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

[Gforce]

Originally Posted by churchx

Gforce: i'd agree on many bits, but you messed one with smallest & lightest disks. You are forgetting heat capacity that smaller disks lack and which is main reason for racing purposes switching to _B_ig Brake Kits. Smaller works only as far as brakes are not overheated with driving specifics intended. Once one goes for longer sessions, once one goes to higher speeds due eg. forced induction installment, heat load put in or accumulated per time grows. No sense from having very slight performance increase from lighter rotational unsprung weight, if you lost your brakes after 15min when planning to go for half an hour. For rest of session car with nonoverheated heavier brakes will run circles around car with faded brakes with boiling fluid, even though later one will still have it's (i doubt that >1%) better acceleration, but for much shorter time to not accelerate to speeds one is unable to bleed to level needed to take turn without going off track & crash.
Either one goes for larger heat capacity of BBK, or enhances cooling (via eg. airducts), or both. Otherwise claim that smallest/lightest is best will work only on daily driving & dragracing.

Heat capacity isn't the relevant factor. You are of course correct that higher heat capacity means you can use softer brake pads.

Boiling brake fluid is an irrelevant consideration. Water contamination in the fluid is often confused with boiling fluid itself. Flush brake fluid completely at least every three years and in very humid climates every two years.

[Gforce]

Originally Posted by wparsons

1) Who are you responding to?? The OP didn't ask anything about any of what you just said.

2) The irony of you calling out misinformation in your post full of misinformation is great.

3) There's two types of fade; pad fade and boiled fluid but both are caused by lack of thermal capacity in the braking system. Rotors that can absorb more heat and/or shed it faster will prevent both types of fade without resorting to higher boiling point fluid or pads that can take more heat.

4) Not all higher performance pads have longer stopping distances when cold, all the aftermarket pads I've run (Ferodo DS2500, Project mU Club Racers, G-Loc R10) have better initial bite and power when cold than stock pads. Do they get better when they're up to temperature, absolutely, but they're still noticeably better than stock even on the very first stop. The real downside to most track pads when cold is they're harder on rotors until they're up to operating temp.

5) The smallest disc that can trigger ABS point only works if you only care about stopping once before pulling over and letting them cool down. You should probably look at how you can get more thermal capacity AND less weight with a good BBK though.

6) Define "wide range of operating temperatures"... my current pads (G-Loc R10) are rated from 47*C to 801*C. I'd say that a 750*C operating range is pretty wide. My previous pads had a very similar range as well.

7) I wouldn't suggest running higher heat capable pads without an equally heat capable fluid, you'll easily boil the stock fluid on a track with better pads.

I was just hoping you'd post.

No misinformation in my post, how about yours?

Most people who think their brake fluid boiled actually suffered from water contamination from failure to flush their system regularly. Standard brake fluid is sufficient. Water boils at only 100C (212F and then only at sea level) as you may recall. I find Stop Tech technical information useful:

http://stoptech.com/technical-suppor...rs/brake-fluid

As for your claim about high performance brake pads stopping as well as street pads when cold, I say total bs. Got any third party facts to back that up?

As you are well aware, my remarks are aimed at people trying to improve their cars for street use. If you are using street tires (especially stock tires) harder pads should be all you need for occasional track use. Trying to turn a BRZ into a race car is just a dumb idea.

[wparsons]

Originally Posted by Gforce

I was just hoping you'd post.

No misinformation in my post, how about yours?

Where are the facts to back up your claims?

Originally Posted by Gforce

Most people who think their brake fluid boiled actually suffered from water contamination from failure to flush their system regularly. Standard brake fluid is sufficient. Water boils at only 100C (212F and then only at sea level) as you may recall.

That's simply not true, where is the data to back up that claim? You can easily boil fresh OEM fluid VERY fast in these cars.

Originally Posted by Gforce

As for your claim about high performance brake pads stopping as well as street pads when cold, I say total bs. Got any third party facts to back that up?

