Guide · Weight-stack adders
Stack adders and machine load limits: is a gym pin safe?
Why a stack adder's stated load is the pin's figure, not your machine's, what GymPin and Bare Steel tell users, and what the ASTM selectorized standards cover.
We may earn a commission if you buy through links on this page. How we make money
Short answer
A stack adder's stated load is the pin's own figure, not your machine's. The machine's permitted load comes first: the frame, cables, pulleys and guide rods all have their own limits, and a stronger pin does not raise them. Use an adder only within that limit, only with the owner's or maker's permission, and never as the selector pin.
The pin's rating vs the machine's
Two different numbers are in play:
- The adder's stated load: what its maker says the pin itself should carry.
- The machine's permitted load: what the machine maker allows on the stack, cable and frame.
GymPin states that a stronger pin does not raise the machine's rating.[1] Its Original product page adds that the frame, cables, pulleys and guide rods have their own limits, that you should not exceed the machine's intended capacity, and that you should not slam the stack.[3]
So the machine's permitted load is your ceiling, counted as the selected stack plus everything on the adder, and the pin's own figure must not be exceeded either.
What adder makers state
| Adder | Stated figure | Scope |
|---|---|---|
| GymPin Original | 60 kg on the product page | The pin; the machine's limits come first |
| Bare Steel 10 mm Stacked Weight Pin | 135 lb maximum | The 10 mm pin only |
| Bare Steel 8 mm Stacked Weight Pin | 100 lb maximum | The 8 mm pin only |
| Torque 2.5 lb Adder Pin | "Up to 10 additional pounds" | A Q&A reply, not a spec |
GymPin's Original product page gives a maximum stated load of 60 kg.[3] Bare Steel's 10 mm pin states a maximum of 135 lb, and its 8 mm pin, a separate product, states 100 lb.[2][4] Do not apply the 10 mm figure to the 8 mm pin. Torque says in a product Q&A reply that its adder pins can hold up to 10 additional pounds.[5] None of these figures increases what your machine may carry.
Before and during use
GymPin advises getting the gym owner's or manufacturer's permission before using its pins on equipment you do not own, and checking that plates clear the full range of motion.[3] It also says to confirm the pin is fully inserted, load plates evenly, and stop if anything is unstable, obstructed, bends, shifts or rubs.
- Permission: at a commercial gym, ask staff first.
- Fit: match the pin diameter to the selector pin; see 8 mm vs 10 mm selector pins.
- Clearance: move the stack slowly through its full travel with the adder loaded before your first working set.
- Stop: if anything shifts, rubs or bends, unload and do not use the adder until you have asked the maker.
Owner inspection
Inspire's safety policy tells owners to inspect cables, nuts, bolts and belts, replace or repair damaged parts at the first sign of a problem, and stay clear of weights and moving parts.[6] That is general guidance, not specific to adders, and an adder puts its load through those same parts, so the same checks apply.
What the standards cover
ASTM F2216 is the Standard Specification for Selectorized Strength Equipment.[7] ASTM F2277 provides test methods for evaluating selectorized equipment for compliance with F2216.[8] They cover how a machine is designed and tested, not add-on pins. A machine built to them does not make an adder approved.
Picks that fit2 products
Only within your machine's permitted load and with the owner's or maker's permission. 8 mm selector pin: the GymPin Original listing here is the 8 mm Raw version. 10 mm: the KingPin (10 mm only).
More on choosing
On Amazon, check that 'Ships from / Sold by' shows Amazon.com or GymPin.
Adder for machines with an 8 mm selector pin
Adder for machines with a 10 mm selector pin
Next
Questions
Can a stack adder overload my machine?
Yes, if the stack plus the added plates exceeds what the machine is meant to carry. GymPin says the frame, cables, pulleys and guide rods have their own limits and that the machine's permitted load takes priority.[1][3]
Can I use a GymPin at a commercial gym?
Only with permission. GymPin advises getting the gym owner's or the manufacturer's permission before using its pins on equipment you do not own.[3]
Does a stronger pin mean the machine can take more?
No. GymPin states that its products do not certify or uprate a machine and that a stronger pin does not raise the machine's rating.[1]