Math Nerds UNITE !! (do some math for me please .....)
03-06-2008, 05:51 AM
#1
wants an I35
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Math Nerds UNITE !! (do some math for me please .....)
ill start off by saying that, other than cosmetic things, my car/engine/drivetrain is entirely stock - i have done nothing but "maintenance mods" in the 5 months i've owned this car.
over this time i have gotten increasingly sick of my butfugly 15" sawblades and finally decided to drop cash on a new set.
after three weeks of waiting, this past Monday i got a set of 02 SE wheels and tires from an org member in NE and put em on.
i never really got a chance to drive around that much on them until yesterday because they needed to be balanced (paid for $42 for balance with lifetime warranty BOOYA)
well i noticed that my car seems a lot more sluggish than it was when stock; i try to pass people going 80 on the highway and it takes longer. i try to gas hard off a green light and its just a little slower.......
while driving, i start thinking about wheel weight......so i come home and search the org and:
the stock sawblades are 16.5 lbs
the 02 SE wheels are 23.4 lbs
yea, almost a 7 lb difference per wheel, so almost 28 lbs all around. i just ASSUMED the stock wheels were heavy, simply by the way they look, but i guess i was wrong. granted they are smaller and, hence, have less material (metal), but i would figure the difference between the two to be negligable, if not in the favor of the SE wheels.
im still happy about my purchase, i got a great deal and they came with BRAND NEW nexen summer tires, but the weight was something i had not thought about.
now the math
so my stock car is 190hp with 15" 16.5 lb wheels. now that ive added almost 7 lbs per wheel, can someone calculate how that has affected horses?
i.e. how much horsepower have i lost ??
and the reason im asking this is i plan on getting a budget Y in a few weeks. That, supposedly, will be adding between 10-15 hp right off the bat. i want to know if that will just cancel out the loss, or add to the overall HP (as in, the Y will add more than ive lost with the heavy wheels), or will i still be below the power i had two weeks ago.....
plus im mildy concerned about working my tranny harder. like when you change anything from OEM, the car is not designed to encompass those new specs - so now i have each wheel weighing that much more on the tranny and potentially causing more wear. is this a legitimate concern?
anyway ill end by saying my car looks badass. knowing what i know now i still would have bought this setup and put em on. im just slightly dissapointed in myself for not doing more research.
over this time i have gotten increasingly sick of my butfugly 15" sawblades and finally decided to drop cash on a new set.
after three weeks of waiting, this past Monday i got a set of 02 SE wheels and tires from an org member in NE and put em on.
i never really got a chance to drive around that much on them until yesterday because they needed to be balanced (paid for $42 for balance with lifetime warranty BOOYA)
well i noticed that my car seems a lot more sluggish than it was when stock; i try to pass people going 80 on the highway and it takes longer. i try to gas hard off a green light and its just a little slower.......
while driving, i start thinking about wheel weight......so i come home and search the org and:
the stock sawblades are 16.5 lbs
the 02 SE wheels are 23.4 lbs
yea, almost a 7 lb difference per wheel, so almost 28 lbs all around. i just ASSUMED the stock wheels were heavy, simply by the way they look, but i guess i was wrong. granted they are smaller and, hence, have less material (metal), but i would figure the difference between the two to be negligable, if not in the favor of the SE wheels.
im still happy about my purchase, i got a great deal and they came with BRAND NEW nexen summer tires, but the weight was something i had not thought about.
now the math
so my stock car is 190hp with 15" 16.5 lb wheels. now that ive added almost 7 lbs per wheel, can someone calculate how that has affected horses?
i.e. how much horsepower have i lost ??
and the reason im asking this is i plan on getting a budget Y in a few weeks. That, supposedly, will be adding between 10-15 hp right off the bat. i want to know if that will just cancel out the loss, or add to the overall HP (as in, the Y will add more than ive lost with the heavy wheels), or will i still be below the power i had two weeks ago.....
plus im mildy concerned about working my tranny harder. like when you change anything from OEM, the car is not designed to encompass those new specs - so now i have each wheel weighing that much more on the tranny and potentially causing more wear. is this a legitimate concern?
anyway ill end by saying my car looks badass. knowing what i know now i still would have bought this setup and put em on. im just slightly dissapointed in myself for not doing more research.
