Does anyone run 17's w/ Low Pro's on their SC?
07-11-12, 03:32 PM
#16
So in other words, I have to lower the car in order to achieve that stance :\
I was hoping I could keep my stock suspension (for now), and still have that same look, 'cus I hate the gap between the tire and wheel-well. Also, I was hoping that having the thinner tires would actually drop the height of the car an inch or so...
Eh, I guess there are no shortcuts, haha.
Coilovers it is then.
So your car got "slower" with the smaller wheels??
I was hoping I could keep my stock suspension (for now), and still have that same look, 'cus I hate the gap between the tire and wheel-well. Also, I was hoping that having the thinner tires would actually drop the height of the car an inch or so...
Eh, I guess there are no shortcuts, haha.
Coilovers it is then.
So your car got "slower" with the smaller wheels??
And no, it didn't get slower, my speedo is just off since it's calibrated for a larger wheel. I now go a smaller distance per rotation, don't know if that makes me faster or not. lol.
07-11-12, 06:07 PM
#17
...With a smaller rolling diameter you actually increase your effective gear ratio.
As far as seat of the pants feel i went from a 275/35/19 to a 225/30/17 (i believe that was the size) just for a couple weeks and i DEFINETLY felt the difference in acceleration at any speed wether from a roll or dig.
As far as seat of the pants feel i went from a 275/35/19 to a 225/30/17 (i believe that was the size) just for a couple weeks and i DEFINETLY felt the difference in acceleration at any speed wether from a roll or dig.
(Im an engineering major
)
07-12-12, 10:02 AM
#19
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lol wow you guys. no. by that logic then running 13 inch wheels with rubber band tires would make the car faster too right? wrong. there are a multitude of reasons/variables why that theory doesnt apply to the real life scenario. i would think an "engineering major" would be able to understand that. but go figure. I'm just using common sense here. you could also make a plausible argument that increasing your wheel diameter and maintaining the same rate or rotations would increase your travel per rotation and thus make the car faster, but it only takes a bit of realistic thinking to realize that theres a point of diminishing returns for both of these theories, and the more optimal rate of travel has already been calculated from the factory design. therefore, going a bit larger or smaller isn't going to get you much of a noteworthy increase or decrease. it all depends on the setup. but if you'd like to be adamantly stubborn about your engineering concepts then be my guest. just telling it like it is.
Last edited by SCrollinSD; 07-12-12 at 10:14 AM.
07-12-12, 10:22 AM
#20
^^^ It all depends what going "faster" means. There are two possibilities. One definition is that it will ACCELERATE faster. The other is that it can achieve a faster CONSTANT speed at the given RPM. Obviously, having a larger than stock wheel will achieve a faster constant/top speed, but having a smaller than stock wheel COULD (and I emphasize this word on purpose) potentially make the car accelerate to a given constant speed at a faster rate than OEM.
This of course assumes that the wheel weights are the same, however.
This of course assumes that the wheel weights are the same, however.
07-12-12, 11:29 AM
#21
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^^i agree. as I said too many variables and too little marginal gain/loss, not worth speaking of. was kinda my original thought. plausible in theory? somewhat. worth making a thread about to go "faster" ? no. that's all.
07-12-12, 11:51 AM
#24
^^^ It all depends what going "faster" means. There are two possibilities. One definition is that it will ACCELERATE faster. The other is that it can achieve a faster CONSTANT speed at the given RPM. Obviously, having a larger than stock wheel will achieve a faster constant/top speed, but having a smaller than stock wheel COULD (and I emphasize this word on purpose) potentially make the car accelerate to a given constant speed at a faster rate than OEM.
This of course assumes that the wheel weights are the same, however.
This of course assumes that the wheel weights are the same, however.
