# Automobile wheel forces?

I am trying to understand all of the forces involved in a vehicles wheel, The weight of the auto on the wheel downward would be radial load, and the force 90 degrees from that would be the thrust load directly perpindicular with the wheel. What I learned is that there is an equal reacting force in the direction of each force so all of the forces should cancel out.

But you also have the tire, which is not rigid and is often described as a ring of short compression springs each tire having a different spring coefficient. And most of the rolling friction is from the tire I am assuming, and also assuming that the friciton in the hub and bearings in negligible unless it is all wheel drive where it is connected to the drivetrain.

I just wanted to check and see if I am missing something, and generally what is creating the motion when on a negative inclination where the vehicle is free rolling downhill essentially. Gravity is the dominant force, however is there anything else.

Any suggestions would be appreciated

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that was some great information. I was hoping that you could confirm some of my suggested forces in the instance of using a FBD of the wheel. I am interested in what forces are exactly interacting on the bearings, tires, axle, wheel. Also what is FE?

Thanks fo the help.

Ranger Mike
Gold Member
see my posts titled Race car Physics and race car suspension class Sep12-09 10:51 AM i posted last year

FE = fuel economy

Going from memory, the bearing drag coefficient should be about .007 but the seal drag associated with any lubricated part can add up to 1/3 more depending.

I'm not quite sure what else you're after. Most of the time the road drag is a lump sum rather than split into individual parts.

Ranger Mike
I found race car suspension class, but never found race car physics.

Mender
What is the tractive energy, and below it gives energy uses for city and highway and composite. What is the composite cycle?

I was also looking for a response in reference to the physical forces within the wheel, with no influence related to suspension, essentially a rigid mass on the wheel. Looking for a possible diagram of a wheel/axle cross section, and maybe a very detailed Free body diagram.

If I'm not being clear please let me know.

thanks

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