Pitch angles of race cars under acceleration and braking

[MadMatt]

I was wondering what are typical pitch angles under acceleration and braking of race cars (F1, GTs, prototypes, etc.).

[Jersey Tom]

Less than 90 degrees.

I feel like that's a pretty broad question. I wouldn't even know how to answer it. And pitch... including static? From inspection? What exactly is it you're after and why? To what accuracy?

I'll go out on a limb and say "probably pretty small" given how critical it is maintaining a stable platform for aero.

[Greg Locock]

For production cars it is typically less than 4 degrees per g, so with the low cg and stiff suspension of F1 cars, I'm guessing very little indeed.

[MadMatt]

As I said, it is pitch under braking and acceleration, so dynamic pitch or whatever you call it. As Greg mentioned, it is given in °/g. I know F1 cars have anti-squat and dive systems but there must be some data available isn't it? If not F1 then lower categories.

[Tim.Wright]

Do you mean body to ground pitch (which includes tyre deflection)? Or pitch just from the suspension? The tyre is often more than half of the total movement because the suspension is pretty stiff. But it depends a lot on the anti setup.

Often pretty unsymmetrical too front/rear because of the anti-x setup.

From memory a GTE car might pitch in the order of couple of degrees.

What do you need the info for?

[MadMatt]

Body pitch, sorry I forgot to mention (thought it was implicit). What I want it how the attitude of a race car changes under braking and acceleration. What typical values are seen in the different series. I know it depends on suspension stiffness, tyres, car, etc. It is just a matter of using the suspension travel sensors and few maths channels to create this value so assuming the amount of data floating around the web on different race cars, someone would have done that already.

[Tim.Wright]

Body pitch, sorry I forgot to mention (thought it was implicit). What I want it how the attitude of a race car changes under braking and acceleration. What typical values are seen in the different series. I know it depends on suspension stiffness, tyres, car, etc. It is just a matter of using the suspension travel sensors and few maths channels to create this value so assuming the amount of data floating around the web on different race cars, someone would have done that already.

Thing is, if you use suspension travel travel sensors you are not taking into account the tyre deflection so its not the body to ground angle but rather the suspension contribution to that total angle.

If you are lucky you can try to find someone on a team who has laser sensors on the car. This will give you the answer you are looking for.

[MadMatt]

Body pitch, sorry I forgot to mention (thought it was implicit). What I want it how the attitude of a race car changes under braking and acceleration. What typical values are seen in the different series. I know it depends on suspension stiffness, tyres, car, etc. It is just a matter of using the suspension travel sensors and few maths channels to create this value so assuming the amount of data floating around the web on different race cars, someone would have done that already.

Thing is, if you use suspension travel travel sensors you are not taking into account the tyre deflection so its not the body to ground angle but rather the suspension contribution to that total angle.

If you are lucky you can try to find someone on a team who has laser sensors on the car. This will give you the answer you are looking for.

You are right but is tyre deflection that big? Depends on the tyres of course, but I would imagine it is not that great. Correct me if I am wrong!

[bigpat]

Not much at all!
An F1 car will actually rise under braking as the speed, and hence downforce wash off, and unload the suspension. Instantaneous pitch upon application of the brakes would be minimal suspension wise, mainly in tyre squash.

I would think same under acceleration, only compression would be as the downforce increases. Even though F1 suspensions are more supple than year gone by, they are still quite stiffly sprung in relation to their total weight....

[Tim.Wright]

You are right but is tyre deflection that big? Depends on the tyres of course, but I would imagine it is not that great. Correct me if I am wrong!

On a road car its almost negligible.

On a race car absolutely not. For a very sporty road car it will be responsible for about 30-50% of the total body movement. In F1 (with very tall sidewalls and rock hard suspension in pitch) I would guess that its in the region of 70-80% of the total body movement in pitch.

[gixxer_drew]

Body pitch, sorry I forgot to mention (thought it was implicit). What I want it how the attitude of a race car changes under braking and acceleration. What typical values are seen in the different series. I know it depends on suspension stiffness, tyres, car, etc. It is just a matter of using the suspension travel sensors and few maths channels to create this value so assuming the amount of data floating around the web on different race cars, someone would have done that already.

Thing is, if you use suspension travel travel sensors you are not taking into account the tyre deflection so its not the body to ground angle but rather the suspension contribution to that total angle.

If you are lucky you can try to find someone on a team who has laser sensors on the car. This will give you the answer you are looking for.

Lasers for ride height are usually part of the standard sensor package, usually this is what is used for aero along with strain gauges. During initial aero testing I put lasers in the uprights if possible but they dont last long there. So I get a baseline on tire deflection and dont equip them during normal season. Budgets may vary though... It can be a pretty significant value depending on how low you are allowed to run. To be honest its usually not too far off from what you can work out in a tire spring rate test. Best to build your own rig for that sort of testing for more reasons than I can count. Some races and some cars can come down to a one millimeter delta being win or lose.

[olefud]

I suspect that a tensioned cable in series with a scale attached to the car at CoG height would provide an accurate answer with a dialed in protractor, i.e. zeroed with no applied load. The car wouldn’t know that the force was generated by a Come Along rather than accelerating the mass. Of course you would have to have track acceleration values to replicate.

With scales it should also yield weight transfer.

[Lycoming]

Less than 90 degrees.

Ideally, yes.



Also, if you needed more evidence as to why tire deflection isn't negligible on racecars, have a look at this:

http://www.youtube.com/watch?v=8gFmU3Fba48

Not quite an F1 car, but an aero heavy, stiffly spring car that pulls several Gs in corners.