Your right, they are kind of opposites in a sense, Since your rear end gear ratio is directly affected by the size of the rear tires the TRUE gear ratio to the ground is often referred to as "effective gear ratio"
When you increase your gear ratio your top speed is lowered, and vice versa if you were to switch from a 4.27 to a 3.90 your top speed would increase slightly and lower your acceleration.
lol wow you guys. no. by that logic then running 13 inch wheels with rubber band tires would make the car faster too right? wrong. there are a multitude of reasons/variables why that theory doesnt apply to the real life scenario. i would think an "engineering major" would be able to understand that. but go figure. I'm just using common sense here. you could also make a plausible argument that increasing your wheel diameter and maintaining the same rate or rotations would increase your travel per rotation and thus make the car faster, but it only takes a bit of realistic thinking to realize that theres a point of diminishing returns for both of these theories, and the more optimal rate of travel has already been calculated from the factory design. therefore, going a bit larger or smaller isn't going to get you much of a noteworthy increase or decrease. it all depends on the setup. but if you'd like to be adamantly stubborn about your engineering concepts then be my guest. just telling it like it is.
Im kinda surprised everyone is coining these as "theories" these are hard facts and are a big part of racing cars. Your rear end gear ratio is not the exact gearing that "hits the ground" that is in fact determines by rolling diameter I.e rim+ tire size
Your comment about running 13 inch tires with rubber bands is actually valid, it WOULD make your car faster but have a lower top speed (if you have the power to even reach it) Just do me a favor, go put on some 19 inch tires with a 35 profile and then switch to a 16-17 with a 30 and tell me you dont feel the difference.
If this werent valid then modified cars wouldnt have speedometer inaccuracies when changing tire size. and we wouldnt have tire calculators.
Is it worth changing rim + tire size to attain faster acceleration? Not in my opinion but i had to set the record straight with all this "theory" talk, this has been proven since like the 1960s.
Last edited by sj408; 07-12-12 at 11:55 AM.
07-12-12, 12:33 PM
#25
No, you are wrong.
Simply, this is because you are looking at it from one extreme or the other. At some point in the middle, there is a grey area of equilibrium that will shift efficiency from one (ie, having a smaller wheel) to the other (ie, having a bigger wheel).
The easier way to understand this is to use an acceleration speed. For example, if the speed goal is 30mph, then it is almost certain that a smaller wheel will out-accelerate the larger wheel. But, once you increase that speed to, say, 80mph, things may very well change as the bigger wheel will compensate on the end of its run to 80mph.
So, the correct answer is "could."
07-12-12, 01:12 PM
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Actually you couldnt make that argument.... see above. The larger the rolling diameter then your top speed will increase but your acceleration decreases. This isnt a new theory, this has been around for years. Type in gear ratio calculators online, dont have time to find you one but you can input old tire size, new tire size, and rear end gear ratio and it will show you what your effective gear ratio changes to.
Im kinda surprised everyone is coining these as "theories" these are hard facts and are a big part of racing cars. Your rear end gear ratio is not the exact gearing that "hits the ground" that is in fact determines by rolling diameter I.e rim+ tire size
Your comment about running 13 inch tires with rubber bands is actually valid, it WOULD make your car faster but have a lower top speed (if you have the power to even reach it) Just do me a favor, go put on some 19 inch tires with a 35 profile and then switch to a 16-17 with a 30 and tell me you dont feel the difference.
If this werent valid then modified cars wouldnt have speedometer inaccuracies when changing tire size. and we wouldnt have tire calculators.
Is it worth changing rim + tire size to attain faster acceleration? Not in my opinion but i had to set the record straight with all this "theory" talk, this has been proven since like the 1960s.
chill out . as I mentioned, plausible, but not to a degree worth speaking of. learn to read. also, no, you're only assuming that all things being equal, the acceleration would decrease with a larger diameter wheel, but it doesnt have to, again depending on a number of factors. and BTW you just said yourself that a larger diameter will increase top speed did you not? some people would consider that "faster" which was why the ambiguity of what "faster" means was brought up. also, my point of diminishing returns was indeed very valid. if you'd like to try and put a 1" wheel on your car and claim that its gonna accellerate faster than a 16-18" wheel then I think you see my point. you might tell me in your wiser-than-thou opinion that a 13 inch wheel is going to increase acceleration, but where does it stop becoming effective? 12? 10? there are many factors, many possibilites, many calculations to consider. there is no absolution so stop claiming as such.
