Axle pads and portable weighbridges: are they good enough?
How axle weigh pads work, why summed axle weights are less accurate than a full bridge, what pads cost, and the jobs they're genuinely good for on a farm.
· 6 min
Axle weigh pads cost £3,000–£8,000 and answer a different question from a weighbridge. A bridge weighs the whole vehicle at once, to about 20kg. Pads weigh one axle at a time, and you add the results up. That summing is where the accuracy goes — a few percent on a good day — which makes pads right for some jobs and wrong for others. The short version: good enough to keep you legal on the road, not good enough to sell grain on.
How axle weighing works
A pair of pads, one per wheel track, sits on level ground. Drive the first axle on, let the vehicle settle, note the reading; pull forward, weigh the next axle; repeat and sum. Fancier setups use multiple pads or weigh-in-motion at a slow crawl, and the top of the price band buys printers, remote displays and software to log the results.
The per-axle figure is genuinely useful — it's the number roadside enforcement cares about. The summed total is where caution starts.
Why summed axles are less accurate
Three things conspire against the total:
- Load transfer. Suspension, tyres and the drawbar shift weight between axles depending on how the vehicle sits. Raise one axle 30mm on a pad while the others sit on the ground and you've changed what each axle carries. Weigh the axles one at a time and those shifts don't cancel out neatly.
- Ground level. For honest readings, every wheel — on the pads and off them — must be on the same plane, which usually means levelling mats or a genuinely flat run of concrete. A yard with a fall to the drain doesn't qualify.
- Repeatability. Weigh the same loaded trailer twice over pads and the totals can disagree by 2–3% — on a 14-tonne load, that's 300–400kg. A full bridge repeats within a division or two.
So a pad total answers "roughly what's on this trailer?" and "is this axle overloaded?". It doesn't answer "did the merchant's intake weight short me 150kg?" — the pads' own error is bigger than the discrepancy you'd be chasing.
What the money buys
| Setup | Rough price | What you get |
|---|---|---|
| Pair of static pads | £3,000–£5,000 | Axle-by-axle checks, manual notes |
| Multi-pad / weigh-in-motion kit | £5,000–£8,000 | Faster weighing, printouts, logging |
Against £25,000–£45,000 for a new bridge — the full sums are in how much a farm weighbridge costs — pads are the cheap seat, and for plenty of farms the right one.
Where pads are exactly right
Overload checks before the road. The main event. A dense sample of wheat heaps a trailer past its plated weight faster than you'd think, and the per-axle numbers are precisely what the law measures. GB limits for agricultural combinations — around 31 tonnes for tractor and trailer, with the trailer capped at 18.29 tonnes laden — carry detail and exceptions, so check current gov.uk/DVSA guidance and see tractor and trailer weight limits. A two-minute pad check as loads leave the yard is cheap against a prohibition at the roadside.
Rented and away land. If you farm blocks twenty miles from the yard, the bridge at home doesn't help. Pads travel in a pickup.
Small acreage. On 300–500 tonnes a year, a bridge never pays. Pads plus the occasional public weighing cover the checking jobs for a tenth of the money.
Weight distribution. Pads tell you things a bridge can't: drawbar load, front-rear split, whether the tank on the back has taken the steering light.
Where pads fall short
Selling is the big one. Axle pads aren't normally approved for trade use, so their readings can't lawfully determine payment — and no buyer would accept them anyway. Grain still sells on a verified bridge weight, usually the buyer's intake. Pads also make a poor referee: if you suspect a merchant's weights, a pad total with a 2–3% wobble settles nothing.
If your real need is per-load weights for yields and shed stock, the honest comparison isn't pads versus bridge — it's the whole ladder of options in how to weigh grain without a weighbridge.
Frequently Asked Questions
How accurate are axle weigh pads?
Per axle on properly level ground, respectable. Summed to a vehicle total, expect a margin of a few percent — 300–400kg on a typical 14-tonne trailer load — because of load transfer between axles and ground-level effects. A full weighbridge reads the same load to about 20kg.
Can I sell grain using axle pad weights?
No. Pads aren't normally approved for trade under weights and measures law, so the reading can't lawfully set the payment, and buyers work off verified bridge weights regardless. Use pads for checking, not settlement.
How much do axle weigh pads cost?
Around £3,000–£8,000. A basic pair of static pads sits at the bottom of the band; multi-pad and weigh-in-motion kits with printing and logging sit at the top.
Are axle pads good enough to avoid overloading fines?
They're the right tool for the check, since enforcement looks at axle weights and gross weight — both of which pads report. Leave yourself a sensible margin below the limits to cover the pads' own error, and check current gov.uk/DVSA guidance for the limits that apply to your combination.
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