If you are referring to the arrow on the lower left, the engineer had also drawn an opposing arrow from the tire. This braking force causes the rotation around the center of gravity.

No, matter, the technical explanation. I have more information. Mercedes identifies the trailing arm as a "trailing arm." As time has progressed, it is more correctly called a semi-trailing arm. A trailing arm runs straight-a-way to the rear of the car. A semi-trailing arm is at an angle, such as in a W123.

I also found terminology of what I have been calling a "dip." It is actually termed "anti-lift" technology. Mercedes, BMW, Porsche have all used this anti-lift technology and it is attributed to the rear semi-trailing arm. Here is a link that discusses these technologies.

April 2000

Here are the specs on a Mercedes W126 - 500ESonder

W126-500SESonder-2-Fahrwerk/en

Please note the third line item (rear suspension) on trailing arms; it says,
semi-trailing arm axle with starting- and braking-torque compensation. At this point the actual physics behind this is inconsequential to me. All that matters is that the rear of the car dips because of anti-lift technology. Under normal braking conditions, my early Mercedes stayed quite flat.

So, Brian, you originally said there is no such thing and that I should patent it. Brian, somebody already has, almost 50 years ago. Now, I see you coming around a little bit, but your thinking is likey (making your last explanation, very, very doubtful) wrong since my calipers are on the rear-side of the axle.

has large full sized diesel cars that get 45 MPG highway?

Is that true, Brian?

In the right hands, four wheel drive racing cars far out-perform two wheel drive cars. See earlier post.

Just because they have anti lift features in the design does not mean it actually dips under braking.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

sure, according to craigslist and ebay, my 240 is under performing. It should be running at least 50mpg.

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Here is some more reading material for you.

Automobile Ride, Handling, and Suspension

A whole write-up on suspensions, but if you scroll down to near the very end, there is a info on Trailing Arm and Semi-Trailing Arm Suspensions. It looks an awful lot like my W123 rear end, and my 280S rear end.

It also seems to say, "Rear end lift during braking is countered by the downward component at the leading end of the arms. (semi-trailing arms, that is).

One need not understand all of the physics, but THAT IS "how it works."

It dips. No, it squats. No, it is anti-lift (huh?).

twalgamuth said,
Just because they have anti lift features in the design does not mean it actually dips under braking.

My 280S surely dipped in the rear end under normal braking conditions.

I still suspect it has to do with the greater gripping power of the organic brake pads that were on these cars when new. So, I decided to see if the organic pads were still available. Organic brake pads are known for their "high initial brake effect," according to Summit Racing. CAll it, "getting ahead of the dip."

T, have you tried organic pads, or did you switch to ceramic to avoid the extra dust? If you did, you did at least one thing to change the dynamics of your rear suspension. Did you put on heavy duty shock absorbers? If you did, you changed the dynamics of your rear suspension. Did you replace your rotors with the same ones Mercedes used in the eighties? Doubtful, so you have changed the dynamics of your rear suspension. If I remember correctly, MB used cast iron rotors, which also may not be around any more. Cast iron would also create a "high initial brake effect," to get ahead of the dip.

So, let's talk about rotors. These cars likely had cast iron rotors when they came out. Brembo states that, cast-iron, "chosen for its superior friction coefficient, high-heat and moisture-absorbtion capabilities." Brembo also no longer makes cast iron rotors. While Brembo is relating this to motor cycles, the technology timeline was similar for cars.

Brembo Rotors

So, what do you have in your car? It is likely a carbon steel rotor, which lasts longer and rusts less easily, BUT, it does not have as high a friction coefficient. Carbon fiber and carbon steel is used today as they have less weight.

So, if you thought you brought your car "up to specs" because you went to J. C. Whitney and bought the latest in ceramic pads and carbon steel rotors, I will tell you that your brakes are only about 75-90% of what they were when new. My guess is that your brakes are more like 75% functional when compared to a car coming off the showroom floor. It takes more pedal power to stop my 1983 240D than the cars I owned new back then, and my master cylinder has an extra 1/16 to 1/8 of an inch bore.

And, I checked again. My rear rotors are still behind the axle.

If they are you better not drive it until you get that straightened out.

You gotta take a rest from this subject Rick. Nobody is with you on this. You cannot change the physics of it no matter how much anti dive is built into the suspension, unless you have a full on active suspension run by a computer you are not going to get squat under braking no matter what position the caliper is on the rotor.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Isn't the Mercedes technology referred to as 'Anti-lift, Anti-squat'??

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

My rotors are kind of centered around the hub...

Front and rear calipers are aft on my w126.

__________________
On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

Behind the rear bumper?

NOOO! Don't do it! Don't do it! Delete that! Now!

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Why a computer? You could have a fully hydraulic compensator actuated by brake-line pressure. Not sure if it would be worth it, but you could. (And if you think about it, Citroen did insane things with their hydraulic systems in the 60s. Not a microchip or transistor in sight.)

I agree. There are plenty of folks in the world that don't understand any physics and they are very similar to yourself. They already KNOW how it works.

Therefore, it is pointless to discuss any physics or engineering with them since they already know the answer.

Okay, here we go:

I was driving our Corolla yesterday, and I made a panic stop for a stopped vehicle. The rear not only dipped down, it went lower than the front end. I have to side with rickymays on this one -- I was with you until now, Brian, but I guess the "laws of physics" can be broken occasionally, just like speed limits. Whatever it is, the rear of the Corolla made a noticeable dip down.

Sorry, but the truth must be known.

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."