Why the heck does additional grip make a racing car go faster?

Factual Questions
1

Okay. So they constantly mention in the Champ Car series and F1 that the additional grip and power in the Champ Car gives it a speed edge over its F1 counterparts.

Additional grip (such as that produced by the revolutionary Ground Effex cars of the mid-80’s) is associated with higher levels of speed and (obviously) better turning and handling.

But I don’t get it about the speed. Wouldn’t it be the less grip a car has, the faster it will go (because theoretically it is less “glued” to the track)? Why the heck does the extra grip make it go faster?

I’m just talking about pure straight-line speed here, and irrespective of the handling.

2

I don’t think additional downforce DOES make the cars go faster in a straight line… but it DOES allow them to use more of the straightaway for acceleration before they have to brake.
My car goes a lot faster after accelerating for 1400 feet than it does after accelerating for 1200 feet… at least it would if it wasn’t an Oldsmobile.

Can you provide a URL linking to a discussion of the type you are commenting on?

3

The downforce doesn’t help a car go faster in a straight line. It helps the car go faster around a turn, by increasing the amount of force that car can apply to the ground in the process of turning. It will also help the car accelerate faster when coming out of a turn into a straight section.

4

Having better traction allows more of the engine’s output to be applied to moving the car than would be the case if the tires slipped on the ground, and wasted some engine output.

5

You can’t take it out of the context of handling and non-straight courses. Only dragsters go in straight lines, and while downforce is an issue with them, it is less so than other types of cars.

More downforce means the cars stick better to the road. Sticking better to the road means the cars have to slow down less when the manuever around corners.

A similar phenomenon is experienced on NASCAR Super-speedways, with very steeply banked corners. The cars slow down a LOT less when they are held on to the road by downforce, be it generated by body shape or track shape.

6

From what I’ve seen, generally, when racing folks speak of grip they’re talking about the downforce generated by the front and rear wings and the undertray. The more downforce, the more ‘grip’ a car has. Downforce on the wings essentially adds weight to the car as speed increases, and the undertray creates a low-pressure area beneath the car, enhancing the high-pressure on the upper surfaces. But this really only makes the car faster when it comes to turns and braking. A car with more downforce can carry more speed into and through a turn, and can get back into the throttle earlier, than an equivalent car with less downforce. This equates to the most commonly thought of idea of grip. I know that’s not you’re ultimate question, but it sets the background. Regarding straight-line speed, downforce is pretty nearly the ultimate enemy, causing excess drag that slows the car in the straights. So, as I understand it, yes, the less “glued” to the track a car is, the faster it can go in a straight line … to an extent. If the car is sufficiently powerful enough, it is possible for a car with little downforce to lose traction due to less weight over the driving wheels. Drag racers (the ultimate straight-line speedsters) use wings to keep the rear planted firmly so they maintain maximum traction. Lost traction=lost race. I don’t know horsepower figures for Champ Cars, but it is most likely that their additional grip over F1 cars is overcome by the additional horsepower, not the grip exclusively. So, essentially their higher speed is achieved by more power. The additional grip is just to ensure they keep that power where it’s needed most … on the ground.

7

Well, it looks like a bunch of other people have explained much of this while I was writing, but here’s my two cents.

Race cars (the kinds you mention) have two types of “grip:” the tires’ grip and aerodynamic downforce created by wings and the car’s underbody, which has special venturi tunnels that create low pressure zones to suck the car down to the track. Ground effects methods were not unique to cars of the 1980s, but are essential to today’s open-wheel series. The techniques used are extremely sophisticated and in many cases are closely guarded secrets.

I’m assuming tire grip is a clear enough concept not to require explanation, and that your question was directed mostly at the cars’ aero features.

On superspeedways (e.g. Indianapolis, Fontana, etc.) which have long straights, teams do indeed reduce downforce, since moving in a straight line does not require much grip and downforce there only slows the car. At these tracks, banking in the turns helps make up for some of that lost grip.

But on road courses (twisty turny tracks, not ovals), downforce allows a car to go faster through curves and turns than the tires’ unassisted grip would permit. The higher ratio of curved track to straight track makes the trade-off between power and downforce worth it. In other words, they may be a little slower on the straights, but they’re faster overall, which is what counts.

An often cited, but still fascinating, fact is that Champ Cars have so much downforce that over 100 mph (and they can go almost 2.5 times that fast) they generate more downforce than their own weight. This means that they could theoretically run upside down “on the ceiling” at that speed. I really wish someone could arrange a real world demo of that.

BTW, I think you’re wrong about Champ Cars beating F1. When the Champ Cars ran in Montreal last year, it was the first time in decades that both series had run the same track. The F1 cars were about 5 seconds faster. The F1 cars have about 100 more horsepower, weigh 250 pounds less, and are permitted to use traction control and launch control.

I gotta run. There’s an Indy Racing League race on tonight.

8

aack! nix the “not the grip exclusively” bit near the end of my post.

Redundant, redundant, redundant.

I’m not all with-it today.

9

Short answer to the OP: it doesn’t, and nobody claims it does.

People who want to drive a car as fast as possible are trying to achieve the optimum balance between two conficting factors: speed and control.

Making sure that the car has good grip is one aspect of trying to make sure the driver can control it at all times, especially when cornering or performing manoevres other than just driving in a straight line.

They do other things to try and make sure the car can achieve as great a speed as possible (e.g. making the car as light as possible, generating as much power from the engine as possible).

10

To answer to OP, increased grip can increase straightline speed because it reduces wheelspin when during acceleration. That said, all wings induce drag, so in general, you’d only want enough downforce to reduce wheelspin, and not a bit more. Thats why dragsters only have tiny wings. An F1 car’s wings are not there to increase straighline speed, but rather to help with grip during braking and cornering.

A slight hijack:

Well you almost got your wish. In terms of downforce, the all time champion is the Chaparral 2J, a Can-Am car from 1970. The 2J was essentially a hovercraft in reverse. It had a snowmobile engine and two fans mounted to the rear of the car. The sides of the car had movable lexan panels along the bottom that rode up and down with the contour of the road. With the fans running, this car could generate nearly 1000 lbs of suction force sitting still. In essence, it would have been possible in theory to park this car on the ceiling. At the time, one of the sponsors planned a television commercial with the car parked over the heads of the drivers. This idea was shelved for obvious safety reasons.

Until this year, F1 cars have had about 100 fewer horespower than Champ cars, not more. The F1 cars not only weigh dramatically less, but their brakes are worlds better, which is what makes them faster than Champ cars, not horsepower.

11

I remember my applied maths teacher asking what force causes the forward motion in a car. We duly resolve the forces in all directions and we have, neglecting air resistance, friction alone acting in the direction of motion. So that’s why increased grip is important.

12

What Andy said is true, neglecting air resistance. However, since F1 and Champ cars race in air, air resistance cannot be neglected.

Racekarl, didn’t Gordon Murray design an F1 car with an engine-driven fan on the back to suck air out from underneath? I recall reading something about that a month or two ago (probably in Formula 1 magazine, if I had to guess). How would its stationary downforce compare to that of the Chapparral?

13

I hadn’t heard this before. Why would F1 brakes be so much better than Champ Cars’? Does the CART formula restrict brake technology?

Reminds be of the story I heard of a sports car driver who was accused of having a secret switch to turn off his brake lights during a race (thus allegedly giving him an advantage by misleading the other drivers). He said: “I never use the brakes. They just slow me down.”