Some Pete Guy

Nope, it's just based upon the opinions of a physicist as verified by field observations...

You should check out The Physics or Racing that he wrote.

It's great reading.

Ok, since there is a "whole bunch" of data out there to support your claim (ultimate stopping distance reduction by using different pads), surely you can find such an article, right?

SteveB

OK-- a couple of excerpts--

4) Braking torque: When we are talking about results in the braking department we are actually talking about braking torque - not line pressure, not clamping force and certainly not fluid displacement or fluid displacement ratio. Braking torque in pounds-feet on a single wheel is the effective disc radius in inches times clamping force times the coefficient of friction of the pad against the disc all divided by 12. The maximum braking torque on a single front wheel normally exceeds the entire torque output of a typical engine.
A few things are now obvious:
1) Line pressure can only be increased by either increasing the mechanical pedal ratio or by decreasing the master cylinder diameter. In either case the pedal travel will be increased.
2) Clamping force can only be increased either by increasing the line pressure or by increasing the diameter of the caliper piston(s). Increasing the size of the pads will not increase clamping force. Any increase in caliper piston area alone will be accompanied by an increase in pedal travel. The effectiveness of a caliper is also affected by the stiffness of the caliper body and its mountings. It is therefore possible to reduce piston size while increasing caliper stiffness and realize a net increase in clamping force applied. This would typically improve pedal feel.
3) Only increasing the effective radius of the disc, the caliper piston area, the line pressure, or the coefficient of friction can increase brake torque. Increasing the pad area will decrease pad wear and improve the fade characteristics of the pads but it will not increase the brake torque.

note: coefficient of friction is a factor

Additionally----an excerpt from a different source


Are Big Brake kits really better?
Big brake kits that are incorrectly designed can acutally perform worse than your stock brakes. Bigger pads and rotors primarily do one thing: They dissipate more heat than the stock brake setup. They do not necessarily stop you in shorter distances. Stopping distances are impacted by the coefficient of friction of the brake pad used and the clamping force applied by the caliper. Bigger brake pads do not apply more pressure- they only apply the same pressure over a bigger area. If heat dissipation is of primary concern- then a big brake kit will reduce the rotor and caliper temperatures. Otherwise, Premium Grade Brake Pads with higher temperature range capabilities and a higher coefficient of friction will provide the best improvement in braking performance.

Draw your own conclusions.

Some Pete Guy

And all of the above doesn't support your theory that higher friction pads reduce the ultimate stopping distance.

Your ML, in stock form, has more than enough brake torque to exceed the traction limits of the tires. Why do you think that potentially increasing the brake torque, when the tire's traction limits are already exceeded, will lower the ultimate stopping distance?

Perhaps it would help if you considered your vehicle ona low friction surface, like a snowy parking lot. This kind of situation highlights the relationship between braking system limits and traction limits

Why do you think that adding different pads would shorten the stopping distance in that situation?

That doesn't address single stop events nor does it address the traction limits of the tires, as most brake maketing ignores this important component.

If you were using five inch wide tires, like the temorary spare ("donuts") all of the way around, do you think that you would improve the single event stopping distances by slapping some aftermarket pads on?

p.s. It's customary to provide a link so folks can read the source material in the proper context, as well as know who authored the text.

p.p.s Here's another link that counters your theory:

Grassroots motorsports link

Horribly formatted, but interesting nonetheless.

"This part might surprise some and offend others, but it is a big misconception that chang- ing brake pad material will magically decreaseyour stopping distances. In fact, you may haveeven seen published “data” which attempts tocorrelate stopping distance to friction coeffi-cient. Although it may appear that there is a relationship between the two, there really isn’t, and here's why"

SteveB

still theoretical text, no test data.

However, here's a test, with method and data, that actually does counter your earlier theory article that claims bigger brakes are a waste of time.


[URL=http://www.zeckhausen.com/testing_brakes.htm[/URL]

It seems as though they went to great lenghts to show the benefits of their big brake setup.

SteveB

Doh!

try again....

big brake test

Some Pete Guy

Sigh...did you even read the article?

These were not test of a single stop (your claim that you have been unable to support despite a "whole bunch of data" that is out there) but rather tests that revealed just what anyone who has driven hard at the track knows...that big rotors are larger heat sinks and are more resitant to fade.

In addition, the most dramatic improvements were on a car with grippier tires. Sounds familiar, eh?

It's become painfully obvious that the "whole bunch of data" doesn't exist and it's also beciome obvious that you are unable to answer the many simple questions that I have posed about how you have been able to determine that your after market pads stop ffaster than stock pads, in addition ot numerous other issues that you've simply ignored.

It seems that you will continue to put faith in myth and lore, in the absence of any personal experience, even in the face of contradictory info from third parties who are much more qualified to address the issue than either one of us.