03-06-2008, 06:12 AM
#2
The simple answer is that you haven't "lost" any horsepower. It may take a negligible amount more torque to turn the SE wheels, but not enough to either feel or worry about. You have increased the unsprung weight of your car just a bit, but again, you'll likely never feel the difference. 7 pounds per wheel of unsprung weight is a lot if you're talking about a 1500 lb. track car, but it's pretty much a non-issue on a 3400 lb. street car. IMO, it's not worth worrying about.
So, post some pics already!
So, post some pics already!
03-06-2008, 06:13 AM
#3
wants an I35
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yea youre right, not horsepower but torque. either way my car feels slower than it did on sunday.
and after i get my car tinted next week, ill get a lot of pics up. some of the 3/16 florida meet too.
and after i get my car tinted next week, ill get a lot of pics up. some of the 3/16 florida meet too.
03-06-2008, 07:36 AM
#4
did you find someone reasonable and good for tint.? whats the price like?.
03-06-2008, 07:38 AM
#5
wants an I35
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i dont know if id call it "reasonable". i could get llumar for 120, but immona get the formula 1 for $230. its in hollywood, called RHODES AUTO. its these two old people, running the place for 28 years. lifetime nationwide warranty.
Rims are 17s tho?
03-06-2008, 08:02 AM
#8
wants an I35
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wwait
youre all saying that there have been no performance changes since i changed from a 17lb wheel to a 24 lb wheel?
but the car has to turn heavier wheels now.
if that is the case, and this is all in my head, why do people spend 3k+ for 11 lbs wheels?
youre all saying that there have been no performance changes since i changed from a 17lb wheel to a 24 lb wheel?
but the car has to turn heavier wheels now.
if that is the case, and this is all in my head, why do people spend 3k+ for 11 lbs wheels?
03-06-2008, 08:21 AM
#9
you kinda have a point,but from how i understand it,it shouldnt change your horsepower at all.you might end up taking off much slower,and this is why they spend so much on lighter wheels.
Last edited by Snypa; 03-06-2008 at 08:33 AM.
03-06-2008, 08:40 AM
#11
Compare it to running in a pair of New Balance running shoes, then putting on some Heavy Timberlands and trying to run. Your legs are still as strong as before, you just have to use more of that strength to run at a decent pace.
When I had (one of) my 4th gen. I came close to getting 5th gen TE wheels but decided not to becuase for the price I could get something much lighter. 5th gen SE wheels look like they were designed for a 4th gen though.
03-06-2008, 09:32 AM
#12
^^^ finally 
Your car did not 'lose' any horsepower or torque, but...
Yes, heavier bigger wheels will make your car accelerate slower. But also what is mostly affecting you is the larger wheel size. Ill give you some minor math considerations. Torque is Force x Radius. And force is a function of mass. Therefore wheels with a larger radius and mass will require more torque to turn. Since these tires you have are both heavier and larger, you are at a double loss here.
However the bigger factor here is inertia. Inertia is a function of mass and radius squared. Inertia sorta represents the resistance to changing movement (IE accelerating from a stop) So since in this relation, the radius is squared, those extra few inches are really causing your tire to be harder to turn. And yes again, the extra mass affects it too some.
So yes you will definately accelerate slower, how much slower?- That would take a lot of calculation but is possible to figure out. But it is definately not in your head. Afterall if it was BBS would not be known for the leight-weight wheels they make.
However there is one plus side to your bigger wheels. Like mentioned, inertia is the resistance to changing movement. That also means that when you are traveling at high speeds...this extra inertia in your wheels will resist slowing down, therefore you will get slightly better gas milage on the highway (but again worse in city traffic).
