lighter wheels

I've read a few threads about removing weight from your bike which makes it lighter and faster however some choose lighter wheels and I was wondering what benefit lightening the wheels have. I have a Mazda CX7 AWD and in the summer I have 245 45 20 wheels which are only 10mm wider than stock and they are about 10 pounds heavier (winter 235 70 18) but the summer tires feel so much more planted on the ground than the stock. So my question why lighter wheels?

 

It is weight that the suspension has to contend with as it goes up and down so it has potential for improvement as well as weight that does not have to be spun up on acceleration or slowed down during braking. A lighter wheel can help more than just a lighter part bolted to the chassis. Now what a set of lighter wheels will do for your wallet is another thread.

 

But if you Randy's money.............
John

 

Less rotational mass makes for a lighter feel and easier cornering. Think of your wheels as a gyroscope, less mass easier to move. Also the above mentioned suspension perks.

 

Reciprocating mass (anything that the motor has to spin, be it the crankshaft, the sprockets, or the wheels) is the worst kind of weight that you can have and therefore the best place to save weight. Saving that weight keeps the motor from having to spin it up and keeps the brakes from having to slow it down, as has been stated.

Also reciprocating mass has a gyroscopic effect that makes changing the direction of the wheel/bike more difficult. Losing weight off these assemblies helps lessen this effect. In a sense making the bike less stable, and more "tossable".

If that wasn't enough, the wheels and tires, along with the brake assemblies and even half the swing arm are all unsprung (discounting the compression of the tire itself). This means that they are not cushioned by the suspension. As all of these parts go over the crest of a bump they will launch off of the road before the suspension is able to push the tire back down to the ground. The heavier these assemblies are the more inertia they have and the more they will leave the road. Obviously for control you want the greatest contact patch at all times, with less weight the suspension is more able to overcome inertia and keep that tire on the ground.

Your experience with the CX7 has absolutely nothing to do with the added weight of the 20" wheels. More likely it has to do with the added width of the tire along with the squarer profile and the shorter sidewall (not to mention the warmer temperatures in the summer) But so much more than all of that is the tire itself, if you are comparing an all weather 70 sidewall tire to a performance summer compound 40 sidewall tire you're comparing apples to zebras.

 

Mysta2 - that has to be the best and most easily understood explanation I have ever read in regards to reciprocating & unsprung weight. Thanks for writing that up!

 

If I were to kick Mysta2 in his ass, I think I'd break your nose.

LOL, just kidding. It was an excellent explanation. Even I understood it.

 

Thanks for all the help it gives me a whole new look at why to lighten your wheels and something else I can look at modifying

 

Lighter wheels are easily the best thing you can do for handling and will help in every way imaginable... they are also one of the most expensive, by a good length.

Thanks Merried

 

gyroscopic affect...do an cbr600f2 conversion if not for weight for the tire selection