Anti Squat or Anti Dive in rear wheel?

[Shangarsshnah]

Do we need to have a 100% anti squat or do we need to consider anti dive when designing rear wheel suspension geometry?

[MCoach]

http://cdn.memegenerator.net/instances/250x250/23591999.jpg

[PatClarke]

Where are you Shangarsshnah? What college FSAE team do you represent?

Pat

[NickFavazzo]

Doesn't really matter where he/she is from.. But honestly Shangarsshnah, if there existed one universally correct and perfect answer would we give it to you without knowing you actually tried to understand and find it?

My suggestion, write down the goals and what specifically you want to achieve in your suspension package design, then learn and implement what is required.

[Shangarsshnah]

https://lh4.googleusercontent.com/-_7tJrefOXeY/UOnf_Jemd0I/AAAAAAAAAKw/B1bnx_i7BmQ/w497-h373/abc.png

For 100% anti sqaut
h/l = e/d

For anti dive
h/l (% Rear Brake) = e/d

I found this from Dr. Richard Hathaway, P.E. presentation.

In which I need to concentrate more...
Anti dive or anti squat?

Team Terasvin - 2013
India

[ThreeColours]

First of all you must read some important books, Shangarsshnah. For example: Race Car Vehicle Dynamics (Milliken & Milliken). Fundamentals of Vehicle Dynamics (T. D. Gillespie). Tune to Win (Carroll Smith)... the answers are there. Cheers

[Shangarsshnah]

Got the answer... Thanks....

[ThreeColours]

Do you have this books ??? If you have this books your problems are solved

[exFSAE]

I can never tell if these posts are real or not.

The answer is.. there is no answer. Take your pick, whatever you think is best. That's how design engineering works.

Might as well be asking whether you should paint your car blue or red.

[ThreeColours]

Always the answer is... ... read.

I'm starting to design my suspension. At first it is a frustrating process, but exciting !!! I didn't know how to start

Cheers

[PatClarke]

Originally posted by Shangarsshnah:
Got the answer... Thanks....

That's great Shangarsshnah!
Now, can you tell us where your centre of mass is, where the pitch centre is, what wheelbase you have chosen, your driveline geometry and all the other little details you needed to 'Get the answer'?

Pat

Pat

[Shangarsshnah]

If we set the geometry for zero pitch angle will the load transfer increase the normal load on the rear wheels?
In 100% anti squat vehicles spring deflection is avoided only to increase the CG of the vehicle thereby increasing the weight transfer or the spring deflection is avoided for any other reasons?

[MCoach]

Anti-squat and anti-dive put more load into the control arms. That is one other thing to consider.

[Warpspeed]

Originally posted by Shangarsshnah:
If we set the geometry for zero pitch angle will the load transfer increase the normal load on the rear wheels?
In 100% anti squat vehicles spring deflection is avoided only to increase the CG of the vehicle thereby increasing the weight transfer or the spring deflection is avoided for any other reasons?
The weight transfer under braking does not really change with or without antidive, at least to the extent that the CG height does not change.

Actually the CG height can, and often does, change a just a little bit, but the overall effect is usually quite small.

The main reason for using some antidive, is to limit excessive suspension travel under braking. That can cause some problems depending how much travel there is available, and perhaps reduce other bad effects such as steep camber curves or sudden changes to the track width (scrub).

It's all a compromise, where you may feel adding some proportion of antidive at either or both ends may be a solution to some other problem or limitation.
It's just one more chassis tuning tool you may or may not decide to use.

[Shangarsshnah]

That means in zero pitch angle most of the loads are transferred through suspension?

[NickFavazzo]

Maybe try think of anti dive and such as %bias to Elastic Long Load Transfer and Geometric Long Load Transfer. Anti dive will cause "some" % of the force to be transferred through the wishbones and not the springs. All that is true for Front view kinematic analysis still holds for side view. ie centres and Roll (pitch) centres

[Warpspeed]

Originally posted by Shangarsshnah:
That means in zero pitch angle most of the loads are transferred through suspension?
Yes.
Dynamic tire/wheel loads hardly change.
All that happens is suspension movement due to pitching is reduced.

[Spetsnazos]

check out tune to win, he covers anti squat and anti dive pretty well...