Handling Diagnostics.

Here is a quick handling diagnostics run through for common handling problems, hopefully it will allow you to pin point any problems and help you maximise your performance suspension set-up. I hope it helps.

 

 Table of Contents:

Instability Suspension Adjustments.

Problem:

Possible Causes:


General Straight Line Instability.


  • Too much toe-in or toe-out settings.

  • Rear toe-out static due to incorrect setting or dynamic due to bump steer setting.

  • Low rear down force levels and/ or too much front down force.

  • Broken chassis, suspension member or mounting point.

Straight Line Instability: Under Hard Acceleration.

  • Worn out or malfunctioning Limited Slip Differential.

  • Too little rear toe-out setting.

Straight Line Instability: Car Darts over Bumps.

  • Too much toe-in or toe-out setting.

  • Uneven front castor setting.

  • Uneven front shock forces or bump rubbers.

  • Front anti-roll bar set too stiff.

Instability Under Braking: Front end Darts or Wanders.

  • Too much front brake bias setting.

Instability Under Braking: Car feels like its going to spin.

  • Too much rear positive camber settings and/ or too much rear brake bias setting.

Understeer Suspension Adjustments.


Problem:

Possible Causes:


Corner Entry Understeer: Car Struggles to Turn In and is Progressively Worse.


  • Braking too hard and too late.

  • Insufficient front track width.

  • Too stiff front anti-roll bar setting.

  • Too soft front anti-roll bar setting.

  • Low front roll centre.

  • Too low front bump setting.

  • Low front down force.

  • Too much positive front camber on outside wheel.

Corner Entry Understeer: Car Turn In Good, then Progressively Washes Out.

  • Too much front toe-in setting.

  • Low front down force.

  • Low front camber roll compensation.

  • Non linear load transfer, due to roll axis inclination.

  • Low front bump or rebound setting.

Corner Entry Understeer: C

Car Turn In Good, then Darts.

  • Low front bump or rebound setting.

  • Too high front down force levels-

Corner Exit Understeer: Slow Corners.

  • Excessive corner entry speeds.

  • Mid corner throttle application, with understeer present and steering lock applied.

  • Adjust driving style to improve throttle application and response.

  • Too hight front rebound setting.

  • Reduce rear anti-squat setting if present.

Oversteer Suspension Adjustments.

 

Problem:

Possible Causes:


Corner Entry Oversteer.


  • Broken or locked front anti-roll bar or rear outside shock.

  • Interference to rear suspension travel.

  • Too stiff rear anti-roll bar or spring rating.

  • Loss of rear down force.

  • Too much rear toe-in and/or rebound.

  • Carrying too much speed into the corner, or lift off oversteer.

Corner Exit Oversteer: Progressively Increasing on Throttle Application.

  • Damaged limited slip differential.

  • Too soft rear anti-roll bar, spring or shock rating.

  • Low rear down force levels.

  • Low rear toe-in setting.

  • Too much rear camber setting.

  • Too stiff anti-roll bar.

Corner Exit Oversteer: Car takes its Set and suddenly breaks loose.

  • Too much throttle application.

  • Sudden rear outside tyre camber change.

  • Lack of rear suspension travel.

  • Damaged rear shock.

  • Too much rear bump setting.

 Suspension Geometry Adjustments.

 

Problem:

Possible Causes:


Too High Front Roll Centre and Too Low Rear Setting.


  • Increased rear load transfer resulting in increased oversteer.

  • Non linear chassis roll and load transfer.

  • Roll axis out of parallel with mass centroid axis.

Too Low Front Roll Centre and Too High Rear Setting.

  • Increased front load transfer resulting in increased understeer.

  • Non linear chassis roll and load transfer.

  • Roll axis out of parallel with mass centroid axis.

  • Possible three wheeled motoring on corner exit.

Too Narrow Front Track Width Compared to Rear Track Width.

  • Increased understeer in slow and medium corner turn in.

  • Increased front track required.

 Ride and Roll Rates Suspension Adjustments.

 

Problem:

Possible Causes:


Too Much Spring Rate: General.


  • Harsh and choppy ride, hard to put power down on corner exit.

  • Sliding and excessive wheel spin on corner exits.

Too Much Spring Rate: Front.

  • Turn in understeer, but car may point to apex well.

  • Front tyres locks on bumps and may break away.

Too Much Spring Rate: Rear.

  • Excessive wheel spin.

  • Oversteer on corner exit.

Too Little Spring Rate: General.

  • Car prone to bottom out on race track.

  • Excessive vertical chassis movement.

  • Floating ride feel.

  • Unresponsive feel.

  • Car may take multiple sets to settle.

Too Little Spring Rate: Front.

  • Bottom out under braking loads.

  • Car rolls excessively during corners.

  • Understeer on turn in.

Too Little Spring Rate: Rear.

  • Acceleration squat and increased negative camber.

  • Power oversteer tendencies on throttle application.

Too Much Anti-Roll Bar: General.

  • Lack of feel with sudden response.

  • Prone to slide or skate rather then taking a set.

  • Darting over one wheel or diagonal bumps.

