blk-majik

iTrader: (6)

I know taking weight off of the engine's rotating mass helps get more power to the wheels. But, in all reality, would it be correct to see the weight of the wheels also as rotating mass? Do the same rules apply? With all forces being considered, the engine rotation forces the wheels to rotate. I know you dont want to sacrafice contact your contact patch, which is basiclly determined by the width more than anything, but how important is rim weight?

quantum

iTrader: (1)

Well the lighter the rims the faster you accelerate, but the price is that if you go too light you will burn out really easy because they are easier for the engine to spin.

Hatorade

iTrader: (1)

Rim weight, AFAIK, is rotating mass, so yes the same rules apply for weight reduction. And unless you're making so much HP that you can't launch properly, you needn't worry about burnout. A little throttle control goes a long way. As road racing goes, yes, it's better to have smaller, lightweight wheels than big heavy 19s or whatever. But the law of diminishing returns applies, and most people don't go beyond a certain point for a certain power level. But for lower powered cars, light rims make a big difference, especially in conjunction with other weight reduction. And every lb. you shave anywhere also affects (to a smaller degree than acceleration in this case, obviously) braking, cornering, etc.

Freddie1111

iTrader: (3)

Some time ago, a friend got rims for his Accord that were 4 pounds lighter than stock (each). He had before and after dyno pulls and made 3-4 more horsepower to the wheels with no other changes. It does make a difference

zeof

remember your physics equation F=ma (second law of motion) where "F" equal force, "m" equal mass, and "a" equal acceleration. if a=F/m, then the bigger the mass, the smaller the acceleration and vice verse. therefore, by reducing the weight on your wheels, your acceleration will be faster.

blk-majik

iTrader: (6)

all makes sense. not to push it a bit further and to find a good equalibrium, what is too much? For performance, power wise, smaller is better. but smaller wheels will have less of a contact patch, even at the same width. This diff will be very small, but it will exist. This will effect launches, as well as overall handling. Also, we have to worry about tire life. If wheel A is 15% smaller than wheel B, wouldnt wheel A have 15% more wear than wheel A? the size diff is causing every part of the wheel to be in contact with the road more, thus cuasing it to wear more.

So, the total pros:

Big wheels Small wheels
PROS handeling weight/HP
tire life

am I seeing the big picture?

whats the widest wheels we can fit on our car /wout any problems?

reimundo

iTrader: (1)

how much do the stock rims weight?

blk-majik

iTrader: (6)

i am guessing ~20lbs each. can anyone get exact #'s ? I could shave at least 3lbs per wheel without a problem. Since its FWD, that would take down 6 lbs of rotating mass. *IF* the same rules apply, that could potentially be like freeing up 16.2 HP! I know those calcs are rough, but if this is even close, its a big difference.

So 17" 17lb wheels would look nice, give a good bit of contact, improve tire wear, and make me faster This would also force me to get new rubbers, which is a plus

Fifty

iTrader: (8)

What? I'm going to leave the math to the mathmaticians, but that seems wrong, are you sure?

blackevoVII

iTrader: (2)

i dont know about 16hp off of 12 lbs. Maybe if you shaved 160lbs you'd get the equivalent of "16.2"

its probably more along the lines of 1-2 hp for 12 lbs

pgmike

iTrader: (27)

im going back to my stock 15s bc they weigh only 15lbs vs my 22lb 17s! im getting 205 width tires on them which is the same as what i have on my 17s so same handling. reducing 7lbs from teh wheels make much more of a diff that 7lbs from teh rest of the car.

captain150

I think the stock rims are about 30-40lbs. Pretty standard as far as factory aluminum rims go (the RSX's are also about 30-40lbs). Since the factory has to make the rims strong enough for a daily driver/bad driver. People who spend money on aftermarket rims can generally handle a weaker wheel, they are not going to fly over tracks/pot holes with them.

pgmike

iTrader: (27)

theres no way that they are 30-40lbs. whered you get this information?

blk-majik

iTrader: (6)

the calculation quoted by others (and accepted) was 2.7 HP per 1 lb of rotating mass. This is why I am trying to establish if tire mass is the same as other rotating mass in the engine.

NOTE: This is not a HP gain, but its an elimination of HP loss between the crank and the road. Eliminating mass will NEVER make a car gain pure HP.

captain150

I read that on this site. Maybe it was 20-30lbs? I know it was much heavier than an aftermarket wheel. I also know an RSX rim is in the 30s, horsepower TV (or some other show) mentioned this.