Data as of: DVSA MOT results to 2025
Triumph Thunderbird vs Harley-Davidson XL
The Harley-Davidson XL passes its MOT first time more often than the Triumph Thunderbird: 87.9% vs 87.8%, a 0.1-point lead.
MOT reliability, side by side
| Metric | Triumph Thunderbird | Harley-Davidson XL |
|---|---|---|
| First-time pass rate | 87.8% | 87.9% |
| Outright fail rate | 6.2% | 5.3% |
| Vs comparable bikes (age & mileage adjusted) | +2.1 pts | -0.1 pts |
| Engine size | 885cc | 883cc |
| Rank among all models | #1669 of 5428 | #1639 of 5428 |
| Median miles at test | 13,106 | 6,108 |
| MOT tests analysed | 56,312 | 18,541 |
| Most common failure | brakes | lamps and reflectors |
First-time outcomes on normal tests, 2005–2025. "Most common failure" is the component group with the most recorded defects on failed tests. Read pass rates against test counts: a smaller sample is noisier. Source: DVSA anonymised MOT results.
"Vs comparable bikes" is the first-time pass rate minus the rate expected for each bike's own mix of age, mileage and test class, in percentage points: positive means better than comparable bikes. How this works.
What fails, side by side
| Component | Triumph Thunderbird | Harley-Davidson XL |
|---|---|---|
| Lights & signalling | 2.2% | 3.0% |
| Brakes | 2.0% | 0.8% |
| Steering & suspension | 1.3% | 0.9% |
| Tyres & wheels | 1.6% | 0.5% |
| Structure & body | 0.3% | 1.0% |
| Fuel & exhaust | 0.4% | 0.1% |
| Drive system | 0.2% | 0.0% |
A test that fails on two components counts once in each. Component links go to the bikes most likely to fail on it.
Pass rate by test year
| Test year | Triumph Thunderbird | Harley-Davidson XL |
|---|---|---|
| 2018 | 87.8% | 87.1% |
| 2019 | 87.7% | 86.5% |
| 2020 | 88.8% | 89.4% |
| 2021 | 88.2% | 88.8% |
| 2022 | 88.9% | 88.5% |
| 2023 | 90.5% | 88.4% |
| 2024 | 88.2% | 87.6% |
| 2025 | 89.5% | 87.5% |
Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.
Pass rate by mileage
| Mileage | Triumph Thunderbird | Harley-Davidson XL |
|---|---|---|
| 0k-10k miles | 90.5% | 89.0% |
| 10k-20k miles | 87.3% | 85.5% |
| 20k-30k miles | 85.4% | 85.6% |
| 30k-40k miles | 84.3% | 83.6% |
| 40k-50k miles | 83.2% | 82.3% |
Bands with fewer than 30 tests for either bike are left out.
Triumph Thunderbird vs Harley-Davidson XL FAQ
Which is more reliable, the Triumph Thunderbird or the Harley-Davidson XL?
The Harley-Davidson XL passes its MOT first time more often than the Triumph Thunderbird: 87.9% vs 87.8%, a 0.1-point lead. Adjusted for age, mileage and test class, the Triumph Thunderbird still comes out ahead: +2.1 points vs comparable bikes for the Triumph Thunderbird, -0.1 for the Harley-Davidson XL. An MOT checks roadworthiness items, not engine or gearbox internals.
What does the Triumph Thunderbird fail its MOT on most?
Lights & signalling: 2.2% of Triumph Thunderbird MOT tests failed on it, then brakes (2.0%).
What does the Harley-Davidson XL fail its MOT on most?
Lights & signalling: 3.0% of Harley-Davidson XL MOT tests failed on it, then structure & body (1.0%).
Which holds up better at high mileage, the Triumph Thunderbird or the Harley-Davidson XL?
They are level: at 40k-50k miles the Triumph Thunderbird passes 83.2% first time and the Harley-Davidson XL 82.3%.
See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.