Problem Statement
Michelin's fleet sales conversations hinge on total-cost-of-ownership: a premium tire costs more upfront but can win on fuel efficiency, longer lifecycle, fewer breakdowns, and lower CO2 across a whole fleet. That math lived in complex internal Excel models — hard to present to a customer, error-prone to tweak live, and impossible to hand over as a polished artifact. Sales needed an interactive tool that produced the exact same numbers as the trusted spreadsheet, but as a usable, shareable web app.
Proposed Solution
A web-based fleet cost calculator built for Michelin Tires (London) that computes fuel savings, tire lifecycle costs, CO2 emissions, and breakdown risk across configurable fleet sizes — visualizing the trade-offs with charts and exporting a branded PDF for the customer. Critically, the calculations are Excel-compliant: they reproduce the client's existing financial model precisely, so the numbers are trusted on day one.
Full Solution Details
- Multi-dimensional modeling — fuel savings, tire lifecycle cost, CO2 emissions, and breakdown-risk cost.
- Fleet scaling — run the model across different fleet sizes to show how savings compound.
- Excel parity — outputs match the client's spreadsheet formulas exactly (the hard requirement).
- Visualization — Recharts-driven breakdowns so a non-technical buyer can see the trade-off at a glance.
- PDF export — a polished, branded report to leave with the customer.
Technical Documentation
React + TypeScript single-page app with Recharts for the financial visualizations. The core engineering challenge is fidelity, not features: faithfully porting a non-trivial Excel financial model into TypeScript, including its rounding, ordering, and edge-case behavior, so results are identical to the spreadsheet a domain expert already trusts. On top of that sits an interactive UI (adjust inputs, see results recompute) and a client-side PDF export pipeline that renders the results into a branded, shareable document.
Tech Stack
React, TypeScript, Recharts; client-side PDF generation; financial/Excel-model porting.
System Design
Inputs (fleet size, tire choice, usage, fuel price, ...)
│
▼
Excel-faithful calculation engine (TypeScript port)
fuel savings · tire lifecycle · CO2 · breakdown risk
│
┌─────┴───────────────┐
▼ ▼
Recharts visualizations Branded PDF export
(trade-off breakdowns) (leave-behind report)
Smart Architectural Decisions
- Fidelity to the source-of-truth model. The decisive call was making the engine Excel-compliant — reproducing the client's existing formulas exactly. Trust is the product here; a prettier tool with different numbers would have been rejected. Prioritizing correctness-to-spec over reinvention is mature client engineering.
- Domain modeling of TCO. Capturing fuel, lifecycle, CO2, and breakdown risk as separate, composable cost dimensions mirrors how the business actually reasons about value.
- Buyer-facing output. PDF export + clear charts turn an internal calculation into a sales asset — building for the user of the output (a fleet customer), not just the operator.
- Client-side only keeps a sales tool simple to deploy and use anywhere, including offline in a meeting.
Impacts
Turned Michelin's trusted-but-unshareable Excel TCO model into an interactive, branded, customer-facing calculator — enabling fleet sales to demonstrate fuel/lifecycle/CO2/breakdown savings live and leave behind a professional report, with numbers the client already trusts.
Demonstrated Skills
Client/consulting delivery (building to an exact, trusted spec); porting complex financial/Excel models to TypeScript with fidelity; data visualization (Recharts); PDF generation; translating internal business logic into customer-facing tools; React + TypeScript.