Hope that sheds some light.
edit: Also Rockart...just double checking, those 02 SE wheels are 18in right? If so going from 15in wheels to 18in is definately a considerable jump and you should be able to feel the decrease in acceleration.
Your car did not 'lose' any horsepower or torque, but...Yes, heavier bigger wheels will make your car accelerate slower. But also what is mostly affecting you is the larger wheel size. Ill give you some minor math considerations. Torque is Force x Radius. And force is a function of mass. Therefore wheels with a larger radius and mass will require more torque to turn. Since these tires you have are both heavier and larger, you are at a double loss here.
However the bigger factor here is inertia. Inertia is a function of mass and radius squared. Inertia sorta represents the resistance to changing movement (IE accelerating from a stop) So since in this relation, the radius is squared, those extra few inches are really causing your tire to be harder to turn. And yes again, the extra mass affects it too some.
So yes you will definately accelerate slower, how much slower?- That would take a lot of calculation but is possible to figure out. But it is definately not in your head. Afterall if it was BBS would not be known for the leight-weight wheels they make.
However there is one plus side to your bigger wheels. Like mentioned, inertia is the resistance to changing movement. That also means that when you are traveling at high speeds...this extra inertia in your wheels will resist slowing down, therefore you will get slightly better gas milage on the highway (but again worse in city traffic).
Hope that sheds some light.
edit: Also Rockart...just double checking, those 02 SE wheels are 18in right? If so going from 15in wheels to 18in is definately a considerable jump and you should be able to feel the decrease in acceleration.
Last edited by black_maxed95; 03-06-2008 at 09:40 AM.
03-06-2008, 09:38 AM
#13
03-06-2008, 09:43 AM
#15
IIRC for every 1 lbs of rotation mass you add/subtract is like doing to same with 10 lbs of dead weight....so basically you have added 280 lbs of dead weight to your car...But like said before we need to get into inertia, rotational forces, size of wheel...
In the 1/4 you could lose upto half a second with these wheels...Dont even get me started on adding these and still having the A32USIM....
03-06-2008, 09:58 AM
#17
However there is one plus side to your bigger wheels. Like mentioned, inertia is the resistance to changing movement. That also means that when you are traveling at high speeds...this extra inertia in your wheels will resist slowing down, therefore you will get slightly better gas milage on the highway (but again worse in city traffic).
The only plus to big wheels is looks IMO.
03-06-2008, 10:07 AM
#18
The Y pretty much boosts your BHP to about 215ish...so 215 BHP into a car thats curb weight is now 3300 lbs....looking at about 15.35 lbs/BHP. Stock is in the neighborhood of 15.24 lbs/BHP... and stock + Y comes to 13.5 lbs/BHP....So even with the Y you would be slower than stock...
Also that is using from the factory specs...
03-06-2008, 10:08 AM
#19
Heavier wheels -2HP
Ypipe +12HP
Net gain of +10HP
However, your braking and handling will still suffer slightly due to the heavier wheels.
03-06-2008, 10:11 AM
#20
03-06-2008, 10:15 AM
#21
wants an I35
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The Y will help with it....You are not going to be as fast as if you had just gotten some lightweight wheels though...
The Y pretty much boosts your BHP to about 215ish...so 215 BHP into a car thats curb weight is now 3300 lbs....looking at about 15.35 lbs/BHP. Stock is in the neighborhood of 15.24 lbs/BHP... and stock + Y comes to 13.5 lbs/BHP....So even with the Y you would be slower than stock...
Also that is using from the factory specs...
The Y pretty much boosts your BHP to about 215ish...so 215 BHP into a car thats curb weight is now 3300 lbs....looking at about 15.35 lbs/BHP. Stock is in the neighborhood of 15.24 lbs/BHP... and stock + Y comes to 13.5 lbs/BHP....So even with the Y you would be slower than stock...
Also that is using from the factory specs...
thanks
and yea down the road in a year or two i will be gettin some 14lb or less wheels.
