Stock brakes too weak?

[CSG Mike]

Originally Posted by qoncept

Oh. Well that's hardly a test. But still, everything else I said. :P

FWIW I'm not going to upgrade my brakes beyond pads, lines and fluid and probably never will on a car. Even messing with the front/rear bias is beyond me so I'm just not going to touch them. Glad to move from a car with insufficient brakes (WRX) to this.

I suggest you read the "pedal dance" thread in my sig, and the effects of electronic brake force distribution.

Brake bias isn't an issue unless you throw it WAY out of whack. The car compensates for it (unless you turn it off via the pedal dance).

[qoncept]

Originally Posted by CSG Mike

I suggest you read the "pedal dance" thread in my sig, and the effects of electronic brake force distribution.

Brake bias isn't an issue unless you throw it WAY out of whack. The car compensates for it (unless you turn it off via the pedal dance).

I've read it, but I'm not sure which part you're suggesting now..?

I've actually never gotten the pedal dance to work. I've tried a handful of times. I turn off everything normally at autox and I don't think it's affected me. But I'm also a pretty mediocre and unattentive driver.

[Dave-ROR]

Originally Posted by CSG Mike

Easy. Apples to oranges comparison. Test on the same surface.

Plus temps. Plus air pressure changes due to temps, plus variance.

Also, data can be used to your advantage of course. If I do ten stops with an average of 100 ft, but got a 95 in one run, then did ten stops with a different pad and got an average of 100 ft, but one with 105 ft... I can make it look like the pads improved it by 10 feet...

Not saying that's what Jeremy did, I don't know the details of his test, but simple surface temp differences between the tests will change braking distance.

[qoncept]

Originally Posted by Dave-ROR

Plus temps. Plus air pressure changes due to temps, plus variance.

Also, data can be used to your advantage of course. If I do ten stops with an average of 100 ft, but got a 95 in one run, then did ten stops with a different pad and got an average of 100 ft, but one with 105 ft... I can make it look like the pads improved it by 10 feet...

Not saying that's what Jeremy did, I don't know the details of his test, but simple surface temp differences between the tests will change braking distance.

Now that I've read the thread it looks like they weren't really making any attempts to make it scientific. Like, that wasn't the goal. Just said "I wonder.." and did it. Really I think including the Motortrend number was dubious but it is what it is.

[CSG Mike]

Originally Posted by qoncept

I've read it, but I'm not sure which part you're suggesting now..?

I've actually never gotten the pedal dance to work. I've tried a handful of times. I turn off everything normally at autox and I don't think it's affected me. But I'm also a pretty mediocre and unattentive driver.

The car automatically proportions braking force between the front and rear axles to minimize braking distance by maximizing available grip, unless you disable it through the pedal dance (or other means).

[rainmonkey]

Look, there's absolutely nothing wrong with stock brakse if you're driving on the street like a sane, rational person.

Given that the BRZ/86 in the philippines comes with a nice 100% tax on top of the base price, AND that the standard of living there is so low, most of the people that buy this car are going to be little rich kids or brats who are in all honesty, incompetent drivers.

To give you some perspective, the ability to buy a brand new honda civic already puts you in the top 5% if not 1% of the population. Civics arent even taxed at 100% mind you, it'd probably end up being around 20k USD if memory serves me.

Now imagine that you have a kid who has maids to clean his house, do his laundry, make his bed, bring food/drink, and cook, in addition to having a driver that'll bring him/her wherever he/she wants, wait on the kid in a parking lot even til the wee hours of the morning. Oh another thing is that for these kids, don't really have to pass a test to get a license. You can literally walk up to the window, slip a few thousand pesos (somewhere around 50USD) and be approved.

Add that stupid kid who probably doesnt drive all that much and is used to being pampered, to a sporty, flashy looking car that is probably really rare still in the philippines. Of course the moron is going to drive like a madman. It's bad enough when it happens in the US, but in Manila traffic you're screwed. People don't signal before changing lanes because they're worried it'll give the other drivers a heads up and they'll move up to block the lane switch.

TLDR: It's not the car, its the driver who's probably a coddled brat.

[SubieNate]

Originally Posted by qoncept

I didn't mean you. The real world results show you're right. But according to everyone else that's impossible because the stock brakes can already lock up the wheels which means the car can't possibly stop any faster. So, anyone else, please explain how this impossible thing happened.

If you watched that video, you'd see that they're running starspec tires. The motortrend article is on the stock tires. That most likely accounts for a HUGE part of the difference.

Performance pads also tend to improve modulation and the linearity of the bite, so it's feasible that they improved the driver's ability to get right up to the limit of the tire's adhesion.

That said, all your talk about coefficients of friction show a flawed understanding of the system as a whole. The wheel locks not because of some magical transition between sliding and static friction. That sudden drop in force caused by switching to kinetic friction from static? That NEVER EVER happens in a car's breaking system, and the phenomenon does NOT work in reverse. Once sliding, it takes a ton of force to lock, and there is no sudden drop off or rise in the needed force like you'd see when dragging a brick from a standstill.

When dragging something on a flat surface, it goes static-force rises-static-force rises past threshold-kinetic. With brakes, the pads area always stopped (attached to the car) and the rotor is [almost] always spinning. That's kinetic friction right off the bat. The force output by the brakes is linear (or close to it) right up until the time they lock.

