Problems with Porterfield Brake Pads?

[nsxtasy]

Originally Posted by descartesfool Also get thinner. I've been trying to lose weight for years, with very little success.

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[slammed_93_hatch]

Darren sorry to hear about the crash!! Glad you ok though.

Get the XR3s and you will be very happy. You should be able to get 8 double weekends out of them at a minimum.

[JOE BD-0]

To the OP.....I'm just curious, are you properly bedding the brake pads prior to track use??

[adrian1281]

OP, did the front left wear down the same as the front right?

[FormulaIntegra]

I'll try to cover as many of the various questions as possible, but first, thanks, Jimmy. Don't worry, your motor is just fine. Fortunately, the tire wall diverted most of the energy upwards so it really wasn't as bad of an impact as it could have been. New bumper cover, fender, and radiator support and I'll be back in business.

No, the right to left sides didn't wear the same. The right set of pads are down to the backing plate at the moment of failure, whereas there is about 3-4mm of pad material remaining on the left set of pads. Gauging how much was used per session, I thought I had enough to get through the final race, but again, I've never seen these pads wear this quickly, however, I know I've gotten WAY more aggressive over the last year. The odd thing however, about the differences in wear: the left side was beginning to develop concentric grooves in the rotor, whereas the right side that failed seemed to have an even, more normal looking surface. Not sure what that means.

Yes, I'm properly bedding the pads and heat cycling the rotors prior to track use (several quick, hard decelerations from about 60mph to 15mph, then 5 minutes of driving to cool them, and repeat 2 to 3 more times before parking it for the night to settle. This is the method I've read of quite a few websites as well as brake pad manufacturer instructions.

Claude, I am going to look into temperature paint, because I'm sure that's going to be a very pertinent bit of information in determining what pad can handle the temps I'm running at. I know back in the hot pits after a cool down lap, the rotors were still in the 500+ F range, but that doesn't necessarily tell me how hot they're getting at the moment of maximum friction.

Ferreira, as for what exactly I want? Tough to say, as I'm still relatively new at this, you threw a ton of valid factors at me, and most likely, what I want will probably be more cost based than anything else. That doesn't mean I will go with the cheapest and just deal with their limitations, but I'm pretty sure I can't afford the most expensive and a new set every weekend. Honestly, I have only ever used the R4's, so I haven't got much to compare them to. I have learned where the lockup threshold is, and I feel if I can still lockup the tires, then the pad's level of friction exceeds the tire's grip. If I couldn't lock the tires, then I wouldn't be able to use all of the available grip. Does that make sense? Needless to say, I've gotten used to the characteristics of the R4, not having used anything else, and would be happy with a pad of the same characteristics that would last longer. I don't know if that's the trade off, though: longer lasting=less braking force vs. greater wear rate=maximum braking force.

As for my comment about getting a refund, that was regarding a new set of completely unused pads that I wish I had put on the car for the remaining race of the weekend. They are still new, in the box, and would definitely preferred to have used them up than mangled the front end of the car. If the Porterfields aren't up to the demands I expect from them, I don't see any reason in hanging on to the new set I have if I can get my money back and put it towards a different brand.

When I think about my braking, I try to brake as late as possible, with as much force as possible without locking the tires up. Each lap, I push my braking point back a little until I lock up trying to slow down in time, or I feel I can't push any later and still make the correct line through the corner. Some corners (depending on the track) I know I'm still braking too early and can actually take a bit faster, but like I said, I am still relatively new and learning every time. When I describe how I brake, I feel like that's how everyone looks at braking at the limit, so I'm not sure how to apply the variables you've given me to what I expect from a pad. I don't feel I gradually apply pressure to the pedal, I think I jump on it as hard as I can, hopefully just shy of locking the tires up. I'm assuming that would be a high initial bite?

Again, I believe I think in the most rudimentary terms when I'm in the heat of a lap. If I think I can take a turn at a faster speed, I push my braking point back a few feet. I try to use the same force on the pedal no matter what speed I'm going or trying to slow down to, modulating as necessary based on the immediate moment of how the car is responding. I do left foot brake any time I don't have to downshift, but again, I try to use as much braking force as quickly as possible to get the car down to the speed I feel I can take the turn at. I do want a pad that will let me be as aggressive as possible because I am becoming quite competetive in my class locally, but I would like a set of pads to last at least 2 double regional weekends for sure, and ideally 3 weekends would be optimal, but I'm starting to feel I can have an aggressive pad, or one that will last several weekends, but not both, or at least not without dropping some serious coin. If you can make sense of what I'm saying, I'm open to any and all advice or suggestions.

Bluntly, I paid $150 for this set of R4's, plus another $40 for the rotors, and they didn't even last me a single weekend. Now I've got about $600 worth of body damage to repair because they failed me when I thought there was still enough material to get through the last race of the weekend. I would rather be putting that $600 towards pads that would last quite a few more weekends at the aggressive level of braking I'm doing now.

