SuCalc
Health & Fitness

Bike Frame Geometry Comparison Calculator

Updated Aug 27, 2026 Reviewed Aug 27, 2026
Compare two bicycle frames by stack, reach, wheelbase, rear-center, angles, BB drop and calculated steering trail.

Direct, size-specific frame comparison

Compare two geometry charts

A

Bike A

B

Bike B

Geometry describes the frame, not the complete fit or handling
Use the same size-specific measurement convention for both bikes. Contact points, suspension sag, tires and mass distribution can change real fit and steering.

Result

Calculation summary

Enter values to see the result

Your result, breakdown, assumptions, and warnings will appear here.

Live overlay preview

See where stack, reach and wheelbase move

Stack B − A

+15 mm

Reach B − A

-5 mm

Trail B − A

+6.3 mm

Bike B is overlaid against Bike A; numeric B-minus-A differences remain the authoritative comparison.

How to use this calculator

  1. 1Copy both size-specific manufacturer geometry charts.
  2. 2Enter the same measurement set for each bike.
  3. 3Read all deltas as Bike B minus Bike A.

Formula

trail = (R cos A − offset) ÷ sin A

Direct dimension differences are paired with trail and stack/reach ratio.

Calculation steps

  • Validate both charts.
  • Calculate ratios and trail.
  • Build the B-minus-A table and overlay.

Worked example

Bike B with 15 mm more stack and 5 mm less reach is taller and shorter at the frame reference point.

Assumptions

  • Both charts share conventions.
  • Dimensions describe static geometry.
  • Wheel radius is loaded.
  • No fit or handling verdict is generated.

Sources

Frequently asked questions

Is more stack always more upright?

Not by itself; stem, spacers, bars and saddle position also matter.

Does more trail guarantee stability?

No. It interacts with wheelbase, tires, mass distribution and speed.

Does this replace Bike Fit?

No. It compares frames rather than riders.

Why loaded radius?

The tire contact geometry used for trail changes with actual tire size and compression.

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