Tire Width vs. Performance

In article 3F78AC77.16022C1D@hocuspocus_ti.com said:

I still don't know why Terry thinks rotating mass doesn't matter (why wouldn't it matter just as
much as any other mass on the bike?).

One must be awfully careful with word choice, I guess.

The fact that the mass *rotates* doesn't matter. Rotating mass is just as important (or unimportant)
as any other mass on the bike or the rider.
--
terry morse Palo Alto, CA terrymorse.combikeOpen ↗

Terry Morse said:

In article said:

Smaller tires are usually lighter. This is good because less energy is consumed when you are
accelerating.

Uh oh, it's the "rotating mass" argument again. Suffice it to say that rotating mass has a neglible
impact on acceleration, and we'll be done with it.

I think you misrepresent the argument. 'Rotating mass' does have a significant effect on
acceleration. No doubt about that.

The reason why you should not be too concerned about 'rotating mass' is that acceleration does
not occur that often when you ride a bicycle. Even when it does, the acceleration is not that
great in magnitude. So in 'real world terms' you might as well ignore the extra inertia effect of
rotating mass.

However the effect of having significantly lighter tyres (contributing to an overall lighter
bike) can certainly provide a tangible benefit in hill climbing. That is a straight weight
reduction argument.

Quoted message said:

Interested parties can search google for a google of arguments on rotating mass.

Yes.

SNOOPY

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te**yso said:

I think you misrepresent the argument. 'Rotating mass' does have a significant effect on
acceleration. No doubt about that.

Let's see. I look, at the one hand, at my 240g tires, and think about how much energy it takes to
accelerate those. OK, twice as much as 240g just hanging on my body. Oops, though, there is a lot
more than 240g hanging on my body. Even more than 480g.

The difference in mass between very light, and very heavy, racing tires and rims is not that much.
200g would be a large difference; that would be going from very heavy rims/tires to very light, as
long as the discussion is about racing equipment. The change in energy requirements between those
wheels is equivalent to either having, or not having, a water bottle. Spend the same amount of time
and money worrying about the tires as about that water bottle. For the finishing sprint you can toss
the bottle to the crowd.

--

David L. Johnson

__o | It is a scientifically proven fact that a mid life crisis can _`\(,_ | only be cured by
something racy and Italian. Bianchis and (_)/ (_) | Colnagos are a lot cheaper than Maserattis
and Ferraris. -- Glenn Davies

But the people who think this have such fat heads that it completely negates any weight advantage
that they might get...

Nick

Quoted message said:

In article <[email hidden]>, "onefred" <[email hidden]> wrote:

Smaller tires are usually lighter. This is good because less energy is consumed when you are
accelerating.

David L. Johnson said:

te**yso said:

I think you misrepresent the argument. 'Rotating mass' does have a significant effect on
acceleration. No doubt about that.

Let's see. I look, at the one hand, at my 240g tires, and think about how much energy it takes to
accelerate those. OK, twice as much as 240g just hanging on my body. Oops, though, there is a lot
more than 240g hanging on my body. Even more than 480g.

The difference in mass between very light, and very heavy, racing tires and rims is not that much.
200g would be a large difference; that would be going from very heavy rims/tires to very light, as
long as the discussion is about racing equipment. The change in energy requirements between those
wheels is equivalent to either having, or not having, a water bottle. Spend the same amount of time
and money worrying about the tires as about that water bottle. For the finishing sprint you can
toss the bottle to the crowd.

I take your point, but let's not get too pedantic about it. 200g is not that significant in itself,
but then you could make that same argument about most 'light weight' cycling components. By the
single component argument, looking at one item at a time, buying almost *any* lighter component is a
waste of time. So you might as well go bcak to your old steel wheeled clunker.

SNOOPY

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