Rotating Wheel Mass Question?

[gtiblklv]

Rotating Wheel Mass Question?
COULD ANYONE TELL ME WHAT THE DIFFERENCE IN E.T. OR HP LOSS IS WHEN HAVING A STEEL 15X10 INCH RIM VS. AN ALUMINUM 15X10 INCH RIM? AND COULD SOMEONE TELL ME WHAT THE WEIGHT SAVINGS WOULD BE ON AVERAGE....?

I AM JUST CUROIUS HOW MUCH OF AN ADVANTAGE IT IS TO HAVE THE LIGHTER RIM. I REALIZE THEIR IS AN OBVIOUS ADVANTAGE BUT COULD SOMEONE ELABORATE ON HOW SIGNIFIGANT OR NON-SIGNIFIGANT IT IS? THANX....

 

[Robbie-87plz]

HTH...

http://www.sportcompactcarweb.com/editors/technobabble/0109scc_technobabble/

Down the middle has something about wheel weights.

 

[gtiblklv]

INTERESTING.....!

CAN SOMEONE TRANSLATE FOR ME WHAT AN EXTRA (10 POUNDS) TO EACH RIM WILL EQUATE TO IN EQUIVILANT WEIGHT GAIN DUE TO RATATING MASS? I WAS A BETTER BASEBALL PLAYER THEN MATHAMATICIAN......LOL.

MY MATH CALCULATIONS ARE PUTTING ME AROUND AN APPROX. 70 EQUIVILANT POUNDS (GIVE OR TAKE 5-10 POUNDS +/- ) OF FLOOR WEIGHT....? KINETIC ENERGY WOULD SEEM TO BE LESS DUE TO A MORE EVENLY DISTRIBUTED WEIGHT THROUGHOUT THE WHEEL VS. A TIRE FOR EXAMPLE BEING FURTHEST AWAY FROM CENTER MASS. SO IF IT'S 2-1 FURTHEST AWAY FROM CENTER MASS THEN I WOULD ASSUME IT WOULD BE CLOSER TO 2-1.5 OR SO AS IN A RIM WEIGHING IN AT AN EXTRA (10 POUNDS)?

OF COURSE YOU ALSO HAVE TO FACTER IN IF YOU CHOOSE THE TALLER TIRE THAT WILL ALSO ADD ADDITIONAL WEIGHT.

SO I'M THINKING THAT ADDING 10 POUNDS TO A WHEEL IS EQUIVILANT TO APPROX. ADDING 70 OR SO POUNDS TO THE CAR. DOES THAT SEEM RIGHT GUYS....?

 

[Robbie-87plz]

The way I see it...

...you buy rims/tires for:
1. looks
2. performance
3. 'cause your wife said she likes it
4. you got a great deal and wanted to lighten the 'ole wallet

some of the above could be combined if you're lucky. Now that we've understood that the heavier the wheel/tire combo, the less "performance" we'll get out of them-unless we're making so much power that you really do need to plant the power to the ground-why should I sweat the details? Knowledge is power, and much knowledge is much power. I'll stick to getting something that would do well for me in my plan, corner carver here in Hawaii.
Light weight 16" rim, sticky tires, brakes to counter the turbo6, and handling mods=my cup o' tea.
What are your goals for the car-is the first question I should've asked you. I'm a fng here with TR's, so someone chime in and correct me if I'm mistaken about something...

p.s. try this...
http://www.chris-longhurst.com/carbibles/index.html?menu.html&tyre_bible.html

 

[gtiblklv]

HAWAII....... MAN, LIFE MUST BE GOOD....! NEW ENGLAND JUST SUX A$$.....! HOW DO CARS RUN OUT THERE ANYWAY? DO YOU HAVE AN STAGE II GN'S OUT THERE?

 

[Robbie-87plz]

Stage who? On what road?

Not sure if they have enough road for a stage II, but there's at least one 350 V8 twin turbo out here...I'm from MN, so when you think you have it bad in New England, reconsider...

