[Skyhigh]

Originally Posted by HighlandPete

You are saying there are 'just' two spring rate/spec options for the model range... Hence the wide fitting tolerances users are seeing. Axle weights will be very different, even for the models listed for a specific spring set.

The other factor as you have mentioned, is actual measurements. Requires a flat surface, more a workshop floor, than roads or parking areas.

Those were just 2 examples. Specifically for F36, ACS 3 different variants.

And yes, I partially agree with you.

On one hand there is plenty of room for variety (essentially weight and weight distribution), even with the main factors taken into account (engine and RWD vs Xdrive).

On the other - springs are not that extremely sensitive either. Although the spring force is progressive and not linear, you do not go 1 cm lower or higher just by having a tow hitch or not.... so I think ACS could have done better, at least for some of the configurations...

[APJ]

Originally Posted by Skyhigh

Yes. And I can show you what it looks like with 2 persons sitting in the back, but you can imagine, I am sure

Lorcan is certainly very helpful and knowledgable. He has however already taken a position, which (surprisingly or not) is in line with ACS official position

A. The cars have reverse rake from factory (not true in my case or at least definitely not to that extent).

B. ACS springs drop the car approximately evenly (clearly not true in every case)

C. The drop (I suspect no matter what, but at least mine specifically) is all within tolerance

D. The front arch is made bigger to ensure the free turning of wheels, which creates an optical illusion (I am not convinced about that, my measurements don't support this theory)

Did you expect anything else? And some of the above is certainly true to some extent - e.g. I have a heavy configuration. Probably the heaviest possible F36. The tow hitch installation alone is about 30kg, from memory...

And YES - there is something which can be done for the rear axle! This is also the recommended mitigation by ACS (I got in touch directly with Aachen), who suggested it as I complained about the uneven drop. You can install the so called "Poor Road Package" spacers (original BMW), which will lift the rear with 6+ mm. Many people in Germany have them installed in combination with the ACS (Eibach) springs.

I still haven't done so, but am more and more inclined to do it. I have the spacers already.

The spacers are 6mm thick, but I have read people claiming the actual lift is a few mm bigger... I can't understand where the extra lift would come from, but even 6 is better than nothing I guess...

Good old tolerances, as long as its between 0 and 25 its absolutely fine

To be fair and not what you wanted to do, but the spacer kit will probably make it it spot on, and maybe a bit stiffer or rather less bouncy at the rear, not that they tend to be too bad once you have the lowered springs, especially if you have the thicker rear anti roll bar.
Any way, best of luck to you and hope it works out, it would be nice to get a new picture once the spacers have been fitted

[Skyhigh]

Thanks. Will report. Let it get a bit warmer first

There should be no difference in terms of comfort or stiffness. The spacers are literally just a shim between the springs and the chassis. The spring properties remain unaffected.
I hope it turns out well...

[johnung]

Originally Posted by weeguy

Just recently fitted my F32 xdrive with Eibach pro’s. Original OEM springs were “FH” front, “GM” back.

Eibach backs have dropped the car 12mm but fronts havent done anything🤷*♂️

That's strange. Are you certain that you took accurate "before" measurements on a flat concrete surface? I found that flat looking asphalt is actually wavy. I couldn't get accurate measurements until I used a concrete surface.

My buddy had your same car and his drop was exactly as expected. I think it was front 0.8" and rear 0.4"

[weeguy]

Originally Posted by johnung

That's strange. Are you certain that you took accurate "before" measurements on a flat concrete surface? I found that flat looking asphalt is actually wavy. I couldn't get accurate measurements until I used a concrete surface.

My buddy had your same car and his drop was exactly as expected. I think it was front 0.8" and rear 0.4"

It’s now dropped as expected at front. Seemed a few days of driving caused it to “settle”. As you say about 20mm front and 12mm rear👍

[johnung]

Originally Posted by weeguy

It’s now dropped as expected at front. Seemed a few days of driving caused it to “settle”. As you say about 20mm front and 12mm rear👍

Excellent! Eibach drop estimates are usually right on the mark! 😀

[APJ]

Originally Posted by johnung

Excellent! Eibach drop estimates are usually right on the mark! 😀

Not always John, the rears always seem to drop by the right amount, but not the fronts, mine only dropped 8mm on one side and 10mm the other, and i do seem to read others were the fronts don't always drop the stated amount.

