M4 Trunk closing springs adjustment?

[pbar]

Several people have mentioned having difficulties closing the trunk lid on the M4 due to its much lighter weight compared to the M3 trunk lid.

I recently signed up for 24 hours of BMW TIS to check out some schematics, and whilst browsing I noticed that the springs for the trunk lid have 3 different position settings - heavy, medium and light. I was wondering if BMW didn't think to set the springs in different positions for the M4?

There is a fairly simple looking adjustment procedure which involves taking off the side liners in the rear luggage area and moving the end of the spring to a different slot.

Has anybody tried this adjustment, or got their dealers to do this?

[ex12psi]

sub'd for answers

[Gomie]

Interested to hear results or other people's experiences with this.

[Lups]

Annoying little shit the trunk. It actually needs to be slammed. Someone do this so I don't have to.

[ES_TRADER]

I like the old trunk better. When popped it stayed closed so the whole world doesn't see your shit in the trunk and when closing you could just let it drop. It also felt heavier and more substantial. New trunk just feel no different than a Camry

[SMOKE EM IF U GOT EM!!]

The official carbon fiber trunk spoiler installation procedures advises the trunk springs be adjusted after the spoiler is fitted. I think they believe it adds just enough weight to affect the closing of the trunk. I installed the spoiler w/o adjusting the springs with no issues.

[Hawaii i8]

My M4 vert has an electronic closing which draws the trunk closed for the final inch or so.. Really like that feature, should be on E80 and 82

[Wah]

Everybody wants beefy doors, heavy trunks lids, bulletproof skid plates, a 3200lbs car, for under $70k. BMW can't win here. lol...

[Green///Hell]

Originally Posted by Wah

Everybody wants beefy doors, heavy trunks lids, bulletproof skid plates, a 3200lbs car, for under $70k. BMW can't win here. lol...

I've stood there complimenting and going on with an owner about how much I love the i8. They'll make sure to mention the CFRP Tub Frame and how light it is and in the same token mention its impossible to get in and too low

[SakhirM4]

Originally Posted by ES_TRADER

I like the old trunk better. When popped it stayed closed so the whole world doesn't see your shit in the trunk and when closing you could just let it drop. It also felt heavier and more substantial. New trunk just feel no different than a Camry

The M4 trunk lid is made from plastic, not metal, for weight savings. That's why is doesn't feel heavier or more substantial - by design.

[Time]

OP, PM me screen shots or a PDF of what the procedure is and Ill try it on my M4 this wknd.

[Wah]

Originally Posted by SakhirM4

The M4 trunk lid is made from plastic, not metal, for weight savings. That's why is doesn't feel heavier or more substantial - by design.

It sounds much cooler if you say CFRP rather than just plain old plastic.

[SakhirM4]

Originally Posted by Wah

It sounds much cooler if you say CFRP rather than just plain old plastic.

Okay, you are right

Carbon-fiber-reinforced polymers (CFRP) are composite materials. In this case the composite consists of two parts: a matrix and a reinforcement. In CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a polymer resin, such as epoxy, to bind the reinforcements together.[1] Because CFRP consists of two distinct elements, the material properties depend on these two elements.

The reinforcement will give the CFRP its strength and rigidity; measured by stress and elastic modulus respectively. Unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber and the proportion of the carbon fibers relative to the polymer.[2]

Despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue endurance limit. This means, theoretically, that stress cycle failure cannot be ruled out. While steel and many other structural metals and alloys do have estimable fatigue endurance limits, the complex failure modes of composites mean that the fatigue failure properties of CFRP are difficult to predict and design for. As a result, when using CFRP for critical cyclic-loading applications, engineers may need to design in considerable strength safety margins to provide suitable component reliability over its service life.


Don't slam your trunk lid on an M4 - it might break!!

[pbar]

Originally Posted by ///MMB

OP, PM me screen shots or a PDF of what the procedure is and Ill try it on my M4 this wknd.

Sorry - I didn't think to save a copy of these schematics for the trunk or the spring adjustment procedure, and my access has now expired.

I just paid $30 for a 24-hour access to this web site:
https://www.bmwtis.com/

The springs are shown in this parts diagram

http://www.realoem.com/bmw/showparts...19&hg=41&fg=60

By default, the end of the springs nearest the tail light hooks into a Z-shaped slot in the body panel, which provides 2 of the adjustment positions. There is an additional diagonal slot in the panel which you can also move the spring to - this is either the 'light' or 'heavy' position (can't remember which!) I had a look, but can't find a diagram of this part of the bodywork on the parts web site :-(

The adjustment procedure was very brief and basically came down to:
1) open trunk
2) remove side trunk liners
3) have somebody support the trunk lid
4) wearing gloves, grab the end of the spring and move it to the desired slot
5) see if trunk closes better!

The only caveat was to make sure that the left and right spring positions didn't differ by more than one (to avoid warping the trunk lid).

Hope this helps!

[Time]

^ ill give it a try on Monday or Tuesday and report back.

[DaBean]

Did anybody ever try this? @Time ?