What DOES happen, is the tire, who's friction coefficient can be fudged and represented by static friction for the purposes of our example, loads up. That "static" friction force applied to the tire by the road, resisting the forward momentum of the car and slowing it down (Basically, the force of the car is translated through the brake system from a linear force to a moment, which is then converted back into a linear force by the wheel/ground interface) increases as the braking force is increased, until it reaches the threshold of the tire's grip, at which point the TIRE transitions into full kinetic friction mode, at which point the tire's desire to continue rolling drops off significantly (Since the brake wants to stop it, and the force the road was previously exerting on the tire to keep it rolling is suddenly decreased), at which point the force the brakes are exerting on the tire, which were previously doing all the work to negatively accelerate the car, now only have to resist the [small] force needed to keep the wheel from spinning since it's already sliding.

Now with all the variables involved, it is possible that given a good driver who can threshold brake well, on the same tires an improved braking system would result in a shorter stopping distance. But, with tires that are likely going to slide and engage the ABS system regardless of peak braking torque (because in either case peak braking torque exceeds the amount needed to lock the tires and make that static==>kinetic transition), the difference will be much smaller, if anything, because it's highly unlikely that the ABS system is tuned well enough to take advantage of the "feel" and linearity improvements uprated brakes provide.

So again, from a road safety, single panic stop perspective, as long as the brakes are strong enough to lock the tires, and the driver isn't Lewis Hamilton, it's likely that the stock brakes, on the stock tires, will stop the car in approximately the same distance as any other brakes on those same tires.

Cheers
Nathan

[qoncept]

Originally Posted by CSG Mike

The car automatically proportions braking force between the front and rear axles to minimize braking distance by maximizing available grip, unless you disable it through the pedal dance (or other means).

Doh.. what else would have have been talking about. But the time it's going to matter is when it HAS been disabled by the pedal dance.

[oofie]

Originally Posted by SubieNate

So again, from a road safety, single panic stop perspective, as long as the brakes are strong enough to lock the tires, and the driver isn't Lewis Hamilton, it's likely that the stock brakes, on the stock tires, will stop the car in approximately the same distance as any other brakes on those same tires.

Cheers
Nathan

Funny because Lewis is having braking troubles (pedal feel) with Mercedes this year :happy0180:, but that's a totally different matter.

[BRZ68]

Its not so much that the brakes are weak, its more of underestimating the stopping distance on slippery tires...my stock Michelin Primacy HP tires easily chirps on 1st-3rd gear, on sudden braking, and even on downshifts. I would say they're dangerous and they should be anyone's first upgrade.

[oofie]

Originally Posted by BRZ68

Its not so much that the brakes are weak, its more of underestimating the stopping distance on slippery tires...my stock Michelin Primacy HP tires easily chirps on 1st-3rd gear, on sudden braking, and even on downshifts. I would say they're dangerous and they should be anyone's first upgrade.

I'm sorry, but they're dangerous? Care to expound on that statement? Thousands of cars use the same exact tires and most, if not all of them go their merry way.

[wparsons]

Anyone claiming the brakes or tires are unsafe needs to rethink how they're driving.

If you expect the car to grip and stop like an F1 car you're going to be sorely disappointed. If you drive reasonably they're plenty safe and good.

If you can lock up the wheels then adding more braking power isn't going to shorten stopping distances at all. The amount of available grip is finite, and it doesn't matter how much power you have over the amount needed to overcome the grip. Now if you add more grip (better tires) you'll find that adding more braking power can help shorten braking distances.

I'll use my car for an example. On the stock tires (or snows) it could EASILY lock up the tires on stock pads. When I switched to 225 width Z2's it could barely trigger the ABS at all with warm tires. New pads/lines/fluid (probably the pads alone did it, but I swapped all together) and it can easily lock them up again.

Now, stopping distances on stock brakes with the sticky tires were most definitely shorter than on stock tires/pads but are even better with sticky tires and new pads.

The lines/fluid do nothing for a single stopping distance, just consistency in feel and heat resistance with repeated stops.

[Bullnettles]

Originally Posted by BRZ68

Its not so much that the brakes are weak, its more of underestimating the stopping distance on slippery tires...my stock Michelin Primacy HP tires easily chirps on 1st-3rd gear, on sudden braking, and even on downshifts. I would say they're dangerous and they should be anyone's first upgrade.

Haha, what you said makes the car fun for me. You can take it to it's limits, then play with them. If you're doing this in a standard scenario, I'd say you're right, but I have to be pushing the hell out of my car to do these things, and of course it's on purpose. My last vehicle spun on the 2-3 shift at 83 mph, and I never wrecked it; the tires were street tires with more than adequate grip when normal driving.

THAT SAID, once I get bored with the car, tires will be an upgrade because it will lift the limits considerably. I'll agree with you on that.

[BRZ68]

Originally Posted by oofie

I'm sorry, but they're dangerous? Care to expound on that statement? Thousands of cars use the same exact tires and most, if not all of them go their merry way.

I worry about braking ahead of time with this car more than the other cars i'm driving almost every other day..that includes a camry, a Lexus es350, and a Mercedes e350. HP primacy tires looses grip way ahead of time more than Yokohamas and Bridgestones that come stock on those sedans. The difference is night and day. Im not saying that the tires are the only out of so many factors in stopping, but theyre a major one.