When pushing on my rear is spot on, but the front still has the dreaded body roll through any bend, which is very annoying and frustrating, why give a car all this wonderful power and then make it handle like a wheelbarrow !!!

[johnung]

Originally Posted by APJ

Not always John, the rears always seem to drop by the right amount, but not the fronts, mine only dropped 8mm on one side and 10mm the other, and i do seem to read others were the fronts don't always drop the stated amount.

When pushing on my rear is spot on, but the front still has the dreaded body roll through any bend, which is very annoying and frustrating, why give a car all this wonderful power and then make it handle like a wheelbarrow !!!

Body roll is directly controlled by sway bars. On every other car make that I have owned, to control body roll I just swapped out the front and rear sway bars for a larger, properly engineered pair such as H&R's.

Note that it's important that front & rear sway bars are engineered to work together on a particular chassis setup or it can dramatically change a car's handling characteristics. A rear bar that is too large in relation to the front bar will increase oversteer. A front bar that is too large in relation to the rear will increase understeer.

So when I got my BMW F3x three years ago it had a lot of stock body roll that obviously needed correction. I was surprised that I read nothing on forums about sway bars. Instead it seemed to mostly be guys installing heavier springs, dampers and coilovers. This was really foreign to me because that causes more harshness.

That's fine if the goal is to track. But on a daily driver those suspension mods can make driving on rough roads very jarring. The stock F3x suspension is teeth rattling as it comes from the factory, especially with the stock runflat tires.

So the F3x suspension mods that I was reading on forums ran counter to my own life experience with my previous cars.

I happened to speak to a BMW rep who was a professional race driver when he was younger before he had a family. He told me that I wasn't crazy. He said that body roll was his biggest complaint with the F3x and that the first thing that he would do is to upgrade the sway bars! So suspension engineering principles hadn't somehow changed with the F3x.

After doing more research into replacing the sway bars on my car, I learned that labor to do it was high because both bars were buried (especially the front) behind a lot of components that had to be removed to get to them. It wasn't especially difficult but it was time consuming and very hard to tackle without a lift.

So it wasn't a typical weekend home mechanic task as I had been used to with my previous cars. And it was difficult to find an independent BMW mechanic with any experience replacing sway bars. They all did what any experienced mechanic does when faced with a task that they had never done before, they quoted very high to protect themselves if they ran into problems. Everyone knows that the first time you tackle something on a car it always takes 2x or even 3x as long as it will the second time.

As it turned out the only mechanics that I could find with experience swapping F3x sway bars worked at dealerships who sold Dinan products, because Dinan offered sway bars. (IMO avoid Dinan sway bars because they are hollow and hollow bars are known to snap. More on that later.) But Dinan purposely places high "book" hours on their products to make them profitably attractive for dealerships to sell.

So I could find mechanics who got do the installation, but the labor was incredibly high and they only installed expensive Dinan hollow bars that I did not want on my car.

So the high labor expense and the relative lack of experienced mechanics is why there is little conversation about upgrading sway bays to control body roll on the F3x chassis.

So that was three years ago. I managed to find a mechanic who would install a set of sway bars for me at a reasonable cost. I installed H&R sway bars. I have used H&R's previously on other cars. They are German high quality solid bars that are engineered for the F3x chassis. The handling is balanced and now my car corners FLAT! I love it!

So with body roll completely controlled, I focused on suspension mods that would eliminate harshness and make my car more responsive and fun to drive. I highly recommend Eibach Springs, Koni Special Active dampers and summer Michelin Pilot Sport 4S tires in a larger than stock width. I went from 225/45-18 to 245/40-18 on my stock 400M wheels.

Below are videos that explain the installation. And attached are photos that compare the H&R Bars to the stock bars that were removed.

Front Sway Bar Installation

Rear Sway Bar Installation

Hope this helps!

[APJ]

Originally Posted by johnung

Body roll is directly controlled by sway bars. On every other car make that I have owned, to control body roll I just swapped out the front and rear sway bars for a larger, properly engineered pair such as H&R's.

Note that it's important that front & rear sway bars are engineered to work together on a particular chassis setup or it can dramatically change a car's handling characteristics. A rear bar that is too large in relation to the front bar will increase oversteer. A front bar that is too large in relation to the rear will increase understeer.

So when I got my BMW F3x three years ago it had a lot of stock body roll that obviously needed correction. I was surprised that I read nothing on forums about sway bars. Instead it seemed to mostly be guys installing heavier springs, dampers and coilovers. This was really foreign to me because that causes more harshness.

