[aremmell]

Tomorrow I'm going to DIY my KW HAS kit. My dealership refused do it, and I don't trust anyone else in this town to do it right.

I've spent all day reading manuals and watching videos, but there's one thing left I don't understand:

What is the standard ride height (or as close as it can get) when considering the position of the KW perch in the front? As low as it will spin towards the axle?

In other words, what is the starting point on the adjustable perch that I can use as a baseline?

Same question for the rear: Is the least amount of ride height change from stock achieved when the adjustable spring stopper is at its closest to the axle?

This doesn't seem to be spelled out anywhere that I can find, and the accompanying installation instructions are essentially worthless. I realize I could just try it and see what the results are, but I would rather get it right the first time rather than experimenting for god knows how long...

Thanks in advance!

[M3SQRD]

What do you mean by closest to the axle?

How much do you want to lower your car? I’d recommend no more than 15 mm and I’d do the same amount front and rear. Altering the forward rake, alters the handling balance (increased forward rake, moves balance towards oversteer). Lowering more than 15 mm will result in your car riding the bump stops more frequently.

Measure your front and rear ride heights at all four corners on a flat surface. Measure from the bottom of the wheel (where the tire and wheel touch) to the center of the fender arch (thru the center of the wheel bore).

Starting with the rear, the lowest ride height setting is when the spring seat (light purple part that rides on the black threaded height adjuster) is threaded all the way down to the mounting flange of the height adjuster - the two flat flanges will be close to touching. If you have a set of calipers, I’d set the height to be 2/3rds up the threads up from the bottom. Set one, measure the length, and then adjust the second one to match the first. Install the rear springs.

Now for the front. Remove the lower spring perches from the front struts and press the two KW adjustable spring perches onto the front struts. Set the light purple spring seat 2/3rds the way up the threaded height adjuster, measure the first, and adjust the second to match. Install the springs and upper spring mount. Reinstall the struts but leave the anti-sway bar links disconnected.

Move the car a few feet forward and back to get the suspension to settle. Measure the ride heights at all four corners, subtract the new ride height numbers from the stock ride height numbers. These four differences are the amounts you’ve lowered each corner. Now the fun begins. Front is much easier to adjust than the rear. The front strut motion ratio is close to the front wheel ratio. This will be important when we get to the rear. Motion ratio, MR, is the distance (D1) of the spring centerline to the pivot point of the control arm divided by the distance (D2) of the wheel centerline to the control arm pivot point:

MR = D1/D2

I don’t know the exact g8x motion ratio but it’s around 0.96 (close across the past three gens). So to get the correct wheel height, the spring height is adjusted by

D1 = 0.96*D2

For example if you want to raise the front ride height by 10 mm, you adjust the spring collar by 9.6 mm. Calculate the adjustment needed at both front corners. Desired ride height = stock ride height - desired lowering amount - initial measured lowered ride height. For example if you want to lower your ride height 15 mm and the stock ride height is 100 mm and your initial measured lower ride height is 90 mm, the height adjustment required is 100 - 15 - 90 = -5 mm (negative number means you have to lower more, positive number means you need to raise the height) - you need to lower the spring seat at that corner 0.96*(-5) = -4.8 mm. If KW supplied the thread pitch of the height adjusters then you’ll know how many mm you get for one full rotation of the height adjuster which means you can calculate the number of turns needed to adjust the ride height. Do this for both fronts. Remember to rock the car back and forth after each time it’s been raised off the ground. Repeat until you get the front ride heights you want.

Now for the rear. Don’t forget to disconnect the rear anti-sway bar drop links. The steps are the same but it’s more involved because you can’t easily raise/lower the rear ride height (unless you’re brave enough to drill and pin the rear height adjusters). You have to relieve the preload on the spring by dropping the lower control arm each time you adjust the ride height. The rear motion ratio is somewhere around 0.57 (f8x rear motion ratio). So:

D1 = 0.57*D2

Measure the initial lowered ride heights, calculate the deltas and multiply them by 0.57. Adjust the rear height adjusters by this amount. Reinstall lower control arm, rock the car and measure ride height. Repeat until you get the desired ride heights.

