When you’re assessing tyre balers, bale density directly affects your transport costs, storage efficiency, and market access. A 900kg bale occupies the same physical space as a 500kg bale, but you’re moving 80% more material per lorry load.
Density is measured in kilograms per cubic metre (kg/m³). Loose tyres average 150kg/m³. Compressed bales achieve 750-850kg/m³. That’s a 5x to 6x density increase, which translates to dramatic reductions in transport frequency and storage footprint.
This guide explains how bale density works, why 900kg is the industry standard, what compression force is required, and how density affects your costs and market options.
Gradeall International manufactures tyre baling equipment at our facility in Dungannon, Northern Ireland. The MKII tyre baler produces bales at 900kg to 1,100kg consistently. The specifications below are based on real operational data from customer sites across 100+ countries over nearly 40 years.
Density is the relationship between mass (weight) and volume (physical space occupied). Higher density means more weight in the same space.
Loose tyre density: A car tyre laid flat occupies approximately 0.33 square metres and stands 200mm high. Volume: 0.066 cubic metres. Weight: 8-12kg. Density: 121-182 kg/m³ (average 150 kg/m³).
When tyres are stacked, voids between them reduce effective density. A cubic metre of loosely stacked car tyres contains approximately 12 to 15 tyres weighing 100 to 180kg total. Effective stacked density: 100-180 kg/m³.
Compressed bale density: A standard tyre bale measures approximately 1,100mm × 1,100mm × 800mm. Volume: 0.97 cubic metres (call it 1.0m³ for calculation purposes). Weight: 900-1,100kg. Density: 900-1,100 kg/m³.
The compression process collapses the air voids within and between tyres, dramatically increasing density. The tyre rubber itself doesn’t compress much (rubber is nearly incompressible), but the air spaces do.
Why this matters: Transport and storage costs are driven by volume, not weight, until you hit vehicle weight limits. An articulated lorry can carry 29 tonnes but the trailer volume maxes out at approximately 80-90 cubic metres. For loose tyres at 150 kg/m³, you’d need 193 cubic metres to reach 29 tonnes. The trailer only has 85m³, so you’re volume-limited at approximately 12,750kg (44% of weight capacity wasted).
For bales at 900 kg/m³, you need 32 cubic metres to reach 29 tonnes. That fits easily in the 85m³ trailer with room to spare. You’re weight-limited, not volume-limited, which is the efficient way to use vehicles.
PAS 108 is the British standard for tyre bales used in civil engineering and construction applications. It specifies minimum density to ensure bales are stable, durable, and suitable for load-bearing applications.
PAS 108 minimum density requirements:
These aren’t arbitrary numbers. Civil engineering applications (road embankments, erosion control, foundation fill) require bales that maintain shape under load, don’t collapse during transport, and stack stably at site.
Lower-density bales (600-800kg) compress further under load, which causes settlement and instability. They’re also more prone to wire breakage during handling because the lower compression means less internal friction holding the tyres together.
Market implications: If your end-market is construction or civil engineering, PAS 108 compliance is mandatory. Non-compliant bales get rejected at site. You’ve wasted time, fuel, and baling costs producing unusable bales.
If your end-market is shredding, pyrolysis, or energy recovery, PAS 108 compliance is less critical. These processors care about volume reduction and transport efficiency but not structural performance. However, even non-construction markets typically pay a premium for high-density bales due to handling and storage benefits.
Let’s calculate transport requirements for 25,000 car tyres annually:
Loose tyres:
Articulated lorry capacity:
Loose tyre loading: You’re volume-limited. At 150 kg/m³, you can fit 85m³ × 150 kg/m³ = 12,750kg per load. That’s 44% of the weight capacity (29,000kg) but 100% of the volume capacity.
Number of loads needed: 250,000kg ÷ 12,750kg = 19.6 loads (round to 20)
Baled tyres at 900kg bales:
Baled tyre loading: Each bale is 900kg and 1.0m³. You can fit 85 bales per lorry theoretically, but you’re weight-limited before you hit volume limits.
29,000kg payload ÷ 900kg per bale = 32 bales maximum (weight-limited) 32 bales × 1.0m³ = 32 cubic metres (38% of volume capacity)
In practice, you load 26-28 bales per lorry (23,400-25,200kg) to stay comfortably under the 29-tonne limit and allow for bale weight variation.