Good luck.

p.s. It seems that you are still unable to understand the "earlier theory article that claims bigger brakes are a waste of time"

From the article:

"So folks, we have discovered the true reason you may need bigger brakes. If your car is driven really hard, such as in track events, and you encounter brake fade, you need to get better heat dissipation for your system so your fluid doesn't overheat or your pads don't go off. To correct this you can use a better brake fluid, get effective brake coolers, get better pads, or (finally) get BIGGER BRAKES."

Some Pete Guy

oops, duplicate post.

SteveB

Don't know what to tell you. I've shown you several sources that illustrate that the coefficient of friction of the brake pad is a major determinant in brake performance.

You seem to wish to ignore this fact, as stated by several sources, including your own.

The test where the data table has 3 of the same model cars, all with the same tires (constant of tire traction-- your big point) where the rows labeled "best 80-0, etc.", which is a SINGLE STOP, all show shortened braking distances with various changes they made.

So, if, as you claim, tire traction is THE ONLY determining factor in a car that has brakes already capable of locking up the wheels, how do you explain the incremental improvement? Certainly we can assume that a 350Z's factory brakes are more than capable of locking up the wheels in stock form.

So, it would seem as though there are other factors at play besides tire traction. Granted, traction is the biggest factor, I'll more than agree with you there. My only point from the beginning of all of this is that upgrading pads can offer some measureable improvement to brakes, even in a single stop case.
All of the articles cited state coefficient of friction as a single variable capable of improving brake performance.

I give you articles that state that, I give you a test with numbers that prove that.

Where's your data?

Get me a test of any sort that proves that changing pads offers no benefit.

There's my beef ! Where's yours??

Some Pete Guy

That's incorrect.

Single stop, with a hot brake system. You're comparing apples and oranges.

Not an ultimate single stop as we have been discussing. They are two different animals.

Obviously big rotors handle higher temps better, that's a given.

Your claim, that adding "better" pads and then coming upon a deer unexpectedly (ultimate single stop) and that your new pads would shorten stopping distances is incorrect, depsite your claims about a "whole bunch of data."

To reiterate, bigger rotors/better pads can absolutely shorten stopping distances when the brake system is being abused because they are more resistant to fade.

It's the difference between a single stop, which is what we have been discussing, and repeated stops where larger rotors handle fade better due to heat dissipation.

You're off on a tangent preaching to the choir.

Sigh. I have never denied that bigger rotors/better pads handle higher heat and are more fade resistant. That's a given.

Heck, anyone who has spent some time on the track knows this basic fact.

You seem intent upon extrapolating all kinds of things from this simple point. Unfortuantely, the experts don't agree with that myth and lore.

Why? An dplease stay focused on the issue at hand rather than beating the bigger brakes/heat dissipation drums again.

That's a red herring.

That's false. In addition, why do you think that increasing the coefficient of friction, and thus increasing the brake torque, will shorten stopping distances if the stock brake torque is more than enough to lock the wheels, in a single stop?

That's the $64 question that you continue to dodge.

Your beef is foul unfortunately.

You made the claim about there being a "whole lot of data."

I have yet to see any that proves your point.

SteveB

I posted data, you're flawed interpretation of the data as being representative of track use, rather than 60-0 stops, etc., as they say in the test leads you to continue to ignore the issue at hand.

So, rather than argue the pros & cons of the data I provided,
since it doesn't seem to do it for you, how about providing some of your own?

It's easy to deflect & re-direct & question extrapolations.

So, once again, let's see your tests that prove changing pads is of no benefit?

No theories, just test data !

Some Pete Guy

Huh? Read the tests again. It's quite representative of track use (see all of the data relating to high/maximun rotor temps).

See my previous posts. Read the info again. Ponder it a bit before making more assumptions.

No deflections, just looking for you to support your claim that adding different pads to your Ml has shortened the stopping distance. I have yet to see any info about that let alone your explanation of how you've gotten your stock brakes to fade. That's a curious, if repeated, omission.

See the previous links.

You're the fellow making the wild claim based upon myth and lore.

The burden of proof lies with you. There is a "whole bunch of data" out there, remember?

Unfortunately, the single test that you provided doesn't address the issue at hand, a single "panic" type stop.

After all,

"Is it overkill for the way I drive? Maybe. But, for that ONE time where it does make a difference................... "

You have yet to explain why or how your new pads help, let alone that you have even come close to pushing the OEM system to its limit.

If it's about dust, I can understand. If it's about "better stopping, that one time" as you have claimed, it's an all too common fantasy.

SteveB

No data to support your claims at all?

That's what I thought.

Well, that was fun!

timdf

all this discussion about improved braking with uprated brakes is all well and good, but I'd up rate my the size of my rotors / pads in a flash if it'd increase the mileage between replacements.

Do they do 6 or 8 pot calipers for ML's with pads which cover about 1/3 of the rotor ;-)

Some Pete Guy

LOL!

Steve, let's review shall we:

Despite never driving your ML to the point that the brakes fade, you replaced your pads and claim that they reduce the ultimate stopping distance. You also claim that there is a "whole bunch of data" out that that supports your position.