Too Much Anti-Roll Bar: Front.

  • Increased oversteer tendencies.

Too Much Anti-Roll Bar: Rear.

  • Increased corner exit oversteer, hard to put power down with excessive sliding.

Shock Absorber Forces Suspension Adjustments.

Problem:

Possible Causes:


To Much Shock: Overall.


  • Car does not absorbed road irregularities, but crashes over them.

  • Harsh ride with a lots of sliding and sudden changes to ride.

To Much Rebound Setting.

  • Wheel can not keep up with road surface changes.

  • Inside cornering wheel could be pulled of road by shock.

  • Car could become jacked down in long corners (lowered ride height)

To Much Bump Setting

  • Initial bump reaction harsh.

  • Slow chassis roll.

  • Car may jack up in long corners (higher ride height).

Too Little Shock: Overall.

  • Floating ride feel.

  • Car will oscillate after bumps (bounce along the road).

  • Slow and sloppy response.

  • Quickly develops chassis roll.

Too Little Rebound Setting.

  • Car will oscillate after bumps (bounce along the road).

  • Hard to put down power.

Too Little Bump Setting

  • Soft bump reaction.

  • Car prone to dive or squats, lots of longitudinal weight transfer.

  • Lots of car roll, inside front on turn in and outside rear on exit could fall over.

Damaged shock on one corner.

  • Hard to identify and isolate.

  • If at rear, increased power oversteer and if at front increased understeer in one direction.

 

Response Suspension Adjustments.

Problem:

Possible Causes:


Car Feels Heavy and Unresponsive.


  • Too much downforce.

Car feels soppy and rolls a lot and is slow to settle in corners.

  • Too little damping settings on suspension.

  • Too soft anti-roll bar settings (roll resistance) or ride rate.

Car Feels on Edge, Responds too quickly to Inputs with Lack of Feel and wants to Slide all the time.

  • Low down force settings.

  • Too stiff anti-roll bar settings (roll resistance) or ride rate.

  • High shock setting.

  • High tyre pressure.

 

Tyres /Tires Suspension Adjustments.

 

Problem:

Effect:



Too Much Tyre Pressure.

  • Harsher ride, especially over bumps.

  • High temperature in the centre of the tyre.

  • Increased tyre wear on centre of tyre.

  • Sliding and wheel spin.

Too Little Tyre Pressure.

  • Soft ride.

  • Unresponsive steering.

  • Higher tyre temperature at inside and outside edges.

  • Increase wear rates at inside and outside of tyre.

  • Reduced overall traction, due to decrease in tyre foot print.

Front Tyres Losing traction.

  • Increased understeer tendencies.

  • More oversteer needs to be dialled in to the handling balance.

  • Anti-roll bar or suspension adjustments needed.

Rear Tyres Losing traction.

  • Increased oversteer tendencies.

  • More understeer needs to be dialled in to the handling balance.

  • Anti-roll bar or suspension adjustments needed.

Wheel Alignment Suspension Adjustments.

Problem:

Possible Causes:


Too Much Toe-In: Front.


  • Car darts over bumps during braking loads and corner entry.

  • Hard to turn in on corner entry, if extreme will turn in then wash out.

Too Much Toe-Out: Front.

  • Car wanders under braking.

  • Unstable in straight lines.

  • Reacts to wind gusts, one wheel or diagonal bumps.

Too Much Toe-In: Rear.

  • Rear end unstable and light on corner entry.

Too Little Toe-In: Rear.

  • Power oversteer on corner exit.

Toe 0ut: Rear.

  • Straight line instability.

  • Power oversteer on corner exit.

Too Much Wheel Castor: Front.

  • Excessive steering effort required.

  • Too much self return action.

  • Transmittal of road shocks to steering wheel.

Too Little Wheel Castor: Front.

  • Car sensitive to steering effort.

  • Lack of steering feel.

  • Self return action and feedback reduced.

Uneven Wheel Castor: Front.

  • Bias steering response on one side.

  • Car prone to swerve on higher castor setting side, on a straight line.


Too Much Negative Camber.

  • Increased inside tyre wear.

  • Increased heat on inside of tyre.

  • Reduced front braking capacity.

  • Reduced rear acceleration capacity.


Too Much Positive Camber: Front.

  • Increased understeer after turn in on cornering.

Too Much Positive Camber: Rear.

  • Increased outside tyre wear.

  • Increased heat on outside of tyre.

  • If extreme could cause turn in response instability.

  • Increased corner exit oversteer.

Too Much toe-in in bump: Front.

  • Increased understeer on corner turn in.

  • Car darts over bumps.

Too Much toe-out in bump: Front.

  • Increase understeer after turn in on corner entry.

  • Car wanders under braking.

  • Car may dart over one wheel bumps or gusts of wind.

Too Much toe-in in bump: Rear.

  • Darting on throttle application on corner exits.

  • Roll understeer on corner turn in.

  • Rear end instability on corner turn in.

Too Much toe-out in bump: Rear.

  • Increased oversteer on power application.

  • Similar to static toe-out, to a lesser degree.

 

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