No more Wilwood Polymatrix "D" Compound?

[Denny Trimble]

We've used the Wilwood Polymatrix D compound since the beginning of time, and I haven't checked with any suppliers, but it's not in the latest Wilwood catalog. Anybody have good luck or advice on other compounds? "A" looks pretty good from the Cf vs. T graph. But we'll have to do our elastic modulus testing again. For those who didn't make it to the 2004 US Motec Seminar, Claude gave a good example of why it's not a BS test.

http://www.wilwood.org/catalogs/polymatrixcatalog.pdf

[Greg]

I called them up a while ago, and they said that the "e" pad is very similar. They also suggested that we do not go with the "a" pad, due to the size of our cars. Give them a call, they were very helpful.

[NovaCat2005]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>But we'll have to do our elastic modulus testing again. For those who didn't make it to the 2004 US Motec Seminar, Claude gave a good example of why it's not a BS test. <HR></BLOCKQUOTE>
Huh? What test? Fill me in on this. Thank You!

[Chris Boyden]

Claude asked us "what is the modulus of elasticity of your brake pad material?"

to which we responded, "uh....I don't know?"

Correct me if I'm wrong,I'm an EE, but I believe if the material isn't very stiff, i.e low modulus, then it introduces compliance in your brake system that may be unexpected if you didn't account for it.

[alfordda]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Chris Boyden:
Claude asked us "what is the modulus of elasticity of your brake pad material?"

to which we responded, "uh....I don't know?"

Correct me if I'm wrong,I'm an EE, but I believe if the material isn't very stiff, i.e low modulus, then it introduces compliance in your brake system that may be unexpected if you didn't account for it. <HR></BLOCKQUOTE>


Exactly, the modulus is just the slope of the stress-strain curve. This means a lower E pad will deflect more at the same level of force, leading to more pad travel, more fluid movement, and finally more pedal travel. Not to mention modulus's are usually affected by heat, not sure how much, but if the two pads have differnt temp dependicies (sp?) thiw will also affect the results.

[Denny Trimble]

Correct, he related a story where a "great new brake pad compound" was tested out, apparently it had great thermal and friction properties. But, the driver couldn't push the car hard because the pedal was traveling twice as far as before, and he had no confidence in it.

[Schumi_Jr]

While Claude makes an interesting point, is it really necessary to run out and test the stiffness of your brake pads? If you don't have a problem with brake pedal stiffness then what's the point?

Besides, don't you think most of your stiffness is lost from the pedal and brake line flexure?

[Denny Trimble]

Aaron,
You're right, you need to know the total system stiffness (pedal/mount flex, hose flex, caliper flex, pad compression).

You don't have to run out and test anything. People build racecars in their garages all the time.

But, if you want to understand the system, brake pad compliance exists and shouldn't be ignored completely, especially if you're having problems with your brakes.

Has anyone thought about removing half the brake pad thickness? That would double the brake pad stiffness, which may or may not be a large part of the system compliance.

Less deflection -> less pedal travel for the same force -> you can increase your pedal ratio or hydraulic ratio and lower the force on the pedal.

[Frank]

E pads are good

B's too harsh on our rotors

T pads (old "tan stoppers") were not good enough

as for...
"what is the modulus of elasticity of your brake pad material?"...

i believe that was a joke

when you have a number of springs in series, the stiffest spring has the least effect

[GTmule]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Frank:
E pads are good

B's too harsh on our rotors

T pads (old "tan stoppers") were not good enough

as for...
"what is the modulus of elasticity of your brake pad material?"...

i believe that was a joke

when you have a number of springs in series, the stiffest spring has the least effect <HR></BLOCKQUOTE>

I hope it was a joke, otherwise, get a life, guys.

[Schumi_Jr]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by GTmule:
I hope it was a joke, otherwise, get a life, guys. <HR></BLOCKQUOTE>

You'd think so...

Claude asked this question in design semis in 2003 and mentioned it at his 2003 and 2004 FSAE seminars.

Denny, how do you determine what constitutes a brake system being stiff enough? It comes down to driver feel, so what you really need to do is test your driver!

[MikeWaggoner at UW]

I think there should be more concentration on fluids, too. A lot of people are running dot 5 and it's squishy.

[DY]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Schumi_Jr:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by GTmule:
I hope it was a joke, otherwise, get a life, guys. <HR></BLOCKQUOTE>You'd think so...

Claude asked this question in design semis in 2003 and mentioned it at his 2003 and 2004 FSAE seminars. <HR></BLOCKQUOTE>Just to reiterate: Claude as a judge during design semifinals asked the teams this question. For that matter I think he asked every teams that asked him to look at their car in the paddocks. Makes perfects sense now, but like many at the time, we were thinking "WTF?"

[Chris Boyden]

Ok, guys, when you're in the design tent and a judge asks you a question, what are you gonna do? laugh and tell them, "you're kidding, right?". I don't think that they have to much time to stand around and bullshit. But, feel free to interpret design questions as jokes, more power to you.

[Frank]

i meant "joke", as in humorous, not stupid

[NovaCat2005]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Schumi_Jr:
Denny, how do you determine what constitutes a brake system being stiff enough? It comes down to driver feel, so what you really need to do is test your driver! <HR></BLOCKQUOTE>

That reminds me of something I read on the StopTech site:

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The feel of the brake pedal should approach the firmness and consistency of a brick. <HR></BLOCKQUOTE>

So yeah, I guess brakes can never be stiff enough basically. Maybe I'll ask a Civil Engineer what's the modulus of a brick. I'll bet they'll just look at me funny.