TOPIC:

I don't know why you are compelled to "explain why what you're saying is a non issue here". I never said it was a major concern.""

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Then why even bring it up ? . Its not even a minor concern, I know its off no concern, you know its of no concern, even though you brought it up, there are plenty of others that know its of no concern but the "reason" i brought it up is, most guys here are enthusiasts, not mechanics / Engineers / experts, so you've made this guy , and probably others doubt they should do this when in fact, there's no tangible reason at all not to do the conversion , as i've repeated numerous times, its completely irrelevant in this situation, you even added your "list" of why the 5 spoke wheels were possibly not as good and the OP then doubted using them, when in fact, he has absolutely nothing to worry about.... I used the words "no effect" because they relate to the fact no reasonable /rational human being would/could measure it for the purpose of their use in this instance, why would you even bother, its an argument for the sake of an argument. I'm outa here, I like useful, practical information that doesn't confuse, hence my attempt at clarification . I brought this up as an example of the "types" of information on the net yesterday, to a Kawasaki mechanic / racer/enthusiast friend of mine and he just shook his head.... I saw some of the bikes in the distinguished gentlemen's ride on the weekend here in Australia, now there was something to "discuss", some of the "engineering" on display was, well , questionalble to say the least...

Hey Ptown. I have a front 5 spoke. I put it on my bathroom scale and it looks to be about 16 pounds with both rotors.

750 R1 wrote:

I don't know why you are compelled to "explain why what you're saying is a non issue here". I never said it was a major concern.""

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Then why even bring it up ? . Its not even a minor concern, ...

Ok, so now at least you can agree where we differ. In my opinion, it's a minor concern. In your opinion it's of no concern.

But here are the facts:
Moment of inertia does affect acceleration.
Moment of inertia increases when the mass is re-distributed toward the rim.
Given two wheels of the same total mass and size, if one has its mass distributed toward the rim, it will be slower.
Those are just pure simple facts whether they agree with your intuition or not.
I'm making no quantitative claim as to the degree to which it will be slower.
And making subjective claims means different things to different people. Racers have different concerns from non-racers.
To them, you get a big advantage by adding up a million tiny advantages. That's why I bring it up.
To say moment of inertia has no practical effect on acceleration is analogous to saying the mass of a bike has no practical effect on the bike's acceleration.

The OP cared enough to ask an engineer, and your response was to insult the engineer, and all engineers in general.

I just showed your post to my cat, and she was shaking her head. So there. No offense intended.

loudhvx wrote:

750 R1 wrote:

I don't know why you are compelled to "explain why what you're saying is a non issue here". I never said it was a major concern.""

,
Then why even bring it up ? . Its not even a minor concern, ...

Ok, so now at least you can agree where we differ. In my opinion, it's a minor concern. In your opinion it's of no concern.

But here are the facts:
Moment of inertia does affect acceleration.
Moment of inertia increases when the mass is re-distributed toward the rim.
Given two wheels of the same total mass and size, if one has its mass distributed toward the rim, it will be slower.
Those are just pure simple facts whether they agree with your intuition or not.
I'm making no quantitative claim as to the degree to which it will be slower.
And making subjective claims means different things to different people. Racers have different concerns from non-racers.
To them, you get a big advantage by adding up a million tiny advantages. That's why I bring it up.
To say moment of inertia has no practical effect on acceleration is analogous to saying the mass of a bike has no practical effect on the bike's acceleration.

The OP cared enough to ask an engineer, and your response was to insult the engineer, and all engineers in general.

I just showed your post to my cat, and she was shaking her head. So there. No offense intended.

Blah blah blah, FFS mate, its a simple wheel swap, not brain surgery. !!! I doubt your cat is as skilled as my Mechanic friend but thanks for the laugh...Just wow....

Here's a little quote i like in these situations...

Engineers like to solve problems, if there are no problems handily available, they will create their own problems.

A simple question about 2 different wheel weights has turned into the Hatfield's and McCoy's. I believe he was just curious if there was significant difference in the wheels. It doesn't seem he was concerned about rotating mass and all of the technical arguments this has created. I told him the weight of wheel with both rotors with no tire. Simple. We are here for friendly advice and sharing our passion for the older bikes that a lot of people don't understand.

Not dissing your engineer friend but in my experience, there are a lot of highly intelligent, anal retentive engineers, some of them just aren't real practical and just like to be the smartest guy in the room, its like working with some architects ....


Why do you think a flywheel has most of it's mass around the rim? Reducing both unsprung weight and polar moment of inertia is the holy grail for all auto engineers,

The current trend of big wheels on Range Rovers etc is all about styling and it noticeably reduces the ride and handling quality.

Some racers remove the flywheel alternator rotor to reduce this angular momentum effect. Drag racers like the old 'pork chop' zed 1000 crank as it is heavier and holds more energy at high rpms. The lighter late GPz crank is lighter and preferred by non drag racers. This all makes a difference.



Good upgrade is the GPz750 3 spoke 18" rims with the bigger 1100/turbo discs. Needs front end swap as earlier leading axle 550 forks don't fit. Later zx uni will be a direct fit I think.

My cat is apparently equally qualified to assess your argument as your mechanic, if he also thinks moment of inertia is of no concern.

BTW any simple google search of wheels and moi shows a lot of results. They must just like wasting money going to great lengths reducing moi. But I guess if the wheels are designed by engineers, it's all hogwash then.

And for anyone interested, it's not that difficult to measure moment of inertia. The most sophisticated thing you need is a stopwatch.

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Its has nothing to do with the weight of the rim, these wheels aren't rolling under their own power, the bike powers the wheels, you take weight off any part of the bike, doesn't matter where, and retain the same power, you've improved its power to weight ratio, which means the bike will be slightly faster given the lesser weight the engine has to move

No, you really don't understand physics at all. This is school stuff.

Just as well Op wasn't looking to channge from leading axle 19" to centre axle 18" front with a differing yoke offset, like I did. But then castor and trail have no effect on motorcyle handling either...still the same length between the wheels innit

“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.”
― Daniel J. Boorstin

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Your comment that I highlighted was wrong.

It is all about where the weight is - again this flywheel analogy. A heavier small radius wheel could have a lower moment of inertia than the lighter larger one, it is where the mass is.

And try writing in paragraphs, it makes it easier to read .

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