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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > F30 DIYs and Coding Discussions > DIY: Koni Sport Shocks (Front) + ACS Springs Install
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      10-27-2021, 11:50 PM   #1
casualDIYer
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DIY: Koni Sport Shocks (Front) + ACS Springs Install

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Another F30 front strut & spring DIY? There are ton of them but for F30 chassis owners who have picked Koni Sport and/or ACS springs, not really. I've skipped over the removal of the OE shock since so many members have contributed great DIYs, both here and on YouTube, on how to do that. Plus, I don't want this DIY to stretch on forever. Think of it more like a supplemental guide rather than a A to Z set of instructions covering everything.

Oddly, it seems between Koni and Bilstein (which has much better documentation) you'd think Koni would have a lot of DIYs. Koni has decided to go with Ikea-esque diagrams-only instructions. For newbies, you really need to look over those instructions, or lack of them, a lot. The goal here is to save a bit of time trying to decipher Koni’s hieroglyphics on strut install.

Disclaimer: These are not official BMW instructions. Be sure to consult authoritative sources for torque values, assembly/disassembly procedures, and part numbers.

TIP: Get a friend to help. It's going to make your life a lot easier.

The Shock Cap
For à la carte spring, damper, bump stop installers (i.e. non coilovers) I’ve covered the shock cap swap process. The shock cap holds the bottom part of the damper protection boot to the shock. Maybe it’s obvious but I didn’t think so. I go over that.

Higher after install?
In doing research on the Koni install, I found cases, where the installer’s car was higher after install than before. It is my belief these installers did not quite understand how deep into the knuckle clamp the damper needed to go. This will be covered.

Bumpstops
There are no instructions by ACS regarding bumpstops. They are not included in the ACS kit. That being said, shorter stops for shorter springs seems to be as old as McPherson struts themselves. Members on this forum, and many across the internet have taken time to explain the role of stops in spring rates. While not a requirement, I replaced the bumpstops on the car (non-M front strut bumps) with the F80 front end bumps.

Initial Setting
For the track, 1 1/2 turns from full soft. For road driving, 3/4 of a turn from full soft.

Getting Started
Here I'll defer to the many great DIYs on getting BMW's struts off the car. Do that first

IMPORTANT: If you are using camber plates, suggest you loosen the camber plate’s slide adjuster (i.e. the part of the plate that sets the camber) while bolted to the car. When removing the camber plate, setting the camber to 0 degrees first makes removing it from the old shock then moving it to the Koni a lot easier. You need an alignment anyway so might as well make your life easier setting camber to 0 degrees.

Use of grease/oil to remove the damper from the knuckle?
BMW does not say you cannot use oil to help release the strut from the knuckle but BMW does say “Keep this area free from grease and oil”, referring to the strut-clamp mating area. I interpret this to mean you can use penetrating oil but make sure you clean it up before you re-install the strut. I used a generous amount of degreaser to remove any oil used to help free the strut from knuckle. Do your best to clean the inside of the knuckle because the paint on the Koni’s is thicker than the OE shock. It’s going to be a struggle to get the Koni into the knuckle. As per BMW’s advice, I did not use oil to re-install the damper to the knuckle. A friend, and a copious amount of foul language, worked.

xDrive? Should you remove the axle bolt?
I have previously removed the strut without removing the axle bolt. But, for me, while it was more work, the work of disassembly and re-assembly was easier with the axle bolt removed. You will need to replace the axle bolt with a new one. On top of the already high torque of 210 Nm, the bolt needs another 90 degrees of torque. Yeah, it’s hell to turn that bolt 90 degrees. But then again, having the front wheel fall off is very inconvenient. On removal, a friend can press the brake while you torque off the bolt with 17mm hex key. As an alternative to using the brake, wedge a screw driver between the caliper and rotor to hold the front wheel in place.

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Loosen Control Arms Bolts?
Breaking the torque on the lower control arm (chassis side) is also very helpful to help lower the knuckle. I use Millway’s uniballs on the thrust arm. It turns out that with a uniball one does not need to loosen the chassis side bolt. Bonus!

IMPORTANT: The car will need to rest on its own weight when re-torqueing control arms bolts. But, as there was not enough space to get under my now, lower-than-before (even on ramps) car I needed another method.

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Instead I jacked up the front wheels, one at time, then applied correct torque. To determine how high to jack up the front control arm, MEASURE BEFORE DISASSEMBLY, the distance between the wheel centre cap and the bottom edge of the fender.

WARNING: When raising the front suspension, you may be tempted to raise it using the front rotor. Keep in mind the front rotor can turn even while the car is in park. With wheels off and car on jack stands, attempt to spin the rotor. You can. Spinability means the jack can slip out front under the rotor while it's under load. Avoid this situation by raising the lower control arm at the point it attaches to the knuckle. Do not/not raise the control arm from its middle unless you really want to end up buying a new control arm. You can damage the control arm raising it from the middle.

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1. With the strut and spring assembly removed from the car, study the strut for a moment, noting the strut protection boot is affixed to point just above the lower spring perch. Continue with disassembly of the shock and coil spring.

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2. Once the camber plate / strut hat has been removed, you can now remove the shock cap from the shock body. Do this very, very carefully. There is no replacement part you can buy if you crack the cap. It is part of the damper. Why? There must be a bin of a million of these things. Can't throw two in an order for front struts?

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3. <Not explained by Koni> When you attempt to move the cap to the Koni you will notice it does not fit. You will need to make it fit using a Dremel tool. Carefully, little by little, remove material from the inside of the cap, and attempt to pressure fit it to the Koni after you’ve made a few even passes around the inside of the cap. You want this to be a very snug fit so do not/not wail away at the cap like you were tunnelling through the Swiss Alps. Take your time here. Patience is the key.

