Eskareon

Newbie moment here guys. I tried to search for others with the same issue but to no avail. Let me know if I'm just overlooking a FAQ somewhere.

I picked up my 2009 C63 with a carbon fiber trunk already installed (pretty sure it's from Stone Carbon). However, the previous owner didn't like the fitment gap, so he removed the springs. I went to reinstall the springs and I have a feeling I didn't do it quite correctly. I've never worked on trunk springs before so I didn't even know where to start except to Google a lot and try to identify the anchor points.

Here's where I installed the spring on the trunk:


There's a black plastic insert on this hole, which came loose (as you can see in the picture), and that makes me think this is not the right anchor point on the trunk lid, as installing the spring hook essentially forces the plastic insert out.

Here's the adjustment hole I used on the body anchor:


And here's how the trunk sits closed:




It doesn't leak in the rain, and the gap isn't a deal-killer for me, but if I installed something incorrectly and I can lessen the gap, that'd be great. Also, the trunk absolutely flies open and bounces at the top, which I would expect going to a CF trunk with stock settings, but if I've correctly put the springs as loose as possible, am I out of options?

Last Q - the foam rectangles... they go inside the springs, right? Edit: I'm thinking I have the spring reversed, given the different lengths of the hooks relative to the anchor points, but that shouldn't affect the spring rate at all, right?

Thanks everyone.

AMG893

All i can add, is yes, the foam goes inside the spring to reduce noise / vibration

Eskareon

Just gonna give this thread a friendly bump.

bluejae

is there any way to decrease the spring rate with a carbon fiber trunk installed? so it doesn't fly open

Eskareon

If you pull back the trunk lining, you can see different anchor points for each side of the spring. If yours is flying open, move it to the farthest hole from where it's seated - I'd imagine that'd be looser. It takes a bit of muscle to really get it there. Open it carefully after you move them.

JimGnitecki

The spring position is variable? I had no idea. My factory trunk lid opens a little too quickly for my taste, and sort of "rebounds" a bit after opening so quickly. So if I move the spring to a different anchor point I can slow it down a bit?

Jim G

Eskareon

Yeah, there are several points you can move it to. I eventually replaced the carbon trunk from my OP in this thread back to a factory trunk lid. The trunk wouldn't open with the spring in the softest point, so I moved it up and now it springs open. It's perhaps a little too fast for my taste, but I don't feel like wrestling it back into the middle setting, hah.

JimGnitecki

Once you expose the mounting points, is it obvious which way to move the spring anchor to get it slowed down (or is it a fancy German over-engineered mechanism that's hard to figure out )?

Jim G

Eskareon

The anchor points on the 'body' (toward the bumper) are easier to understand: toward the center of the car is less tension, farther is more tension (less distance for the spring to stretch vs more).

If I recall, the ones on the trunk lid arm took me a second to go, "ah-hah." You'll want to stick your head in there and slowly 'close' the trunk and watch the anchor points. What'll happen is they will rotate down and back with the motion of the arm, so whichever one ends up closer to the body anchor points with the lid closed will give you less spring tension when you open the trunk (since it's a shorter distance for the spring from arm-to-bumper points).

I was originally picking the anchor hole with the lid fully open, but I didn't realize that as the lid closed, the points rotate down and back, thus stretching the spring as you close the trunk. The one I originally chose for being a longer distance ended up being a shorter distance with the trunk closed, so it wouldn't open the stock metal lid.

Does that make sense? I think once you poke around in there it will.

Note: The arm point I chose had a plastic sleeve in it. I believe that's to reduce noise, so there's no metal-on-metal contact. One of my sleeves cracked/popped out after a few open/closed cycles, so I have to add a little lubricant every few months to that spot or it'll creak. So be sure you carefully notch the spring through any plastic sleeves so it sits as flush against it as possible.

JimGnitecki

This is a GREAT explanation! I get it, and really appreciate it. I also suspect that if I really have any problem understanding the movement of the springs, I can simply pop the rear seatbacks down and watch what happens as I have my wife or a friend open and close the trunk lid.

Thanks for taking the time to write the detailed explanation!

Jim G