Reconnect front and rear anti-sway bar links. Done.

[BIGW0RM]

I did 14.25" front and back gap from the center of the wheel hub to the fenders edge with my KW HAS kit. That is not slammed, but its not stock height either. I have about 1 finger gap front and back from tire to wheel well. I orginally had it set to 14" from the wheel center hub to fenders, but found the ride to be "jarring". 14.25" keep the ride quality nice and still looked good to me.

[aremmell]

Originally Posted by M3SQRD

What do you mean by closest to the axle?

How much do you want to lower your car? I’d recommend no more than 15 mm and I’d do the same amount front and rear. Altering the forward rake, alters the handling balance (increased forward rake, moves balance towards oversteer). Lowering more than 15 mm will result in your car riding the bump stops more frequently.

Measure your front and rear ride heights at all four corners on a flat surface. Measure from the bottom of the wheel (where the tire and wheel touch) to the center of the fender arch (thru the center of the wheel bore).

Starting with the rear, the lowest ride height setting is when the spring seat (light purple part that rides on the black threaded height adjuster) is threaded all the way down to the mounting flange of the height adjuster - the two flat flanges will be close to touching. If you have a set of calipers, I’d set the height to be 2/3rds up the threads up from the bottom. Set one, measure the length, and then adjust the second one to match the first. Install the rear springs.

Now for the front. Remove the lower spring perches from the front struts and press the two KW adjustable spring perches onto the front struts. Set the light purple spring seat 2/3rds the way up the threaded height adjuster, measure the first, and adjust the second to match. Install the springs and upper spring mount. Reinstall the struts but leave the anti-sway bar links disconnected.

Move the car a few feet forward and back to get the suspension to settle. Measure the ride heights at all four corners, subtract the new ride height numbers from the stock ride height numbers. These four differences are the amounts you’ve lowered each corner. Now the fun begins. Front is much easier to adjust than the rear. The front strut motion ratio is close to the front wheel ratio. This will be important when we get to the rear. Motion ratio, MR, is the distance (D1) of the spring centerline to the pivot point of the control arm divided by the distance (D2) of the wheel centerline to the control arm pivot point:

MR = D1/D2

I don’t know the exact g8x motion ratio but it’s around 0.96 (close across the past three gens). So to get the correct wheel height, the spring height is adjusted by

D1 = 0.96*D2

For example if you want to raise the front ride height by 10 mm, you adjust the spring collar by 9.6 mm. Calculate the adjustment needed at both front corners. Desired ride height = stock ride height - desired lowering amount - initial measured lowered ride height. For example if you want to lower your ride height 15 mm and the stock ride height is 100 mm and your initial measured lower ride height is 90 mm, the height adjustment required is 100 - 15 - 90 = -5 mm (negative number means you have to lower more, positive number means you need to raise the height) - you need to lower the spring seat at that corner 0.96*(-5) = -4.8 mm. If KW supplied the thread pitch of the height adjusters then you’ll know how many mm you get for one full rotation of the height adjuster which means you can calculate the number of turns needed to adjust the ride height. Do this for both fronts. Remember to rock the car back and forth after each time it’s been raised off the ground. Repeat until you get the front ride heights you want.

Now for the rear. Don’t forget to disconnect the rear anti-sway bar drop links. The steps are the same but it’s more involved because you can’t easily raise/lower the rear ride height (unless you’re brave enough to drill and pin the rear height adjusters). You have to relieve the preload on the spring by dropping the lower control arm each time you adjust the ride height. The rear motion ratio is somewhere around 0.57 (f8x rear motion ratio). So:

D1 = 0.57*D2

Measure the initial lowered ride heights, calculate the deltas and multiply them by 0.57. Adjust the rear height adjusters by this amount. Reinstall lower control arm, rock the car and measure ride height. Repeat until you get the desired ride heights.

Reconnect front and rear anti-sway bar links. Done.

Thanks. Very informative. The included documentation is more or less worthless.