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4. With the cap on the shock, continue re-assembly. The order is:
  1. Cap
  2. Lower spring perch. Place on perch holder (a rubber guide pin orients the perch),
  3. Spring (AC Schnitzer logo & part number oriented up). End of coil spring MUST buttress spring perch coil stop. Forget to do this and likely the spring will rip the perch to pieces. Ooops.
  4. Protection boot. Note the bottom of the boot will fit into a groove in the lower part of the cap. The boot must fit over cap just as it did in the OE shock
  5. BUMPSTOP. DO NOT FORGET THIS or you'll be taking apart your shock again. I used the F80 front bump stop (Part No. 31336859768).
  6. Upper spring perch. Buttress end of coil with coil stop. Forgot to do that? The perch may meet an earlier death. Note the upper perch has a coil guide. That should go OVER the coil.
  7. Upper strut bearing
  8. Camber plate / Strut hat (if not using camber plates)
  9. Koni supplied spring washer. This is critical to ensure proper torque for Koni's supplied nut.
  10. Koni supplied 19mm nut. You cannot/cannot use the BMW flange nut.
  11. To attach fasten the camber plate / strut hat to the damper you will not / not need a coil compressor. It’s a true gift here. You will need
    • 1 x 19mm pass-through socket
    • 19mm combo wrench
    • 1 x 9mm socket
    • Socket wrench (ideally, it fits that 9mm socket you just picked up)

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      Note regarding photo: The arrow points to 'Koni Nut' which is under the 19mm pass-through socket being turned by the 19mm combo wrench.

You’ve now got a way to re-assemble your strut-spring assembly. Koni illustrates this in a picture . . . with no details on size. Wonderful.

5. <not explained by Koni> With an assembled strut spring you now need to put it back in the car. Maybe it’s just so obvious Koni thought “If you need this explained, you shouldn’t be taking this apart”. Google sleuthing reveals a few E90 chassis owners with cars that rode higher with Koni shocks AND lower springs. What could have gone wrong?

Note how deep the knuckle clamp is. On my car, it’s roughly 51 mm. 51 mm of knuckle clamp needs to grab 51 mm of damper. Note at the bottom of the strut there is a tapered end. Ignore the tapered end (because the clamp can't use that) and measure 51 mm from the top of the tapered end up toward the top of the strut, drawing a black line around the shock to help guide you when placing the shock into the clamp. The damper must be 51 mm deep (not counting the taper) into the knuckle.

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The damper does need to be oriented into proper position to allow the anti-roll bar link to be re-attached in the correct location. Like BMW, the Koni damper has an orientation pin that must align with the knuckle clamp seam. Koni, more details please. Should the pin go into the knuckle or stay out? Will the pin interfere with the pinch clamp when tightened? Or does a few millimetres matter? Maybe I’m overthinking it here. The Koni design does prevent the alignment pin going in too deep by using a stop that prevents the shock from exceeding a certain depth into the knuckle.

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Once into the clamp use a jack to move the knuckle up a bit, align the camber plate/top hat, and snug in bolts, then tighten to their assigned torque, which is different depending on whether you are using BMW’s strut hat, or 1 of 6 camber plate options for the F30. After that replace the knuckle clamp bolt (‘head first’ i.e. pointed to front of car), not forgetting the ABS and brake pad sensor bracket and making sure the ABS sensor wire is IN FRONT of the strut, not behind it. The bolt is torqued to 44 Nm. Also, re-connect the anti-roll bar end link to the the strut. The end link-strut connection bolt is torqued to 56 Nm.

If you removed the axle bolt, you will need to make sure the splines of the axle are mated with the wheel housing. Match splines by hand, thread bolt by hand, snug bolt with 17mm hex key, then test the connection by turning the rotor. You should not hear a 'clank' sound. If connected properly, torque to 210 Nm. Next, torque the bolt another 90 degrees. Pressing the brake may not work during bolt TTY (torque to yield) but using the screw driver wedged between caliper and rotor does. Once the bolt is back in the axle, torqued, and stretched, smear the inside of the axle bolt with a bit of grease to prevent rusting. Auto mechanics can be hard work. Really hard.

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As your final step, raise the front control arms so the middle of the axle bolt is the same distance away from the fender (measured above during ‘Loosen Control Arms Bolts?’) and re-torque the chassis side bolts to 100Nm for both lower control arm and thrust arm (chassis side). These are stretch bolts but do not re-stretch them as they could end up shearing. Perhaps on a future DIY to replace the control arms, swap out the bolts. Also, check the headlight levelling sensor has also been reconnected.

Good luck.
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Last edited by casualDIYer; 11-03-2021 at 07:41 PM..
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      05-17-2023, 04:09 PM   #2
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Man why does no one talk about this stupid little shock cap on the front struts for the dust boot?? I was hoping to assemle my koni / eibachs as a complete strut and then just swap out the whole strut together w the OEM
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      05-29-2023, 10:36 AM   #3
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Quote:
Originally Posted by pauli18c View Post
Man why does no one talk about this stupid little shock cap on the front struts for the dust boot?? I was hoping to assemle my koni / eibachs as a complete strut and then just swap out the whole strut together w the OEM
I was really surprised no one mentioned it either. I guess if you've done a few suspension swaps it seems obvious but the first time, it's not. Even more shocking was the fact buying a replacement cap seemed to involve buying a whole new shock from BMW. God, I hope I'm wrong about that but that seems pretty stupid if that's the case. Why didn't Koni include it? If they wanted a few Netherlandian sheckle-pescos for the caps I would have sent them the money.
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