BRake Issues

Dug through Raybestos.com a little more and found the excerpt below. Sounds a whole lot like the first thing I posted. Somebody must be pirating stuff from the Raybestos site.

SURFACE FINISH
We’ll finish up with a few comments about surface finish. Smoother is always better because it affects the coefficient of friction, noise, pad seating, pad break-in and wear. As a rule, most new OEM and quality aftermarket rotors have a finish somewhere between 30 and 60 inches RA (roughness average) with many falling in the 40 to 50 RA range. It’s unlikely you’re going to improve this any by "cleaning up the rotors" on a bench lathe prior to installing them. In fact, you may make the finish worse if you cut the rotors too quickly or use bits that are dull.

New rotors should always be installed "as is" — and indexed on the vehicle with a dial indicator to minimize runout. Few technicians take the time to do this, but if they did they’d probably see fewer comebacks because of pedal pulsation complaints.
 
I dont think the Q's are the wrong application, I mean after you get rid of the pulse BS they work great!

I wonder what would happen if you put a set of Qs in a truck that is currently running Qs with no Pulse?
 
I don't think they are wrong for the application either, I just think they are incompatible with the surface finish on the rotors. It seems like once the rotors are ground smooth by a nice aggressive track pad there is no ore pulsation.
 
From running the E's at the track my rotors look like a mirror. So far after a week and 600 miles, the Q's are working great. I noticed the part about washing the rotors with soap and water.....I have never done that. Maybe that's part of my problem.


Jerry
 
I've got some Hawk HPS pads now for anyone who was thinking of a kit but not wanting to work with the Q pads. Be interesting to see how they compare.
 
Todd, I noticed that Raybestos makes the pads for Wilwood. Any chance you could try to persuade them to put one of the WW pad compounds on an OE backplate for the rear of our trucks? Since Raybestos has both the compounds and the plates it seems like they could do that fairly easily.
 
Just thought I'd drop my .02 in ...

The Greenstuff is total garbage on our trucks ... wrong compound, poor construction, tolerances suck ... (on my
Brembos the interior of the pad was rubbing agaist the hat.)

I have run the HPS for a few events and then moved to the HP+,
and I have to say that the HP+ is a very good compromise. Any
more aggressive, and you chew up rotors (at $365 EA), bit they
do stop just fine on track and street.

You must break the pads in though. Like Todd said. The marriage
at the friction interface is critical to performance. I break them in, then
scratch pad position (I,II,III,IIII) on ea pad so I can match them
up again on race day.

They DO dust more than most any other pad. Period. As discussed
elsewhere, you either STOP and DUST or DON'T DUST and DON'T STOP.

I prefer the STOPPING part.

My local race shoppe has almost got me talked into trying the Blacks or Blues,
but the rotor cost along with the tire cost is probably prohibitive.

Good luck on the quest, guys ... I'm out there testing wit' ya!!
 
I think the real problem (if that's fair) is that you're trying to treat a 4500lb truck like a race car! Pretty tough act to follow. Like I tell others; want the vehicle to brake better, longer? Take off 1000lbs!
 
Todd TCE said:
I think the real problem (if that's fair) is that you're trying to treat a 4500lb truck like a race car! Pretty tough act to follow. Like I tell others; want the vehicle to brake better, longer? Take off 1000lbs!
Click to expand...
I agree...somewhat.
You still have to remember that Ke=1/2mv^2. With that in mind, you could apply the same reasoning to a guy/girl who wants to upgrade their racecar's brakes. The response would be "go slower."

To illustrate the point,
3400 lb racecar
4800 lb Lightning
assume brakes are limiting factor (not tire grip)

The Lightning traveling at 70 mph has the same amount of Kinetic energy as the racecar traveling at 83 mph.

In tabular form (Lightning's speed / Equivalent speed of racecar with equal Ke):

0 0
10 12
20 24
30 36
40 48
50 59
60 71
70 83
80 95
90 107
100 119
110 131

In other words, a racecar traveling at 119 mph has the same kinetic energy as a Lightning traveling at 100, although the Lightning weighs 1400 lbs more.

Because the velocity is squared, it is more significant than the weight.

Todd - thoughts?
 
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And I'll agree with that. Didn't mean to sound like I was dis'n the truck, only pointing out that what we are asking for is a pretty tall order for serious open track application.

The only points I'd make on this is that you are comparing the truck and car to be nearly the same in its energy requirements by way of making the car faster. The problem is that most of you have 'boosted' the trucks performance to damn near equal that of the car! Or at least tried to get close.

Re run the table to have the car at 120 and the Lightning at 115. I think that's more rep of what some of you see.