Don't suppose anybody has factory torque specs for items like the bolts on the rear lower control arm, the top nut on the rear shock, and the 3 bolts that attach the rear shock to the body?

And on the front end... the strut bracket that clamps on to the bottom of the strut, and the bolts topside that mate the strut tower with the strut?

[M3SQRD]

Originally Posted by BIGW0RM

I did 14.25" front and back gap from the center of the wheel hub to the fenders edge with my KW HAS kit. That is not slammed, but its not stock height either. I have about 1 finger gap front and back from tire to wheel well. I orginally had it set to 14" from the wheel center hub to fenders, but found the ride to be "jarring". 14.25" keep the ride quality nice and still looked good to me.

Looks nice!

It’s amazing what a little change in ride height does for looks. Before looks like the family grocery getter whereas after looks like it deserves a speeding ticket just sitting there! Nice thing is the after can still do the grocery trips but with a much more aggressive/purposeful attitude.

[M3SQRD]

Originally Posted by aremmell

Thanks. Very informative. The included documentation is more or less worthless.

Don't suppose anybody has factory torque specs for items like the bolts on the rear lower control arm, the top nut on the rear shock, and the 3 bolts that attach the rear shock to the body?

And on the front end... the strut bracket that clamps on to the bottom of the strut, and the bolts topside that mate the strut tower with the strut?

No problem

I currently don’t have access to ista. Try asking your questions in the maintenance forum. You could also look up the bolt/nut sizes in a BMW ETK site (similar to realoem.com because it doesn’t have anything newer than 2019). You’ll get diagrams and parts lists like this:

[aremmell]

Originally Posted by M3SQRD

No problem

I currently don’t have access to ista. Try asking your questions in the maintenance forum. You could also look up the bolt/nut sizes in a BMW ETK site (similar to realoem.com because it doesn’t have anything newer than 2019). You’ll get diagrams and parts lists like this:

I bought a 24 hour subscription to TIS. I still cannot locate the specs I am looking for by part number or description (I am guessing lost in translation when describing the part). I am searching AIR, and hitting nothing but air...

[M3SQRD]

Originally Posted by aremmell

I bought a 24 hour subscription to TIS. I still cannot locate the specs I am looking for by part number or description (I am guessing lost in translation when describing the part). I am searching AIR, and hitting nothing but air...

For the rear, i think it’s 2, 3, and 9. The front is 6 and 7. Not sure about the bottom?

[aremmell]

Originally Posted by M3SQRD

For the rear, i think it’s 2, 3, and 9

Yeah, unfortunately when searching part numbers on AIR, I get an error message about "loading the package." I've tried 3 web browsers, so it's a problem on their end.

I wrote support, but not holding my breath. My dealership will come through with the numbers tomorrow morning.

[aremmell]

For posterity, and in case I don't decide to do a DIY write-up on the KW HAS install:

G8X Suspension torque specifications (front):

- Strut pinch bolts: 56nm
- Strut topside bolts: 28nm + 180º (TTY, do not reuse)
- Strut top nut: 71nm

G8X Suspension torque specifications (rear):

- Lower control arm: 100nm + 90º (TTY, do not reuse)
- Shock absorber to lower control arm: 100nm + 90º (TTY, do not reuse)
- Shock absorber top nut: 38nm
- Shock absorber to body (3): 28nm

M3SQRD If you know the answer to the following, it would also be helpful for me today:

1. The KW installation instructions (page 11) use 3 separate measurements for the distance onto the strut the new perch should be fitted (from the neck):

- 76 mm in the German text
- 85 mm in the English text
- 50 mm in the illustration/photo

Which one of these is correct? On the following page (12), 50mm is repeated, so I am currently planning to try that first.

