Harley-Davidson XL 1200 T Superlow SPORTSTER18 vs Triumph Thunderbird

The Harley-Davidson XL 1200 T Superlow SPORTSTER18 passes its MOT first time more often than the Triumph Thunderbird: 94.1% vs 87.8%, a 6.3-point lead.

MOT reliability, side by side

first-time pass rate, outright fail rate and tests analysed · 2005–2025

Metric	Harley-Davidson XL 1200 T Superlow SPORTSTER18	Triumph Thunderbird
First-time pass rate	94.1%	87.8%
Outright fail rate	1.7%	6.2%
Vs comparable bikes (age & mileage adjusted)	+5.7 pts	+2.1 pts
Engine size	1,202cc	885cc
Rank among all models	#153 of 5428	#1669 of 5428
Median miles at test	6,724	13,106
MOT tests analysed	290	56,312
Most common failure	tyres	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.

Pass rate by test year

first-time MOT pass rate in each calendar year both bikes were tested

Test year	Harley-Davidson XL 1200 T Superlow SPORTSTER18	Triumph Thunderbird
2021	87.9%	88.2%
2022	95.4%	88.9%
2023	95.5%	90.5%
2024	97.9%	88.2%
2025	94.0%	89.5%

Each year mixes bikes of different ages, so a fleet that is getting older tends to slip.

Pass rate by mileage

first-time MOT pass rate by miles on the clock at test

Mileage	Harley-Davidson XL 1200 T Superlow SPORTSTER18	Triumph Thunderbird
0k-10k miles	94.7%	90.5%
10k-20k miles	92.3%	87.3%

Bands with fewer than 30 tests for either bike are left out.

HARLEY-DAVIDSON XL 1200 T SUPERLOW SPORTSTER18 94.1% pass · 290 tests TRIUMPH THUNDERBIRD 87.8% pass · 56.3k tests

See each bike's full report (trend, mileage curve, failure breakdown and rivals) on its own page.