KW Street Comfort coilovers bottoming out too easily

turtlepower · 05-31-2021, 05:58 PM

I have a 2017 330i Touring and put KW Street Comfort coilovers onto it about a month ago. The car seems to slam pretty hard into the bump stops if I hit a moderate dip or pothole above 30 mph. I'd like to eliminate this but I'm not sure what I can do at this point. I've tried raising the ride height to create more damper travel, but this hasn't helped much. I'm now at the maximum height that KW allows in their installation instructions. The dampers are at 15 out of 21 clicks towards the stiff side right now. I've slowly been increasing it, but there isn't much adjustment left.

I'm not a suspension expert by any means so I'm hoping somebody might have some insight. It just feels like the springs are too soft or there isn't enough travel in this suspension. The shock has about 0.5" of travel before the bump stop engages. Even on an average road where the car doesn't slam down hard, the shock still ends up making contact with the bump stop from time to time. I assume it's just compressing the softer part of the stop and it doesn't quite reach the hard part where there's no travel left. These are the KW bump stops that came with the kit. There aren't any unusual marks on the coil springs, so I don't think the coil is slamming together and losing all travel.

Is there much I can really do? Continue tweaking my ride height and damper stiffness? Find a kit with more suspension travel? Does one even exist? I went with the Street Comfort kit because I only wanted a small ride height drop. I have an Integra lowered on some Tein springs and KYB shocks, it hasn't bottomed out once on these same roads where my 330i will bottom out every couple days. I feel like I expected more from the KW kit compared to some cheap springs and shocks on an Integra.

cfm56d7b · 05-31-2021, 06:03 PM

Were the coilovers brand new when installed?

Very unusual problem. My previous car had KW Street Comfort coilovers without any problems / symptoms as described.

Did you install these coilovers by yourself or was the installation performed by an experienced shop?

turtlepower · 05-31-2021, 07:50 PM

Quote:

Originally Posted by cfm56d7b

Were the coilovers brand new when installed?

Very unusual problem. My previous car had KW Street Comfort coilovers without any problems / symptoms as described.

Did you install these coilovers by yourself or was the installation performed by an experienced shop?

They were brand new and installed by an experienced shop. Here's a video from today. It feels as bad as it sounds. I have a canoe on the roof, but that hasn't affected anything, the canoe only weighs about 60 pounds.

FaRKle! · 06-01-2021, 12:04 PM

From the video it seems like your bottoming out issue is only in the front, right? I would check your springs for evidence of coil bind. You should see marks on the tops/bottoms of the coils from them slamming into each other if you have it. This can be done just looking through the gap between the tire and fender with a flashlight, or if you need to, jacking that part of the car up to create a larger gap to see through. You get a bottoming out effect if the spring runs out of travel and goes to solid block height.

Counter-intuitively, raising the ride height makes coil bind worse, because you're moving the bump stop away from engaging. If you're getting coil bind you actually want to lower the front so the bump stop can engage sooner. Alternatively you can put packers/shims on the damper shaft to effectively make the bump stop longer so it engages sooner. You want your bump stop to engage soon enough to prevent coil bind.

The other thing you can do is move to a stiffer front spring to get less compression, and have more compression stroke.

On the damper adjustment side, going stiffer commonly makes things worse. This is because the dampers are heavily rebound biased, which means the damper wants to keep the spring compressed instead of letting it extend back. So what happens when you hit a dip like in your video is the spring and damper get compressed when the tire hits the bottom of the dip, and then stays compressed hitting the exit/rising edge of the dip which compresses things even more. It also has the same effect hitting a bump. You hit the bump, damper/spring compress, and then stay compressed coming off of the bump with the wheel/tire maybe not even being on the ground, so the front end falls to the ground (think like when you ride your bike off of the sidewalk curb).

rcaso26 · 06-01-2021, 12:26 PM

I had the same exact bottoming out issue with KW SC coilovers on my 328 xdrive and ended up selling them and switched to eibach pro kit springs with Koni special active struts. The whole process was very frustrating and cost me a lot of money. Check out some of my posts on this same topic I believe there's a separate thread on it.

turtlepower · 06-01-2021, 03:18 PM

Quote:

Originally Posted by FaRKle!

From the video it seems like your bottoming out issue is only in the front, right? I would check your springs for evidence of coil bind. You should see marks on the tops/bottoms of the coils from them slamming into each other if you have it. This can be done just looking through the gap between the tire and fender with a flashlight, or if you need to, jacking that part of the car up to create a larger gap to see through. You get a bottoming out effect if the spring runs out of travel and goes to solid block height.

Yes, it only seems to be crashing hard on the front. It looks like the driver's side coil has had some coil bind. The passenger side is still clean. I'll try lowering the ride height and softening the damping. Thanks for the tips!

Unfortunately, my car is already much lower than I expected. KW says that the kit lowers the car 0.4" - 1.6" at the front, but in my experience it's been more like 1" - 2.2". If I have to do significant lowering to eliminate the coil bind, then I feel like the ride height will no longer be practical for a daily driver.

