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Discussion Starter · #1 ·
Ok, so my mate - a mechanic/ mechanical engineer? - tells me that lighter wheels only improves the unsprung weight of a bike but doesn't affect the rolling mass & therefor doesn't really contribute to improved handling other than better acceleration because its lighter overall. Comments anyone?


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Ask your expert if he ever played with a gyroscope when he was a kid. :)


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Does he ride a motorcycle? ;)

Lighter wheels = less gyroscopic effect at speed = quicker turning at speed

Tmnstr


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OK, so my mate - a mechanic/ mechanical engineer? - tells me that lighter wheels only improves the unsprung weight of a bike but doesn't affect the rolling mass & therefor doesn't really contribute to improved handling other than better acceleration because its lighter overall. Comments anyone?
I am not sure how he is defining rolling mass. If he means the whole bike then of course it has effected the rolling mass because it reduced the over all weight of the bike. If he is talking polar moment of inertia of the wheels then of course it has changed that too. The more mass you reduce further out on the wheel the better it works but any mass reduction will make the wheel have less inertia. Like the second post stated just try and see what happens with a gyroscope.

Physics lesson: Take a bicycle wheel with the axle and hold it on either side of the hub. Sit on a bar stool that the seat will turn. Spin the wheel and after you get it going pretty good try to turn the wheel and see what happens. Kind of fun if you do not end up on the floor. The less mass the less it will do this.

The over all result of lighter wheels is two fold. One it reduces un-sprung weight which makes a big difference in how the wheel will track the bumps on the ground. When I put Carrozzeria wheels on my Paul Smart LE it reduced them 17 pounds. The bike rides so much smoother now. The second advantage of the lighter wheels is the lower polar moment of inertia. You actually get three benefits from this. One it will accelerate faster, two it will slow faster and last but not least the reduced gyroscopic effect will make it turn faster.

Ops I got carried away sorry for the long post but I am a big believer the best dollars you can spend on a bike and especially the SC series with their heavy wheels is lighter wheels.

Jim
 

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I am a big believer the best dollars you can spend on a bike and especially the SC series with their heavy wheels is lighter wheels.

Jim
+1

I installed Marchesini forged aluminum wheels and saved about 20 lbs over OEM, then installed BST wheels and saved nearly 30lbs over OEM and finally ended up with OZ forged aluminum wheels that saved about 25lbs over OEM.

The wheels improved turn in, braking, acceleration and even ride quality. The lighter wheels eliminated the shimmy in the front end as well.

-M
 

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Discussion Starter · #6 ·
Thanks guys, I really appreciate the instructive, and even the lengthy, responses. That was really helpful. And yes, your explanations with applied physics was.. illustrative ;-)


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I thought rolling mass is different then spinning mass? Reducing spinning mass will improve handing. Im no brain but that is what I was taught/told? Is this wrong?

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Mechanical Engineers are the jacks of all trades, and masters of most of them. But, they're not always right. I'm a ME, and have had many an argument with other MEs about the plane on treadmill, which is about as simple and basic as you can get
 

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From a seat of the pants point of view especially since I just swapped over the stock SC wheels for the 5 spoke OZ wheels, the change is significant. As a point of reference, the bike was stock with the original tires. The bike now feels livelier and more responsive. Turn-in's feel sharper and crisp. I am looking forward to many miles and would do it again in a heartbeat.
 

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I thought rolling mass is different then spinning mass? Reducing spinning mass will improve handing. Im no brain but that is what I was taught/told? Is this wrong?

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English is not my native language, so I might be wrong with terms, but you could think of whole bike + you as rolling mass. Spinning mass is all the parts in your bike which is spinning, causing centrifugal force. Reducing the spinning weight will improve handling as the centrifugal force gets lowered, and therefore easier to affect.
 

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English is not my native language, so I might be wrong with terms, but you could think of whole bike + you as rolling mass. Spinning mass is all the parts in your bike which is spinning, causing centrifugal force. Reducing the spinning weight will improve handling as the centrifugal force gets lowered, and therefore easier to affect.
^ +1

Also, reducing unsprung weight will affect your suspension operation, as the springs will have less work to perform in controlling the up-and-down movement of the wheels.

If you are planning on modifying your suspension, do not do so until you have made a choice on your wheels (even if that choice is to keep the stock wheels/tires) - that way, you'll be modifying the suspension based on your future wheels weights.
 

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I studied Engineering.. but failed... and flunked out of University... so I have NO credentials at all.. However, I have swapped the stock rims on my SC to the 999 Aluminium rims on a 999... the difference in "flickability" was very noticeable...

I couldn't help myself and ended up sourcing a pair of FORGED aluminium rims from a 999R... and the increase in flickability was again extremely noticeable.

If you buy some lighter rims from Moto, which you should, you will be extremely happy with the result.
 

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I thought rolling mass is different then spinning mass? Reducing spinning mass will improve handing. Im no brain but that is what I was taught/told? Is this wrong?

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You are correct. I was questioning what the engineer friend was talking about because I thought he was wrong and maybe did not understand the term he was using. If you reduce the weight of your wheels you are reducing your rolling mass as wall as your rotational mass. The latter just makes more difference and why so many articles talk about it and how important it is. I have changed out the wheels on many bikes and have never been really disappointed. The greater the difference between the wheels the more you notice it. When it is a total of two or three pounds I never feel very much but if the delta is more like 10+ pounds the difference is profound.

Jim
 

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From a seat of the pants point of view especially since I just swapped over the stock SC wheels for the 5 spoke OZ wheels, the change is significant. As a point of reference, the bike was stock with the original tires. The bike now feels livelier and more responsive. Turn-in's feel sharper and crisp. I am looking forward to many miles and would do it again in a heartbeat.
I am contemplating the same change. What color is your bike, and what color OZs (I assume black). Any pics?
 

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From a seat of the pants point of view especially since I just swapped over the stock SC wheels for the 5 spoke OZ wheels, the change is significant. As a point of reference, the bike was stock with the original tires. The bike now feels livelier and more responsive. Turn-in's feel sharper and crisp. I am looking forward to many miles and would do it again in a heartbeat.
Sorry Dave, but no real world seat of the pants opinions are allowed. In future posts please limit yourself to techie engineering nerd-speak only.;)
 
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