Contrology Calculator

Your Springs · Balanced Body Reformer

Preliminary estimates, not verified. Balanced Body does not publish their springs’ pounds per inch (lb/in), which is why Contrology Coach uses this spring force calculator to work them out. The rates below are preliminary estimates from his 2025 Spring Force Guide, and he does not stand behind them yet. They will be replaced by measured values once he tests his springs with a spring force gauge. Until then, treat every number on this page as an estimate.

Preload is a calibration setting: how far a pegged spring is already stretched before the carriage moves. The Contrology guide treats it as tunable. Default 1.0 in.

Carriage Position

Total Force

Example: a chest expansion on two reds at mid carriage is about 60 lb of pull in these preliminary estimates (two red springs on hooks at 20 in = 60.0 lbf).

Per-Spring Breakdown

Model & Sanity Notes

Each spring follows Hooke’s Law, F = k × x. Springs work in parallel, so the total is the sum of every spring. The rates used here (Green 2.5, Red 1.5, Blue 1.0, Yellow 0.5 lb/in) are preliminary estimates from Omar’s 2025 Spring Force Guide. They are not verified and not Balanced Body specifications. Omar will replace them with measured values once the springs are tested with a spring force gauge.

On a hook, the spring starts with no tension, so x is just the carriage displacement. This matches Balanced Body’s B position, which starts with no starting tension. On a peg, the spring starts pre-loaded, so F = k × (x + preload). This matches Balanced Body’s pre-loaded A (button) position.

Balanced Body does not publish lb/in spring rates. Its manuals publish only approximate “up to” maximum loads: Yellow up to 19 lb, Blue up to 30 lb, Red up to 48 lb. Real springs also carry initial tension: Merrithew’s published model defines force as initial tension + rate × extension. This calculator folds that starting tension into the preload setting instead of modeling it per spring.

Treat every number here as a preliminary estimate. Springs vary by maker, age, and machine, so calibrate the preload against the reformer in front of you.