As a result, I did some research last night (including reading a few of your very helpful posts!) and might go for some Eibach springs and Koni shocks like rcaso26 suggested. In particular, I'm considering the E10-20-031-15-22 or E10-20-031-16-22 spring kits. The 15-22 kit is supposed to lower the car 30mm front / 15mm rear. The 16-22 kit has front springs for the six-cylinder cars that are a little stiffer, and I'm estimating that they would lower the car around 23mm front / 15mm rear. Right now I'm leaning towards the stiffer springs for a little extra height. The shocks would probably be either the red Special Active or the yellow Sport shocks.

rcaso26 · 06-01-2021, 04:30 PM

reach out to johnung or check out his numerous posts on this topic. He has done a ton of research on the eibach / koni combination and is very helpful.

cfm56d7b · 06-01-2021, 04:58 PM

Quote:

Originally Posted by rcaso26

reach out to johnung or check out his numerous posts on this topic. He has done a ton of research on the eibach / koni combination and is very helpful.

Just read my mind. johnung provided many insightful comments about Eibach Pro springs and Koni Special Active shocks.

Logicoeur · 06-01-2021, 05:04 PM

Quote:

Originally Posted by turtlepower

Quote:

Originally Posted by FaRKle!

From the video it seems like your bottoming out issue is only in the front, right? I would check your springs for evidence of coil bind. You should see marks on the tops/bottoms of the coils from them slamming into each other if you have it. This can be done just looking through the gap between the tire and fender with a flashlight, or if you need to, jacking that part of the car up to create a larger gap to see through. You get a bottoming out effect if the spring runs out of travel and goes to solid block height.

Yes, it only seems to be crashing hard on the front. It looks like the driver's side coil has had some coil bind. The passenger side is still clean. I'll try lowering the ride height and softening the damping. Thanks for the tips!

Unfortunately, my car is already much lower than I expected. KW says that the kit lowers the car 0.4" - 1.6" at the front, but in my experience it's been more like 1" - 2.2". If I have to do significant lowering to eliminate the coil bind, then I feel like the ride height will no longer be practical for a daily driver.

As a result, I did some research last night (including reading a few of your very helpful posts!) and might go for some Eibach springs and Koni shocks like rcaso26 suggested. In particular, I'm considering the E10-20-031-15-22 or E10-20-031-16-22 spring kits. The 15-22 kit is supposed to lower the car 30mm front / 15mm rear. The 16-22 kit has front springs for the six-cylinder cars that are a little stiffer, and I'm estimating that they would lower the car around 23mm front / 15mm rear. Right now I'm leaning towards the stiffer springs for a little extra height. The shocks would probably be either the red Special Active or the yellow Sport shocks.

Could be the angle but it looks like one perch (first photo with the dirt lines showing where the spring coils see contacting) is adjusted higher than the other? You may have also pushed the damper farther into the knuckle. I'd take a look at both sides to make sure one isn't in farther than the other.

turtlepower · 06-02-2021, 03:37 PM

I lowered the coil perch and softened the damping to eliminate the coil bind. The car still hits just as hard as before over that same bump from the video, so I don't think coil bind was the primary problem. The coil bind issue should now be solved, but still no success in keeping the car from bottoming out.

Quote:

Originally Posted by Logicoeur

Could be the angle but it looks like one perch (first photo with the dirt lines showing where the spring coils see contacting) is adjusted higher than the other? You may have also pushed the damper farther into the knuckle. I'd take a look at both sides to make sure one isn't in farther than the other.

Yes, it looks like the damper with the dirt lines is deeper into the knuckle by around 0.25". WTF. I guess that's another problem to look at, but I don't think it's directly causing the bottoming out.

casualDIYer · 06-13-2021, 11:45 AM

Wouldn’t having one strut deeper into the knuckle affect the anti-roll bar? Effectively your anti-roll bar is always loaded even when the car drives straight.

It has been my observation that in order to remove a strut from the knuckle many apply a lubricant. That’s fine but before reassembly that lubricant needs to be removed. BMW makes a big deal about no lubricants in the knuckle-strut mating area.

As Logicoeur mentioned, left and right do need to be the same. They are tied together by the anti-roll bar.