Number of loads needed: 294 bales ÷ 27 bales per load = 10.9 loads (round to 11)
Transport cost comparison: At £300 per load average:
For higher volumes (100,000 tyres annually), the saving scales proportionally:
The mathematics get even more compelling for long-haul transport. At £600 per load for 150+ mile journeys:
For international shipments, bale density becomes critical for container optimization.
40ft shipping container specifications:
Loading loose tyres in a container: Practically impossible to load loose tyres efficiently in a container. Even with careful stacking, you’d achieve approximately 150-200 kg/m³ effective density. At 175 kg/m³ average:
67.5m³ × 175 kg/m³ = 11,812kg of material
You’re using 100% of volume but only 42% of weight capacity. Very inefficient.
Loading baled tyres at 900kg: Standard bale dimensions: 1,100mm × 1,100mm × 800mm
Container floor: 12,032mm ÷ 1,100mm = 10.9 bales lengthwise (round to 10) Container width: 2,352mm ÷ 1,100mm = 2.1 bales wide (round to 2) Container height: 2,385mm ÷ 800mm = 2.9 layers high (round to 2 safely loaded)
Theoretical capacity: 10 × 2 × 2 = 40 bales
Weight check: 40 bales × 900kg = 36,000kg (exceeds container weight limit)
Actual loading: You’re weight-limited at approximately 28 bales (25,200kg), which uses 28 cubic metres (41% of volume).
At 900kg bales with 85 tyres per bale, 28 bales = 2,380 tyres per container.
Compare to loose tyres: approximately 1,000 to 1,200 tyres per container (volume-limited).
Shipping cost per tyre: £4,000 container to Australia (example):
You’ve just cut shipping cost per tyre by 54% through better density.
Floor space costs money whether you rent or own. Reducing storage footprint delivers immediate savings.
25,000 loose tyres storage: Single layer: 25,000 × 0.33m² = 8,250 square metres (completely impractical)
Stacked to 2.5m height (maximum for stability): 8,250 ÷ 2.5 layers ≈ 3,300 square metres
More realistic stacking with aisles, access, and safety margins: 2,000 to 2,500 square metres
25,000 baled tyres storage: 294 bales at 1.0m³ each = 294 cubic metres
Stacked three bales high (typical safe stacking with forklift access): 294 ÷ 3 layers = 98 square metres floor space
Add aisles and access (50% additional space): 150 square metres total
Space saving: 2,000-2,500m² reduced to 150m² (85-94% reduction)
At £75 per square metre annual rental (UK industrial warehouse average):
Most operations don’t store the full annual intake simultaneously. You process and ship continuously. But even at one month’s intake stored at peak (2,100 tyres):
If you own the building, the space saving has opportunity cost value. The 2,000m² freed up can be used for additional processing lines, storage of other materials, or subletting to other businesses.
Achieving 900kg+ bale density requires specific hydraulic pressure. The MKII tyre baler applies approximately 200 bar (20 MPa) of hydraulic pressure with a 7.5kW motor.
Why pressure matters: Lower pressure produces lower-density bales. A 4kW motor might only achieve 140-160 bar, which produces bales of 600-750kg. These bales don’t meet PAS 108 standards and waste transport capacity.
Higher pressure (beyond 200 bar) doesn’t proportionally increase density. Tyres have physical limits to compression. The steel belts and sidewall structure resist beyond a certain point. Applying 250+ bar might increase bale weight from 900kg to 950kg (5% gain) but increases energy consumption by 20% and accelerates wear on hydraulic components.
200 bar at 7.5kW is the optimal balance: sufficient pressure for PAS 108 compliance without over-stressing components or wasting energy.
Pre-processing increases density: Whole tyres compress less efficiently than pre-cut tyres. The sidewalls and steel beads resist compression. A sidewall cutter removes these rigid structures, which allows tyres to compress 15% to 25% more.
With pre-cut tyres, the same 200 bar pressure produces bales of 1,000-1,100kg instead of 900-950kg. That’s an extra 100-150kg per bale (11-17% improvement) from the same equipment.
