FLO Cycling - The Contact Patch. Why Wider is Better

[economicaltriathlete]

It makes sense that a smaller contact patch is faster on a perfectly flat surface. However, most races are on roads with many tiny and big bumps. Therefore having a small contact patch or hard tire makes these bumps more apparent and effectively slows the wheel because it bumps up and down. If the tire is softer these bumps are less apparent and therefore less force is needed to overcome them.

Anyway, I think the wider rims are faster because they are more aero and that's another conversation.

[FloCycling]

@economicaltriathlete,

You are talking about 2 completely different things. The contact patch and the "firmness" or "softness" of the tire are different components of rolling resistance. To look at the effect of a contact patch on a tires rolling resistance, you have to keep all other variables equal. You are correct though. The effects of rolling resistance are very small compared to the effects of aerodynamics. The main reason to add width is for the improved aerodynamics!

Chris

[330MillionGods]

@FloCycling,

//where did you hear recumbants and trikes have less drag :

From wikipedia. It seems in recumbants, since the cyclists body is more parallel to air flow, there is much less drag. Thats why they have world speed record and not upright bicycles.

// It's not to often you run out of gears on a ride -

IMO, that is because of resistive forces such as wind drag and rolling resistance of tyres etc.

Wind drag increases as the square of speed.

[330MillionGods]

@FloCycling,

//You also have to consider how hard it would be to push a gear ...

I suspect, once we reach the speeds appropriate for 11th gear, IMO, it should be easy to push the 12th gear wheel. But if we try to push 12 th gear while we are at speed apropriate for 7th ( for example) gear, then it would be difficult.

[330MillionGods]

Have you guys tought of a gearbox for bicycle with more than 10 gears ?.. I wonder why max. no. of gears found on any bicycle is 10 ?... I think a 15th or 20th gear should give much higher top-speed especially for recumbant bikes/trikes where wind drag is much less.

[FloCycling]

@330MillionGods,

The number of gears in the back is limited by the size of the chain and the amount of space between the bike frame and hub body. Campy has an 11 speed system and I believe Shimano is also working on one.

You also have to consider how hard it would be to push a gear any bigger than a 53x11. It's not to often you run out of gears on a ride.

Finally, where did you hear recumbants and trikes have less drag? They have a lot more frontal area than a tri bike.

[330MillionGods]

friction happens only when there is slippage. Wider tyre means less slippage; and hence less friction.

[FloCycling]

@330MillionGods,

That is not entirely true. What happens when an object is on an incline and not sliding down? Friction is holding it there. Additionally, this video is more about rolling resistance. You can search our blog or wikipedia for more on what rolling resistance is.

Thanks for your comments,

Chris