Modified vehicle geometry: angles, load, and the GeoWheels workflow
Many drivers who lower, lift, or widen the track of their vehicle find that alignment shops still work mostly from OEM values — which are poorly suited once the suspension has been modified. This guide sets out the physical framework, then shows how the GeoWheels app structures data (suspension, springs, load, use case) to produce consistent targets before visiting a rack. The angle trade-offs covered by use case are detailed in alignment by use case.
GeoWheels workflow (steps)
The app moves through screens that follow the logic of an informed workshop: first context (where do you drive, which vehicle), then the suspension, modifications, load, and finally results (recommended angles, tolerances, technical notes).
- Region & language — Europe, North America, Asia, or Oceania; country and interface language.
- Vehicle profile — Sedan, compact, sports, SUV, 4×4, pickup, or van; this suggests a typical suspension type (which can be overridden).
- Intended use — Daily road, spirited road, track, drift, or off-road.
- Suspension — Guided assistant (questions about solid rear axle, body style, front type) or manual front/rear selection.
- Modifications — Lift or lowering by corner, front and rear track separately (asymmetric spacers, different widths…), tires/wheels.
- Spring type — OEM, lift kit, progressive, coilover, sport-lowering springs (see dedicated section).
- Vehicle load — Occupants, trunk/roof rack, expedition equipment; see distribution below.
- OEM values / rack sheet — Manual entry or AI scan of a rack-sheet photo.
- Results — Camber, toe, caster, deltas vs stock, PDF export, and optional save.
Suspension types recognized by the app
GeoWheels does not "guess" the vehicle: a suspension assistant asks visual questions (solid rear axle? MacPherson or double wishbone at the front?). You can also force the front/rear type manually. The app labels are as follows:
| Type | Short description (in-app) | Typical context |
|---|---|---|
| MacPherson | Telescopic strut — very common | Front of compacts and sedans |
| Double wishbone | Sports architecture, good geometric control | Sports cars, pickups / 4×4 front often |
| Multi-link | High precision | Rear of modern sedans / SUVs |
| Torsion beam | Torsion bar | Rear of city cars / compacts |
| Solid axle front / rear | Wheels linked by a beam | 4×4, pickups, some vans |
| De Dion, trailing arms, semi-trailing arms | Platform-specific layouts (e.g. older BMW generations) | Platform-dependent |
The kinematic engine accounts for the suspension type when modeling how angles evolve as ride height or load changes — including non-linear effects on MacPherson beyond roughly 30 mm of travel.
Spring types (and their link to dampers)
In GeoWheels, the spring type category mainly drives how much the suspension compresses under load (OEM spring vs reinforced vs rigid coilover). The labels and descriptions shown to the user are:
- OEM — Manufacturer springs; standard compression under load.
- Lift kit — Reinforced kit springs; less compression under load than stock.
- Progressive — Variable rate: softer unloaded, firmer under load.
- Coilover — Adjustable spring/damper assembly, very stiff, minimal compression.
- Sport-lowering springs — Lowering and stiffened; lower ride height, firmer behavior.
In practice, a damper alone does not change static geometry; it is static ride height (spring, coilover preload, arm geometry) and load that move the suspension under the vehicle's weight. This is why entering both spring type and real-world load matters.
Vehicle load: what the app accounts for
The Vehicle Load screen groups several fields present in the app:
- Occupants
- Driver + passengers (kg) — distributed approximately 60 % front / 40 % rear in the model.
- Trunk / roof rack
- Load carried mostly at the rear.
- Jerry cans, water, expedition equipment
- Typical distribution of 30 % front / 70 % rear.
These distributions allow the app to estimate the differential front/rear sag and therefore geometry under load. For pickups, the app also provides fields for curb weight, payload, and GVW (registration card entry, depending on jurisdiction) when the vehicle flow allows it. For permanent load or canopy setups: pickup & canopy case study.
Intended use cases
The selected use case guides the handling/wear trade-off: Daily road, spirited road, track, drift, or off-road. This is not cosmetic: it influences the recommendation logic (stability, tire warm-up, controlled slip, suspension travel…). For a lifted, loaded 4×4 in off-road use, the sensible target is not the same as for a lowered sedan used purely on road. For cause-and-effect chains: sport sedan case study, 4×4 case.