How about I get a video of a car on stock pads vs mine on a cool day with cold brakes? Qualitatively, it's easier to engage ABS on the track pads on the first stop of the day on a cool morning (~15*C) than on stock pads. Same car, same alignment, same wheels/tires. The stopping distance is also noticeably shorter. I don't have measurements, but I do swap pads at least twice a year and have done enough test drives before/after swaps to be confident in the findings. What have you done to prove otherwise?

Originally Posted by Gforce

As you are well aware, my remarks are aimed at people trying to improve their cars for street use. If you are using street tires (especially stock tires) harder pads should be all you need for occasional track use.

"Harder" pads aren't actually a thing despite you constantly using it, and if you mean less compressible that doesn't actually mean they have higher heat capacity. Compressibility, co-efficient of friction and heat capacity are not all directly linked, and most pad manufacturers offer different options depending on the pedal feel, modulation and heat range you want.

You also don't ever qualify your statements for usage, and make blanket statements claiming universal facts. I've never seen you ask someone "how do you plan to use it", instead you just go off on tangents with no facts to back up your opinion.

Originally Posted by Gforce

Trying to turn a BRZ into a race car is just a dumb idea.

Yet another unfounded opinion not based on any facts at all.

[Gforce]

Originally Posted by wparsons

Where are the facts to back up your claims?



That's simply not true, where is the data to back up that claim? You can easily boil fresh OEM fluid VERY fast in these cars.



How about I get a video of a car on stock pads vs mine on a cool day with cold brakes? Qualitatively, it's easier to engage ABS on the track pads on the first stop of the day on a cool morning (~15*C) than on stock pads. Same car, same alignment, same wheels/tires. The stopping distance is also noticeably shorter. I don't have measurements, but I do swap pads at least twice a year and have done enough test drives before/after swaps to be confident in the findings. What have you done to prove otherwise?



"Harder" pads aren't actually a thing despite you constantly using it, and if you mean less compressible that doesn't actually mean they have higher heat capacity. Compressibility, co-efficient of friction and heat capacity are not all directly linked, and most pad manufacturers offer different options depending on the pedal feel, modulation and heat range you want.

You also don't ever qualify your statements for usage, and make blanket statements claiming universal facts. I've never seen you ask someone "how do you plan to use it", instead you just go off on tangents with no facts to back up your opinion.



Yet another unfounded opinion not based on any facts at all.

You first.

If you quote one of my facts I'll get you the back up.

I say bs to your brake fluid boiling "easily". What were the measured caliper temperatures at which you say you boiled your "fresh" brake fluid (from a previously unopened container and into a fully flushed system,presumably).

How will anyone know your video is objectively correct? How about a brake pad supplier who makes the same claim as you do. Just btw, your Ferodo 2500 are just a hard street pad, if you want proper track performance Ferodo makes much more suitable pads, not streetable though.

I use "harder" to mean higher temperature. In fact, competition brake pads are harder, wear more slowly and require higher line pressures to work as designed. "Harder" is an appropriate adjective. Higher temperature resistance seems a bit cumbersome as a description albeit more accurate. Heat capacity is not something you want in a brake pad. You want heat insulating capability to keep the heat going into the rotors and away from the calipers (duh). Heat capacity needs to be in the rotors and, more accurately, heat dissipation capability.

The op was clearly asking for useful replies to his valid concerns that he was unsure whether his brake modifications were an improvement over stock and if so how to determine by how much. He clearly stated it was for a street application. My reply was intended to broaden the scope of investigation of the topic of improving the street capability of the stock BRZ brake. My opinion is that the stock BRZ brakes are way over spec for street driving and cannot usefully be improved at all. It will be interesting to see if the factory Brembo option actually changes brake performance for road use. My prediction is that it will not. The stock BRZ brakes are already from a much heavier model, the Impreza WRX.

