How To Use Curbing

Posted on August 30, 2015

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How To Use Curbing

By: Rob Oakman

Even big frogs can jump. (Courtesy of porsche.com)

Even big frogs can jump. (Courtesy of porsche.com)

Curbing is sometimes risky but always fun. Everyone loves watching race cars hoping curbs, catching air and lifting wheels. But we have also seen racers thrown offline, break suspension parts, flatten tires, and lose momentum using them as well. So how and when should you use a curb?

A big note here: be aware that you can bottom out your chassis, grind off suspension parts over time and if you have ground effects, you will lose all downforce briefly when the undertray lifts off the track. Still, curbs can be very effective for most machines.

What does a curb do?

Basically a curb does three things:

1. It increases the weight transfer to the outside tires. This means that your outside tires are planted harder into the track, increasing grip.

2. It increases the distance the inside tires have to travel in the corner.

3. They allow you to cut the corner and shorten the distance through it.

The curbing itself doesn’t actually add grip. In fact most curbs are concrete which has less traction than asphalt. It gets worse if they are painted – especially in the rain when paint acts like ice. Curbs work by increasing the distance the inside tires have to travel and by causing those tires to accelerate. This added distance slows that side of the chassis down slightly, while the added acceleration to the wheels as they climb up the curbing further creates a pull to the inside. All this makes the chassis want to rotate and turn into the corner. It is similar to how some active systems in high end supercars will activate the inside brakes to “pull” the car into the corner. A curb is a manual version of this.

Put the extra rotation in combination with the extra grip created by the weight transfer, and using less distance, and you increase your corner speed in spite of the fact you are making the corner tighter by cutting it slightly.

On a long corner, the curb will help shift weight to the outside tires to add grip while helping the chassis through the corner. This gives you the chance to carry extra speed. In tighter corners you are generally using the curb to shorten distance more than anything, although it will still help you carry more speed than if you drive around the curb.

When to use a curb?

A curb can be used anywhere you can save time on track without breaking things. The stop watch and your ground clearance determines if you should or shouldn’t.

How to use a curb

You want to hit your turn in early so that your apex is inside of the racing surface and on the curb. Turn in sharply and smoothly and keep your grip on the wheel tight. When you mount the curb the steering wheel is going to move sharply and then settle again once you are up on top. Don’t try to wrestle with the wheel or you will either slip off the curb and/or scrub off speed. You still want to be as smooth as you can be even if you have lifted a wheel. As long as your speed is good the steering will settle immediately and you can continue with your smooth steering input. When you exit the curbing be ready for the wheel to pull again, this time the opposite way. Also be ready for the chassis to slide out on you as the weight spreads back across the tires more evenly.

(Video) Daniel Riccardo gets a bit greedy at Eau Rouge. (Courtesy of formula1.com)

(Video) Daniel Riccardo gets a bit greedy at Eau Rouge. (Courtesy of formula1.com)

How many tires can I use?

You can hit a curb using more than one tire. Each way will affect your chassis differently. Remember that every type of racing machine is different, so I will speak in general terms.

a. One front tire

One front tire riding up on the curb will drag the front end around the corner while shifting a lot of weight onto the opposite rear tire.

This is good if you have a push and/or you are having trouble turning through the center of the corner. It can cause a very sudden loose condition when you first hit the curb and/or a sudden push when you come back off.

The con is that this is very hard on the rear tire and can also cause premature wear on the inside of the front tire if you have a lot of camber.

b. Two inside tires

Running both inside tires tends to be the most stable way through a corner. As the front hits the curb you will feel the chassis rotate and pull itself into the corner. Then, as the rear hits the curb the rotation stabilizes and the chassis feels like it is turning itself. As you come off the curb the weigh spreads back out across the wheels so you will often find yourself in a four wheel slide. This is because the curb allowed you to carry more speed than you could have otherwise in that corner.

The con is also premature wear on the outside tires and/or wear on the inside of the tires when running a lot of camber.

c. Two fronts and an inside rear tire

Now you are getting aggressive. This is usually more a matter of cutting distance out of a corner rather than gaining extra grip from weight transfer. The front will rotate as the first tire hits, then grab again as the second tire bites into and climbs the curb. If it is a tight corner or it has a high curb then you have to turn in aggressively because at some point one, if not both of the front tires are going to leave the track surface. If the outside front tire stays on the curb then the front should slide out in a controlled fashion. If both tires leave the surface be ready to not over steer. Keep your hands as steady as you can for landing.

Depending on the corner your inside rear may hit before your outside front or – if the corner is tight – just after. You will feel it hit and stabilize the rotation like before.

The major con’s here are that you need to be ready for a push on exit. With both tires on concrete instead of asphalt you will lose grip. If the front end jumps then you have no grip at all and often chassis will bounce like basketballs when you land again so this is not always a good idea.

4 tires on the curb can be too much even for an Aussie V8 supercar (Courtesy of dsf.my)

4 tires on the curb can be too much even for an Aussie V8 supercar (Courtesy of dsf.my)

d. All four

Pure aggression. I love it. This tends to be a way to legally cut the track. You are going to lose grip no matter how you do this. Often you are going to launch a tire or two or three or four into the air. Sometimes though, in a corner where grip isn’t an issue (like a full throttle situation), or where the corner is concrete all the way through so you don’t lose grip on the curb, then this can totally work. When it is concrete it feels like a bumpier version of running two tires. You can feel the grip come in a wave of front, rear, front, rear.

The con is that often this is going to result is two or more tires leaving the surface so keep a good grip on the wheel and let the chassis stabilize on its own on landing. If you fight it you will often lose whatever you had gained. It is common to see drivers pull too hard on the wheel here and you see the chassis leave the curbing sideways which scrubs off speed. Be smooth on the wheel.

Types of curbs:

a. Rounded

This is the king of curbs and the type most of us picture in our minds. Usually they have a steady rounded surface all the way to the top. This makes for a steady mount when you first hit them and a smooth dismount.

b. Flat top

These usually have an abrupt rise, a chamfered or rounded edge with a flat, smooth or a dimpled top. Better for cutting distance than shifting weight, they can still be useful.

c. Rumble Strips

Little bumps or dimples placed a few inches apart and an inch or more deep into a curb. Usually relegated to the exit of corners, these annoying things sometimes end up at the apex of corners. They don’t help you like a proper curb and can sometimes hurt you. Usually they just allow you to cut the corner a bit. Run over them if you can to shorten your corner, but don’t expect much help from them. Avoid them if your suspension is fragile or if they upset your chassis.

The most important advice I can give you is to let the chassis work when using curbs. Don’t fight it or it will throw you off and scrub off speed. Hold the wheel really tightly but keep your arms loose. It may sound weird in your head right now but as you get better at this you will understand exactly what I mean.

A final note. Remember that you can bottom out your chassis and grind off suspension parts over time so inspect your chassis regularly if you use a lot of curbs, even if it is only in one corner on the track. If you feel your machine bottom out anywhere, keep an eye on things.

Remember to have fun out there and thanks for reading.
Subscribe for new articles and follow on twitter at @oakmanonracing. If you have any questions or comments about this topic, or anything else, feel free to ask.

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Posted in: How to Race