..in relation to handling feel and dynamics? I ask this because I bit the bullet and lowered the rear height, evening out the stance with the front eliminating nearly any measurement of rake. ( front is lowered all the way on stock bolts )

Now shortly after I quickly noticed the "feel" of the car changed. It was less precise and turn in was less immediate. Now I plan to raise the rear back up again however I wanted to chime in and hopefully get some answers as to what or why I experienced what I did.

 

i feel with my car being lowered all the way on stock bolts that the car handles better on smooth roads but if it gets bumpy then with the suspension having less time to react i have lost some of the maneuverability.

 

I didn't notice a change. As far as the rake...if you're lowering only on stock bolts it doesnt make much of a difference imo.

 

I've lowered and raised my car before but only recently have I disregarded the rake that GM themselves recommend

 

 

Very important for any speeds over 80 mph. The rake helps hold the car to the ground. Bernoulli effect like sails on sail boats. high pressure above and low pressure below the car. The rake causes the low pressure air under the car to escape quickly in back of the car, helping to hold the car down to the road.

Lowering your car any more then 1" also needs to have a bump steer kit installed for proper steering and handling.

Slammed cars look cool as heck but hand poorly. and most guys dont even know.

 

very knowledgeable post.

 

 

In the book, "All Corvettes are Red", about the development of the C5, it states that the different tire sizes, and resulting rake, were chosen entirely for looks.

Although there was extensive wind tunnel testing done on the C5, I doubt that the slight rake has anything to do with aerodynamics or road holding. The smooth bottom and front air dams do negate lift at high speeds. Also the rear end has a lot to do with it.

GM managed the air flow over and under the car so as not to produce lift.

Now for the technical: Although Bernoulli's Principle can be used to calculate the lift force on an airfoil, for example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface then Bernoulli's principle implies that the pressure on the surfaces of the wing will be lower above than below. This pressure difference results in an upwards lift force. Whenever the distribution of speed past the top and bottom surfaces of a wing is known, the lift forces can be calculated (to a good approximation) using Bernoulli's equations—established by Bernoulli over a century before the first man-made wings were used for the purpose of flight. Bernoulli's principle does not explain why the air flows faster past the top of the wing and slower past the underside. To understand why, it is helpful to understand circulation, the Kutta condition, and the Kutta-Joukowski theorem. These explain how the shape of the Corvette's body manages the airflow so as not to produce lift.

 

an airfoil on an airplane doesnt have a flat ground 4 inches underneath it. bernoullis principle also states that fast air moving between two bodies creates lower pressure. thats why it "sucks" the car to the ground. air flows under the car at great speed causing low pressure. this is the whole reasoning behind a splitter. this effect is much stronger than that of the airfoil effect from the greater surface area over top of the car. if you are in a car with much looser suspension than a vette and sitting still, when a semi passes you at 60mph, your car rocks back and forth. this is because the low pressure between the semi and your car pulls your vehicle towards the semi. after it passes, the force is released, and your car rocks back and forth.

 

You should be fine - "BUT" I would suggest that you get a Corner Balance done so that it weighs the same on all corners and get a 4 wheel alignment then you will not have to worry about handling issues or uneven tire wear

Thanks,Matt

 

Very interesting stuff. I feel like I just sat through an engineering class. And to think ,this all started while talking about lowering a car...

 

and we have not even got into bumpsteer.

 

^^Pretty much agree with all that you said.

Rake comes into play because of aerodynamic forces.

Aerodynamic force increases with the square of speed. So even at speeds lower than 60 mph they can come into play.

Rake provides more frontal area for air to push down on, which is good for keeping the front of the car planted. As already stated it also lowers the front of the car which lets less air pass under the car and speeds it up thus lowering pressure.

 

The only bump-steer kit i found was on Westcoastcovette.com Any other options?

 

doesn't a change in rake also affect suspension geometry? ..
had mine aligned right after lowering.

 

I am about to lower my car some good information in this thread

 

Mine is lowered a bit and i have felt nothing that i'd consider an issue other than potholes and speed bumps the size of Mt Everest!

 

Yes

lowing the front first, no more then one inch, then lower the rear to match the one inch. Then raise the for the 1/4 to 3/8" rake.

next would be the alignment. which is a must after lowering. as you are correct about changing the suspension geometry when lowering.