When pressed for proof, you provide one marketing blurb from a pad manufacturer that doesn't even discuss pads in relation to ultimate stopping distance and then attempt to deflect the conversation to address a tangential issue, the efficacy of bigger rotors (the Stoptech 350 test).

It's obvious that the person who made the tall claims about pads changing stopping distances (that would be you...) has been unable to find that "whole bunch of data" that he imagines to exist.

The placebo effect lives!

SteveB

You're boring me now.

I gave you several articles citing coefficient of friction as a variable affecting performance.

I gave you tests, with data, showing improved stopping distances with changes in brake setups, single stops-- not track times-- all with same tires, etc.

You still cannot come up with anything besides useless rhetoric, re-direction, & reiteration of previous rants.

My data stands.

You still have nothing, besides your seat of the pants opinion.

Go fish.

Some Pete Guy

Then why bother to reply, you truly are so bored?

Only meaningful if the stock brake torque is unable to lock the tire.

Your ML is capable of doing this so your "upgraded" pads cannot, as defined by the articles (without links to check context, BTW), shorten the ultimate stopping distance.

Sigh, you're trying to morph my comments again. Very poor form Steve...

I made no mention of track times. "track usage" is what I wrote. To understand this spend some time on a track and then read the Stoptech article again. The point is moot however since the article made no mention of your claims about pads shortening stopping distance.

p.s. One test is not "tests," but nice try anyway.

Reiteration works just fine when you are unable to prove your claims, refute my claims or even answer the simple questions that I pose about your driving experience, etc. etc.

The fact that you continue to ignore these simple questions speaks volumes about your understanding of the issue, as well as your personal experience.

That's too bad. Apparently you are unable to read and/or comprehend the numerous links, including the expert opinion of a physicist who is also the acclaimed author of the Physics of Racing series.

That's the only explanation that can be given for your "seat of the pants" silliness.

SteveB

Ok, let's take this one step at a time..

try to stay focused

You're still stuck on locking up the tire as the test of ultimate braking force.

So, for the first part, let's deal with that:

Which generates more heat in the brakes?

a) stomping on the brakes to immediately lock up the wheels

b) threshold braking to a complete stop

Some Pete Guy

Steve, what you can't seem to understand is that I'm not stuck on locking up the brakes.

It just illustrates how silly your claim is.

If there is sufficient brake torque in a brake system to stop the wheels. or ecxeed the tire's maximum grip(your Ml's system for example) then increasing the brake torque (adding higher friction pads) does nothing since the tire's maximum grip hasn't changed.

It should be quite simple, even for someone who professes to be bored.

SteveB

Still can't provide data to back up your claims?
Still can't answer simple questions to address a point?
Still resorting to useless rhetoric?


Ok Matlock, I'm done.

Some Pete Guy

Steve, Steve, Steve.

That is a very apt description of your participation in this thread.

Good luck in your search for understanding.

SteveB

Ok, thanks!

Bernman

Now that you guys are done beating each other up, I have a few questions.

Our 00 ML320 with 50K miles is ready for the third set of pads in the front, and second set of pads in the rear. The rotors are ready to be changed front and rear as well. This really is not within the norm for any of vehicles that I have ever owned (cars, trucks, vans...) or I have even read about, but such is life. The design is what it is.

I used OEM Mercedes pads the first time in the front, and Mintex the second time. Both pads have had equivalent life, though the Mintex had better initial "bite". The only issue I had with the Mintex is that the pad on the leaf spring side does not have the feature that locks it into place during assembly, so they were difficult to install. No squeals or other issues during their *short* life though.

So the questions...

Is there an aftermarket pad that will last longer and still stop reasonably?

Which pad do you use? (where did you get them?)

Which rotor do you use?

I will be doing the installation, just as I have with all the upgrades to my BMW (go bimmerforums.com !), and if anyone is interested will share my experiences with whatever new pad I decide on.

Thanks for your help guys,
Bernman

SteveB

That was dumb, you're right. It was getting amusing, though.

Anyway, to answer your question:

I had a 2000 ML320 which I changed the pads to Rotex metallic when it was fairly new. I think it had less than 2000 miles on it when I changed them. I sold it to my neighbor with 24,000 miles on it, and the pads were less than 50% worn, and the rotors had no visible signs of strange wear. Obviously, a micrometer would determine if actual wear was taking place, but all looked fine. The rear pads looked virtually new.

There are so many factors that affect brake wear, it's really hard to say what is normal.

I've installed the Rotex pads on several cars with very good results. Since you're unhappy with the stock parts, why not try something different?
Contact brakewarehouse.net, talk to Randy. Ask him which manufacturers make rotors as well, he may be able to suggest a different rotor that would work better.

I had a similiar problem with my BMW wearing out rotors, he was aware of the problem BMW has had with rotors & suggested a different manufacturer. So far they seem to be a lot better.

Hope this helps.

Some Pete Guy

OEM pads.

They seem to be sourced from either Pagid (what I used on the front) or Texstar (rears).

The OEM rotors are made by Brembo.

germanstar.net has good stock, prices, and delivery.

DIY rotor/pad swap