Selling Spare Parts Online: Aftermarket eCommerce for Equipment Manufacturers
Every machine a manufacturer has ever shipped is still generating demand. Filters, seals, belts, bearings, wear parts, service kits — the equipment sold five, ten or twenty years ago needs feeding for as long as it runs, and the margins on those parts are typically far healthier than the margins on the original equipment sale. Yet at many equipment manufacturers, this most profitable line of business is still transacted the way it was in 1995: a maintenance engineer rings the parts desk, someone looks up a part number in an internal system, a quote goes out by email, and a purchase order comes back the same way. Aftermarket parts eCommerce is, for most equipment manufacturers, the single highest-margin digital opportunity on the table — and the one their buyers are now actively asking for.
The catch is that a spare parts catalogue is not a normal product catalogue. Fitment, supersession chains, exploded diagrams, service kits and part-number cross-references break the assumptions that standard eCommerce platforms are built on, which is why so many first attempts at spare parts eCommerce for manufacturers stall at a glorified price list that the parts desk still has to interpret. In this article we look at why the aftermarket opportunity is worth taking seriously, what makes a parts catalogue genuinely different, and how a composable approach handles those differences where rigid platforms fight you. It draws on our B2B eCommerce work with businesses in the manufacturing and industrial engineering sector, where these patterns come up on almost every engagement.
The Highest-Margin Channel Most Manufacturers Haven’t Digitised
The economics of the aftermarket are well understood inside most equipment businesses, even where nobody has acted on them digitally. New equipment sales are competitive, hard-won and often thin-margin. The installed base those sales create, however, behaves like an annuity: a predictable, recurring stream of parts and service demand that runs for the life of the machine, at margins the original sale could never sustain. The larger and older your installed base, the bigger that annuity is.
The problem is that the annuity is not automatically yours. Independent parts resellers and will-fit manufacturers have spent years making their alternatives easy to find and easy to buy online. When a fitter needs a seal kit and the OEM route means a phone call during office hours while a pattern-part supplier offers a searchable webstore with visible stock, the OEM loses the order not on price or quality but on convenience. Every parts order that leaks to the independent channel takes the margin with it — and takes the customer relationship data too, so you never see the demand you are losing.
Buyer expectations have moved decisively. The people ordering spare parts — maintenance engineers, dealer parts staff, procurement teams working from a bill of quantities — increasingly expect the same self-service they get everywhere else: find the part, confirm it fits, see availability, order it, track it. We have written before about self-service buyer portals in B2B, and the aftermarket is where self-service pays back fastest, because parts demand is frequent, urgent and repetitive. A machine that goes down at six o’clock on a Saturday morning does not wait for the parts desk to open on Monday. A well-built parts store takes those orders around the clock, deflects routine order-taking from your parts team so they can handle the genuinely difficult enquiries, and captures a stream of demand data — what is failing, on which machines, in which markets — that a phone-and-email operation never sees.
Why a Parts Catalogue Breaks Standard eCommerce Assumptions
Standard eCommerce platforms embody a retail worldview: a customer browses to a product, picks from a modest set of options, and adds it to a basket. A parts buyer does not start from a product at all. They start from a machine — a model, a year, often a specific serial number — and work towards the one part that fits it. Correctness matters more than merchandising: the wrong part is not a mild disappointment, it is a machine that stays broken while a return is processed. That inversion is the root of everything that makes parts catalogues hard, and it shows up in five specific places.
Fitment: Which Part Fits Which Machine
The foundational question a parts store must answer is “does this fit my machine?” — and the data behind that answer is genuinely complex. A part’s compatibility varies by model, by model year, and frequently by serial number range, because engineering changes made mid-production mean that machines either side of a serial break take different parts. Fitment is a many-to-many web of relationships between machines, assemblies and parts, and it has to be treated as first-class catalogue data, not as text in a description field.
Get fitment right and the buying experience becomes the one parts buyers actually want: select your machine (or enter its serial number), and see only the parts that fit it. Get it wrong — or omit it — and the store generates wrong-part orders, returns, downtime and mistrust, until buyers conclude it is safer to ring the parts desk after all. A parts store that cannot answer the fitment question has not digitised the aftermarket; it has just published a price list.
Supersession: The Part That Replaces the Part
Part numbers do not stand still. Parts get redesigned, suppliers change, ranges get consolidated, and each of these events retires one part number in favour of another. Over a machine’s life this produces supersession chains — A was replaced by B, which was replaced by C — along with messier variants: one part superseded by a kit of several, or two old parts merged into a single new one.
A parts store has to resolve supersession gracefully and honestly. When a buyer searches for the part number printed on a fifteen-year-old parts book page, the store should recognise it, explain that it has been superseded, and offer the current equivalent — not return “no results” and lose the order. Saved order templates and reorder lists need to keep working as the numbers beneath them change. That means supersession must be modelled as a first-class relationship in the catalogue, with direction, dates and replacement notes, rather than bodged in as redirects or buried in free text.
Exploded Diagrams and BOM-Driven Navigation
Ask a maintenance engineer to find a part and they will not type a description into a search box — they will find the machine, find the assembly, look at the exploded diagram, and read off the callout number. Visual, bill-of-materials-driven navigation is how the aftermarket has always worked on paper, and a credible parts store reproduces it digitally: machine, then assembly, then an exploded view where each callout links to an orderable part.
Two practical points follow. First, the service bill of materials is not the engineering bill of materials: the groupings that make sense for manufacturing are not the groupings a fitter needs, so the sellable structure requires curation. Second, the diagrams and BOM data almost always live in engineering and ERP systems, so publishing them into the store is a systems integration exercise as much as a catalogue one. Interactive hotspotted diagrams are the gold standard, but even a static diagram beside a callout-to-part table transforms findability compared with search alone.
