Antisquat geometry

[Big Pablo]

Hello,
looking at pics on the web, it seems that the most common srategy to achieve antisquat in the rear suspensions is to create an angle between suspensions mounts line and ground so that the bottom mount is lower than the forward mount.

Well, I've seen this applied on the upper arm (Audi R8) or on the lower arm (Dodge Viper), while the other arm remains almost parallel ti the ground.

What are pro and cons of each design ?

Is it correct to say that in first case (Audi R8) the caster angle increases under suspension pressure while in the second case (Dodge Viper) the caster decreases ?

I hope that it make sense....

[Big Pablo]

Hello,
looking at pics on the web, it seems that the most common srategy to achieve antisquat in the rear suspensions is to create an angle between suspensions mounts line and ground so that the bottom mount is lower than the forward mount.

Well, I've seen this applied on the upper arm (Audi R8) or on the lower arm (Dodge Viper), while the other arm remains almost parallel ti the ground.

What are pro and cons of each design ?

Is it correct to say that in first case (Audi R8) the caster angle increases under suspension pressure while in the second case (Dodge Viper) the caster decreases ?

I hope that it make sense....

[OspreysGoSWOOP]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:
Hello,
looking at pics on the web, it seems that the most common srategy to achieve antisquat in the rear suspensions is to create an angle between suspensions mounts line and ground so that the bottom mount is lower than the forward mount.

Well, I've seen this applied on the upper arm (Audi R8) or on the lower arm (Dodge Viper), while the other arm remains almost parallel ti the ground.

What are pro and cons of each design ?

Is it correct to say that in first case (Audi R8) the caster angle increases under suspension pressure while in the second case (Dodge Viper) the caster decreases ?

I hope that it make sense.... </div></BLOCKQUOTE>

I'm probably not qualified to answer this question, so take my response with a grain of salt. There are much smarter people on here that might chime in.

Your anti is determined by your inboard points. Changing them affects your pitch axis.

Whether it increases or decreases caster depends on your outboard points...I think.

Also, you need to clearly define what 'suspension pressure' is.

Your vehicle can experience roll, have/jounce, and steer.

Each of these three motions will affect your suspension in different ways.

Read Chpt 17 in RCVD for a more thorough explanation.

[woodsy96]

As far as I know (like Osprey's, people on here know more than me) one of the main differences is your pitch centre. Imagine the effect on your roll centre if your wishbones in the front view had your upper arms parallel to the ground and your lower arms where pointed upwards towards the centre of the car.

On our 2010 car we kept all of our inboard points of the lower arms parallel to the ground, mainly for simplicity of design. Then we tipped the front upper arm backwards to give anti squat and the rear upper arms forward to achieve our desired pitch centre location (longitudinally and height). Obviously this is not an ideal solution but was practical and achieved much of our desired goals - we had a lot of other things to test that had a much bigger effect than pitch centre height /anti dive/ anti-squat.

The other effect of doing it "Dodge Viper" styles is the change in wheelbase with ride/pitch - kinda like the pitch equivalent of scrub.