OK... A friend of mine just got S2, and I was on the phone with him last night when he started talking about a setup he was making for the MRT. He'd deliberately put enough braking force to lock the wheels - arguing that he might need to lock the wheels up. I thought this was very strange, and he said that racing drivers sometimes lock up the wheels to get out of trouble.

I should've asked him for an example, but I didn't. Why would you lock up the wheels deliberately if you were heading for disaster? Is he right, or is he getting his cause and effect mixed up?

I'll be seeing him in the pub tonight so it'd be nice to be able to confirm how wrong he is, which is why I'm asking here.

A lockup can flat-spot your tyre(s). Race drivers avoid that generally. Perhaps they hit the brakes hard (causing a lockup) to get out of trouble, but it won't do your tyres any favours.

hes confused; locking up your wheels only leads to one thing... trouble, and if you dont unlock them fast enough, consider yourself lucky enough to get out of it

locking up your wheels will only cause the car to slide more than if they were not sliding

i'll see if i can find some videos of what happens when you lock up your tires on an F1

heres what happens when you lock up a motogp front brake lol (obviously this isn't good)
http://www.youtube.com/watch?v ... mp;search=locked%20brakes

champ cars.. you loose your position lol
http://www.youtube.com/watch?v ... mp;search=locked%20brakes

well the fastest way to slow down on dry tarmac is to lock your tyres 100%, so in that way he's right.

Locking wheels on purpose!? That seems like complete stupidity IMO. No one in F1 deliberately locks brakes, or at least the top drivers don't. Locking up brakes is all bad and not a single bit good about it. Locking up brakes = Flatspots, Lose 30% of slowing down power and you can't turn. I don't know what your friend was thinking, but it seems completely illogical to me. Just wondering, does your friend like to smoke a lot?

well.. i cant find any F1 videos, but i will tell you that if you've ever seen an F1 completely lock up their brakes.. you will see that they will most likely slide off the track REAL fast

and probably do a 360 along with it

the only use for locked tyres i know of is induced understeer used to catch unexpected oversteer ... but its more of a rally technique than one for track driving where you know exactly what speed you should enter the corner with

Hint: Nascar

(if you lose the back end in high speeds the easiest way to get it back is to fully lock the front brakes. It will ruin your tires but you won't hit the wall. Of course this doesn't applu if you are already in 90degree slide )

Quote from Hyperactive :

Hint: Nascar

(if you lose the back end in high speeds the easiest way to get it back is to fully lock the front brakes. It will ruin your tires but you won't hit the wall. Of course this doesn't applu if you are already in 90degree slide )

and how wierd are your brakes gonna be if they lock up the front, but dont touch the rear? how the hell would you do an emergancy stop!

I can understand the concept of running a setup where 100% brake pedal movement gives you a lockup on all four corners. But a locked wheel provides less grip on any surface. Coming from GPL I always had my setup able to lock all four corners to 'teach' me to respect the brake and not over use it. I find that most setups in LFS do not have enough 'bite' with thier braking and I have to adjust it so that I 'could' lock the wheels at about 75-80% pedal movement. The only thing I can think of is to induce a slide, either understeer or oversteer, but I can't think how either of those would avert disaster as you'd lose more control than you gain. Perhaps he has seen too many accidents where the driver has locked his brakes and has been fortunate to escape and put 1 and 1 together to get 3.

Quote from Jakg :

and how wierd are your brakes gonna be if they lock up the front, but dont touch the rear? how the hell would you do an emergancy stop!

Brakes should be always set up so that the rear tires won't lock up. (maybe in rally they can but not on track). So applying full brakes should lock up the fronts. Locking up the fronts will "transfer/give" more lateral grip to the rear tires (which are sliding) and as a result the rear tires regain grip and stop sliding. As a result the the car stops sliding.

It's about getting the car back straight, not to get it stopped. And not very safe thing to do if there are people driving just behind you.

Quote from Hyperactive :

Brakes should be always set up so that the rear tires won't lock up. (maybe in rally they can but not on track). So applying full brakes should lock up the fronts. Locking up the fronts will "transfer/give" more lateral grip to the rear tires (which are sliding) and as a result the rear tires regain grip and stop sliding. As a result the the car stops sliding.

It's about getting the car back straight, not to get it stopped. And not very safe thing to do if there are people driving just behind you.

i was refering to his nascar example - picture this:

Car a hits the wall, spins into the middle of the track, Cars C & D block your (car B's) way to avoid it, so you jam the brakes, the fronts lock, but of course its not about stopping, so you hit him and loose your legs illepall

Quote from Jakg :

i was refering to his nascar example - picture this:

Car a hits the wall, spins into the middle of the track, Cars C & D block your (car B's) way to avoid it, so you jam the brakes, the fronts lock, but of course its not about stopping, so you hit him and loose your legs illepall

Are we even talking on same subject?

The quastion that was presented in the first post was: " Why would you lock up the wheels deliberately if you were heading for disaster?"

In my case I presented the disaster as a continuing slide occuring in high speed (a nascar racecar losing the back when accelerating out of a corner at a high speed oval). When a nascar race loses its back end at high speeds it is very hard to get it back. As a result of this loss of control the car usually hits the inside wall of the track and/or spins. If you are quick enough, you stab the brakes and hold for a while the rear end regains grip. So you can avoid an accident.

