Understanding how brakes work (for dummies like me)

[Dan]

Dan, the build up of pad material will have been from the pads overheating. Suspension is all good, albeit presently setup for sharper turn in than previously. Recently aligned and corner weighted. I don't do anything as a driver to make it steer randomly left and right and in my head it's saying high/hot spots on the rotors are causing one side to brake harder than the other on then off and the overall imperfect coating of pad material on the rotor is causing the general reduction in stopping power. All fine on the road by the way, as the track temps simply don't happen.

Yeh I agree with the build up of pad material and uneven wear, the car leaping side to side is what I was saying might be something different.

How bad is it steering left or right? Is it sort of like the tramlining feeling you get on an uneven road where the car follows the roads grooves or is it literally 'leaping'?

The reason I ask is because if you have an aggressive race setup with lots of negative camber you should expect the car to get a bit of a tramlining feeling during heavy braking also if you did something like adding toe out at the front to get that sharper turn in you mentioned that will also make the car more unstable under brakes.

Insufficient front brake bias will also cause the car to become loose when braking. I know this is about Sim racing but read the front brake bias section on this site http://www.racelinecentral.com/RacingSetupGuide.html (since you play iRacing now this might also be helpful to you on there).

If it had a distinct pull in a certain direction then I would say it is more likely to be something to do with the brakes.

[project.r.racing]

It is a biasing issue. Dont over think it.

[davekmoore]

Thanks for everyone's thoughts.

Tyres were near new NT01s.

The brakes are not dragging.

All brake components are inspected after every event.

Rotor temps weren't measured. The fact that 800 rated pads lasted less than one track day and the 1000 ones last 2-3 days, and the other symptoms mentioned, lead me to believe the pads are not coping with the temps. As Dann says, 400hp at the flywheel has an effect on brake temps, particularly when combined with a driver who is slower than the car.

The steering feel is indeed more like tramlining but at 210kmph it feels more like leaping. Trail braking into turn 1 at Sandown makes the steering settle into turning quite hard left, which is less bad than it could be, because it's a left hander.

Yes, toe-out was added, and some will be removed. The camber is only -2 at the front and -1.5 at the back.

[Dan]

Yeh, take some of that toe out and maybe try adjusting the brake bias towards the front a bit if you aren't already at a high percentage and have the ability to adjust it.

More front brake bias will also help with making the car less skittish on corner entry while trail braking.

As you go faster the car will start feeling less composed but it will sort of become normal. My Evo is downright scary braking from over 200 down to 100 through the turn 1 kink setting up for turn 2 at Wakefield, it's just how things are in a powerful car

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[Magpie]

Fix the cause not the symptoms. Get the rotors cooler! Do you have brake ducts?

[madjak]

With brake bias, if I move the balance too far rearward, I get the rear of the car squirming under hard braking which really feels like the tail of the car is wiggling. I find my car is very composed under hard braking on a race track, but on some street circuits I get a completely different feeling of the car 'walking' sideways on camber changes or large bumps. I doubt this is what you're experiencing on a race track though. What you are describing sounds more to do with suspension setup than brakes, with maybe some loose bushings allowing the alignment to change slightly under braking load.

As for brake overheating, the power of the car doesn't necessarily dictate brake temps. A car with half the horsepower but with smaller rotors can overwork the brakes just as easily. Also pad choice makes a massive difference. I really suggest people have a look at the endurance pads like they run in LeMons. They are very long life, high temp capacity and whilst you loose a little in the friction coefficient, you gain in consistency over their entire temperature range so you don't get that dip in friction as they overheat. They are also much more friendly to the rotors although not so great on the wallet (high upfront costs but saves $ in the long term)

[davekmoore]

Not that I've seen it here, nor have I intentionally checked, but I'm amazed when viewing in other forums at the amount of instances where the words "break" and "brake" are used incorrectly.

Maybe it's the mechanical engineer inside that's taking notice
..and goes to show we MX5 owners are just a class above

Great articles, thanks for sharing.

Many other words are apparently impossible to spell and/or use correctly. How about pedal and peddle, for instance?

[davekmoore]

Fix the cause not the symptoms. Get the rotors cooler! Do you have brake ducts?

Yes. Thanks for the thought.

[davekmoore]

With brake bias, if I move the balance too far rearward, I get the rear of the car squirming under hard braking which really feels like the tail of the car is wiggling. I find my car is very composed under hard braking on a race track, but on some street circuits I get a completely different feeling of the car 'walking' sideways on camber changes or large bumps. I doubt this is what you're experiencing on a race track though. What you are describing sounds more to do with suspension setup than brakes, with maybe some loose bushings allowing the alignment to change slightly under braking load.

I might wind more bias back to the front.
There are brand new poly bushes throughout.

As for brake overheating, the power of the car doesn't necessarily dictate brake temps. A car with half the horsepower but with smaller rotors can overwork the brakes just as easily. Also pad choice makes a massive difference. I really suggest people have a look at the endurance pads like they run in LeMons. They are very long life, high temp capacity and whilst you loose a little in the friction coefficient, you gain in consistency over their entire temperature range so you don't get that dip in friction as they overheat. They are also much more friendly to the rotors although not so great on the wallet (high upfront costs but saves $ in the long term)

Better pads are indeed part of the plan.

[BlackLeaf]

Not that I've seen it here, nor have I intentionally checked, but I'm amazed when viewing in other forums at the amount of instances where the words "break" and "brake" are used incorrectly.

Maybe it's the mechanical engineer inside that's taking notice
..and goes to show we MX5 owners are just a class above

Great articles, thanks for sharing.

Many other words are apparently impossible to spell and/or use correctly. How about pedal and peddle, for instance?

Tyres and tires!

[JBT]

There, their, they're....