As for spending money on your BRZ to create a track car I support my opinion by referring to the factory stated objective of making a proper sports car with a comfortable ride for the street. I further support my opinion by referring to the factory upgrades for 2017 decreasing the rear spring rate and rebalancing the chassis for more understeer and less abrupt oversteer. These virtues can be improved upon further by making the modifications I have made over the four years I have owned my BRZ.

With the supercharger fitted and the carefully chosen modifications I have made I have produced a car that my racing addicted buddy claims is one of the best little sportscars he has ever driven. His daily driver? A Mclaren 12C. His racecars include a F1 Shadow and a Canam car.....

Over to you now Mr racecar

[venturaII]

Go away.

[wparsons]

Originally Posted by Gforce

You first.

If you quote one of my facts I'll get you the back up.

No you won't, we've done this dance before. You just change the subject anytime you're asked for proof.

Originally Posted by Gforce

I say bs to your brake fluid boiling "easily". What were the measured caliper temperatures at which you say you boiled your "fresh" brake fluid (from a previously unopened container and into a fully flushed system,presumably).

@CSG Mike, any chance you have that data? I've seen it enough times, but haven't cared to measure it.

The DOT 3 boiling point spec is 140C wet and 205C dry, and wet boiling point is the only one that matters because it'll start absorbing moisture as soon as you open the bottle. Entry level performance fluids have wet boiling points >= 200C, the fluid I've been running (Castrol SRF) is 270C wet.

Originally Posted by Gforce

How will anyone know your video is objectively correct?

Because I have better things to do than fake a video to prove someone on the internet wrong? Fly yourself out this way and drive for the video.

Originally Posted by Gforce

How about a brake pad supplier who makes the same claim as you do.

Brake pad manufacturers don't know which car they're going in, so they'll never make that claim. They also have to deal with people that might try to run a track capable pad in the middle of a Canadian winter. Their legal team would never allow it, but you should know that given your profession. Look at the operating temperature range though, it has to be pretty cold to have rotor/pad temperatures under ~50*C (minimum rated temp on my pads is 47*C).

Originally Posted by Gforce

Just btw, your Ferodo 2500 are just a hard street pad, if you want proper track performance Ferodo makes much more suitable pads, not streetable though.

Your reading comprehension is getting worse every post. I haven't had the DS2500's in years. Current pads are G-Loc R10, and the ones before that were Project mU Club Racers. That was spelled out quite clearly, maybe try reading the full post before responding?

Originally Posted by Gforce

I use "harder" to mean higher temperature. In fact, competition brake pads are harder, wear more slowly and require higher line pressures to work as designed. "Harder" is an appropriate adjective. Higher temperature resistance seems a bit cumbersome as a description albeit more accurate.

Again, that's simply not true as a blanket statement. Most race pad manufacturers have different options for co-efficient of friction, modulation and maximum temperature before they start to fade. Some drivers like a brake pedal that is like an on/off switch, others like more modulation. Some like a rock hard pedal, some like a bit more travel.

Where's the data backing up needing higher line pressures? A higher co-efficient of friction pad will actually need less pressure to slow the car down the same amount. I need VERY little pedal pressure to stop my car on the R10's, significantly less than the stock pads (same day, same wheels/tires, etc).

Read through the heat ranges and descriptions here: http://www.g-locbrakes.com/products/brake-compounds/

A lot of race pads actually wear faster to be more gentle to the rotors, but that varies by manufacturer and compound.

Honestly, it sounds like you're basing what you post on information that is about 20 years outdated. Modern pad compounds are WAY different than a couple decades ago.

Originally Posted by Gforce

The op was clearly asking for useful replies to his valid concerns that he was unsure whether his brake modifications were an improvement over stock and if so how to determine by how much. He clearly stated it was for a street application.

If you actually read his question, he asked about measuring rotor temperatures side to side and front to back to measure the quality of his work and if rotor temperatures overall were a good measurement of how well the brakes are working.

