Downforce on bikes

[camthepyro]

How do you get in that thing?

[Sev]

Looks like the top flips up, I want to know how you stop without falling over.

[The Grinch]

Those indy cars generate so much HP that if they didn't have those aerodynamics the cars would be impossible to drive forwards, you'd just spin the tires until they exploded. With the design that they do have the cars just literally suck themselves into the ground and away they go.

How do you explain how these cars accelerate from a stop (such as from a pit stop)? There's no forward velocity at this point, therefore no downforce. Why doesn't the car just spin its wheels?

[Sev]

Because you don't use all of your HP/Torque from a dead stop, a clutch can be slightly slipped meaning you aren't putting all of the cars force to the pavement at once. You can spin the back tires on a car by revving high and dumping the clutch, but if you let it out smoothly and slowly you'll get underway.

The faster the indy car is going, the more it gets pushed into the ground. The more it gets pushed into the ground the more power it can transfer into the wheels.


Go back and take a look at that video posted a while back where Honda races one of their Indy cars, a CBR1000RR and a power boat. At the end he breaks the wheels loose in a half second to do some victory donuts.

Just because you CAN do something doesn't mean you're GOING to.


Then again, I should have explained it better and said that the cars wouldn't be able to get to the speeds they do, or use all the energy of thier engines because it'd just spin the tires.

Sorry.

[pseudopod]

I notice that bike manufacturers don't seem to make an issue out of downforce at all, especially in comparison with race cars, which throw so much wind upward that they can ride on a level, upside-down track and not fall off.

Why is there this discrepancy?

The reason you don't want downforce on a bike is because of how it leans when it turns. A spoiler would work great when you are going straight, but once you lean into a turn the spoiler would no longer be pointing at the ground, but at an angle. So it would be pushing the bike at an angle. This isn't good because even though the bike is leaned over, the contact patch is still directly below the tires (now on the side of the tires) and so the "downforce" would actually decrease your traction through turns.