Geometry principles (educational refresher)
The formulas below give intuition; they do not replace full vehicle kinematics or rack measurement.
1. Ride height and camber (diagram)
Lowering the body often tilts the wheel plane relative to the road: a tendency toward negative camber (exaggerated if not corrected on a rack).
ΔCamber ≈ arctan(ΔH / L)
ΔH: ride-height change (mm). L: reference arm length (mm) — simplified model.
Purely illustrative diagram: angles and proportions do not correspond to a real vehicle.
2. Scrub radius
Changing the wheel and offset shifts the point of application of lateral forces relative to the steering axis — resulting in heavier or more nervous steering, and different wear patterns.
SR ≈ |contact patch − pivot|
Cross-check against actual tire fitment.
3. Roll and anti-roll bars
Stiffer bars or a higher center of gravity change lateral load transfer in corners; this shows up mainly as asymmetric wear and limit behavior, not just on a static alignment sheet.
Modification comparison table (examples — non-prescriptive)
| Modification | Camber trend | Toe trend | Caster / steering | Tire wear risk | Suggested action |
|---|---|---|---|---|---|
| Lift kit (+5 cm) | Often more positive | Highly arm-dependent | May reduce | Outer shoulder | Extended arms / adjustable camber + rack |
| Wider-section tires | Often minor on its own | Must be recalibrated (total) | SR affected | Feathering / sidewall | Per-wheel toe measurement |
| Lowering (−3 cm) | More negative | Increased toe-in | May increase | Inner shoulder | Ball joints, steering, corrected geometry |
| Track spacers | Minor | Must be rechecked | — | Shoulder | Toe measurement after fitting |
| Wheel offset | Suspension-dependent | Yes | SR | Variable | Simulation + road test |
| Uprated anti-roll bars | Little static effect | Under lateral load | — | Cornering wear | Front/rear balance |
| Permanently loaded vehicle | Under load | Under load | — | Heel/toe / sidewall | Target with real load in GeoWheels |
The calculator: GeoWheels engine
Rather than a static spreadsheet, the app recalculates a complete chain: profile + suspension + Δ ride height + Δ track + spring type + load + (optional) OEM sheet or rack measurement. The Results screens display recommended angles, tolerances, deltas vs stock, and technical notes — all exportable as PDF for the workshop file or vehicle resale documentation.
Typical cases (overview)
1. Lifted SUV, road + leisure use
Moderate lift, larger tires, widened track. Classic risk: excessive positive camber and uncorrected toe → outer-edge wear. GeoWheels: SUV profile, multi-link / MacPherson per assistant, lift kit, front/rear tracks, family load + luggage.
2. Lowered sedan on short springs
MacPherson front axle. Risk: negative camber and inner-edge wear if the alignment shop stays within OEM ranges. GeoWheels: spring type "sport-lowering springs", measured corner height, scan of a previous rack sheet as a starting point.
3. Pickup, variable load
Solid rear axle typically: behavior under payload changes significantly. Enter curb / payload weight when the flow offers it, and two load scenarios (empty / loaded) via separate saved setups to compare targets.
Platform-specific guidance
The app suggests typical front/rear suspension combinations based on the profile (e.g. pickup: double wishbone front and solid rear axle; compact: MacPherson + torsion beam). These are not absolute truths: always confirm visually or from a spec sheet, then adjust manually in the app if needed.
Best practice remains: measure on a rack after modification, compare against GeoWheels targets, iterate with the professional — especially if adjustment parts (ball joints, arms, shims) have been changed in the meantime.
Other useful features
- VIN decoding (17 characters, NHTSA feed) for the United States and Canada to speed up vehicle identification in the regional catalog.
- Regional catalogs (Europe, North America, Asia, Oceania) — makes, models, years.
- AI rack-sheet scan: photo or scan (JPG, PNG, WebP) to pre-fill camber, toe, and caster with a confidence level.
- Units: metric or imperial (angular minutes for US rack sheets).
- Multiple saves: several configurations (summer/winter, loaded/empty, before/after parts).