Cutting Bump Stops for Koni / Eibach?

[dukeofchen]

While inspecting my suspension last week I found that my front bump stops are beat up and it's time for some fresh ones.

In the process I remembered this post a while back about Dinan offering pre-cut factory bump stops in their version of the kit, and I'm thinking it might be worth trying with the new ones. But discussion on this is surprisingly slim considering this is one of the most popular combos for our cars.

Given that the BMW bump stops are designed to provide some progressivity at the end of travel, it seems like it would stand to reason that retaining original bump stops would unnecessarily remove compliance from a setup that's near OEM rates. I would love to get a little less crashiness over potholes and bumps so long as it doesn't increase the risk of damage or negatively impact handling characteristics.

I'm wondering if anyone has anecdata on cutting bump stops to compensate for the drop provided by the pro-kit springs? If so, how much did you cut?

[maupineda]

As long as you don’t cut much… is not a 1:1 ratio, but if you lower 10mm, that is what I would cut, that said, as you cut, what is left is stiffer assuming you cut the softer part of the stop, they are progressive

[dukeofchen]

As long as you don’t cut much… is not a 1:1 ratio, but if you lower 10mm, that is what I would cut, that said, as you cut, what is left is stiffer assuming you cut the softer part of the stop, they are progressive

Ah, I had been thinking about it in reverse but that makes sense regarding the remaining stop being stiffer if the flat part at the top is cut.

Perhaps somewhat of a test and see approach will be needed, starting with a conservative cut and seeing how it goes before taking it further.

It seems like there's a tradeoff then between more compliance over smaller to medium bumps, but once it approaches bottoming out the increase in stiffness will be more drastic. So big potholes will still feel like the car is being slammed, and perhaps even more so if it's taken too far.