Originally Posted by Gforce

As for spending money on your BRZ to create a track car I support my opinion by referring to the factory stated objective of making a proper sports car with a comfortable ride for the street. I further support my opinion by referring to the factory upgrades for 2017 decreasing the rear spring rate and rebalancing the chassis for more understeer and less abrupt oversteer. These virtues can be improved upon further by making the modifications I have made over the four years I have owned my BRZ.

First, you originally said race car, not track car. But, how does any of that mean that making a race car from an FRS/BRZ is dumb? Have you ever seen BTCC races, those are all based on family sedans, are they dumb too? At most what YOU want out of the car isn't served by making it into a track car, that doesn't mean that it's dumb at all, it's just not for you.

Originally Posted by Gforce

With the supercharger fitted and the carefully chosen modifications I have made I have produced a car that my racing addicted buddy claims is one of the best little sportscars he has ever driven. His daily driver? A Mclaren 12C. His racecars include a F1 Shadow and a Canam car.....

Relevance? Your friend saying he likes it means absolutely nothing in the big picture. How do we know he a) actually said that, and b) wasn't just saying that to shut you up? Has he driven it back to back with a stock one to see if it's actually better than stock? I have friends with race cars that love the way my car drives too, doesn't mean anything in the context of this thread.

[CSG Mike]

Originally Posted by Gforce

You first.

If you quote one of my facts I'll get you the back up.

I say bs to your brake fluid boiling "easily". What were the measured caliper temperatures at which you say you boiled your "fresh" brake fluid (from a previously unopened container and into a fully flushed system,presumably).

How will anyone know your video is objectively correct? How about a brake pad supplier who makes the same claim as you do. Just btw, your Ferodo 2500 are just a hard street pad, if you want proper track performance Ferodo makes much more suitable pads, not streetable though.

I use "harder" to mean higher temperature. In fact, competition brake pads are harder, wear more slowly and require higher line pressures to work as designed. "Harder" is an appropriate adjective. Higher temperature resistance seems a bit cumbersome as a description albeit more accurate. Heat capacity is not something you want in a brake pad. You want heat insulating capability to keep the heat going into the rotors and away from the calipers (duh). Heat capacity needs to be in the rotors and, more accurately, heat dissipation capability.

The op was clearly asking for useful replies to his valid concerns that he was unsure whether his brake modifications were an improvement over stock and if so how to determine by how much. He clearly stated it was for a street application. My reply was intended to broaden the scope of investigation of the topic of improving the street capability of the stock BRZ brake. My opinion is that the stock BRZ brakes are way over spec for street driving and cannot usefully be improved at all. It will be interesting to see if the factory Brembo option actually changes brake performance for road use. My prediction is that it will not. The stock BRZ brakes are already from a much heavier model, the Impreza WRX.

As for spending money on your BRZ to create a track car I support my opinion by referring to the factory stated objective of making a proper sports car with a comfortable ride for the street. I further support my opinion by referring to the factory upgrades for 2017 decreasing the rear spring rate and rebalancing the chassis for more understeer and less abrupt oversteer. These virtues can be improved upon further by making the modifications I have made over the four years I have owned my BRZ.

With the supercharger fitted and the carefully chosen modifications I have made I have produced a car that my racing addicted buddy claims is one of the best little sportscars he has ever driven. His daily driver? A Mclaren 12C. His racecars include a F1 Shadow and a Canam car.....

Over to you now Mr racecar

He must not daily drive much then...

[CSG Mike]

There's a lot of homebrew theory here, so I'm gonna correct the incorrect conclusions you've reached via good initial data and hearsay.

Originally Posted by Gforce

Brakes are heat dissipating devices. They convert kinetic energy into heat and then dissipate that to the atmosphere. There are water cooled brakes but not on road cars.

Brakes work best at very high temperatures because heat rejection reaches a maximum at very high temperatures. Racing brakes are run as hot as the materials available will allow for this reason.

