Braking Differences in GT5 are Non-existent?

[Sele1981]

Hmm very interesting thread! Sad thing... Yeah it´s not an real sim but these things are important...

 

[CivicInLake]

try driving with ABS OFF.

 

[atteiros]

My take on this is that the physics that Scaff posted are accurate, but comparing it on different cars (Rover vs Lotus or Truck vs F1) will not determine the results as factors on tire size and weight transfer between the two will be different. It does show that even with all those factors, a difference in weights will not necessarily stop cars faster/slower. Testing should be done on a car (or even something which isn't a car, like a platform with wheels ) wherein the suspension will react the same under different loads (So maybe taking off the suspension system entirely in the first place?) and then testing the stopping distances.

For those who had experiences with a loaded car vs when there is only one passenger... One factor which can cause a loaded car to stop slower than a car with just 1 passenger is the weight distribution front to back as well as how the suspension reacts to the added weight.

Did I get this right Scaff?

 

[Wolfe]

For anyone still trying to understand (or doubting) the physics of this, consider the following:

As we all know, the braking system acts upon all four wheels, and in most vehicles, it has sufficient strength that it can rather easily lock the wheels (if we ignore ABS). Imagine the "opposite" case. That is, a 4WD vehicle with locked differentials (no open diffs or overwhelmable LSDs) and a powerful enough engine to break traction and spin all four wheels at once.

If you had two vehicles like this, with equivalent tires and differing weights, you'd likely get similar acceleration rates off the line. How much they weighed would be less of a factor than how well the tires could grip the pavement; drag racers know exactly how important it is to have tires that let you transfer as much torque to the pavement as possible. Remember, we're assuming the engine in each car is capable of spinning all four wheels with too much throttle, even if that means it's more powerful in the heavier car.

For a real-world example (minus the ability to perform four-wheel burnouts), consider the curb weights and similar 0-60mph performances of some of the fastest AWD cars available today -- the Bugatti Veyron SS (2.4s, ~4200lbs.), the Porsche 911 Turbo S (2.7s, ~3500lbs.), the Nissan GT-R (2.9s, ~3800lbs.) and the Gumpert Apollo Sport (2.9s, ~2400lbs.). Such incredibly fast, brief acceleration times do muddle comparisons a bit. However, even with curb weights spanning a difference of nearly 2000lbs., they're all in the same neighborhood, and probably couldn't do much better on the same tires (or any tire, given current tire technology).

Even compared to those cars, a locked-diff 4WD machine that can spin all four wheels if you boot the throttle a little too hard is insane. Yet that's a reverse analog of what we're looking at when we talk about the average car's braking system. That's why tires are the number one factor.

It's not a perfect analogy, but I hope it helps.

 

[Scaff]

Did I get this right Scaff?

You did indeed.

Additional passengers have an effect on braking because of the additional load transfer that occurs, that passengers sit up high in a car (most of the rest of a vehicles mass is considerably lower than passengers, also does no favours as it changes not just the transfer but also the cars CoG (centre of gravity).

However its the changes in transfer far more than the mass that does it, and these changes in transfer can throw out the brake bias for the car, its the reason behind the development of brake force distribution systems.

http://www.obd-codes.com/faq/ebd-explained.php

For anyone still trying to understand (or doubting) the physics of this, consider the following:

As we all know, the braking system acts upon all four wheels, and in most vehicles, it has sufficient strength that it can rather easily lock the wheels (if we ignore ABS). Imagine the "opposite" case. That is, a 4WD vehicle with locked differentials (no open diffs or overwhelmable LSDs) and a powerful enough engine to break traction and spin all four wheels at once.

If you had two vehicles like this, with equivalent tires and differing weights, you'd likely get similar acceleration rates off the line. How much they weighed would be less of a factor than how well the tires could grip the pavement; drag racers know exactly how important it is to have tires that let you transfer as much torque to the pavement as possible. Remember, we're assuming the engine in each car is capable of spinning all four wheels with too much throttle, even if that means it's more powerful in the heavier car.

For a real-world example (minus the ability to perform four-wheel burnouts), consider the curb weights and similar 0-60mph performances of some of the fastest AWD cars available today -- the Bugatti Veyron SS (2.4s, ~4200lbs.), the Porsche 911 Turbo S (2.7s, ~3500lbs.), the Nissan GT-R (2.9s, ~3800lbs.) and the Gumpert Apollo Sport (2.9s, ~2400lbs.). Such incredibly fast, brief acceleration times do muddle comparisons a bit. However, even with curb weights spanning a difference of nearly 2000lbs., they're all in the same neighborhood, and probably couldn't do much better on the same tires (or any tire, given current tire technology).

Even compared to those cars, a locked-diff 4WD machine that can spin all four wheels if you boot the throttle a little too hard is insane. Yet that's a reverse analog of what we're looking at when we talk about the average car's braking system. That's why tires are the number one factor.

It's not a perfect analogy, but I hope it helps.

Not perfect but still damn good.

👍


Scaff

 

[niky]

Think I mentioned EBD a while back... forgot to spell it out... Electronic Brake Force Distribution. It helps keep the braking distances between unloaded and fully loaded as small as possible given the braking hardware.

Always wondered what would happen if you turned it off. Though such testing might be problematic, as I think most EBD systems are integrated into ABS, and you can't turn off just one.

One thing... considering Wolfe's input... would tirewall deformation play as big a role in braking as it does in acceleration? Because one of the best stoppers in our test was on terrible tires, but it was on tall, terrible tires... and that could have made a difference, right?