Quote:
Originally Posted by 97 SL320
Except for a lightly loaded pickup / van, the front brakes will lockup before the rear by design.


OK, I'll rephrase. For most passenger cars without ABS, front brakes will lock up before the rears by design. You stated that the rears will lock up first by design and that statement is completely untrue for passenger cars. No matter how I word the response, you are still wrong for most passenger cars.

However, non ABS, lightly loaded pickups / vans without height sensitive proportioning valves do tend to lockup the rears.

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Quote:
Originally Posted by 97 SL320
Your above supports why rear lockup is bad.

You had stated that "
If the driver doesn't modulate, then he goes in whatever direction the vehicle decides to go, based upon the friction of each individual tire. "

I was using your words to reinforce that rear lockup is bad, are you saying your own words are "IRRELEVANT" ?

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Quote:
Originally Posted by 97 SL320
Even in a ABS equipped car, the brakes can be modulated until the ABS activates.

This was to counter your statement that " Of course, your vehicle predates the day of ABS where the manufacturer ___removed the capability for the driver to modulate the brakes ___and put it in the capable hands of a computer. "

Even in an ABS equipped car, the driver still has the capability of brake modulation.
( For those on the sidelines, did you also find "in the capable hands of a computer. " somewhat Orwellian? I did.)

#########

I used the 90's pickup as a simple, easy to follow example that a driver does have capability of brake modulation even with ABS.

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I'll leave it to others to decide who can't read and who makes very condescending remarks to the original poster. In fact, I'll go with whatever the OP thinks of our posts, are you game?

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Again, I'll leave that for others to judge.

I'm now convinced it isn't a question of mercedes having a flawed braking system and that's better than where I was a the start. At this point I want to get a second person and see if it isn't the rear axle that is locking up early. I have that established one way or another I can go from there. Again, this group is great an i appreciate everyone's thoughts.

Did you verify the same pad material and brand front and rear?

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[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.

The fundamental problem with any braking system without ABS is that the proportional braking between the front and the rear wheels is fixed. What this means is that the designer must pick a specific point in the range of braking and establish a proportional relationship between front and rear at that one specific point.

When the driver brakes the vehicle with exactly the designed pedal force at the designed specific point, the vehicle is perfectly balanced with respect to how close each wheel is to skidding.

Unfortunately, the point that is selected, while probably close to the point where the rear wheels will skid, is not an exact science. The variables are many..............vehicle weight on the rear wheels, pad material, condition of the rotors............all of which serve to move the point from the designed specification.

If the driver applies less force than the design point, the rear wheels have more weight and can accept more braking force. This is desirable for general driving conditions and allow the rear wheels to do some work. Therefore, the design point will not be right at the limit of capability of the rear wheels during a panic stop.

If the driver applies more force than the design point, the rear wheels have less weight and can accept less braking force. This will cause a lockup of the rear wheels first in a very heavy panic stop and, there is nothing short of ABS that can be done to prevent it, short of moving the design point closer to the panic stop. If the manufacturer did this, the vehicle would be stopping with its front brakes for 95% of all daily driving and the front pads would wear considerably more than they currently do.

Therefore, in conclusion, due to the design of the system, a lockup of the rear wheels on a panic stop is considered normal for such a vehicle.

IME the brakes on my 240D feel better than I remember from Volvo 240's that I've had and remember, but no ABS like I think the last one had. When bled & w/ good hoses, the brake pedal feels like there's a brick under it, & you don't feel any displacement as you modulate the brakes. The control makes a fast stop feel pretty comfortable, like a SAAB I used to have. I don't lock a wheel unless I'm in the snow or checking the brakes after working on them.

Somebody suggested that maybe your front brakes aren't working the best, so you're locking up the rears, I'd look into that. You could have an internally disected hose, some air or other compliance in the system. A pressure bleeder, 4 brake hoses and a quart of DOT 4 might not be a bad idea.

__________________
CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

I strongly suggest you replace the hoses due to age/failure, regardless of diagnostics.

#1. The industry standard average safety life of a brake hose is six years. FYI data SAE: J1401, J1703, J1705, J1873, J1406, J1288, J1403, J1833, J1402.
#2. Brake hoses deteriorate from the inside as well as the outside.

When I get a used vehicle, new brake hoses are installed before it goes on the road, and every eight years after.

I agree.
The brake calipers may also have issues, but you can not effectively test or totally eliminate hoses as an issue.
* New hoses are cheap safety insurance.
* A brake fluid flush is essentially part of the job.
* Some caliper issues go away with good input/output flow and fresh fluid.

Brake fluid flush is critical to the DURABILITY of your brake system.

Brake flush every two years?! U'r kidding right?

Why should I flush my brake fluid every year, you ask?


Brake:

.

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