Racing brakes run hot because they're limited in capacity by the rules of a given class.
F1 brakes run hot because they are mandated to not run anything larger.
Temperature = heat input / thermal capacity. They have very little thermal capacity due to mass and surface area. Note, that I use the word mass,
not size.

Originally Posted by Gforce

Maximum effective brake temperatures are limited by pad material. Unfortunately, nobody has yet invented a brake pad material that is optimal across a very wide range of operating temperatures. Racing brakes at the pinnacle of Motorsport are based on carbon technology. These are unsuitable for road cars.

Incorrect. They are perfectly usable by road cars, but have elevated levels of noise, and typically harder on rotors at lower temperatures. Maximum effective brake temperatures are limited by rotor temp, not pad temp.

Originally Posted by Gforce

Braking effectiveness is measured by stopping distances. If you are not reducing your stopping distances your brakes have not been improved. Stopping distances are limited by the grip developed by your tires. That in turn is affected by weight transfer which is why rear brakes are smaller and generally cannot be run as hot as front brakes. If you could run rear brakes as hot as front brakes then total brake performance would improve.

Even the most basic braking system can lock up tires on a car, meaning you can threshold brake, aka 100% capacity for the braking ability of the car. Improving pads, or brakes, does not magically increase the threshold of maximum braking; increasing adhesion to the road (via tires, or aerodynamic aids) does.

Originally Posted by Gforce

The better upgrade route begins with tires. If you can fully activate ABS on best grip available then your brakes are sufficient. Any increase in potential braking force above ABS actuation is a waste of money. Disc brakes don't fade. Brake pads fade if the operating temperatures achieved exceed the temperature range for which the pads were designed. The next upgrade after grippier tires should be harder pads. Be aware that harder pads do not reach proper operating temperatures on the street. Therefore, generally speaking you need two sets of pads if you experience brake pad fade under some conditions. High performance brake pads will generally produce longer stopping distances unless fully heated up. Obviously you don't want those for street driving.

If you can ABS, your brakes are sufficient for *hitting that capacity in a limited fashion.

Disk brakes do indeed fade, because the pads paired up with them fade.

I use the same pad compound on my BRZ as what I prescribe for NASCAR and Indy teams I consult for. I have zero issue braking at cold temps.

In fact, my cold bite is greater than that of the OEM pad by a long shot. Brake dynos of my pad verify that. No I will not be releasing this information, as the teams that have paid for it own the dyno graphs.

Originally Posted by Gforce

You also want the smallest and lightest brake discs that will produce the brake forces you require to lock up the tires. Anything larger than that is counter productive. Larger brake discs are less useful than harder pads if you're looking for shorter stopping distances and heat is a problem. Brakes are 100% unsprung weight.

Porsche/Ferrari/Mclare/Lamborghini/etc. must all be doing it wrong. Subaru definitely must be wrong putting larger brakes on the 2018 STI.

Larger brakes = more thermal capacity = more sustained performance over repeated braking events.

Originally Posted by Gforce

Carbon ceramic brakes are a complete boondoggle invented by marketing guys, unless all you do is drive at racing speeds on a track. They are also a real pita to drive daily.

Actually, quite the opposite. They're a pleasure to daily drive, and generate ZERO brake dust. The temperature range for CCB pads are broader than most "street" pads, without making noise or significant brake rotor wear.

However, when CCB rotors fail, they fail catastrophically, unlike steel rotors. Big budget racing teams replace the rotors *EVERY* event to prevent this type of failure.

Originally Posted by Gforce

Almost as much misinformation gets bandied about concerning brakes as oil changes.

The BRZ stock brakes are exceptionally good. Harder pads for track work is all you really need unless you are running slicks.

Pads alone are a formula for overheating your braking system.

https://www.instagram.com/p/BOGJxgJjVo5/

That maximum temp was exceeded on *stock* tires *in the rain*.

I also set a new class record that day in semi-wet weather.

