Pit Box · Rear End

Where are we racing?

Track

Tracks and the car itself are edited on the front-end page. Both pages share the same saved setup for each track.

Rear geometry

Left

Right

Panhard / J-bar ht (in)

Bar type

Frame side

Trailing arm angle °

Arm length (in)

Third link angle °

Third link mount

Third link type / rate

Pinion angle °

Rear tires

Cold psi

Durometer

Circumf. (in)

Rear stagger: –

Wheel offset (in)

Stagger is right minus left. More stagger frees the car through the middle and off. Wheel offset moves the tire in or out on the hub.

Springs, rubbers, shocks

Spring (lb/in)

Rubbers

Shock comp. (clicks)

Shock reb. (clicks)

Spring mount

Rear sway bar

Weight, heights, gear

Weight (lb)

Rear percent: –

Ride ht (in)

Right minus left: –

Gear

Brake bias, front %

Rear notes

The run

Laps

Best lap (sec)

Session

Air °F

Track °F

Sky

Quick adjust, rear

The between-races levers on the back of the car. Each tap changes the sheet and goes in the log.

Panhard / J-barboth ends. Up = freer, down = tighter. Half a hole on a modified is a real change.

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Bar, left endraise the frame side to steer the housing on roll

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Bar, right end

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Third link anglemore angle = more anti-squat = more forward bite, tighter on throttle

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LR arm anglemore = more rear steer, freer through the middle

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RR arm anglemore = tighter off the corner

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RR rubberin = stiffer = freer off

LR rubberin = stiffer = freer on entry

LR reboundclicks. More holds cross weight in, more forward bite, frees entry

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LR compressionclicks. More frees entry, tightens exit

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RR reboundclicks. More = tighter off, holds the RR down

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RR compressionclicks. More = freer on entry

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RR airhalf pounds. Up = freer off

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LR airhalf pounds. Down = tighter on entry

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Brake biasfront %. More rear = looser under braking, turns in

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Stagger change (tire swap)

Rear tire temps (°F)

Inside is the edge toward the middle of the car. Right rear first.

Inside

Middle

Outside

Avg

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LR hot

RR hot

LR gain

RR gain

Pressure

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Front temps go on the front-end page. If you took them, put them there too; the balance call uses both.

What did the driver say about the back?

Under braking, into the corner

Middle, off the gas

On the throttle, off the corner

Forward bite

Late in the run

Driver notes

Run log

One log for the whole car. Front-end runs and rear-end runs both land here.

Show

Export and import live on the front-end page.

Wish list

Want the sheet to do something it does not? Tell us in one line and we try to have it for the next race. The button in the corner does the same thing from any page.

How this sheet was built

What it knows, where the numbers came from, what it assumes and how far to trust it. Read it here.

How the back of the car works

The panhard or J-bar holds the housing sideways and sets the rear roll center. Higher bar, higher roll center, less rear roll, the car frees up. Lower tightens. On a modified the bar is short, so every hole is a big step. Frame side higher than the pinion side steers the housing left as the car rolls, which helps it turn.

The third link sets anti-squat. More angle plants the rear on throttle and gives forward bite, at the cost of a car that can push off the corner. Moving the mount toward the left rear loads the left rear on throttle.

Trailing arm angle is rear steer. Arms angled up at the front make the housing steer left as the chassis rolls. More angle in the left rear frees the middle. More in the right rear tightens exit.

Stagger is the fastest rear change there is and the one you undo fastest, a tire swap. More frees, less tightens. Softer rear springs let you run less stagger and keep forward bite.

Shocks shape the transitions. Left-rear rebound holds cross weight in the car on throttle: more of it is forward bite and a freer entry. Left-rear compression frees entry and tightens exit. Right-rear rebound holds the right rear down off the corner.

Rear levers, quick reference

Complaint	Proper fix	Fast fix
Loose under braking	Bias toward the front, less LR arm angle, wedge in	Bias +1 front, bar down a quarter
Tight in the middle	Bar up, more LR arm angle, more stagger	Bar up a quarter, or a tire swap for stagger
Loose on throttle / spins	Less stagger, softer RR, more third-link angle, more LR rebound	RR rubber out, RR air down half, LR rebound +2
Tight on throttle / pushes up	More stagger, stiffer RR, less third-link angle	RR rubber in, RR air up half
No forward bite	More third-link angle, more LR rebound, softer springs with less stagger	LR rebound +2, third link +1°
Hops on throttle	Less third-link angle, check pinion angle and shock rebound split	Third link −1°
Loose late in the run	RR going off: pressure, durometer, softer RR	RR air down half for the feature

Generic asphalt tour-modified rules from JOES Racing's three-link and panhard lessons, the Harris modified manual, and Advanced Racing Suspension's asphalt modified shock notes. The chassis builder's sheet wins.

Rear End