7 Post Shaker Rig vs. K&C Rig

What is a Shaker Rig (or 7 Post)?

A shaker rig (or 7 post rig) is a type of suspension test machine that applies vertical loads to the vehicle at a high frequencies in order to analyze vehicle response, typically across a specific road or track profile.

How Is a 7 Post Shaker Rig Used?

For racing applications, 7 post shaker rigs are used primarily for tuning suspension dampers. The typical goals are to minimize contact patch load variation over known road/track profiles, and improve vehicle pitch behavior for improved aerodynamics. Since shaker rigs apply only vertical loads (no braking, cornering, or tractive loads), they cannot measure the jacking force effects resulting from roll centers, anti-dive, and anti-squat characteristics. Further, no measurement is made of toe, camber, or wheel center motion, so suspension geometry and stiffness characteristics cannot be evaluated.

Shaker Rig Testing vs. K&C Testing

K&C testing is used to tune the vast majority of a vehicle’s dynamic fingerprint. A K&C rig doesn’t “shake” cars or report results in the frequency domain and the results are not difficult to understand. 

K&C rigs are used for tuning everything else in the suspension, beyond the dampers. The typical goals are to optimize the loaded and unloaded suspension geometry over known road/track profiles, and maximize the mechanical grip of each tire by optimizing longitudinal and lateral weight transfer.

Shaker Testing AND K&C Testing

K&C testing and 7-post testing actually complement each other in many ways because K&C tests capture information that is not available from shaker rig testing.

 

K&C and 7-post testing can be used together to create comprehensive tuning maps for a vehicle suspension, particularly for pitch and aerodynamic stability. Be cautioned, however: 7-post rigs cannot introduce cornering or braking/tractive loads. Without the inclusion of jacking forces, 7-post rig-tested tire loads will not be correct. (This is discussed in more detail and illustrated with some examples on the page comparing K&C vs. Pull-Down rigs.

What is a Shaker Rig (or 7 Post)?

A shaker rig (or 7 post rig) is a type of suspension test machine that applies vertical loads to the vehicle at a high frequencies in order to analyze vehicle response, typically across a specific road or track profile.

How Is a 7 Post Shaker Rig Used?

For racing applications, 7 post shaker rigs are used primarily for tuning suspension dampers. The typical goals are to minimize contact patch load variation over known road/track profiles, and improve vehicle pitch behavior for improved aerodynamics. Since shaker rigs apply only vertical loads (no braking, cornering, or tractive loads), they cannot measure the jacking force effects resulting from roll centers, anti-dive, and anti-squat characteristics. Further, no measurement is made of toe, camber, or wheel center motion, so suspension geometry and stiffness characteristics cannot be evaluated.

Shaker Rig Testing vs. K&C Testing

K&C testing is used to tune the vast majority of a vehicle’s dynamic fingerprint. A K&C rig doesn’t “shake” cars or report results in the frequency domain and the results are not difficult to understand. 

K&C rigs are used for tuning everything else in the suspension, beyond the dampers. The typical goals are to optimize the loaded and unloaded suspension geometry over known road/track profiles, and maximize the mechanical grip of each tire by optimizing longitudinal and lateral weight transfer.

Shaker Testing AND K&C Testing

K&C testing and 7-post testing actually complement each other in many ways because K&C tests capture information that is not available from shaker rig testing.

Key Suspension Items	K&C	7-post
Apply braking, cornering, and traction forces at all tires	Yes!	No
Simulate true trim with steer, tire loads, roll, pitch, & heave	Yes!	No
Measure ride and roll rates with scrub relief	Yes!	No
Find roll center heights, instant centers, and jacking ratios	Yes!	No
Measure toe, camber, and caster (geometry and stiffness)	Yes!	No
Locate center of pressure for each tire contact patch	Yes!	No
Identify Ackermann and loaded steering geometry	Yes!	No
Measure steering system friction & stiffness characteristics	Yes!	No
Measure suspension friction levels	Yes!	No
Measure local chassis deflections from real tire loads	Yes!	No

K&C and 7-post testing can be used together to create comprehensive tuning maps for a vehicle suspension, particularly for pitch and aerodynamic stability. Be cautioned, however: 7-post rigs cannot introduce cornering or braking/tractive loads. Without the inclusion of jacking forces, 7-post rig-tested tire loads will not be correct. (This is discussed in more detail and illustrated with some examples on the page comparing K&C vs. Pull-Down rigs.