[CSG Mike]

Originally Posted by Gforce

Heat capacity isn't the relevant factor. You are of course correct that higher heat capacity means you can use softer brake pads.

Boiling brake fluid is an irrelevant consideration. Water contamination in the fluid is often confused with boiling fluid itself. Flush brake fluid completely at least every three years and in very humid climates every two years.

Higher heat capacity does not change the heat impulse of a braking event. You cannot use lower grade brake pads because the capacity of a system is higher.

Brake fluid does not degrade faster in a more humid climate, unless your braking system is not sealed (compromised). But, if your system is not sealed, you got bigger issues.

[CSG Mike]

Originally Posted by Gforce

I was just hoping you'd post.

No misinformation in my post, how about yours?

Most people who think their brake fluid boiled actually suffered from water contamination from failure to flush their system regularly. Standard brake fluid is sufficient. Water boils at only 100C (212F and then only at sea level) as you may recall. I find Stop Tech technical information useful:

http://stoptech.com/technical-suppor...rs/brake-fluid

As for your claim about high performance brake pads stopping as well as street pads when cold, I say total bs. Got any third party facts to back that up?

As you are well aware, my remarks are aimed at people trying to improve their cars for street use. If you are using street tires (especially stock tires) harder pads should be all you need for occasional track use. Trying to turn a BRZ into a race car is just a dumb idea.

I can make virtually any brake fluid mush on a stock BRZ braking system, because the capacity of the system is not enough.

https://www.instagram.com/p/BN2nVdJjUAY/

[churchx]

CSG Mike: you are doing it wrong, trying to convince troll with real facts. One should use flattery/bribes or threats for that!

[Lynxis]

Originally Posted by Gforce

I was just hoping you'd post.

No misinformation in my post, how about yours?

Most people who think their brake fluid boiled actually suffered from water contamination from failure to flush their system regularly. Standard brake fluid is sufficient. Water boils at only 100C (212F and then only at sea level) as you may recall. I find Stop Tech technical information useful:

http://stoptech.com/technical-suppor...rs/brake-fluid

As for your claim about high performance brake pads stopping as well as street pads when cold, I say total bs. Got any third party facts to back that up?

As you are well aware, my remarks are aimed at people trying to improve their cars for street use. If you are using street tires (especially stock tires) harder pads should be all you need for occasional track use. Trying to turn a BRZ into a race car is just a dumb idea.

For a 3rd party source, I am one. I have Winmax W5 pads. They are a proper track/race pad and I have daily driven them for about a month. Dead cold, they bite harder than my OEM pads did. The reason they are considered a dedicated track pad is because they make too much noise, dust like mad, and wear too quickly while cold to be feasible on the street and that is why I stopped daily driving on them. As a bonus, they are also really difficult to modulate with low pedal effort although this isn't nearly the issue the other ones I mentioned are.

[Gforce]

Originally Posted by CSG Mike

Higher heat capacity does not change the heat impulse of a braking event. You cannot use lower grade brake pads because the capacity of a system is higher.

Brake fluid does not degrade faster in a more humid climate, unless your braking system is not sealed (compromised). But, if your system is not sealed, you got bigger issues.

Braking system cannot be sealed.

You'll need to explain the heat impulse idea. The capacity remark is also incomplete.

Are you talking about making a hot brake system suddenly hotter when you first apply the brakes hard or a cold system suddenly hot?


Are you suggesting the BRZ needs larger brake caliper cylinder volume?

My point is that any road car needs brake pads that deliver maximum performance from cold. The very first stop of the day might be your last. Using track pads on the street is just plain dangerous.

[Gforce]

Originally Posted by CSG Mike

I can make virtually any brake fluid mush on a stock BRZ braking system, because the capacity of the system is not enough.

https://www.instagram.com/p/BN2nVdJjUAY/

You'll need to explain this one. You must mean the car needs bigger caliper pistons. There's not much fluid circulation in a brake hydraulic system unless ABS is working hard.