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Suspension Geometry Calculator

2026-09-27 6 min

Alignment severity index and caster trail index from camber, caster and toe settings.

Alignment Index
2.00 pts
Caster Trail Index
1.20 in
Relative stability index

Calculator

Camber(deg) Help
deg

Negative = top tilted in

Caster(deg)
deg
Toe (Total)(deg) Help
deg

Positive = toe-in

Results update live as you type

Live statistics

Alignment Index

2.00 pts

Caster Trail Index

1.20 in

Relative stability index

Results

Optimal

Alignment Index

2.00pts

Caster Trail Index

1.20in

Relative stability index

Planning estimate from standard automotive formulas. Validate with dyno, timeslip or datalog data when precision matters.

Visualizations

Results overview

2Alignment Index
1.2Caster Trail Index

Alignment Index

2pts
010

Formula

Toe weighted 5x because small toe errors eat tires fastest; caster scaled to a trail proxy.

Index = |camber| + |toe| x 5; trail = caster x 0.3

Alternative Form

Indexes for comparing setups, not absolute geometry

Variables

SymbolNameUnitDescription
camberCamberdegTire lean vs vertical
toeTotal toedegTire point-in vs straight

Explanation

Toe dominates tire wear per degree, camber dominates cornering grip — the index keeps both visible in one number.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Record the inputs.

Camber:-1.5 deg
Caster:4 deg
Toe (Total):0.1 deg
Result: 3 inputs ready
Step 2

Apply the formula.

Index = |camber| + |toe| x 5; trail = caster x 0.3
Result: Primary result = 2.00 pts
Step 3

Read every derived output.

Alignment Index:2.00 pts
Caster Trail Index:1.20 in
Result: Alignment Index = 2.00 pts
Final Answer
2.00

Worked Examples

See how the calculator works with different scenarios.

Scenario

Sporty street alignment.

Inputs

Camber:-1.5 deg
Caster:4 deg
Toe:0.1 deg

Calculation

1.5 + 0.5 = 2.0; trail = 1.2 in

Result

Index 2.0, trail 1.2 in.

Interpretation

Mild track-street setup; raise toe weight concern if wear appears.

Understanding Your Result

Your Result: Alignment Index: 2.00 pts

What This Means

Relative scores summarizing alignment aggression and straight-line stability.

Why It Matters

Lets you compare setups and predict wear vs stability trade-offs.

Professional Interpretation

Treat the primary result as a planning estimate, then validate on a dyno, at the track, or with logged sensor data. If measured numbers disagree by more than ~10%, re-check inputs (units are the usual culprit) before changing parts.

Recommendations

  • •Double-check units on every input before trusting the result
  • •Compare against the worked example below to sanity-check magnitude
  • •Validate with measured data (dyno, timeslip, datalog) when it matters

Learn — fuel economy, deeply

Alignment is three angles with very different consequences.

1 · Where the gallon goes (energy path)

Engine heat

60–70% lost

Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.

Driveline

5–15% lost

Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.

Aero drag

∝ v²

Doubles from 55→78 mph. Roof boxes hurt more than trunks.

Rolling + brakes

10–20%

Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.

4 · Measure like a pro (the 3-tank protocol)

  1. Fill to first click at the same pump, record the odometer (Tank 0).
  2. Drive normally for 2–3 tanks; always refill to first click at the same pump.
  3. MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
  4. Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
  5. Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.

Practical Tips

  • •Toe wears tires fastest per degree
  • •More caster adds stability and steering weight
  • •Record hot pressures alongside alignment

Common Mistakes

Mixing units (inches with mm, psi with kPa)
Convert every input to the unit shown on its field before calculating.
Trusting a single output blindly
Cross-check with the worked example and, when it matters, a dyno or datalog.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-state model: Formulas assume stabilized conditions; transients, heat soak and traction limits are excluded.
Standard factors: Empirical constants (BSFC, VE, drivetrain loss) use typical values — your combination may differ.

Limitations

Be aware of these limitations when using this calculator:

Estimate, not measurement: Predictions carry real-world scatter of roughly ±5–15% depending on the model.
No transient effects: Shift time, wheelspin, spool lag and heat soak are not modeled here.

Frequently Asked Questions

Answers to common questions about this calculator.

Why is toe weighted 5x?
A tenth of a degree of toe scrubs continuously down every straight; camber mostly works in corners.
Are these real geometry values?
No — documented planning indexes. True trail needs spindle geometry and tire data.

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Related Guides

Deepen your understanding with these educational resources.

Glossary

Technical terms used in mortgage calculations explained in plain language.

MPG
Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
L/100 km
Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
MPGe
Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
CAFE
Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
Rolling resistance
Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
Aerodynamic drag
Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
Hypermiling
Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
OBD-II
On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

EPA Fuel Economy Testing (40 CFR Part 600)CAFE — Corporate Average Fuel Economy Standards (NHTSA)WLTP — Worldwide Harmonised Light Vehicle Test ProcedureSAE J1321 / J1711 — Fuel consumption test proceduresISO 2575 — Road vehicles symbols & efficiency markings

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