Are mountain bike tyres actually faster than gravel tyres? Recent trends suggest they might be, with top gravel pros maxing out tyre clearance and opting for wider MTB tyres in major races. But do the claims hold up in real-world conditions?
In this episode, we dive deep into the numbers with John Karrasch, a bike fitter, physiotherapist, performance tester, and Escape Collective member who has been conducting rigorous field testing using the Chung Method.
Unlike traditional drum tests, which measure rolling resistance in controlled lab conditions, John’s testing focuses on real-world gravel surfaces, combining rolling resistance, aerodynamics, and surface effects.
We explore:
- The surprising results that challenge long-held assumptions about gravel tyre performance
- Why traditional rolling resistance tests might not tell the full story
- How real-world testing methods like the Chung Method work
- The impact of tyre width, casing compliance, and aerodynamics on speed
- What these findings mean for your own gravel bike setup
If you’re serious about tyre selection for gravel, or just want to know if you can enjoy the grip and puncture resistance of a wider tyre without the speed penalty you might expect this episode (paired with our earlier deep dive with Robert Chung) is essential listening.
Escape Collective members get full access to John’s test data and in-depth analysis: sign up today to unlock the full results!
Episode Timestamps
0:00 - 2:45 | Introduction to John Karrasch and His Background
- Ronan Mc Laughlin introduces John Karrasch, highlighting his roles as a professional bike fitter, coach, and physiotherapist assistant.
- John mentions his extensive experience in mountain biking since 1999 or 2000 and his recent deep dive into aero testing.
- Ronan expresses his curiosity about John's background in cycling and aero testing.
- John explains his transition into aero testing over the past two to three years and his involvement in the Chung method of testing.
2:45 - 4:18 | Discussion on Bike Fitting and Crank Length
- Ronan asks John about his frequent engagement in bike fitting discussions on the Escape Collective forum and Discord.
- John shares his thoughts on the trend of shorter cranks used by Visma-Lease a Bike riders and his own experiences with crank length.
- John mentions his crank lengths on different bikes and the variability in what works best for different riders.
- Ronan and John discuss the lack of a one-size-fits-all approach to bike fitting and the importance of individualised adjustments.
4:30 - 10:00 | John's Journey into Tyre Testing
- John explains his motivation for tyre testing, stemming from his experience with a gravel bike and mountain bike tyres.
- He describes his initial observations and the decision to use the Chung method for testing tyre performance.
- John highlights the challenges of using Strava and Training Peaks data to draw definitive conclusions about tyre performance.
- He emphasises the importance of field testing with rolling resistance and CDA data to optimise bike and rider performance.
24:56 - 32:08 | Challenges and Adaptations in Tyre Testing
- John discusses the difficulties of finding a suitable test course and the importance of maintaining consistency in testing conditions.
- He describes the process of using beer cans as markers for turns and the challenges of riding without using brakes.
- John shares his initial frustrations with the Chung method and the guidance he received from Robert Chung to improve his testing.
- He explains the importance of reconstructing an elevation profile using speed and power data to accurately measure rolling resistance.
32:08 - 33:12 | Detailed Testing Methodology
- John provides a detailed description of his testing methodology, including the use of a dual-sided power meter and a speed sensor.
- He explains the importance of maintaining consistent CdA values by wearing the same clothing and carrying the same water bottle.
- John discusses the challenges of testing on different days and the need to adjust for variations in temperature and weather conditions.
- He highlights the importance of using a GPS unit that has stabilised to the ambient temperature to ensure accurate elevation data.
33:12 - 42:30 | Tyre Testing Results and Findings
- John lists the tyres he has tested, including the Continental Terra Speed, Terra Hard Pack, and Race King, Maxxis Aspen, and Vittoria Peyote XC Race.
- He shares his findings that the Race King 29x2.2 was faster than the Terra Speed and Terra Hard Pack on gravel roads.
- John explains the significance of the rolling resistance values and the power savings achieved by using the Race King.
- He discusses the performance of the Maxxis Aspen and Vittoria Peyote XC Race on gravel roads and their comparison to the Race King.
42:30 - 48:01 | Impact of Gravel Surface on Tyre Performance
- John explains the differences in tyre performance on different gravel surfaces, including cat one and cat two gravel.
- He notes that the Race King remained faster on Category 2 gravel, while the Vittoria Peyote XC Race performed better on Category 1 gravel.
- John discusses the trend of wider tyres having higher CDA values and the impact of tyre size on rolling resistance.
- He highlights the importance of testing on a variety of surfaces to understand the performance of different tyres.
50:41 - 55:28 | Future Directions and Ongoing Testing
- John mentions his plans to continue testing more tyres and exploring different tyre sizes and compounds.
- He discusses the potential for using larger tyres on gravel bikes and the impact of aerodynamics at higher speeds.
- John emphasises the importance of consistent testing conditions and the challenges of maintaining these in real-world scenarios.
- He shares his thoughts on the potential influence of consumer testing on future tyre design and the need for more data to inform decisions.
54:33 - 56:35 | Conclusion and Final Thoughts
- Ronan and John discuss the importance of virtual elevation testing for determining the fastest tyres and pressures.
- John highlights the potential for virtual elevation testing to become more widespread and influence tyre design.
- They discuss the challenges of testing in different weather conditions and the need for patience and consistency.
- John encourages listeners to follow his testing results on Instagram and engage with him on the Escape Collective Discord and website.
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