Brake rotor temperature right/left and front/rear comparison questions

[Gforce]

Originally Posted by wparsons

Ummmmmm... you do realize what causes the pedal to go to the floor, right? Boiled fluid is what causes a soft (up to zero pressure) pedal.

You've just proven once again you don't actually know what you're talking about.

Just BTW, EBC and Alcon brakes don't agree with your statement about fade:

https://alconkits.com/drmassets/Brake-Fade-Solved.pdf
https://ebcbrakes.com/articles/what-is-brake-fade/
https://ebcbrakes.com/articles/brake-fluid-vapour-lock/

Not in a drum brake system. Boiling fluid is not brake fade. Read the second link you posted.

[Gforce]

Originally Posted by venturaII

Wow...you really don't know how ANY of this works...lol. A brake fluid reservoir is such a fundamentally simple part and yet you have it all wrong. Quelle surprise.

Check your calculations. Ask yourself what replaces the fluid in the mc as the pads wear and where that "space" comes from. Also, consider that every time you apply the brakes the fluid leve in the mc drops by the amount of fluid pumped into the four brake caliper cylinders (or more than four on some systems).

[venturaII]

You know, if it were obvious that you were simply wildly uninformed but were willing to learn, it'd be worthwhile explaining where and how you are wrong (which seems to be a common theme in just about any thread you comment in). TBH, I'm surprised everyone else has gone to the length they have to show you real data which very clearly shows how wrong you really are, when it's pretty clear that you're just trolling. "Not in a drum brake system"...lol..priceless. Good luck fishing.

[stevesnj]

anyway, to the OP, we have EBD, rotor temps will vary.

[Gforce]

I think stop Tech knows a few things about brakes. Here's their take on this issue:

http://www.stoptech.com/technical-su...nd-other-myths

And this should be reviewed by anyone thinking bigger is better:

http://stoptech.com/technical-suppor...alance-matters

Note the final warning comment that only improved stopping distances can give you objective confirmation that your brake modifications were successful.

ABS and EBD provide much more brake balance assistance than you might think. Ironically, they also make detail changes to brake systems very hard to evaluate. The more grip you get from your tires the worse this brake imbalance becomes due to weight (load) transfer effects, which vary only with braking force, not suspension design or spring rates (ignoring for simplicity the effects of the slight lowering of CG you get with brake dive).

[HappyMonkey]

Originally Posted by Gforce

The responses include the obvious: it's the tires. I am firmly in that camp. Unless the tires can develop grip to exploit the additional brake performance then you cannot tell if the brakes have been improved. The stock tire is a very good tire in its category, one of the best in fact. Michelin builds the HP version of its grand touring tire and this version of the Primacy has many virtues, light weight being first among those. Wet grip is also very good. But, no grand touring tire can match a high or ultra high performance tire.

The responses also include some conundrums. The op fitted drilled brakes which reduce the heat sink capability while lowering unsprung weight and improving cooling. Net benefit? Apparently not since the stock brakes are heat limited. More disc mass is deemed preferable to lower pad temperatures.

OP here. This turned into a fun thread.

These upgrades are getting her prepared for 3 HPDE days coming up. My plan was to focus on tires/brakes, then a lot of driver improvement before messing with any suspension/power. Everything on her is StopTech. Their lines, rotors, and Street Performance pads. I'm considering swapping out street/track pads but I'll try an upgraded street pad first and see how it goes.

Tires: I've already made some improvement and will have have even more of that sweet sweet grip in a few days. She's currently running Pirelli P Zero All Season Plus. (FWIW TireRack considers them Ultra High Performance All-Season) The traction improvement over stock from that upgrade was surprising. Although my stock ones were pretty worn down by then so the comparison wasn't 100% fair. I have a set of Yokohama Advan Neova AD08 getting installed this week. Looking forward to seeing what 'Extreme Performance Summer' feels like.

So those rotors... the slotting probably improves grip but drilling reduces thermal capacity. (I'll admit I think the drilled looks cool and that helped sway the decision on which rotors went in my cart) I still have the stock rotors in the garage. Which is more important for a HPDE event, the stock thermal capacity or the grip of the StopTech? For a track day would you put the stock ones back on or keep the StopTech slotted/drilled?

[churchx]

HappyMonkey: given choice go for blank rotors, as far as track / HPDE usage is considered. Reliability wise blank > slotted > drilled > drilled and slotted. Don't think much of something like increasing bite .. you get that with more agressive pads. Don't think much of cooling/heat capacity changes, those slots/holes won't change it much. Reliability/cracking what should matter imho most.
As for current slotted-drilled .. i'd probably wear those down, and when next disks purchase is due (probably not that soon, if just few HPDE evens per year), then - blanks.
Also don't take too far arguments on heat capacity/boiling and such .. it usually isn't as on/off switch, after which - instant death , just when after closer to limits driving after a while you start to feel mushier pedal, when for same braking you may need now push pedal much more, worth thinking about some cool-off lap & going in pits to cool them off, that's all there is to it. It's just question of when it happens with specific brake setup, sooner or later .. and sometimes even shorter session lengths, eg. 10-15m with stock brakes may coincide with generic tiredness/attention loss due it .. so why not cool brakes, check tire air pressure, have short rest, some coffee/water drink (and also cigarette, in my case ), to keep at top shape at same time?
BTW, is that stoptech BBK or just few stoptech aftermarket parts for stock replacement? In former case i'd use on track that BBK, due higher thermal capacity & possibly cheaper wearables & lighter weight & easier to swap pads. In later case .. i'd keep those lines/pads .. but probably switch back drilled-slotted rotors to stock.

