Slow speed on gravel bike. Advice?

[TrekCentury]

@CodyS

What is the important of low RR tires vs fitness for extended distance efforts. I

Fitness for sure. A pro will beat you with the worst tires on his bike. Now with your improved fitness, you throw on some fast tires and you will feel like a pro.

[Fewdfreak]

@CodyS

What is the important of low RR tires vs fitness for extended distance efforts. I have a 165km ride planned for later this year. Effort wise it’s fine, I’ll aim for a power value that’s sustainable. I assume then the tires would speed that up, marginally only?

Ahh yes, marginal but often noticeable (or we would like to think), especially as much as we cyclists obsess over and stack marginal gains . That being said I’d have to brush up on my physics but going from say a stock tire such as a Bontrager Girona at 40w RR to a G-One variety at around 20w RR will make a big difference in the amount of time you are on the bike for that 165k. You could hold the same flat power number for the entire course on either set but the faster tire will get you to the end first–how much quicker will be course dependent and that is a question for a program like Best Bike Split. There are also quick maths you can do (and I remember Jonathan talking about them on an old TR podcast) about how much certain variables “cost” such as 1lb, 1w, or x mph of wind. Sometimes you have to consider how long you want to be out on course as well as avg speed, etc and if something comes down to like going from 22kph to 25kph for 165k due to a faster tire it could save you almost an hour of riding. Now this is probably in an ideal circumstance but I’d sure optimize for that gain.

[FrankTuna]

@Fewdfreak

how much quicker will be course dependent and that is a question for a program like Best Bike Split

This is a great point! I believe you can put in the CRR (rolling resistance) numbers and upload your course to get an idea of the impact.

From a purely subjective view though, the stock Gironas on my Checkpoint made it feel like I was riding through mud (even on dry pavement) compared to better tires (Tracers in my case). If nothing else, it’s a more enjoyable ride when it feels less like you’re fighting the bike with each pedal stroke.

I personally wouldn’t swap tires to save a few watts (definitely marginal gains territory) but going from the bottom of the BRR list to one of the better tires would be a solid plan IMHO.

[Nin]

As an example, suppose a 90 kg system weight, 0.4 CdA and flat ground with smooth pavement (so we can use BRR numbers) at 200 watts. Comparing the Bontragers to a G-one RS Pro yields the following:

• 28.4 kph with the Bontragers
• 30.8 kph with the G-one RS’s

Usually these things would be pretty marginal, but those tires are phenomenally slow, as in, the rolling resistance is twice as high as the Schwalbes. Changing the assumptions will move the numbers around a bit but the difference will still be large.

You can play around with the numbers yourself here:

An interactive model-based calculator of cycling power vs. speed

Alternatively, you’d only need to put out 163 watts on the Schwalbes to go the same speed as at 200 watts with the Bontragers. That’s a lot of training hours.

[wik04]

Agree. While being stronger obviously is the best way to go faster, those tires are terrible so you might as well throw something on the bike that at least doesn’t suck. There are lots of good options now. Tackle the issue from all directions.