Why do some bike hold speed better than others?

[skiezo]

What makes some bike hold speed better than others?
On my gravel bikes my Pivot vault holds better/easier than my T Labs Ti. Weight is within 14 ozs .
My Ti Desalvo seems to hold speed better than my steel AR but the AR get the nod on comfort and long rides.

[NateFrentz]

If everything is maintained well, then it's probably the stuff that affects your positioning on the bike / aero. You could try replacing the chains plus all bearings in the BBs and wheels in the "slower" bikes to eliminate those sources. How different are the tires, tubes, and psi?

[Ken Robb]

Heavier wheels are probably slower to get up to speed but may provide a flywheel effect to maintain speed on rolling terrain?

[prototoast]

Rolling resistance from the tires is probably the biggest factor.

[Fat Cat]

Weight and friction rule the world.

[Ken Robb]

Originally Posted by Fat Cat

Weight and friction rule the world.

Are you a marriage counselor?

[cmg]

Deep rims coupled with light tires and tubes hold speed better. It's really mixture of fit and wheels.

[Mark McM]

Originally Posted by cmg

Deep rims coupled with light tires and tubes hold speed better. It's really mixture of fit and wheels.

This effect is often exaggerated. It is true that effective inertia of mass at the periphery of the wheel is double the inertia of the non-rotating parts of the bike. But mass at the periphery of the wheel (rims and tires) is just a small portion of the total inertia. Take for example, a rider that weighs 170 lbm wearing clothing, shoes and helmet that weighed 6 lbm, and that the weight of their bike is 20 lbm, for a total mass 196 lbm. Further, the rims + tires on this bike weight 4 lbm, and since the effective inertia of rotating mass is double, the effective inertia of the bike is 200 lbm. Now let's increase the weight of each rim + tire by 1/2 lbm, or 1 lbm for both wheels, which increase the total effective inertia by 2 lbm, for a total effective inertia of 202 lbm. This is just 1% increase the total inertia. On any given day and on any given road, the rider's power output, or total drag (rolling resistance plus aero drag) may vary by more than that, so on a good day the rider may be able hold speed better on the lighter wheels, and on a bad day they won't be able to hold speed as well on the heavier wheels.

Or consider this: A full water bottle weighs about 2 lb. this adds the same inertia as adding 1 lb. to the rims + tires. When was the last time you heard someone remark, "boy, my bike sure does hold speed better when I've got a water bottle on the bike!", or, "I'm going to be riding rolling terrain today, I better make sure my water bottles are full so my bike can hold speed better!"

[Talrand]

99-101% placebo.

[jimoots]

Assuming both bikes are well maintained, tyres and aerodynamics is the answer here.

[Black Dog]

Originally Posted by Talrand

99-101% placebo.

Agree

[adub]

Originally Posted by skiezo

What makes some bike hold speed better than others?
On my gravel bikes my Pivot vault holds better/easier than my T Labs Ti. Weight is within 14 ozs .
My Ti Desalvo seems to hold speed better than my steel AR but the AR get the nod on comfort and long rides.

How have you verified this?

[unterhausen]

I have used tires that made it feel like my bike was going through molasses. Some of them only while turning. I had some on my commuting bike that were awful, and easily got punctures too.

[Spdntrxi]

wheels and tires mostly...

[FastCanon]

Going uphill or downhill?