Laboratory values
In contrast to the measurements taken in practice, the rolling resistance on the test bench is much more varied. For both tyre manufacturers, the 29ers rolled best, followed by 27.5-inch tyres and the plus tyres at the end by a clear margin. At Schwalbe, the plus tyres rolled 29 percent worse than the 29ers and at Specialized 43 percent worse. The large discrepancy to the practical values can be explained by the uneven and loose surface of the uphill test track. Although the Plus tyres have a higher rolling resistance, which is particularly noticeable on asphalt, they benefit from better traction with less slippage off-road and can absorb obstacles better thanks to the low air pressure without having to lift the entire system weight of rider and bike.
Rolling resistance: 27.5+: 0 | 27.5: 1 | 29: 2
Practical test
With the help of a power measurement crank (Sram Quarq), we rode all six pairs of tyres against each other at a constant speed on a 220 metre long uphill trail (23 vertical metres). In order to minimise dispersion, each tyre was ridden four times on the varied terrain with roots, loose gravel and solid rocks. Although the Specialized Plus tyres feel much more sluggish compared to the narrower ones and the higher weight causes more lifting work, the extremely small differences of only 2.4 percent in the overall performance required are surprising. The 29er performs best with 294.3 watts, closely followed by the 27.5 inch with 300.8 watts and the 27.5+ with 301.3 watts. With an incredible 0.4 percent difference, the three Schwalbe tyres are even closer together. So a tie on the climbs.
Rolling resistance: 27,5+: 1 | 27,5: 1 | 29: 1
Roll out
To check how much speed the tyres lose when rolling over obstacles, we carried out three roll-out tests with each tyre. After rolling off from a fixed starting point on a hill, we rolled over a board with five bolted-on obstacles (6 cm high) followed by another five with a height of three centimetres. Both the Specialized and Schwalbe Plus tyres lose the least speed and roll the furthest. The combination of the lower air pressure of 1.0 instead of 1.5 bar and the relatively large diameter favours rollover behaviour. The small 27.5 tyres stick to the obstacle the most and come to a stop sooner. Advantage of plus tyres.
Rolling resistance: 27.5+: 2 | 27.5: 0 | 29: 1
What rolls best?
Despite the higher weight, the Plus tyres do not require more energy on the climbs.
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