05-31-2021, 05:58 PM	#1
turtlepower New Member 6 Rep 15 Posts Drives: 2017 330 Touring Join Date: Jul 2020 Location: Winnipeg iTrader: (0)	KW Street Comfort coilovers bottoming out too easily - F31 wagon I have a 2017 330i Touring and put KW Street Comfort coilovers onto it about a month ago. The car seems to slam pretty hard into the bump stops if I hit a moderate dip or pothole above 30 mph. I'd like to eliminate this but I'm not sure what I can do at this point. I've tried raising the ride height to create more damper travel, but this hasn't helped much. I'm now at the maximum height that KW allows in their installation instructions. The dampers are at 15 out of 21 clicks towards the stiff side right now. I've slowly been increasing it, but there isn't much adjustment left. I'm not a suspension expert by any means so I'm hoping somebody might have some insight. It just feels like the springs are too soft or there isn't enough travel in this suspension. The shock has about 0.5" of travel before the bump stop engages. Even on an average road where the car doesn't slam down hard, the shock still ends up making contact with the bump stop from time to time. I assume it's just compressing the softer part of the stop and it doesn't quite reach the hard part where there's no travel left. These are the KW bump stops that came with the kit. There aren't any unusual marks on the coil springs, so I don't think the coil is slamming together and losing all travel. Is there much I can really do? Continue tweaking my ride height and damper stiffness? Find a kit with more suspension travel? Does one even exist? I went with the Street Comfort kit because I only wanted a small ride height drop. I have an Integra lowered on some Tein springs and KYB shocks, it hasn't bottomed out once on these same roads where my 330i will bottom out every couple days. I feel like I expected more from the KW kit compared to some cheap springs and shocks on an Integra.
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05-31-2021, 06:03 PM	#2
cfm56d7b Lieutenant General 5886 Rep 10,256 Posts Drives: 2017 440i Gran Coupe & 2015 X5 Join Date: Nov 2012 Location: Orange County, CA iTrader: (2)	Were the coilovers brand new when installed? Very unusual problem. My previous car had KW Street Comfort coilovers without any problems / symptoms as described. Did you install these coilovers by yourself or was the installation performed by an experienced shop?
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06-01-2021, 12:04 PM	#4
FaRKle! Brigadier General 4016 Rep 3,540 Posts Drives: 328d Wagon, M2 Comp, i4 eD35 Join Date: Sep 2016 Location: Bay Area, CA iTrader: (4) Garage List 2023 BMW i4 eDrive 35 [0.00] 2017 BMW 328dx Wagon [0.00] 2021 BMW M2 Competi ... [0.00]	From the video it seems like your bottoming out issue is only in the front, right? I would check your springs for evidence of coil bind. You should see marks on the tops/bottoms of the coils from them slamming into each other if you have it. This can be done just looking through the gap between the tire and fender with a flashlight, or if you need to, jacking that part of the car up to create a larger gap to see through. You get a bottoming out effect if the spring runs out of travel and goes to solid block height. Counter-intuitively, raising the ride height makes coil bind worse, because you're moving the bump stop away from engaging. If you're getting coil bind you actually want to lower the front so the bump stop can engage sooner. Alternatively you can put packers/shims on the damper shaft to effectively make the bump stop longer so it engages sooner. You want your bump stop to engage soon enough to prevent coil bind. The other thing you can do is move to a stiffer front spring to get less compression, and have more compression stroke. On the damper adjustment side, going stiffer commonly makes things worse. This is because the dampers are heavily rebound biased, which means the damper wants to keep the spring compressed instead of letting it extend back. So what happens when you hit a dip like in your video is the spring and damper get compressed when the tire hits the bottom of the dip, and then stays compressed hitting the exit/rising edge of the dip which compresses things even more. It also has the same effect hitting a bump. You hit the bump, damper/spring compress, and then stay compressed coming off of the bump with the wheel/tire maybe not even being on the ground, so the front end falls to the ground (think like when you ride your bike off of the sidewalk curb). __________________ -328d Wagon Build Log (with helpful reference links) -My YouTube Channel for some of the best DIYs and in depth information Please don't PM me for suspension recommendations unless interested in paid private consultations.
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06-01-2021, 12:26 PM	#5
rcaso26 Lieutenant 331 Rep 472 Posts Drives: 2015 328i xdrive Join Date: Oct 2017 Location: Long Island, NY iTrader: (0)	I had the same exact bottoming out issue with KW SC coilovers on my 328 xdrive and ended up selling them and switched to eibach pro kit springs with Koni special active struts. The whole process was very frustrating and cost me a lot of money. Check out some of my posts on this same topic I believe there's a separate thread on it.
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06-01-2021, 04:30 PM	#7
rcaso26 Lieutenant 331 Rep 472 Posts Drives: 2015 328i xdrive Join Date: Oct 2017 Location: Long Island, NY iTrader: (0)	reach out to johnung or check out his numerous posts on this topic. He has done a ton of research on the eibach / koni combination and is very helpful.
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06-13-2021, 11:45 AM	#11
casualDIYer Major 446 Rep 1,369 Posts Drives: 340i xDrive M Sport Join Date: Nov 2008 Location: Toronto iTrader: (0)	Wouldn’t having one strut deeper into the knuckle affect the anti-roll bar? Effectively your anti-roll bar is always loaded even when the car drives straight. It has been my observation that in order to remove a strut from the knuckle many apply a lubricant. That’s fine but before reassembly that lubricant needs to be removed. BMW makes a big deal about no lubricants in the knuckle-strut mating area. As Logicoeur mentioned, left and right do need to be the same. They are tied together by the anti-roll bar.
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