Also remember that the current offerings, at least mine, limit rotor diameter or mass to 13.1" or about a 16lb rotor. In the grand scheme of things going up to 14,15 or 16" and about 19lbs. would prove valuable.

The point was more that we're working an upper level auto kit pretty hard in some instances on a heavier truck.

I often explain a BBK as something you can compare to operating your stock brakes at 95% all the time or a larger system at 80% with the same results. Affording more reserve capacity.

In the case of this truck on a hard road course use it's probably more like 99% stock/fade vs. 95%+ BBK. The reserve is not near as effective. There are still some limitations. Taking out weight can be equally as effective to putting on more rotor, remember; it's still about reserve cap or repeated stopping more than torque. We've simply raised the bar.
 
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And don't forget the huge wheels and tires we are trying to stop. The stock wheels and tires are nearly 70 lbs a piece vs. probably half that for a race car. One lb of rotating weight is supposed to be equal to 8 lbs of dead weight.
 
Oilwell,

I do the calcs later on and post the actuals vs speed (based on assumptions), not a "supposed" constant. I'll also compare it to the kinetic energy of a moving mass.
 
I just did a quick calc and in comparison to the kinetic energy of the moving car/truck, the rotating mass of the wheel/tire is irrelavant in the big picture (over several stops). It's a measurable figure, but not enough bother with regarding the brakes. Yet, I'll double check my calcs later to verify it.

BTW, the weight of a Hoosier 295/35/18 is 21 lbs, which fits a lightning.

The weight of a stock lightning wheel is about 32 lbs.
The weight I used in my calcs for a light wheel is 20 lbs.

Combined weights would be 53 for the Lightning and 41 for the "race car". This assumes they both use the same tire. Since the rotational mass of the tire would be identical for both vehicles, it's irrelevant in the equations. The difference is the angular momentum of the racer's wheel vs the Lightning's wheel at an assumed radius, which is less than the actual. I wasn't interested in calculating the moment of inertia of the composite wheel, so I assumed the effective radius was .9r for both, which is conservative.

Todd,

I know you weren't putting down the Lighting.
 
Most of the L's I've seen on track are on stock rubber. A stock 01 wheel and a 99/00 tire combination is 66 lbs. I don't think I've ever seen a racecar with as much wheel and tire as a Lightning. Most run something like a 275/40/17 or 315/35/17. I'll have to weigh one of our SS wheels and see what it weighs, it's a 275/40/17. I know it is a featherweight compared to the rolling stock on the L.

I want to see what you get for I on the composite wheel; where's your sense of adventure?
 
oilwell1415 said:
I want to see what you get for I on the composite wheel; where's your sense of adventure? [/B]
Click to expand...
Why don't you do some of the calcs using your wheel/tire weights and post the results. Then, results can be compared and would also be a worthwhile doublecheck of the calculations.
 
I know this thread has been dead for a while, but thought maybe some of you would be interested in seeing the difference between the rotor finish provided vs. the finish Raybestos recommends. The first pic is of the rotor as delivered. Notice the visibly rough texture of the finish. It feels like coarse finger nail file.

76865.520.390


Here's a pic after turning and applying the non directional finish. You can't feel anything with your finger when you run it over the surface.

76866.520.390


Another thing I discovered when I had them in the lathe is that one of the rotors had about 0.012" of runout, the other was about 0.010". The hats were dead on, but the rotors had lots of runout. The max. allowable for stock rotors is 0.002". This might also contribute to the pulsation.

I'll find out soon if the Q's still chatter with this finish, but I'm certain they will be OK.

This means I am FINALLY getting around to installing the brakes.
 
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Got the brakes installed on Friday. So far no chattering or noise issues at all. I had forgotten what brakes were supposed to feel like. Two thumbs up for Todd!

As for the moments of inertia.....well, I forgot. I get I for the set of 4 L wheels and tires as 190.1 lb-ft^2 and our Camaro wheels and tires at 96.8.

For the L:

KE for the linear motion = 1/2mv^2. Bypassing all the dimensional analysis and using m=5000 and v=100 ft/sec (66 mph) we get 25000000. KE of the wheels = 1/2 I&^2. & at 100 ft/sec = 42.9 rad/sec. KEW=175000, roughly .75% of the energy.

For the Camaro we get 19000000 for linear energy, 46.2 for &, and 103000 for KEW. The wheels account for about .54% of the Camaro's energy.

The proportions from car to truck are about what I expected, but I thought the truck wheels would be about 3% of the engergy and the car's wheels would be about 2% of the energy. It's amazing what you learn when you put a pencil to a problem instead of just shooting from the hip.
 
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