10 October, 2026 | 
Admin
Crane Hire and Outrigger Pads
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Read moreOutrigger Pad Thickness: Deflection, Crush Rating and How to Choose
09 October, 2026 | Admin
Short answer: outrigger pad thickness controls how stiff the pad is, how well it spreads the load to its edges, and how much load it is rated to carry. A pad that is too thin for its size bends under the outrigger float, so the load concentrates in the middle and the outer area of the pad does little work. Choose the pad area from the ground, then choose the thickness from the leg load and the pad’s rated capacity.
Area and Thickness Do Different Jobs
When you size a pad, two separate checks matter:
- Area protects the ground. A larger area lowers ground bearing pressure. See ground bearing pressure for cranes.
- Thickness protects the pad and makes the area effective. A thicker pad is stiffer, carries a higher rated load and spreads the load more evenly across its footprint.
A large but thin pad can pass the area check on paper and still fail in practice, because it bends and only the central part bears on the ground.
What Happens When a Pad Is Too Thin
- Deflection (bending): the pad dishes under the float. The effective bearing area shrinks toward the float size, and ground pressure rises.
- Permanent set: repeated overloading can leave the pad permanently bowed, which makes it rock and sit unevenly next time.
- Crushing or cracking: local overload under the float can damage the pad surface, especially with small floats or point loads.
SafeRig Thickness and Rated Capacity
The SafeRig range shows how rated capacity rises with thickness for the same footprint. Figures below are from the SafeRig square pad table:
| Pad size (mm) | Thickness (mm) | Rated capacity (t) | Weight (kg) |
|---|---|---|---|
| 800 × 800 | 50 | 50 | 32 |
| 800 × 800 | 60 | 55 | 38.4 |
| 800 × 800 | 70 | 75 | 44.8 |
| 800 × 800 | 80 | 80 | 51.2 |
| 1000 × 1000 | 50 | 75 | 48 |
| 1000 × 1000 | 60 | 80 | 60 |
| 1000 × 1000 | 70 | 100 | 70 |
| 1000 × 1000 | 80 | 120 | 80 |
| 1000 × 1000 | 100 | 160 | 100 |
| 1200 × 1200 | 60 | 180 | 86.4 |
| 1200 × 1200 | 80 | 220 | 115.2 |
| 1200 × 1200 | 100 | 220 | 144 |
For the full range, from 300 × 300 mm up to 3000 × 1000 mm, see SafeRig outrigger pads.
How to Choose Thickness
- Find the minimum area from the leg load, allowable ground pressure and safety factor. Our crane outrigger load calculation guide shows the formula.
- Shortlist pads with enough area.
- Check rated capacity. The pad’s rated capacity must be at least the outrigger reaction. If two thicknesses pass, the thicker one gives more stiffness margin.
- Consider the float size. A small float on a large pad concentrates load in the centre; choose a thicker pad, or use a smaller pad under a larger spreader.
- Consider handling. Thicker pads are heavier. For boom trucks that move every day, weight matters.
Thickness and Ground Conditions
On soft ground, such as sabkha, wet fill or sand, stiffness matters even more, because the ground offers little support at the pad edges. A thicker pad keeps the load spread over the full area. On sabkha the required area can also exceed a single pad; see sabkha crane outrigger pads.
Material Matters Too
UHMWPE pads flex slightly under load and recover, rather than cracking like brittle plastics or splitting like dry timber. Steel plates are very stiff but heavy and can slide on smooth surfaces. For a full comparison read steel plate vs plastic outrigger pads and outrigger pads vs timber cribbing.
Inspection Tips
- Check pads for permanent bowing by laying them on a flat floor.
- Look for deep gouges, cracks or crushing under the float area.
- Retire pads that rock or no longer sit flat. See safe use of outrigger pads.
Not sure which thickness you need? Use our Outrigger Pad Size Calculator, or send us your crane model and ground conditions. For the full selection process see our guide on how to choose outrigger pads.
Frequently Asked Questions
Does a thicker outrigger pad reduce ground pressure?
Not directly. Ground pressure depends on the effective area. But a thicker, stiffer pad keeps the full area working, so it prevents pressure concentrating under the float.
What thickness of outrigger pad do I need?
Choose the pad area from the ground conditions, then pick a thickness whose rated capacity is at least the outrigger reaction. SafeRig pads list rated capacity for every size and thickness.
Why do outrigger pads bend?
A pad that is thin relative to its size and the load deflects under the float. Repeated overload can leave it permanently bowed.
Is a 1000 x 1000 x 50 mm pad the same as 1000 x 1000 x 100 mm?
No. Both have the same area, but the 100 mm pad is stiffer and has a much higher rated capacity (160 t vs 75 t in the SafeRig range).
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