Why did MB do away with the conical door locks?
 

They always advertised them as being a safety feature, strong (just one was claimed to be enough to support the weight of the entire car) and the cone prevents jamming in an accident.

Plus they make the doors sound and feel so solid when they are closed.

I heard that they are the only door locks that wont open in a roll over so your arms, legs and head wont be crushed, i think.

This is a good question, I'd especially like to know which year this change was made?

Any techies know how to answer this?

The 1984 190's (W201) were the first chassis to have the new style locks. The W123 and W126 continued to have them until the end of their production run (1985 and 1991, respectively). But each "new" chassis that came out after the W201, had the new style locks (non conical). W124, R129, W140, and so on.

Any ideas anyone? It'd be interesting to hear what any techs have to say.

In a nutshell what are conical door locks?

If you look at the door lock of a W123 or W126, you will find a metal cone on the door side that fits into a hole on the pillar side. This cone design holds the mating pieces of the locks firmly in place relative to each other in all directions along the vertical plane of the door, as the cone/hole are circular in cross-section.

This design was adopted supposedly to hold the two mating parts firmly in place relative to each other in the event of a collision, to prevent the lock from jamming, so the door can easily be opened. A cone instead of a cylinder design was adopted because it is inherently more jam-resistant. The MB literature claimed that each lock can support the weight of the entire car.

In the W201, a triangular hole on the door side mates with a wedge on the frame side. The wedge shape of the mating pieces seems to be designed to hold them rigidly in place relative to each other only in the vertical direction, while possibly allowing some movement in the horizontal longitudinal direction (i.e., front-back).

While this seems strange, it is consistent with the design of the door edges: the trailing edge of the front door and the leading edge of the rear door are designed such that the front door will "ride over" the rear door in the event of a massive front impact, preventing jamming at the door edges.

The door edge design is documented in the MB literature, but not the new lock design. As such, this is just my $0.02 opinion on the design of the new-style locks.

Judging from the numerous other nosedives MB has taken in quality and workmanship since the mid-80s, I imagine the change was made purely because the "new-style" latches were cheaper to produce and/or install.

I'm just guessing, of course....but it wouldn't surprise me.

Mike

The W201 began as a "fresh page" for Mercedes in the late 70's and the design element for safety in the smaller envelope called for redesigned crumple/crush zones. From a safety perspective, the newer latches allowed for better protection and with the mandatory passive 3 point belts, passenger ejection was not as much of an issue. Also, for rollover safety the a-pillars of the W201 and W124 were greatly strengthened.

The W140 used the best of everything, it was the last MB built and designed to a standard and came in way over budget because of it. So the new style door latches must be pretty good if the W140 used them.

Thanks to bobbyv for the explanation -- very clear.

Re-reading the thread I now see the mention of conical door locks 'make the doors sound and feel so solid when they are closed.'

I have a W124 (not conical door locks), and find the doors closing sound quite solid and reassuring (incidentally, same for the hood). Not hearing similar sound on most other brands.

I should check out the sound on those conical door locks.... perhaps when I park close to a W123 or W126 next time and see people closing doors, keep my ears open.

Perhaps I am biased but I think the Mercedes w116 doors sound the best. It has the mechanical noise of a bank vault opening and closing. ;)

I have a 116 and they *are* solid locks. The are also called tapered pin locks.

"I should check out the sound on those conical door locks.... perhaps when I park close to a W123 or W126 next time and see people closing doors, keep my ears open."

Finally heard it. Walked by a W126 today when the front & rear doors closed. Solid, bank-vault sound, yet very smooth. Better sounding than the W124.

BTW, I was at a BMW dealership last week to watch the 3-series launch. Tried the doors on the current 5-series, and could not believe the sound (or lack of it). Granted newer technology probably implies more safety, yet the sound is like that from a much lesser vehicle, and night-n-day from the W126 or even W124.