The springs on a pilates reformer do more than add resistance. They set it, grade it and adjust it for every exercise, and the colour, material and count all affect the practice you get. This guide covers what the colours mean, how the load changes through the stroke, what piano wire is, and how long springs last.
What do the springs on a pilates reformer do?
Springs set the resistance for every movement, pulling the carriage back toward the foot bar and providing the load the body works against throughout the stroke. Adding springs increases the total load; removing them lightens it.
The load also changes within a single rep. Align's published spring data shows the tension rising as the carriage moves out: a yellow spring reads 2.6 kg at 25% of travel and 9.2 kg at full extension. Moving the carriage out raises the working load; moving it in lowers it.
A heavier spring does not mean a harder exercise. Pilatesology's research notes that heavier tension does not automatically make an exercise harder, and FOLD's reformer guides point out that extending the carriage away from the springs is what raises intensity. The combination of spring selection, carriage position and body position determines the actual load at any moment.
What do the spring colours mean?
Colour coding varies by maker: there is no universal standard across the industry. The same colour can mean different tensions on different reformers. Always check the chart for the machine you own.
| Colour | Relative tension | Typical use | Milaron load at full extension |
|---|---|---|---|
| Red | Heaviest | Footwork, leg press, advanced exercises | 28.7 kg per spring (2× red standard) |
| Blue | Medium | Most exercises, intermediate load | 18.2 kg per spring (2× blue standard) |
| Yellow | Lightest | Arm work, rotational exercises, reduced load | 10.3 kg per spring (2× yellow standard) |
Every Milaron reformer carries six springs: two red, two blue, two yellow, the same set across all three models. The load figures above are measured at full extension (approximately 105 cm of carriage travel).
How other makers assign colours: Balanced Body uses red for medium, green for heavy, blue for light and yellow for very light. Merrithew uses red for 100%, blue for 50%, black for 125% and white for 25%. A cross-maker survey confirms that tensions vary widely across manufacturers, and classical apparatus makers use identical springs with no colour coding at all.
Cite this table with the colour chart from your own machine's documentation. The Milaron figures above are from the product pages; figures from other makers are from their published specifications and are cited as theirs.
What are reformer springs made of, and why does piano wire matter?
Piano wire, also called music wire, is a defined material standard, not a marketing phrase. In the United States it is covered by ASTM A228, which specifies cold-drawn steel wire "for the manufacture of springs subject to high stresses or requiring good fatigue properties."
The property that matters for a reformer is fatigue life: the ability to be stretched and released repeatedly without the resting length drifting. Gibbs Wire & Steel, a music wire supplier, describes it as having "one of the highest tensile strengths" of common spring materials, able to "withstand higher stresses under repeated loading," with fatigue life that is "excellent."
When a spring goes soft over time, that is fatigue: the coil has taken a permanent set and the resistance it delivers no longer matches what you selected. Music wire is the material chosen for applications where that must not happen.
"German" refers to provenance. The steel specification is German; "German Piano Wire" reflects the manufacturing tradition and the wire's origin, not that the springs themselves are assembled in Germany. Milaron's springs are nickel-plated German Piano Wire. Two other studio brands, Balanced Body and Align, publish that their springs use nickel plating as well.
How heavy are reformer springs?
Milaron's six springs load at 28.7 kg (red), 18.2 kg (blue) and 10.3 kg (yellow) per spring, each measured at full extension. The total loaded tension across all six at full extension is approximately 114 kg.
These figures are specific to Milaron and measured at full extension. Makers publish their figures differently (at different points in the stroke, or as relative percentages rather than absolute loads), so direct comparisons across brands on a number alone are not meaningful.
Align Pilates publishes their spring loads at 25%, 50%, 75% and 100% of maximum carriage travel, and the figures show the load rising through the stroke on each spring. Their data is on the Align website and is cited as Align's.
How long do reformer springs last, and when should you replace them?
The three studio makers with published guidance give consistent intervals: Merrithew recommends replacement every two years; Balanced Body warranties springs for two years or 3,000 hours of use; Align Pilates recommends every two years or 2,000 hours.
The clearest sign a spring needs replacing is that the resistance feels inconsistent: one spring that used to match the others no longer does, or a resistance setting delivers less load than it should. Visual inspection matters too: look for corrosion, uneven coil spacing or any deformation along the coil length.
For a full care routine (checking ropes, straps and the carriage rail), see our pilates reformer maintenance guide.
What else is a reformer built from?
Springs are the most discussed component, but the frame, carriage and upholstery carry the practice over time. A short summary of what goes into a Milaron reformer:
Frame. The Pearl Studio and Pearl Foldable use 6063-T5 aluminium, the most common extrusion alloy, used in architectural and precision applications for its ability to form complex shapes and hold tight surface tolerances. The Maple Studio uses AAA-grade solid maple.
Springs. Six nickel-plated German Piano Wire springs, mounted in two rows of hooks (Pearl models) or three rows (Maple Studio). The springs are covered under Milaron's 1-year warranty; the frame, carriage rails, gear bar and footbar are covered for 5 years.
Upholstery. Premium Microfibre Leather: soft, breathable, easy to wipe clean. The carriage and shoulder blocks are covered for 4 months under the standard warranty.
Built to be used daily for a decade. See the full range or compare models in our guide to the best pilates reformers in Australia.