can buy from Bilstein for example. If you don't have the correct spring preload on full drop, you're starting from the softest part of the springing.

50-60mm drops are garbage. All you achieve is a car with no suspension travel that crashes and bangs over potholes where the tyres are doing all the work. The long term result is multiple stress cracks in the bulkhad and inner wings. Great for a race car, not for the road.
35mm is plenty low enough for proper suspension, 60mm is for Councillors. Slammin', innit Bruv?

[superclarkey]

I'm not going to get into a Internet theroy fact debate with you about this, i use the car on track, any time you fancy popping down and doing a few laps agenst me let me know ;) we will see how "garbage" my setup is,

becuase your right, i see all the touring cars and race cars running only 30 mm drops.... thats bollox, have you seen how low some of the cars are, so please, enlighten me on some roll center advice while your at it, would be interested for you to explain this too me as i have no idea.

clarkey.

[Andyboy]

i have no idea.

clarkey.

Clearly not!! The very fact that you reckon standard BMW springs are loose in their seats on full drop tells me all I need to know about your level of expertise...................it just alarms me when this kind of Internet misinformation is bandied around where those who don't know any better might actually believe it.

Touring cars are not the same as road cars Dear Boy. Touring cars have fully seam welded shells, cages tied into the suspension pick up points and absolutely rock hard suspension with very sticky tyres. They are eminently unsuitable for road use. Race tracks don't have potholes or speedbumps iirc!

A track challenge is one thing; I trust your driving is superior to your knowledge of the linear properties of coil springs!

[Andyboy]

By the way ALL coil springs are progressive rate. That means they stiffen up the more they are compressed. The kind of springs you are on about with more coils at the top are VARIABLE rate. The first bit to compress is for ride comfort only - nothing to do with a performance application.
As for roll centres - very late E30 M3 race cars were so low that the front and rear turrets were moved up in the shell to provide extra suspension travel - I assume you've done this to your car? The engine and gearbox were also dropped and moved back - yours too??

[superclarkey]

Well if this is how you feel about the stuff i talk, i'll keep it to myself, as i have no gains, and i was going to sort people out with axles, but your the kinda guy that would shoot me down in flames for trying to help people,

i'll leave you E30 guys to enjoy your internet theroy fact bullshit.

clarkey.

[old_skool]

Actually, Andy usually knows what he is talking about. As a respected writer for a mainstream BMW magazine, then I suppose he should.

If you disagree with what he, or any other member has to say then please feel free to make your point. If there were nothing to discuss then there would be need for internet forums!

Everbody gets an ear here. That's the whole point.

[superclarkey]

Its ok, i'll keep my mouth closed as i know nothing.

clarkey.

[Rosc0PColtrane]

Don't be dispondant, keep the debate going, it's helpful. If you knew nothing you wouldn't have posted here. You cannot expect to be 100% right or 100% wrong all of the time. I'd personally use this thread to probe Andy's knowledge rather than curling up into a ball!!

People like me have been reading this with interest. It's what a forum is all about. (Platform for debate)

[munky30]

I have toe in.

Only got round to looking the other day and I do.

Ah well, such is life.

[stonesie]

Is there a way of fitting eccentric bolts to the inner trailing arm bushes? that would give a bit of rear toe adjustment

[Andyboy]

Its ok, i'll keep my mouth closed as i know nothing.

clarkey.

Nobody is seriously saying that and I'm sure your car is quick around a track as most cars with rock hard suspension, low centre of gravity and sticky tyres are. You've clearly got your car exactly as you want it, but the fact that it shags tyres like that says quite clearly that the rear wheels are not putting the entire footprint down - far from it in fact.

This is a test for those who don't believe what I'm saying. Jack up the front corner of your (standard) E30 until the wheel is off the ground and measure the distance bewteen the tyre and the top of the wing. Let it down again, let it fully settle and measure it again. This is the suspension travel you have. On an E36 for example you have 120 mm damper rod length and with the car on the ground this is reduced to 60mm. That means you have 60mm of suspension travel............and that doesn't take into account the fully compressed length of the bump stop.

Now fit some 60mm lowering springs. You now have a car sat on its bump stops. Because the springs are so short they aren't even under that much tension because the bump stops are basically holding the car up. Take the bump stops out and an E36 with a 60mm drop would have almost no suspension at all. This is not internet BS, this is fact.

Now, an E30 has a little more travel than an E36 - about 150 mm iirc and the longest travel E30 shock is a 316i Boge unit from the 45mm strut with a whopping 180mm. Is this better? Nope, it's much, much worse. Fit a 60mm lowered spring to this and on full drop the spring would actually be completely loose. This is where you see such appalling bodge ups as tie wraps holding the spring in.

A simple way to understand is to get a coil spring off a car. Notice how with both hands you can compress it a little. See how easy it is to compress the spring an inch. Now imagine that spring on a car with long damper rods. Imagine how weak the springing will be. Fact is, a spring needs to be under considerable preload before it can start to work properly otherwise you'll have over soft springing and the dampers working like mad to do both jobs and the poor bump stops being squashed flat. This is why extreme lowering springs need dampers with shorter damper rods so that the spring is always under tension.

Race and track cars have their own agenda, but for a road car 35mm is plenty. As for the rear toe/camber issues, the racing E30's were as low as this but they weren't using standard rear beams/trailing arms and geometry!