[nomiS330d]

After fitting bilstein b8’s and H&R springs I seem to have a bit of rake to the car which I don’t mind too much but wondered if it’s normal.
I have just gone and measured mine from the floor past the centre of the wheels to the arch. The fronts are 62.5cm and the rears are 64cm. The thing that keeps catching my eye is there is more gap between the tops of the rears to the fronts.
One explanation could be I fitted Powerflex subframe mount inserts a while ago which makes the gap between the subframe and the body about 0.75cm larger.
Does anybody mind measuring theirs and posting?

Curiosity that’s all

[RajB]

I know most lowering spring options from the likes of H&R and Eibach will bring the front/rear in line with the arches from the top of the tyres but will still give a rake look.

However what you describe with the large rear gap does suggest that the bushes you've fitted are giving the extra lift at the rear.

I'm on coilovers so can't compare unfortunately but if you google H&R springs on an E9* should be plenty of pics to show what it should look like.

[rasa bmw]

about the same as when im walking,,sorry couldnt resist

[King Rudi]

I'm 5' 9" but I tend to hunker down at top speed, you know with the aggressive runners lean forward and whatnot. Not sure about height at top speed but I will say that hair no longer grows on my melon so either I have shitty genes or the aerodynamics takes care of my hair for me.

On a serious note, I do plan to drop the IS 350 about an inch and a half in the next few months. Looking forward to it.

[rasa bmw]

Originally Posted by Now_Rudi

I'm 5' 9" but I tend to hunker down at top speed, you know with the aggressive runners lean forward and whatnot. Not sure about height at top speed but I will say that hair no longer grows on my melon so either I have shitty genes or the aerodynamics takes care of my hair for me.

On a serious note, I do plan to drop the IS 350 about an inch and a half in the next few months. Looking forward to it.

im 5ft 8 so hanker down lower than you,,thus less drag ha ha

[Tambohamilton]

Originally Posted by nomiS330d

One explanation could be I fitted Powerflex subframe mount inserts a while ago which makes the gap between the subframe and the body about 0.75cm larger.

That would lower the rear, not raise it.

Mine still has near-factory front end in the air look. Measurements from the bottom of the rim to the wheel arch, as per BMW specs (don't ask me why; I think it's pretty weird!)...

615mm Front
595mm Rear

In the next couple of months I'm going to lower the front by about 13mm.

[nomiS330d]

Originally Posted by Tambohamilton

That would lower the rear, not raise it.

Mine still has near-factory front end in the air look. Measurements from the bottom of the rim to the wheel arch, as per BMW specs (don't ask me why; I think it's pretty weird!)...

615mm Front
595mm Rear

I'm the next couple of months I'm going to lower the front by about 13mm.

Yeah that’s a weird place to take measurements. I don’t see how the inserts would lower the car tbh. I may be overlooking something obvious but the subframe and everything attached to it are set. The gap between the mounts and the car body has increased slightly so surely that raises the body???

[Tambohamilton]

The spring and shock are in contact with the chassis directly, not the subframe, at the top end. So if you lower the subframe away from the chassis, the hub end of the suspension arms is raised towards the chassis (effectively pivoting on the spring), so the wheel sits higher....and therefore car is lower.

[RajB]

Measuring the height from the bottom of the rim of the wheel to the arch is the correct way to measure the heights as this removes any slight discrepancies from the tyre wall heights.

I don’t think you’d quite get the pivoting effect either with the spring and subframe due to the spring not being a solid piece. It’s an interesting one and do still think the increased gap with the subframe is the reason for the slightly larger arch gap. Unless the springs aren’t fitted correctly which could be the case.

[Tambohamilton]

It's not a matter of opinion, it's fact. Move the rear subframe down away from the body, and you will lower the rear of the car. I 100% guarantee it.

In fact, we could use the motion ratio at the spring to calculate how much the car would be lowered by, given a certain increment of subframe movement. The motion ratio is approximately 0.5 at the spring (from memory), so any movement at the subframe will produce roughly the same movement in the opposite direction at the wheel. You moved your subframe 7.5mm lower; the rear end will be sitting 7.5mm lower as a result.

[RajB]

Yes I agree with you in theory, but I wasn't being opinionated just as you can't say it's fact and 100% that by lowering the subframe by an exact amount would cause the exact amount decrease on the ride height.

I was simply stating that I didn't think it would 'quite' get the pivoting effect.

Anyway, OP, might be worth checking that the control arms etc were all tightened with the car sat on the wheels in it's natural position as that could also be the cause as the bushes are under preload potentially.

[Tambohamilton]

Sure there are other variables. But the rest is just physics (or kinematics to be a bit more specific); it always works the same way, and it's not optional. My saying that the car will be lowered by 7.5mm if the subframe is lowered by 7.5mm is a lot more accurate than 'I think it'll increase the arch gap'. It might be 2mm or it might be 12mm, but it'll definitely sit lower.

Sorry to keep banging on about this, but it grinds my gears to give misinformation to people who are seeking advice. If I wasn't completely confident in my assessment, I certainly wouldn't be so vocal about it. I've spent years developing suspension systems though, as well as working on my own car, so I'm properly qualified to state what is fact or not on this matter.

As a side note, I actually raised the rear of my car by around 5mm by replacing the old, soft SE subframe bushings with new M3 ones. The old ones were allowing the subframe to move away from the body when loaded, and therefore the car was sitting lower. So maybe the result of the OP fitting his new bushings is actually around net 0, due to the new bushings being stiffer.

I agree that checking that the arms were torqued at ride height is good advice. Good call.

[nomiS330d]

Just measured, albeit with the iPhone measure app, the distance between the tops of the arches and the bottom of the rims. 540 front and 550 rear.
Having said all of that I’ve had another look at the picture Adam sent me of his car with the suspension fitted to his car and it looks like mine does so maybe it’s as it should be.
The car is handling a lot better than it did on the old, probably original shocks so I’m happy enough. It’s just that I’d have preferred the arches gaps to be more similar.

[nomiS330d]

I did let the car down on its wheels before tightening the bolts up so that should be ok. I’ve ordered some new bushes for the rear so will re-check everything when I do that awful job.