Kits, Service Bundles and Scheduled Maintenance
Aftermarket demand often arrives in bundles: the 500-hour service kit, the pump rebuild kit, the annual consumables order. Kits need to be sellable products in their own right, with their own part numbers and their own component lists — and those component lists are themselves subject to supersession, so a kit’s contents must update as its constituent parts change. Done well, kits raise order values and reduce the “I ordered the gasket but not the bolts” failure mode; service-schedule prompts against a customer’s registered machines take that a step further.
Search Is Part-Number-First
Parts buyers search differently. The dominant search is an exact part number — frequently mangled with spaces, hyphens, leading zeros or an OEM prefix that your system does not store. The second most common search is somebody else’s part number: a competitor’s reference, a previous supplier’s number, or the number from an acquired brand’s legacy catalogue. Cross-reference tables mapping those external numbers to your parts are commercial gold, because they let you capture demand that was never expressed in your own numbering scheme.
All of this argues for a dedicated search engine tuned for tolerant part-number matching alongside text search — the approach we took on the Astrak platform, where Algolia provides the product search in front of an Elastic Path catalogue. Search quality is not a polish item in a parts store; for a large proportion of sessions, search is the store.
The B2B Layer on Top
Everything above concerns the catalogue. Around it sits the standard set of B2B realities. Account-specific commercial terms are one: most manufacturers need customer-specific pricing served from the ERP, a deep enough subject that we will treat it properly in a separate article rather than skim it here.
Availability is another, and in the aftermarket it is decisive. A buyer with a stopped machine cares about one thing after fitment: can you supply it, and when? Stock positions and lead times live in the ERP and warehouse systems, and surfacing them credibly in the store — without hammering back-office systems on every page view — is an integration design problem we examined in detail in our article on real-time inventory and order orchestration in composable commerce. A parts store that shows no availability, or worse, wrong availability, sends urgent buyers straight back to the phone.
Channel structure is the third. Many equipment manufacturers sell through dealers, and a direct parts store raises immediate questions about channel conflict. There is no single right answer — some manufacturers sell direct, some route online orders to the servicing dealer, some give dealers their own branded parts storefronts, and many run a deliberate mixture by market. What matters architecturally is that the platform can present different catalogues, assortments and journeys to different channels without duplicating the underlying parts data, so the channel strategy remains a commercial decision rather than a technical rebuild.
Why Rigid Platforms Fight You — and Composable Doesn’t
Attempt all of the above on a conventional monolithic eCommerce platform and you will spend the project fighting the platform’s assumptions. Fitment becomes a sprawl of custom tables bolted onto a product model that never expected them. Supersession gets faked with redirects. Exploded-diagram navigation fights a templating system built for category grids. The part-number search behaviours buyers need exceed what the built-in search will do. Each workaround is individually survivable; collectively they produce a store that is expensive to change and fragile to upgrade — which matters, because your parts catalogue will keep evolving for as long as you keep making machines.
A composable architecture takes the opposite approach: choose a strong component for each job and integrate them. A flexible commerce engine such as Elastic Path provides the catalogue, cart and order core, with a product model open enough to carry fitment relationships, supersession links and kit structures as proper data, hierarchies that support machine-based navigation, and multiple catalogues for different channels and markets. A dedicated search service handles tolerant part-number and cross-reference matching. Your own front end owns the diagram-driven buying experience. And an integration layer connects the ERP and engineering systems that remain the source of truth for BOMs, stock and lead times.
This is not theoretical for us. For Astrak Group, we delivered a composable B2B eCommerce reseller platform built on Elastic Path, Algolia, Next.js and Microsoft Azure, with customers involved directly in shaping how search and ordering should work — and the platform added around £300,000 in new monthly revenue after launch. For Norgren, part of IMI Precision Engineering, we replaced a bespoke, externally maintained global web store with a composable eCommerce store assembled from off-the-shelf services around Elastic Path — cutting the cost of ownership, removing single points of failure, achieving a 100% Google Lighthouse score at launch, and freeing development effort for innovative features rather than platform maintenance. Different businesses, same lesson: when the catalogue is the hard part, the platform must bend to the catalogue, not the other way round.
Getting Started Without Boiling the Ocean
The biggest risk in an aftermarket eCommerce programme is not the technology — it is scope, and specifically data scope. Fitment, supersession and service-BOM data is often scattered across ERP records, engineering systems, dealer portals and institutional memory, and cleansing all of it for the entire installed base before launch is a route to never launching.
The pragmatic sequence is narrower: start with the parts that matter — the fast-moving consumables and wear parts that dominate order volume — and one or two machine families where the fitment data is strongest. Launch, measure what buyers search for and fail to find, and let that evidence drive which data you enrich next. Astrak’s experience is instructive here: unusually high customer involvement during the build produced a simpler buying journey than anyone would have specified upfront. Treat the store as a product that grows with your data, not a monument that must be complete on day one.
How McKenna Consultants Can Help
McKenna Consultants has spent more than 25 years building software for manufacturers and industrial engineering businesses, and B2B eCommerce for manufacturers is one of the areas where that experience runs deepest. We designed and delivered the composable Elastic Path platforms behind Astrak’s reseller business and Norgren’s global web store, and we build the systems integration that connects commerce to the ERP and engineering systems where parts data actually lives.
If you are weighing up an aftermarket parts channel — whether that is a first move from phone-and-email ordering or the replacement of a parts store that never quite worked — we can help you scope the catalogue model, the integrations and the phasing that make it succeed. Get in touch to talk it through.