my whole point was that this dude came in here asking about putting 17 inch wheels on an SC, as if it were some monumental, never-before-done thing, that would make his car "faster."
now, if you're going to sit here and tell me that it will, plus or minus a degree that is so minute that it barely quantifies a discussion, then that's your M.O., but don't call me out like I don't know what I'm talking about. both theories (yes, theories) have validity depending on the variables, but that's really all nonsense when in reality, for the applications we're talking about here, it's all more or less neglect-able.
that is all. Good Grief.
Last edited by SCrollinSD; 07-12-12 at 01:23 PM.
07-12-12, 04:47 PM
#28
Secondly, I dunno why you're being so condescending; I am in fact an engineering major, and I know what Im talking about.
Lemme tell ya a lil' sumtin' about Angular Velocity (ω)...
First off, let's define Velocity (V)
Velocity is speed in a particular direction.
Basically, "speed" is "how fast" whereas "velocity" is "how fast, toward...".
Now, Acceleration, is the rate of change in velocity.
Eg: Velocity = Distance over Time, or V = D/T
In other words, if a bullet travels 1000 meters in 2 seconds, and V = ΔD/ΔT, or 1000m/2s,
then V = 500m/s.
Since we're talking about "wheels", we have to work in Radians.
Radians are the ratio between the length of an arc (in this case, the roll of the wheel), and the radius; whereas the arc-length = The radius.
That said, a smaller wheel will result in a different angular velocity than a larger wheel.
Angular Velocity is measured in "radians per second", or ω = r/s, which is the rate of "spin".
So if our wheel makes e.g. 1 revolution per second, and there are 2π radians in a revolution, then 1rev/s = 2π r/rev = 2π r/s = Angular Velocity.
Now since were arguing about "speed", that means we need to consider a distance traveled; therefore we need to know the radius (R), and measure in meters (m).
How many meters are traveled per second?
1rev/s · 2πR m/rev = 2πR m/s = Speed.
In sum, given the radius and revolutions per second, we can determine an objects velocity; meaning we can have a good idea about what the results might be, per wheel-size.
ω = 2π R/s, also V = 2πR m/s.
Since you mentioned mounting 13" wheels, what's really going to make the difference in that case is the tires ("Frictional Force").
Yes, a smaller wheel will help you accelerate faster, DEPENDING on whether or not you have traction, or force upon the ground. As long as you don't have craaazy wheel spin (which would occur when you have too small a wheel, and alotta power), then you should get going somewhere, as a result of the angular velocity of the wheels.
I think Mike made a good point, about the difference in Top Speed, one I hadn't considered. Im hardly ever going to drive at that speed however; what I'm looking for is some exhilaration, the thrill of being pressed into my seat, when I sometimes open the throttle, or wanna amuse some chicks. I want to improve the driving experience ... But I digress.
Anyway, thats why crazy-power cars like the new GT-R have 20" wheels from the factory. They NEED to, and width is especially important.
That said, when a car drives, it has various forces acting upon it; in this case we're focused on the Frictional Force of the tires to the ground, and the Gravitational Force (Downforce) such as the weight of the vehicle, and inertia imposed upon it. Further, in regards to a stand still, or launching from a re light, there exists the Static Force of friction, as well as the Kinetic Force of friction, in which the coefficient is always between 0 and 1, because you'll never have to push on something horizontally (in order to move it) with more force than is required to lift it off the ground.
Thus, as long as we have good tires, we can have smaller wheels and see a positive difference in acceleration from our vehicle. (Provided we do a few more calculations like determining the weight of an SC300 w/ a driver, etc. and take into account RPM's and diameter, we can determine which setup would be optimal for our machine; 17, 18, 19, 20).
I was just hoping someone already knew the answers from experience, so I don't have to figure all this sh* out myself
That's all...
Last edited by SEIDO; 07-13-12 at 10:11 PM.
07-12-12, 05:31 PM
#30
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