If something happens by surprize, the fastest way to stop a car is to press the brake pedal at full force. This way you get the biggest braking power in to use in shortest time.

The fastest way to stop a car is to not lock up the tires. But you won't be able to do this succesfully if you get 0.5 seconds to react. For example a moose running in front of you, when you are doing 80kph.

But with locked wheels you can't steer the car

Quote from Hyperactive :

Hint: Nascar

(if you lose the back end in high speeds the easiest way to get it back is to fully lock the front brakes. It will ruin your tires but you won't hit the wall. Of course this doesn't applu if you are already in 90degree slide )

same i was on about ... induced understeer to catch a slide

You guys are right locking brakes lead to trouble. THere is one thing though. On most cars the faster you go the harder it is to lock the brakes up, even harder to lock them up on a car with downforce. Because of this, it's good practice to set your braking force to lock up while you are at high speeds then back them off until they won't lock when you jam on them. DOing this insures that you are getting the maximum braking possible while racing. Of course you'll have to ease up on the pedal as you start to really slow down to avoid locking them up. You guys try that and watch your lap times take a dive as you get used to it.

My setups are all about getting the maximum breaking possible. Because the wheels are more difficult to stop turning when you're going fast, I usually find myself slamming on the brakes (but they don't lock) and then gradually easing off them as my speed drops, always listening for them to begin squealing.

Cars, whose wheels don't lock up, stop faster. It's a common misconception that locked up, skidding wheels are the fastest way to stop. Cars with anti-locking brakes stop faster than cars without, and going the opposite direction, F1 cars get away quicker with traction control on than with it off and wheels spinning.

Sorry.. too late for the pub. I strongly recommend phoning him, but wait til 2 or 3am

Quote from SamH :

Cars, whose wheels don't lock up, stop faster. It's a common misconception that locked up, skidding wheels are the fastest way to stop.

Yep, because when you apply the brakes, you are slowing down the wheel. But, when the tires are locked, the slip ratio is null. This means that you only have the friction of the the tire, and the weight of the car to slow the car down. This in turn means that the tire is no longer connected to the ground.

EDIT: Think of it this way, if there are two gears touching, and one has a motor attatched to it, and the other one is attatched to the spinning gear. Lets say you stripped all of the teeth off of the gear which is not powered. It would no longer be spinning!

Quote from Tukko :

well the fastest way to slow down on dry tarmac is to lock your tyres 100%, so in that way he's right.

Care to elaborate Tukko? This is flat wrong as far as I know: a locked wheel has less friction against the road than a rotating wheel and so slows you down less.

I know nothing about this stuff, I just keep hoping someone will turn up telling why that guy is correct, making all of you guys look like morons

And not thinking scientific... If I think about it... It would make more sense if the car slows down harder when wheels are locked than if they still roll, don't know why, something just tells me it makes sense... But who am I?

locking up the wheels is useful for me sometimes, probably more in the road cars, when i might need to avoid crashing into someone and the only way is to lock the brakes up to get the car to slide a bit. I know ive done this a few times and its worked at the exspense of tyres. otherwise i avoid locking them up

Quote from sgt.flippy :

And not thinking scientific... If I think about it... It would make more sense if the car slows down harder when wheels are locked than if they still roll, don't know why, something just tells me it makes sense... But who am I?

That's the common misconception The physics (and the F1 and modern cars with ALB systems bear it out) actually don't work this way.

Try placing your palm firmly on your desk. Try sliding it along the desk, while applying downward force (simulating the car's weight, and even downforce).

While you're applying pressure to slide your palm, but your palm is still gripping, that exertion is the same as a wheel being SLOWED, but not STOPPED. It's a powerful force.

When the grip lets go (and your palm slides) that's the same as the wheel skidding. That's the difference (you should be able to feel a big difference) between the two

[edit] sweaty palms work best! :-\

[edit] don't do this if you have a glass desk!

When is the guy with the smart answer coming to say it IS useful?? I want to see the opposite of SamH here! Where's he at?? And btw, I actually was thinking about the hand test thingy... But it's late again so I don't bother thinking about it

I always have sweaty palms... I hate it.. But it does work good in these circumstances!!

hehehe!!

As SamH said a locked wheel is not the most effective way to stop I'm sure when you're heading for disaster at high speed IRL you'd probably not care about this and lock your brakes anyway but that's not the point. I've yet to hear a situation where locked brakes are useful.

Racing brakes/tires IRL are designed for the initial braking to be very hard then releasing the pedal as the wheel beigns to lock. I think a lot of people struggle with this concept, feeling safer gradually applying pressure and then ending up in a lock up.

Quote from jtr99 :

Care to elaborate Tukko? This is flat wrong as far as I know: a locked wheel has less friction against the road than a rotating wheel and so slows you down less.

i seem to recall hearing an explanation to this, and why locked wheels will stop you quicker. however the reason the whole ABS was invented is because it simply isn't safe to stop with all 4 wheels locked.

i certainly remember in S1 i had a drivable set which was brakes split 50/50 with max power, locked up instantly everytime but it pulled up quicker than anything else out there

however with the realism of tyre wear, locking up all 4 wheels may pull you up quicker, but you'll be stuffed trying to race again from that point onwards.