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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Suspension Bottoming Out



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      05-04-2014, 01:41 PM   #1
Stackedacc
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Suspension Bottoming Out

I have the stock xi suspension with 18s and rft tires. The suspension bottoms out with a loud 'bang' all the time even with fairly small potholes.

I was going to go to konis with zsp springs but I'm afraid the bottoming out will only get worse. Does anyone know if the konis will help the bottoming out? Are the konis shorter than the stock shock?
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      05-04-2014, 02:06 PM   #2
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I doubt it's "bottoming out". What you're experiencing is probably the first reactions to the stiffness of the RFT sidewalls. Google "pothole explosion" for some amusing threads on this phenomenon.

You can do several things: avoid potholes, get used to it, go to 17" rims with more sidewall, or (many people advocate this) change to go-flat tires.

Personally, my go-flat winter wheels/tires are just as bad as my RFT sport package wheels/tires.
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      05-04-2014, 02:24 PM   #3
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Quote:
Originally Posted by Stackedacc
I have the stock xi suspension with 18s and rft tires. The suspension bottoms out with a loud 'bang' all the time even with fairly small potholes.

I was going to go to konis with zsp springs but I'm afraid the bottoming out will only get worse. Does anyone know if the konis will help the bottoming out? Are the konis shorter than the stock shock?
I doubt you're bottoming out, the factory run flats and springs are just incredibly stiff. You need to ditch the RFT and/or get aftermarket springs.
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      05-04-2014, 07:55 PM   #4
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You're not bottoming out. It's the RFT's with the stock suspension that's causing the "bang" when you hit potholes and etc. If you swap out to shorter springs such as ZSP or most aftermarket, make sure that you swap out the bumpstops to shorter ones or you will continue to experience the same, if not more so.
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      05-05-2014, 10:43 AM   #5
Stackedacc
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Did a quick search. It looks like the pothole explosion is actually the bottoming out of the suspension (a few guys went to non-runflats and still had the issue).

The solution of swapping to shorter bump stops also suggests bottoming out of the shock is the issue....more travel means less bottoming.

What I really want to know is the length of the koni yellow. Have they made it sufficiently shorter to reduce the chances of bottoming out?

On a side note, I can't believe bmw designed a suspension with such an obvious flaw. Brutal. My E46 never bottomed out, nor should any car.
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      05-05-2014, 10:26 PM   #6
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Quote:
Originally Posted by Stackedacc View Post
Did a quick search. It looks like the pothole explosion is actually the bottoming out of the suspension (a few guys went to non-runflats and still had the issue).

The solution of swapping to shorter bump stops also suggests bottoming out of the shock is the issue....more travel means less bottoming.

What I really want to know is the length of the koni yellow. Have they made it sufficiently shorter to reduce the chances of bottoming out?

On a side note, I can't believe bmw designed a suspension with such an obvious flaw. Brutal. My E46 never bottomed out, nor should any car.
I agree. I have bilstein eibach combo with no front bump stops ( they are inside the bilsteins) and they 100% do bottom out. Anyone who doesn't must not live in New Jersey and drive our battle damaged roads. The only solution I have seen is the Koni yellows adjusted by TC Kline or get the TC Kline coilover kit. I am so tempted since my ride is so good but on certain bumps it hit so damn hard it rattles my soul.
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      05-06-2014, 11:11 AM   #7
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I am so tempted since my ride is so good but on certain bumps it hit so damn hard it rattles my soul.
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