2. Is the following a correct statement?

"If you set the KW HAS front perch to its maximum height setting, this is still an automatic 0.6" lowering of the front; if you set the rear to its maximum height setting, this is still an automatic 0.2" lowering of the rear"

[M3SQRD]

Originally Posted by aremmell

For posterity, and in case I don't decide to do a DIY write-up on the KW HAS install:

G8X Suspension torque specifications (front):

- Strut pinch bolts: 56nm
- Strut topside bolts: 28nm + 180º (TTY, do not reuse)
- Strut top nut: 71nm

G8X Suspension torque specifications (rear):

- Lower control arm: 100nm + 90º (TTY, do not reuse)
- Shock absorber to lower control arm: 100nm + 90º (TTY, do not reuse)
- Shock absorber top nut: 38nm
- Shock absorber to body (3): 28nm

M3SQRD If you know the answer to the following, it would also be helpful for me today:

1. The KW installation instructions (page 11) use 3 separate measurements for the distance onto the strut the new perch should be fitted (from the neck):

- 76 mm in the German text
- 85 mm in the English text
- 50 mm in the illustration/photo

Which one of these is correct? On the following page (12), 50mm is repeated, so I am currently planning to try that first.

2. Is the following a correct statement?

"If you set the KW HAS front perch to its maximum height setting, this is still an automatic 0.6" lowering of the front; if you set the rear to its maximum height setting, this is still an automatic 0.2" lowering of the rear"

I find the directions regarding the installation of the front adjustable spring-sway bar mount confusing. I think the 50 mm measurement is the distance from the stepped diameter on the strut to the top of the adjuster - the top of the adjuster is pressed 50 mm so the bottom (where the sway bar lug is) is pressed farther than 50 mm. If it was measured from the bottom then 50 mm wouldn’t fully seat the entire height adjuster. Whether it’s 50, 76 or 85 mm I don’t know. I’d measure the diameter of the strut and then scale by eye the distance from the step in the strut to the top of the height adjuster knowing the diameter of the strut, if that even makes sense.

[aremmell]

Originally Posted by BIGW0RM

I did 14.25" front and back gap from the center of the wheel hub to the fenders edge with my KW HAS kit. That is not slammed, but its not stock height either. I have about 1 finger gap front and back from tire to wheel well. I orginally had it set to 14" from the wheel center hub to fenders, but found the ride to be "jarring". 14.25" keep the ride quality nice and still looked good to me.

Yours looks perfect!

My dealership's service foreman told me that the maximum allowable amount of lowering from stock is 10mm, or your drivetrain warranty is kaput. It's not that I'm worried about losing the warranty; I'm going to automatically lose it next week when I do a stage 1 CarBahn flash tune. I'm concerned because I don't want to put undue / excessive stress on the xDrive system by changing the angle of the axles outside of their intended range.

Yours is an xDrive, right? Do you drive your car hard (i.e. launch control, "spirited" driving through the twisties, taking all your friends for a ride so you can scare the hell out of them, etc.)? At 14.25", have you had any issues at all, such as:

• Weird noises
• Decrease in ride quality/drivability/performance
• CELs?
• Hitting the bump stops
• Scraping on driveways/speed bumps

The reason I ask is because as far as I can glean from the data tables in the instructions, page 4. (NOTE: the version on their website has different values, and is 2 years older than than the one that came in my kit, so I'm going off of the newer one), 14.25" is below the minimum for the rear on my car (14.4").

My document says that for my M4 Comp xDrive, the min/max values for distance "B" (fender edge to wheel hub center) are as follows:

Front:
Min = 355mm / 14.0"
Max = If M3SQRD is correct about the ratio of mm change in the adjustment being a factor, rather than one-to-one at 0.96: 372.27mm / 14.66"

Rear:
Min = 365mm / 14.4"
Max = at 0.57: 382.54mm / 15.06"

However, you've got the G80 Comp xDrive, and the min/max values for distance "B" on your car are:

Front:
Min = 355mm / 14.0"
Max = at 0.96: 372.27mm / 14.66"

Rear:
Min = 339mm / 13.34"
Max = at 0.57: 356.54mm / 14.03"

This is quite curious! Your car, with the same KW kit, has identical numbers for the front, but the rear is radically different (M3SQRD can let us know what's going on probably, since he's an actual engineer. The minimums are the values from the KW docs, but I am extrapolating the max by dividing the allowable range of the adjuster by the factor to get the resulting adjustment range: for example, if the adjuster's range is 10mm: 10/0.57 = 17.54 -> 339+17.54 = 356.54).