 

[gtiblklv]

LOL...... YEA, I GUESS THATS PROBABLY A LITTLE COLDER. RETIREMENT TO A WARMER CLIMATE COULDN'T COME ANY SOONER...! TAKE CARE.

 

[Robbie-87plz]

Any new wheel decisions?

Did those articles help at all? Some people laugh when I mention that the weight of the wheels are important. Oh well. Happy Memorial day.

 

[turbo39151]

A couple of sites I found helpful :

http://www.wheelweights.net/

http://www.wheelspecs.com/main/index.php

I went from a 16 lb stock rim on my GF's WRX to a 14.6lb forged 5Zigen rim. Seat of the pants dyno feels a difference.

I need to swap those heavy a$$ stock GN rims, almost broke an arm pulling the rim off the car the other day.

BTW, I thought I saw a post on this board about rotatin mass being the equivalent of 8 times that of stationary mass. It was in some chat about driveshafts.

 

[gtiblklv]

GOOD STUFF. THANX....

 

[Turbo6inKY]

Turn off your caps lock.

 

[Robbie-87plz]

Turbo6

Come on, share your knowledge with us, lower class folk down here. What in your opinion/experience are light yet strong wheels? Do you think it's worth the price? Some feedback please, sir?

 

[Turbo6inKY]

Light and strong is like fast and cheap. They rarely go together.

If you want light and strong, look at CCW or Kodiak. You're going to pay through the nose (to the tune of $450-$550 a wheel) but they'll be light and moderately curbable.

 

[Robbie-87plz]

ANy advantage of a 17" over a 16"? I'm putting on Bilsteins soon and I have yet to decide on springs... stock backspacing?

 

[Turbo6inKY]

Wheel diameter doesn't affect backspacing, width does.

17" will be much more prone to damage and probably ride hard. Some say the shorter sidewall on a plus-sized tire helps handling, but that only works to a point. These cars are so heavy, they need some sidewall to take up the side loads. Without some flex, they'll actually break traction sooner.

 

[turbo39151]

You can do light and strong and even keep it cheap if you shop around. I got the 5Zigen's for $900 w/tires installed. (cheap tires but still good price) BTW, I used 17's @14.6 lbs If I'd have stayed with 16's, which is still bigger than the stock 15" for GN's, the rims would be in the neighborhood of 11lbs each. And they're forged, not cast....

 

[mechanical73]

wheels

in general, the lighter the rim the better you'll stop and accelerate due to the lower rotating mass.

if i had to take a guess from my experience at what the difference is in your example (assuming a mildly modified car), i would say about 1-2 tenths in the quarter mile.

If anything, i would probably opt for skinnies up front as that will help on the weight transfer. Of course, you don't want to drive around too far w/ these.

 

[Robbie-87plz]

I'm thinking corner carver actually, could care less about weight trans at the drags...

 

[Ormand]

When you look at wheel size, check out tire availability. It is harder now to find good performance tires in 15 inch sizes than it was a few years ago. In 16 inch sizes, there are more to choose from, and in 17, still more. Also, the bigger wheels give more options when/if you decide on a brake upgrade. With 17" wheels, you can get to some really humongous front discs, good for corner carving.

 

[bruce]

Originally posted by Robbie-87plz
ANy advantage of a 17" over a 16"? I'm putting on Bilsteins soon and I have yet to decide on springs... stock backspacing?

More room for brakes.

Faster corner turn in, since there's less sidewall to flex.

Cooler running, due to less side wall flex.

If you go with a wider 17 tire, you'll lose a lil in gas mileage.

I think it was both Car&Driver, and Road&Track that some years ago did a comparo on 15s-16s-17s. 16s at the time were slightly quicker, but that was before the BFG KDWs. The KDWs have worked really well for me.

I got tired of isking having a sort rear spring fall out so went to Coil-Overs in the rear. The QA-1s are nice. I still have my Bilsteins up front, FWIW.