03-06-2008, 10:21 AM
#22
03-06-2008, 10:22 AM
#23
having larger wheels, traveling a long distance on a highway will result in better mpg. Is it worth it compared to all the downsides...IMO no. I was just saying. I agree looks is the biggest plus.
Last edited by black_maxed95; 03-06-2008 at 10:26 AM.
03-06-2008, 10:28 AM
#24
wants an I35
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yea and right now im still such a noob with cars period, that looks will go a lot further than performance.
i only got "into cars" in the past 6 months, so im still learning basic things
down the road ill start doing more performance-oriented mods (MEVI, b pipe, 11-14 lbs wheels, etc).
i only got "into cars" in the past 6 months, so im still learning basic things
down the road ill start doing more performance-oriented mods (MEVI, b pipe, 11-14 lbs wheels, etc).
03-06-2008, 10:36 AM
#25
yea and right now im still such a noob with cars period, that looks will go a lot further than performance.
i only got "into cars" in the past 6 months, so im still learning basic things
down the road ill start doing more performance-oriented mods (MEVI, b pipe, 11-14 lbs wheels, etc).
i only got "into cars" in the past 6 months, so im still learning basic things
down the road ill start doing more performance-oriented mods (MEVI, b pipe, 11-14 lbs wheels, etc).
dont worry about it...i wasnt into cars either til i got my max, now i swear i could tear it apart and put it back together blind folded.
03-06-2008, 11:36 AM
#26
what size tires and how heavy are the tires?? maybe look into some lighter tires to help lessen the gap. tires are heavy man, sometimes heavier than the wheels themselves. or look into shorter tires diameter-wise....depending on what you have on there already.
03-06-2008, 11:49 AM
#28
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So to sum it up.
1.Weight not your problem
2.Larger diameter = longer distance from shaft to tire = more force needed to spin wheel at same speed or with same force.
3.Yes your gas millage is worse.
4.More momentum at high speeds.(off the line slower, top end faster.)
5.Your dyno reading will be lower with larger wheels on.
03-06-2008, 11:54 AM
#29
This is not a strictly math question this is a physics question. 15" wheels as opposed to 17" wheels it is the force required to move the wheels. So the distance that the force has to travel to make the wheel start spinning has increased. yes the weight has a little bit of an effect on the drive ability but your main problem is the new diameter size. but with a larger diameter size you now have a increase in momentum at higher speeds.
So to sum it up.
1.Weight not your problem
2.Larger diameter = longer distance from shaft to tire = more force needed to spin wheel at same speed or with same force.
3.Yes your gas millage is worse.
4.More momentum at high speeds.(off the line slower, top end faster.)
5.Your dyno reading will be lower with larger wheels on.
So to sum it up.
1.Weight not your problem
2.Larger diameter = longer distance from shaft to tire = more force needed to spin wheel at same speed or with same force.
3.Yes your gas millage is worse.
4.More momentum at high speeds.(off the line slower, top end faster.)
5.Your dyno reading will be lower with larger wheels on.
Very true. My question to this is, would this still hold true given that the overall diameter of the tire + rim = stock overall diameter? Given that weight stays constant of course.
03-06-2008, 12:00 PM
#30
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03-06-2008, 12:04 PM
#31
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If you have ever watched top speed dragsters you may notice that the tire recoils a bit at launch. this is a factor a tire can move if it has more space to move. so with a larger side wall it their for retains that space and this will effect the rigidity of the force needed.
The force coming from the shaft still has to travel 2 more inches to get to the tire.
Good Question.
03-06-2008, 12:32 PM
#36
that tire weighs in at 24 pounds, u can get a tire that weighs around 21 or 22 pounds and save 8-12 pounds right there, and at the same time change the size of the tire and maybe help a tiny bit. im not sayin go do that now, but when these tires need replacement its something to look at if acceleration is your concern.
03-06-2008, 12:33 PM
#38
03-06-2008, 12:48 PM
#39
03-06-2008, 12:50 PM
#40