This can't be correct, or at the highest possible adjustment on your rear, you'd be below your 14.25" that you have... so now I need to know where the discrepancy is; is it in the KW document? Is it in my math? Is it in the ratio values M3SQRD provided? Is it in my understanding of how this works?

This has been my struggle for the last few days; if my rear's minimum is truly 14.4" then here's what I am thinking: since I took measurements before I installed the kit, I know that the rear was 10mm taller than the front from the factory. That means that if I place the fronts at 14.25", my rears should be at 14.64", right?! There must be a good reason that BMW had the rear 10mm higher than the front, so now I'm stuck, until someone with more experience doing this type of thing (this is my first adjustable lowering kit) tells me what the right thing to do here is...

Anyone? I apologize for the lengthy post, but I have nowhere else to get these answers from. I will write KW but I'm not holding my breath.

Thanks in advance for any thoughts you guys have on this.

[M3SQRD]

aremmell

I’m having trouble following the numbers you have listedulled from the kw directions.

Is value B at each corner, your oem stock height or the kw recommend max lowered height? Basically, trying to understand what B: 355 mm F, 365 mm R represent. Also, I personally find it easier, and more accurate (repeatable), to measure the height from the bottom wheel lip (where the tire and wheel meet closest to the ground) to the center of the arch.

After repeatedly reading the directions, measured values of A correspond to the max & min ride height values allowed are based on measurements made on the strut (F) and shock (R). If correct, this mean for Amin (F=180 mm/7.1”, R=13 mm/0.51”), you’d get the lowest drop values of Bmin (Flow =355 mm, R=365 mm:24.4”).

Regardless, I’m convinced KW’s minimum height values Bmin corresponds to the KW Amin values. You still may need to adjust your heights at each corner even if you nailed Amin to the closet 1 mil (0.001”) because no two cars will have the same oem static heights due to manufacturing and assembly tolerancing.

Where did the max height values come from? I’m not following how the MR was used to calculate the max heights…where did the following come from:

Max = If M3SQRD is correct about the ratio of mm change in the adjustment being a factor, rather than one-to-one at 0.96: 372.27mm / 14.66"

Rear: Max = at 0.57: 382.54mm / 15.06"

How did you calculate the 372.27 mm F and 382.54 mm R?

aremmell - I missed the second half of your post for some reason. I’m looking at the numbers now…

[BIGW0RM]

The reason mine is off is because I am still on the V1 KW has KIT which came out with the wrong rear springs. My rear springs are shorter and thinner than what the KW kit comes with now. I am also using a KW spacer to make up some height.

I use to hear some clicking noises when I would turn the front wheels side to side. I assumed my lowering had something to do with it. My dealer would not look into it unless I returned my suspension back to stock. I lived with the clicking. Fast forward a year. I needed new tires and got an alignment. Got that done and my clicking mysteriously disapeared.

So I hear no suspension sounds now. Yes I am x drive.

[M3SQRD]

aremmell BIGW0RM

Do either of you know if the B min value listed by kw is when the strut height adjuster is at its lowest height (two flanges are next to each other) or tallest height (two adjusters are farther apart)? To me, B min would correspond to the lowest possible ride height (A has its flanges close to each other) so when A is increased, B also increases.

[BIGW0RM]

Originally Posted by M3SQRD

aremmell BIGW0RM

Do either of you know if the B min value listed by kw is when the strut height adjuster is at its lowest height (two flanges are next to each other) or tallest height (two adjusters are farther apart)? To me, B min would correspond to the lowest possible ride height (A has its flanges close to each other) so when A is increased, B also increases.

No, Im sorry, I dont. I had my kit installed by a shop. Im just the guy who reached out to KW about the low rear spring they where using in the KW HAS KIT V1. Which come to find out, was wrong. I still havent installed the rear replacment springs me. Mine drives nice and smooth so I left mine alone.