[wparsons]

Originally Posted by Gforce

Actually the mc needs a diaphragm type seal under the cap otherwise the piston would create a partial vacuum every time you tried to apply the brakes. Make no mistake, water contamination of brake fluid remains a problem. Car makers and brake system makers all recommend routine and regular flushing of brake fluid for this reason.

Again, go take your cap off and have a look.

If you read the links I posted, they also talk about how the rubber lines are semi permeable and allow some moisture into the system.

Originally Posted by Gforce

As for the performance of "race pads" equalling that of street pads under all conditions I will defer to your racing experience. Whether race pads are better for a road car then street pads is the issue I am discussing. On that metric race or track pads are dangerous, in my opinion. Brake pad makers agree. The first time you rear end someone would prove my point. However, most drivers will be unaware that they do so because of their track biased brake setup.

Again, you're simply flat out wrong. Look at this image, Winmax doesn't agree with what you're saying at all. Where is your source to prove a manufacturer agrees with what you're saying?

Originally Posted by Gforce

Unlike a drum brake which fades to nothing regardless of mc piston stroke, lining material or driver strength. That is the fundamental difference between real brake fade, as is still experienced by heavy truck drivers, and disc brake "fade" which rarely occurs in reality. Just recently I observed a Red Bull F1 car with a dragging left front brake resulting from overheating of the brakes, the mechanic was using a dry ice cooled blower to free up the caliper. Thermal expansion assists the driver using disc brakes.

Do you honestly believe that the fluid or fluid pressure between drums and discs is magically different? A soft pedal, or pedal going all the way to the floor, is caused by air in the system, in this case from boiled fluid. Fact. There's simply no disputing that. Drums are easier to overheat and pass the heat into the fluid, but the reason for a soft (or no) pedal is exactly the same.

[wparsons]

Originally Posted by Gforce

Not in a drum brake system. Boiling fluid is not brake fade. Read the second link you posted.

What makes the pedal go to the floor in a drum system if it isn't air in the lines (from boiling fluid)?

[wparsons]

Originally Posted by Gforce

I think stop Tech knows a few things about brakes. Here's their take on this issue:

http://www.stoptech.com/technical-su...nd-other-myths

I assume you're talking about this point in that article?

MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade
A) When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off,
B) When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.

I don't know what your point is, considering that says basically the exact same thing as what I said before and the link I posted states:

Brake fade is caused by overheating of the brake pad, therefore any vehicle which uses the action of a brake pad rubbing on a brake rotor to convert the vehicle’s kinetic energy into heat has the potential to develop brake fade, including motorcycles, cars and trucks. Because brake fade occurs when the brake pads are overheated, the phenomenon is only temporary and braking performance usually returns once the brakes have cooled down.
(Note: it is worth knowing that brake fade is not the cause for a long or spongey brake pedal/lever. If you experience a spongey pedal/lever you’ve probably got air in your brake hydraulics or have boiled your brake fluid and should read our article on fluid vapour lock to resolve your issue. Or another article on bleeding brakes.)

[cjd]

Originally Posted by HappyMonkey

Tires: I've already made some improvement and will have have even more of that sweet sweet grip in a few days. She's currently running Pirelli P Zero All Season Plus. (FWIW TireRack considers them Ultra High Performance All-Season)

The stock are summer tires, not all season... But are low rolling resistance so I could see better feel from good all seasons... Unsure about lap times, assuming you're consistent.

Tires, brakes, brake fluid... Temperature management is the issue. If you're driving 10/10 you'll run short on overheated pads with the street compounds, but may hit fluid boiling first being on the brakes longer (tires and eventually brake compound contributing to longer stopping distance). Watch the tires for bad behavior too. Keep a close eye on those drilled rotors for cracking. At least bring blanks as backup.

[venturaII]

Originally Posted by wparsons

What makes the pedal go to the floor in a drum system if it isn't air in the lines (from boiling fluid)?

Magic unicorn dust.....

[wparsons]

Originally Posted by venturaII

Magic unicorn dust.....

Effing unicorns!

[OND]

Originally Posted by HappyMonkey

OP here. This turned into a fun thread.

These upgrades are getting her prepared for 3 HPDE days coming up. My plan was to focus on tires/brakes, then a lot of driver improvement before messing with any suspension/power. Everything on her is StopTech. Their lines, rotors, and Street Performance pads. I'm considering swapping out street/track pads but I'll try an upgraded street pad first and see how it goes.

Tires: I've already made some improvement and will have have even more of that sweet sweet grip in a few days. She's currently running Pirelli P Zero All Season Plus. (FWIW TireRack considers them Ultra High Performance All-Season) The traction improvement over stock from that upgrade was surprising. Although my stock ones were pretty worn down by then so the comparison wasn't 100% fair. I have a set of Yokohama Advan Neova AD08 getting installed this week. Looking forward to seeing what 'Extreme Performance Summer' feels like.

So those rotors... the slotting probably improves grip but drilling reduces thermal capacity. (I'll admit I think the drilled looks cool and that helped sway the decision on which rotors went in my cart) I still have the stock rotors in the garage. Which is more important for a HPDE event, the stock thermal capacity or the grip of the StopTech? For a track day would you put the stock ones back on or keep the StopTech slotted/drilled?

No need to overthink the discs, I'd prefer stocks over a slotted and drilled rotor, but brake fluid and brake pads are much more important.

AFAIK Stoptech pads are still too much street oriented, so you might have some fade with them. The thread is kind of hard to follow, but which brake fluid are you running again?

I started out with Project Mu HC+ and Motul RBF600 and I think it is a pretty good setup to begin with.