Here's a question I just thought of, too. Should the pad wear rate over the course of two 15 minute sessions be equal or less than that of one 30 minute session? Would I gain anything by using one set of pads/rotors for practice and qualifying, and another set for the 30 minute race? Would I gain overall longevity out of both sets, or would that just be a better way of preventing a catastrophic failure during the race?

I like this discussion that's going on, I think I'm learning alot here. If I haven't answered someone's question, ask me again here, or pm me so we can keep the info flowing. Thanks, guys.

[descartesfool]

Originally Posted by FormulaIntegra

When I think about my braking, I try to brake as late as possible, with as much force as possible without locking the tires up. Each lap, I push my braking point back a little until I lock up trying to slow down in time, or I feel I can't push any later and still make the correct line through the corner.

That how I like to brake. Keep the throttle pedal down for as long as possible, and then use the brakes as hard and for as short a time as possible. And that is hard on brakes.

Here is some more info from AP Racing on temperature control recommendations for discs:

"DISC TEMPERATURES
In order to achieve optimum racing brake performance and prolong
disc life it is essential that the brakes operate at the correct
temperature. In general discs should run at similar temperatures
front and rear and from side to side, dis-similar temperatures will
lead to varying brake balance. Temperature balance can be
checked as soon as the car stops in the pit lane using a
Pyrometer such as AP Racing Pyrometer kit CP2640-24 (see
below). However a pyrometer reading is not a good indicator of
disc operating temperature which decays rapidly with time when
the brakes are not being applied. Under racing conditions disc
bulk temperatures should normally be maintained in the range
400°C to 600°C for best performance. Disc face peak temperatures
may be higher but should not exceed the maximum recommended
for the pad material being used. An effective method of checking
maximum disc operating temperature is by using temperature
paints applied to the disc. A suitable paint kit can be obtained
under AP Racing Part Number CP2649-1, this kit contains three
paints, Green (430°C), Orange (560°C) and Red (610°C) plus
thinners and brushes. When assessing brake temperatures it is
important to complete several successive laps (5 or preferably
10) at race speeds and vehicle weight to allow temperatures to
stabilise at a representative level. Typically when running within
the correct temperature range the Green paint (430°C)will turn
throughout, the Orange paint (560°C) 50% to 100% throughout
and the Red paint (610°C) turned up to 5mm from each brake
face. If the Red paint (610°C) turns throughout, the discs are
running too hot. Circumferential disc face ridges are also an
indication of running too hot. Circuits and drivers vary enormously
in the amount of work they demand from the brakes and therefore
the brake system has to be tuned for each circuit by adjustment
of the cooling airflow. The temptation to over cool the disc
should be resisted. The aim is to keep the temperature as
stable as possible within the working temperature range.
High maximum to low minimum temperature cycles are the
enemy of disc life and cause performance variations."

Notice the comment about circumferential grooves meaning rotor is running too hot. And this:

"SAFETY AND CARE OF DISCS
Cast iron brake discs should not normally be operated at bulk
temperatures in excess of 610°C and above rotational speeds
of 3000 revolutions per minute. Discs must be regularly and
frequently inspected for excessive heat crazing and cracking.
After heavy and prolonged use some surface crazing will often
be evident, if this turns into distinct surface cracks which are
radiating towards the inside or outside diameter the disc should
be changed. Discs with cracks emanating from mounting holes
/ slots, inside diameter, scallops, or outside diameter should be
changed immediately."

[ScottBell]

I'm not sure you are bedding in your pads properly. A properly bedded pad will show a small strip of material that is a white/grey/ash color at the edge of the friction surface. If you do not have that then you are not bedded in. My method is to put heat into the brakes untill I start to detect some fade, and maybe hot brake smell. Then I do a couple of laps with light braking to start to cool the brakes.

When you get back to the paddock you should have some smoke coming from the brakes, which will scare you and make people point and laugh. Drive around the paddock for 10 minutes are so to allow the brakes to cool, and prevent the hot pads from transferring material to the rotor in one spot. Let everything cool off and look for the white line on the pads.

I agree with everyone that you are probably using the wrong pad. However if you dont bed them in properly no pad is going to work right.

I might also suggest a change in your driving. If you are looking for higher corner entry speed, dont keep changing your brake points. Instead keep the same braking point and use less and less pressure untill you feel you have reached the fastest turn in speed you can handle. Then make a brake point adjustment. There is a lot less time to be gained than you think by coming in to a turn with the brakes on fire. I see it all the time on data. Crazy braking might pick up .05, but you loose it my mid corner. There is a great example of this in the data logging article in this months Sportscar Magizine.

[slammed_93_hatch]

Darren,

glad to here its just superficial damage.

Another plus about the cobalts there is no bed-in procedure, you just drive and they just work and always work!!

About bed-in transfer layers. Every pad is different, some pads "good" transfer layer would be horrible for another brand.

I have never dealt with the pads he uses though.

[ScottBell]

Originally Posted by slammed_93_hatch

Darren,


About bed-in transfer layers. Every pad is different, some pads "good" transfer layer would be horrible for another brand.

I was not talking about transfer when I was writing about the white line. Ill post a picture