CRR and tire width

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GooseRider
Posts: 58
Joined: Wed May 10, 2017 10:52 am

CRR and tire width

Post by GooseRider »

Hi,

I went to http://www.analyticcycling.com/ForcesTires_Page.html to understand your CRR model. Is it correct that the CRR model is for 23C tires? Running 28C tires allows lower tire pressure for the same rolling resistance. See https://www.bicyclerollingresistance.co ... i-23-25-28

For this tire (GP4000ii) 23C at 120psi has similar rolling resistance as 25C at 100psi and 28C at 80psi.

So if I use 80psi in my rear 28C tire and 70psi in my front 28C tire, what tire pressure should I use in your model?

Thanks,

Morten
Velocomp
Velocomp CEO
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Joined: Fri Jan 11, 2008 8:43 am

Re: CRR and tire width

Post by Velocomp »

75PSI, the average of the two...
John Hamann
GooseRider
Posts: 58
Joined: Wed May 10, 2017 10:52 am

Re: CRR and tire width

Post by GooseRider »

Wouldn't that overestimate the rolling resistance significantly? To my undestanding the CRR model does not take tire width into account and a 28mm wide tire at 75psi has the same rolling resistance as a 23mm tire at 100psi according to the link I shared.

Thus, I am thinking I should use an equivalent pressure of 100psi in the model?

Thanks,

Morten
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: CRR and tire width

Post by Velocomp »

If you believe their data, then use their number...
John Hamann
GooseRider
Posts: 58
Joined: Wed May 10, 2017 10:52 am

Re: CRR and tire width

Post by GooseRider »

You don't find the reference credible?

What CRR would you suggest I use for 700x28C Yksion Elite tire with latex tubes run at 70 psi front and 80 psi rear?

Thanks,

Morten
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: CRR and tire width

Post by Velocomp »

Common sense tells me that wider tires and lower tire pressure would increase Crr. I would set Crr to 0.0056, a bit higher than the default number. Please post a ride file with this setting.
John Hamann
GooseRider
Posts: 58
Joined: Wed May 10, 2017 10:52 am

Re: CRR and tire width

Post by GooseRider »

John,

Any specific riding conditions to make the data most useful?

Morten
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: CRR and tire width

Post by Velocomp »

GooseRider wrote:John,

Any specific riding conditions to make the data most useful?

Morten
None in particular. Just do your normal ride, then post the results.
John Hamann
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