For operations targeting maximum transport efficiency or PAS 108 compliance with margin, pre-cutting is worth the additional equipment cost (£8,000-£15,000 for a sidewall cutter).
There’s a balance between maximising density and maintaining bale integrity. Over-compressed bales can fail:
Wire breakage: Excessive compression puts enormous tension on baling wire. If pressure exceeds optimal levels, wires snap during handling or transport. This is more common with lower-quality wire or incorrect wire gauge.
Use 3.15mm high-tensile baling wire with 900kg bales. Lighter wire (2.5mm) is inadequate. Heavier wire (4mm) is unnecessary and more expensive.
Bale bulging: If tyres are compressed beyond their elastic limit, they spring back when pressure releases. This causes bales to bulge in the middle, which makes stacking unstable and increases volume.
Proper compression to 900-1,000kg avoids this. The tyres compress to a stable state where internal friction and wire tension maintain shape without excessive spring-back.
Rubber damage: Extreme over-compression can damage rubber compound, particularly if tyres have aged or weathered. Cracked or brittle tyres compress poorly and produce weak bales.
Inspect tyres before baling. Remove tyres with severe cracking, chunking, or dry rot. These should be processed separately or rejected.
Downstream processors and end-users typically pay more for high-density bales due to handling and storage efficiency.
Typical UK pricing (early 2026):
The premium for high-density bales ranges from £20 to £70 per tonne depending on end-use. For an operation producing 250 tonnes annually, that’s £5,000 to £17,500 in additional revenue just from achieving proper bale density.
Construction applications pay the highest premium because PAS 108 compliance is mandatory. If you can serve this market, it’s usually the most profitable outlet for tyre bales.
Why processors pay more for density:
Even markets that don’t require PAS 108 compliance prefer high-density bales for operational efficiency.
Density consistency matters almost as much as absolute density. Bales ranging from 700kg to 1,100kg cause problems:
Transport inefficiency: If you’re loading a lorry with mixed bale weights, you hit weight limits before volume limits (good) but you’ve wasted space with lighter bales. A lorry carrying 24 bales of 900kg each (21,600kg) is efficient. A lorry carrying 18 bales of 700kg and 6 bales of 1,100kg (19,200kg) has wasted space where additional 900kg bales could have fit.
Stacking instability: Lighter bales compress under the weight of heavier bales stacked above. This creates leaning stacks and safety hazards. Warehouses and construction sites require consistent bale dimensions for stable stacking.
Processing complications: Automated shredders and processing lines are set up for specific bale sizes. Variation beyond ±50mm causes jams, misfeeds, and downtime.
PAS 108 requirements for consistency:
Achieving this consistency requires:
The MKII and MK3 are designed for consistency. PLC-controlled pressure and automatic wire-tying systems eliminate much of the variation that manual systems introduce.
Different baler models achieve different densities based on motor power and compression force:
MKII tyre baler:
MK3 tyre baler:
The MKII’s higher power delivers the pressure needed for PAS 108-compliant bales. The MK3 produces useful bales for non-construction markets but doesn’t achieve construction-grade density.
For operations targeting construction markets or maximum transport efficiency, the MKII is the only suitable choice from these two models. The MK3 serves operations with lower volumes selling to shredders or processors where PAS 108 isn’t required.
If truck tyres or OTR tyres are in your mix, you need even higher pressure. A dedicated truck tyre baler with 11kW to 15kW motors achieves 1,200-1,500kg bales for large tyres.
To verify your baler is achieving target density:
Equipment needed:
Procedure:
Repeat for 5 to 10 bales and average the results. Variation should be within ±10%.
Target densities:
If your bales consistently measure below target, check:
For construction applications (PAS 108 compliance): minimum 900kg for car tyre bales, 1,200kg for truck tyre bales. For shredding, pyrolysis, or energy recovery: 700-900kg is acceptable but higher density improves transport efficiency and usually commands better pricing. The MKII produces 900-1,100kg bales consistently, meeting all market requirements.
Transport efficiency. A lorry carries 26-28 bales of 900kg each (23,400-25,200kg total, weight-limited). The same lorry carries only 45-50 bales of 500kg each before volume limits (22,500-25,000kg, volume-limited with wasted cubic capacity). For the same transport cost per load, 900kg bales deliver more material per trip, reducing transport frequency and annual costs by 30-45%.