That's fine if the goal is to track. But on a daily driver those suspension mods can make driving on rough roads very jarring. The stock F3x suspension is teeth rattling as it comes from the factory, especially with the stock runflat tires.

So the F3x suspension mods that I was reading on forums ran counter to my own life experience with my previous cars.

I happened to speak to a BMW rep who was a professional race driver when he was younger before he had a family. He told me that I wasn't crazy. He said that body roll was his biggest complaint with the F3x and that the first thing that he would do is to upgrade the sway bars! So suspension engineering principles hadn't somehow changed with the F3x.

After doing more research into replacing the sway bars on my car, I learned that labor to do it was high because both bars were buried (especially the front) behind a lot of components that had to be removed to get to them. It wasn't especially difficult but it was time consuming and very hard to tackle without a lift.

So it wasn't a typical weekend home mechanic task as I had been used to with my previous cars. And it was difficult to find an independent BMW mechanic with any experience replacing sway bars. They all did what any experienced mechanic does when faced with a task that they had never done before, they quoted very high to protect themselves if they ran into problems. Everyone knows that the first time you tackle something on a car it always takes 2x or even 3x as long as it will the second time.

As it turned out the only mechanics that I could find with experience swapping F3x sway bars worked at dealerships who sold Dinan products, because Dinan offered sway bars. (IMO avoid Dinan sway bars because they are hollow and hollow bars are known to snap. More on that later.) But Dinan purposely places high "book" hours on their products to make them profitably attractive for dealerships to sell.

So I could find mechanics who got do the installation, but the labor was incredibly high and they only installed expensive Dinan hollow bars that I did not want on my car.

So the high labor expense and the relative lack of experienced mechanics is why there is little conversation about upgrading sway bays to control body roll on the F3x chassis.

So that was three years ago. I managed to find a mechanic who would install a set of sway bars for me at a reasonable cost. I installed H&R sway bars. I have used H&R's previously on other cars. They are German high quality solid bars that are engineered for the F3x chassis. The handling is balanced and now my car corners FLAT! I love it!

Hope this helps!

Many thanks for the very detailed and informative explanation, a great write up. I have already been down the route of having a 15mm OEM rear sway bar fitted, which probably explains why the rear doesn't have a lot of body roll.
I have considered having the front changed, but then when you read on various forums that the job is a pain in the ar@e, and then like your good self you have to find someone who is willing to do it and not charging you an arm and a leg, i did try my local Independent BMW for the rear, and he'd never done one before, so i imagine he will probably not have done a front either.
Then there is the problem of which one to buy, the rear was easy, you buy the thicker oem one, this has been covered quite a bit on the various forums, but there are very few covering the front and that is generally for track guys, which i don't intend to do, i just want to stop the front rolling and understeering when having a bit of fun. So now i just have no idea what to do !!

[johnung]

Originally Posted by APJ

Many thanks for the very detailed and informative explanation, a great write up. I have already been down the route of having a 15mm OEM rear sway bar fitted, which probably explains why the rear doesn't have a lot of body roll.
I have considered having the front changed, but then when you read on various forums that the job is a pain in the ar@e, and then like your good self you have to find someone who is willing to do it and not charging you an arm and a leg, i did try my local Independent BMW for the rear, and he'd never done one before, so i imagine he will probably not have done a front either.
Then there is the problem of which one to buy, the rear was easy, you buy the thicker oem one, this has been covered quite a bit on the various forums, but there are very few covering the front and that is generally for track guys, which i don't intend to do, i just want to stop the front rolling and understeering when having a bit of fun. So now i just have no idea what to do !!

So you have an F36 xdrive that already has Eibach springs. And you want to decrease Front body roll.

Your stock rear bar may have been about 12mm. It's typically written on the label on the bar that contains the part number. Since you replaced it with a heavier 15mm rear bar, that should have decreased the natural understeer that is built into the F3x suspension.

Typically I'd suggest H&R solid sways which are Front 28mm and Rear 20mm. But since you have already installed a rear 15mm bar, installing a Front 28mm will definitely cut down body roll, but it may cause more understeer.

If it were mine I would install the front 28mm H&R sway bar since eliminating body roll is important to me. If understeer turned out to be a little too much then the rear sway bar could be increased to 17mm (KC Designs), 18mm (Eibach) or 20mm (H&R). I've got the front 28mm/rear 20mm and I like the setup.

Hope this helps!

