Fat Bike Science: An Extremely In-Depth Guesstimate on the Influence of Weight on a Fat Bike


Test Subject making a 33 degree right hand turn. Jack Kline, also pictured. 


We asked the question, and we had a pretty good feeling about how riding a heavy fat bike in a race would go. Science called. We answered. Hypothesis: We expected that a heavier fat bike would have an exponential detrimental impact on the rider’s result, with the long the race, the more impact. We also anticipated that more elevation on a course, the more detrimental the impact would be.

Procedure: We used last week’s Hanson Hills race as our benchmark. The Hanson race was 21.3 miles in length with 899 feet of elevation, with a total race time of 1:40. It was totally a part of the plan to have this race for this experiment, because it’s the only race in the area that is in the same ballpark in length as the 42km Vasa from yesterday.

The benchmark carbon bike weighed in at 24 pounds, a full nine pounds likes than our 33 pound Salsa Mukluk 3 from 2013. Aside from the weight, we also considered some variables that are impossible for us to account for perfectly, as far as the bikes themselves. These variables include:

-Gear ratio (1×11 GX, 34t oval and 10-42 cassette vs 1×10 round 32t and 11-36 cassette)
-Tubeless vs tubed wheels
– Rotating weight (45NRTH Flow/Dunderbeist combo vs 27 tpi Surly Nates)
-Rider fatigue (5 points more fatigue for Vasa than Hanson)

The course were markedly different as well, with asphalt-like, fast and tacky snow for Vasa and primarily soft, slow rut racing at Hanson Hills. However, we will assume that the increased elevation at Hanson (899 feet to 410 at Vasa) also contributed to lowering the average speed as well.

We’ll assess the impact of a heavy bike on two variables, compared to other riders on results, and by the effort of the rider as measured by heart rate, the very scientific Suffer Score, and kilojoules as a form of total energy output.

Results: Wakeley won both races, but he’s on a different level, so we’ll use Rick Wetharald as our benchmark. And, he’s a good one. Rick finished behind our test subject at Fat Bike Nationals by around a minute, then beat our test subject the next day at Fat Bike States by around 20 seconds.

At Hanson, Rick was second to Wakeley, with a 1:19 gap to Test Subject after one lap and putting another :13 into him on the second lap. That’s an important element for our study; on a light bike, our Test Subject was much closer to Rick’s pace after the race went over the 45 minute mark.

At Vasa, Rick finished 2:57 ahead of our test subject, one hour and thirty minutes dead for second place overall. With no lap data to look at, our closest benchmark for a halfway gap comes from spectators at the Singletrack, where riders headed back out without returning the six minutes or so back to Timber Ridge. Our most accurate source had the gap at 30 seconds, meaning the wheels came off for Test Subject on the second lap and finish. If that’s true, he lost roughly two and half minutes on the second circuit. That’s a big difference from 13 seconds in the second half of the race at Hanson.

The physical exertion numbers are also interesting. At Hanson, the race was rated a 128 Sufferscore, with 43% of the race in Tempo (145-163bpm) and 57% at Threshold (164-181bpm). The Vasa, was actually a lower Sufferscore, likely from faster, perfectly groomed trails. The zone output was very similar, 43% of the race at Tempo and 56% at Threshold.

The average heart rates were 165 at Hanson and 164 at Vasa, very similar. Total calories burned were, according to a Wahoo Elemnt, 1645 at Hanson and 1495 at Vasa.

Conclusions: Zero surprises here, really, but there’s kind of a big qualifier. Our data shows that, assuming the rider is capable of a consistent effort, the penalty of a heavy bike is exponential, but it’s not such a big deal on shorter rides. For rides under 1 hour, it’s a minimal difference from an expensive, light bike, except on the climbs. When the race or ride gets longer, the fatigue of pushing the weight of a heavy bike becomes more and more of a penalty as the race continues, especially as more elevation is introduced.


Salsa Mukluk 3. This is what it looks like while riding it.



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