Data as of: DVSA MOT results to 2025
Harley-Davidson XL1200S vs Triumph Thunderbird
The Triumph Thunderbird passes its MOT first time more often than the Harley-Davidson XL1200S: 87.8% vs 87.3%, a 0.5-point lead.
MOT reliability, side by side
| Metric | Harley-Davidson XL1200S | Triumph Thunderbird |
|---|---|---|
| First-time pass rate | 87.3% | 87.8% |
| Outright fail rate | 6.4% | 6.2% |
| Vs comparable bikes (age & mileage adjusted) | +1.7 pts | +2.1 pts |
| Engine size | 1,200cc | 885cc |
| Rank among all models | #1818 of 5428 | #1669 of 5428 |
| Median miles at test | 11,095 | 13,106 |
| MOT tests analysed | 4,168 | 56,312 |
| Most common failure | lighting and signalling | brakes |
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 | Harley-Davidson XL1200S | Triumph Thunderbird |
|---|---|---|
| Lights & signalling | 3.2% | 2.2% |
| Brakes | 1.8% | 2.0% |
| Tyres & wheels | 1.2% | 1.6% |
| Steering & suspension | 1.1% | 1.3% |
| Fuel & exhaust | 0.6% | 0.4% |
| Structure & body | 0.5% | 0.3% |
| Drive system | 0.1% | 0.2% |
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 | Harley-Davidson XL1200S | Triumph Thunderbird |
|---|---|---|
| 2018 | 84.6% | 87.8% |
| 2019 | 90.0% | 87.7% |
| 2020 | 88.2% | 88.8% |
| 2021 | 83.5% | 88.2% |
| 2022 | 88.6% | 88.9% |
| 2023 | 91.4% | 90.5% |
| 2024 | 89.1% | 88.2% |
| 2025 | 91.9% | 89.5% |
Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.
Pass rate by mileage
| Mileage | Harley-Davidson XL1200S | Triumph Thunderbird |
|---|---|---|
| 0k-10k miles | 88.8% | 90.5% |
| 10k-20k miles | 88.1% | 87.3% |
| 20k-30k miles | 84.2% | 85.4% |
| 30k-40k miles | 84.2% | 84.3% |
| 40k-50k miles | 81.5% | 83.2% |
Bands with fewer than 30 tests for either bike are left out.
Harley-Davidson XL1200S vs Triumph Thunderbird FAQ
Which is more reliable, the Harley-Davidson XL1200S or the Triumph Thunderbird?
The Triumph Thunderbird passes its MOT first time more often than the Harley-Davidson XL1200S: 87.8% vs 87.3%, a 0.5-point lead. Adjusted for age, mileage and test class the two are level (+1.7 vs +2.1 points against comparable bikes), so the raw gap is mostly down to how old and how used each fleet is. An MOT checks roadworthiness items, not engine or gearbox internals.
What does the Harley-Davidson XL1200S fail its MOT on most?
Lights & signalling: 3.2% of Harley-Davidson XL1200S MOT tests failed on it, then brakes (1.8%).
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%).
Which holds up better at high mileage, the Harley-Davidson XL1200S or the Triumph Thunderbird?
At 40k-50k miles the Triumph Thunderbird passes first time more often: 81.5% for the Harley-Davidson XL1200S vs 83.2% for the Triumph Thunderbird.
See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.