PAS 108 specifies minimum bale weights: 900kg for car tyre bales, 1,200kg for truck tyre bales. Bale dimensions must be consistent within ±50mm. This translates to minimum density of approximately 850 kg/m³ for car tyre bales and 1,100 kg/m³ for truck tyre bales. The standard focuses on weight and dimensional consistency rather than explicit density values.
Yes, but diminishing returns. Achieving 1,100-1,200kg bales requires 220-240 bar pressure (higher-powered motor or longer cycle times). Energy consumption increases 15-25% for a 10-20% density gain. Most operations find 900-1,000kg optimal: PAS 108 compliant, good transport efficiency, no over-stressing of equipment. Pre-cutting tyres is more effective than higher pressure for density gains.
Construction markets reject non-compliant bales (under 900kg). Transport efficiency suffers: you hit volume limits before weight limits, wasting payload capacity. Storage requires more space per tonne of material. Market pricing is typically £20-£40 per tonne lower for sub-900kg bales. Equipment with inadequate pressure (4kW motors or worn hydraulics) produces low-density bales consistently.
They prefer high density but don’t mandate PAS 108 compliance. Dense bales take up less yard space, handle more easily with forklifts, and cause fewer jams in automated feed systems. Shredders typically pay £20-£40/tonne premium for 900kg+ bales vs 600-700kg bales due to operational efficiency gains.
1,000 car tyres produce approximately 11-12 bales of 900kg each (85 tyres per bale). At 1.0 cubic metre per bale, that’s 12 cubic metres total. Stacked three high: 4 square metres floor space. Compare to loose tyres: 1,000 tyres at 0.33m² each = 330m² single layer, or 132m² stacked 2.5 layers high. Baling saves 97% of floor space.
Generally yes. PAS 108-compliant bales (900kg+) command £20-£70/tonne premiums over lighter bales for all end-uses. Construction applications require PAS 108 and pay £150-£200/tonne. Non-construction markets pay less but still premium for density. At 250 tonnes annually, the revenue difference between 700kg bales and 900kg bales is £5,000-£17,500, which justifies investing in higher-powered baling equipment.
Bale density determines transport costs, storage efficiency, and market access. High-density bales at 900kg+ meet PAS 108 requirements for construction applications, maximise lorry and container payloads, and reduce storage footprint by 85% to 90% compared to loose tyres.
The transport mathematics are compelling. For 25,000 tyres annually, baling at 900kg reduces lorry loads from 20 (loose) to 11 (baled), saving £2,700 to £5,400 annually depending on haulage rates. For international shipping, bales reduce cost per tyre by 50% to 60% through better container utilization.
Achieving 900kg+ density requires adequate compression force. The MKII tyre baler with 7.5kW motor and 200 bar hydraulic pressure consistently produces PAS 108-compliant bales. Lower-powered equipment (4kW motors) produces 400-700kg bales that don’t meet construction standards and waste transport capacity.
Pre-processing with sidewall cutters increases density by 15% to 25% (from 900kg to 1,000-1,100kg) by removing rigid sidewall structures that resist compression. For operations targeting maximum efficiency or handling truck tyres, pre-cutting justifies the additional equipment investment.
Market pricing reflects density value. Construction applications pay £150-£200/tonne for PAS 108-compliant bales. Non-construction markets pay £20-£40/tonne premiums for high-density bales due to operational efficiency gains. Over a typical equipment lifespan, density-driven revenue premiums exceed £75,000 to £175,000.
Don’t compromise on bale density to save on equipment costs. A £35,000 baler producing 700kg bales costs more in lost transport efficiency and market premiums than a £50,000 baler producing 900kg bales. Calculate total cost of ownership including transport, storage, and revenue implications, not just equipment purchase price.
Request bale density specifications and sample bales from Gradeall when assessing tyre baling equipment. We provide density verification, PAS 108 compliance documentation, and transport efficiency calculations for your specific operation.
* The prices and running-cost figures below are based on real UK customer examples and are correct at the time of writing, but should be treated as indicative only.
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