Bespoke Wheel Specs: Offset, PCD, Dish And Load Explained
On a busy farm or hire yard a wheel mismatch is obvious: a tractor sidelined with a wobbling wheel, a telehandler suffering premature bearings, or a trailer tyre shredding its sidewall. If you’re a fleet manager, contractor or workshop fitter in the UK, this guide helps you take measurements that avoid those failures and specify wheels that last. In our experience at Fieldens OTR Ltd, accurate specs cut downtime and rework—this article tells you what to measure, what to watch for and how to send a quote-ready pack.
Preparation: Tools And Machine Data
Have vernier calipers, a steel rule, tape measure and straight edge. Clean the hub face and photograph it with a tape or calipers in-frame. Record machine model, axle rating, hub type, brake clearances and any attachments that change loads or steering geometry. If you’re unsure, send details to us for review—see our manufacturing overview at https://fieldensotrltd.co.uk/manufacturing/ and contact pages at https://fieldensotrltd.co.uk/contact/ for assistance.
Measuring The Hub: PCD, Stud Count And Centre Bore
Count studs first. For even stud counts measure centre-to-centre across opposite studs for the PCD. For 5-stud patterns measure from a stud centre to the outer edge of the stud two positions away, then confirm against a PCD chart or with us. Measure the centre bore (spigot) with calipers—hub-centric fitment reduces vibration. Note fastener type, seat (taper or spherical), thread and shank length; these are critical to clamping and stud life.
This image was generated with AI and may not always represent the product or service exactly.
Offset, Dish And Track Width: Stance And Clearance
Offset (ET) is the distance from the wheel’s centreline to the hub face: positive ET pulls the wheel inboard, negative ET pushes it out. Dish/backspacing and offset together set track width, bearing loads and mudguard clearance. A common issue we see is choosing ET to “look right” rather than checking steering lock and brake clearance—always check full lock and suspension travel before ordering.
Rim Size And Profile: Diameter, Width, Bead And Valve
Match rim diameter and rim width to the tyre’s approved ETRTO/TRA range. A rim that’s too narrow or too wide alters the tyre footprint and accelerates casing wear. Confirm bead seat diameter, flange height and whether you need reinforced discs or multi-piece rims for serviceability. Decide valve position for access and consider TPMS-ready or guarded valves when operating in tight plant environments.
Load Index And Speed Rating: Match To Duty
Work out worst-case axle loads: machine kerb weight + attachments + payload, then distribute across axles. Include dynamic loads from slopes, braking and towing. In our experience, under‑specifying for road speeds causes heat build-up and premature failure—select centres, disc thickness and rim spec to suit the highest approved speed and load.
Corrosion Protection And Puncture-Proofing: Polycoat Tyrefill
On demolition, quarry or forestry sites punctures reduce productivity. Fieldens Polycoat Tyrefill replaces air with a resilient polyurethane fill for puncture immunity and consistent ride without slosh. It also reduces internal moisture and corrosion risk. Learn more about Tyrefill at https://fieldensotrltd.co.uk/tyrefill/.
This image was generated with AI and may not always represent the product or service exactly.
Applications: Agriculture, Construction And Industrial
Flotation sets for tractors use wider rims and lower pressures to spread load on soft ground while retaining a balanced offset for road use—see agricultural wheel options at https://fieldensotrltd.co.uk/wheels/agricultural-wheels/. Telehandlers and loaders need heavy‑duty centres to resist side‑loads; check boom and tyre‑to‑chassis gaps at full lock—industrial wheel details: https://fieldensotrltd.co.uk/wheels/industrial-wheels/. For complex machines consider bespoke centres: https://fieldensotrltd.co.uk/wheels/bespoke-wheels/.
Specification Checklist And Measuring Template
Provide this data for a fast, accurate quote: PCD and stud count; centre bore; offset/ET or target track; dish/backspacing; rim diameter and width; valve position; tyre size; axle rating and machine model. Photos should show a tape or calipers for scale and the machine ID plate. For guidance on choosing wheels for farm setups see https://fieldensotrltd.co.uk/how-to-choose-the-right-agricultural-wheels/.
Quick Checklist
- PCD, stud count and centre bore
- Offset/ET and target track width
- Rim diameter, width and valve position
- Axle rating, tyre load index and speed symbol
- Photos: hub face, ID plate, full machine view
What Most People Get Wrong
Most people assume factory model listings cover every hub variation—measure on the vehicle. Also, choosing offset without testing full lock or suspension travel often leads to clearance or wear issues that are easy to avoid with a quick mock-up check.
When This Doesn’t Apply
If you’re replacing identical wheels on a like-for-like machine with verified build sheets and no changes to loads or attachments, the full measurement protocol is less critical. Even then, confirm the centre bore and PCD before ordering.
How Fieldens OTR Ltd Builds Bespoke Steel Wheels
At Fieldens OTR Ltd we review your measurements, validate the spec and model centres in CAD. Discs are CNC cut, formed and welded in jigs, then checked for run-out and fitment. ISO 9001 controls track material traceability and final inspection. We can supply complete wheel-and-tyre packages and fit Tyrefill where required—see manufacturing at https://fieldensotrltd.co.uk/manufacturing/.
Get A Quote: What To Send
Email your machine model and axle rating; PCD/stud count; centre bore; offset/ET or target track; rim size and valve position; tyre size; photos with tape in view; site duty and expected speeds. For complex machines we can arrange a site visit—start via https://fieldensotrltd.co.uk/contact/. Bundling tyres and Tyrefill saves fitment time and ensures compatibility.
FAQs
How Do I Choose The Right Rim Width For My Tyres?
Provide the tyre size and load/speed symbols. We’ll match rim width and diameter to the tyre’s approved ETRTO/TRA range and recommend suitable offsets for your application.
What Photos Help You Confirm PCD And Bore?
Clear photos from above the hub showing a tape measure across the studs, a close-up of the centre bore with calipers if possible, and the machine ID plate are most useful for quick confirmation.
How Precise Must My Measurements Be?
Aim for ±0.5 mm on bores and ±1 mm on offsets. Use calipers for bores and measure twice. If you can only estimate, send photos and we will advise on verification steps.
Can You Advise If I Need Polycoat Tyrefill?
Yes. Tell us site conditions, duty cycle and whether puncture immunity or ballast stability is the priority—Tyrefill suits high‑risk sites where downtime costs are high.
Do You Deliver Wheel And Tyre Packages Ready To Fit?
Yes. We can supply assembled wheel-and-tyre units, fit Tyrefill and deliver ready to bolt on to reduce in‑field labour and alignment issues.
How Quickly Can You Turn Around A Bespoke Order?
Lead time depends on spec, finish and duty. Share your measurements and duty description and we’ll provide a firm turnaround and delivery option.