I personally would install the front 28mm bar

[APJ]

Originally Posted by johnung

So you have an F36 xdrive that already has Eibach springs. And you want to decrease Front body roll.

Your stock rear bar may have been about 12mm. It's typically written on the label on the bar that contains the part number. Since you replaced it with a heavier 15mm rear bar, that should have decreased the natural understeer that is built into the F3x suspension.

Typically I'd suggest H&R solid sways which are Front 28mm and Rear 20mm. But since you have already installed a rear 15mm bar, installing a Front 28mm will definitely cut down body roll, but it may cause more understeer.

If it were mine I would install the front 28mm H&R sway bar since eliminating body roll is important to me. If understeer turned out to be a little too much then the rear sway bar could be increased to 17mm (KC Designs), 18mm (Eibach) or 20mm (H&R). I've got the front 28mm/rear 20mm and I like the setup.

Hope this helps!

I personally would install the front 28mm bar

Thanks for the advice, yes the original sway bar was 12mm. So you'd recommend the H&R, think the KC maybe a problem as i don't think its stocked in the UK and is a fortune to get it posted here. Is there not an Eibach 28mm version ?
Looks like i might have to start looking around for someone to fit it, what's a fair estimate for fitting time, do you have any ideas ?

Thanks again

[johnung]

Originally Posted by APJ

Thanks for the advice, yes the original sway bar was 12mm. So you'd recommend the H&R, think the KC maybe a problem as i don't think its stocked in the UK and is a fortune to get it posted here. Is there not an Eibach 28mm version ?
Looks like i might have to start looking around for someone to fit it, what's a fair estimate for fitting time, do you have any ideas ?

Thanks again

I believe that the Eibach front 28mm is hollow compared to the solid 28mm from H&R and in US they won't sell them separately, only as a set. But actually the front Eibach 28mm may be your best solution to match with your 15mm rear bar. The Eibach rear bar is 16mm so they are very close.

If you can't find the Eibach front bar, just install the H&R 28mm front bar. It's available separately and it's the highest quality.

It was so long ago that I don't recall how long my front bar took. Here I would expect my independent BMW mechanic to charge me 3-4 hours at $120/hour. I recall getting labor estimates on Dinan bars from Dinan dealers knowing that whatever number of hours they told me was highly padded by Dinan.

Good luck!

[APJ]

Originally Posted by johnung

I believe that the Eibach front 28mm is hollow compared to the solid 28mm from H&R and in US they won't sell them separately, only as a set. But actually the front Eibach 28mm may be your best solution to match with your 15mm rear bar. The Eibach rear bar is 16mm so they are very close.

If you can't find the Eibach front bar, just install the H&R 28mm front bar. It's available separately and it's the highest quality.

It was so long ago that I don't recall how long my front bar took. Here I would expect my independent BMW mechanic to charge me 3-4 hours at $120/hour. I recall getting labor estimates on Dinan bars from Dinan dealers knowing that whatever number of hours they told me was highly padded by Dinan.

Good luck!

Cheers and to you

Though have had a quick look, and both H&R and Eibach seem to be sold only in pairs
I maybe looking for a while

[johnung]

Originally Posted by APJ

Cheers and to you

Though have had a quick look, and both H&R and Eibach seem to be sold only in pairs
I maybe looking for a while

H&R definitely sells their sway bars separately.

[APJ]

Originally Posted by johnung

H&R definitely sells their sway bars separately.

I will have another look then

[johnung]

Originally Posted by APJ

I will have another look then

H&R Part Numbers. Those are list prices and the street prices are less

[Skyhigh]

APJ

As promised, some feedback:
I added the BMW Poor Road Package to the ACS Springs a couple of weeks ago. I must say I have been hesitating for months whether I should and whether it would be worth it, but now I know the definitive answer... YES, it was absolutely worth it!



The effective lift at the wheels is ~8mm as I had read somewhere in the forum, (although initially it looked more like 10mm, which would have made more sense as a round number and also in terms of the geometry).

The result is that the rocks from my boot are now mostly gone



The rear is still visually lower (now <1cm difference in the distance wheel centre - arch, front and back), but this is quite normal and common for BMW. I noticed even the new M4 has that out of factory.
It is however no longer as obvious and no longer unaesthetic and impractical.

Went on a few days ski trip up in the mountains and whilst I had one of the lowest cars on the parking at the ski lift, even with luggage, it did not look as "heavily loaded" as it did previously.