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Rolling Resistance - front vs rear tyre
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thinking in terms of gravel riding where grip on the front is important and low RR is important everywhere but especially on the back:
- what is the rough proportion of rolling resistance front to rear tyre?
- is this directly proportional to the weight distribution which silca quote as 47/53 for gravel bikes or is it a more significant exponential relationship?
- does the drive force play into this at all?

the point being, i expect RR is more significant on the rear than front but is it enough so to make it a sensible choice to run a slower but grippier tyre on the front and not lose too much speed?
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Re: Rolling Resistance - front vs rear tyre [pk1] [ In reply to ]
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pk1 wrote:
- is this directly proportional to the weight distribution which silca quote as 47/53 for gravel bikes or is it a more significant exponential relationship?
Yes. It’s easy to approximate too, with a bathroom scale and a 2x4


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- does the drive force play into this at all?
Probably at low speeds and high power, though it’s not usually discussed. Practically, it may not impact your choice of tires, ie you’ll still want low rolling resistance.
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Re: Rolling Resistance - front vs rear tyre [pk1] [ In reply to ]
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My guess: much like chain wear and chain friction have a very strong correlation, I assume tyre wear and rolling resistance also have a strong correlation. i.e., due to the weight and drive loads, the rear tyre will be contributing significantly more to the overall drag, as demonstrated by its significantly faster wear rate.

The major (e.g. BRR) rolling resistance tests only focus on passive rolling (like a front wheel), right? I'd be interested to see what effect a drive load through the wheel to the road contributes in terms of watts lost. Should be eminently measureable.

That said, I wouldn't go out of my way to put on a known worse tyre anywhere I could avoid it. But a wider rear makes a lot of sense (lower RR, more comfort, and not impacted as much by aerodynamics - wins all round)
Last edited by: MattyK: Nov 15, 20 22:56
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Re: Rolling Resistance - front vs rear tyre [MattyK] [ In reply to ]
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MattyK wrote:
My guess: much like chain wear and chain friction have a very strong correlation, I assume tyre wear and rolling resistance also have a strong correlation. i.e., due to the weight and drive loads, the rear tyre will be contributing significantly more to the overall drag, as demonstrated by its significantly faster wear rate.

The major (e.g. BRR) rolling resistance tests only focus on passive rolling (like a front wheel), right? I'd be interested to see what effect a drive load through the wheel to the road contributes in terms of watts lost. Should be eminently measureable.

That said, I wouldn't go out of my way to put on a known worse tyre anywhere I could avoid it. But a wider rear makes a lot of sense (lower RR, more comfort, and not impacted as much by aerodynamics - wins all round)

yes, the wear and noise levels from the rear are part of what makes me wonder whether there is something more than weight distribution in play here.
i think the wear will be largely due to the drive force which may or may not relate to RR
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Re: Rolling Resistance - front vs rear tyre [pk1] [ In reply to ]
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pk1 wrote:
yes, the wear and noise levels from the rear are part of what makes me wonder whether there is something more than weight distribution in play here.
i think the wear will be largely due to the drive force which may or may not relate to RR
It's still a loss of power, as the tyre carcass will be flexed to provide drive force and the rubber will be gripping the road in a different direction to the front wheel. It should definitely be measureable, the unknown I have is whether it would be directly proportional to front wheel RR or different depending on the tyre itself.
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Re: Rolling Resistance - front vs rear tyre [MattyK] [ In reply to ]
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MattyK wrote:
The major (e.g. BRR) rolling resistance tests only focus on passive rolling (like a front wheel), right? I'd be interested to see what effect a drive load through the wheel to the road contributes in terms of watts lost. Should be eminently measureable.

The BRR tests *are* driven, I think, just by the roller. Which should, in theory, be no different than being driven by the wheel? But BRR probably waits until the system reaches a steady-state speed before measuring. It'd be the acceleration phase where the "drive" losses would take effect, I think. E.g. while a real-world bike is coasting at a steady speed the only difference between front and rear wheel would be weight distribution.
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