Does a lighter car go faster? (TOP SPEED)
- Thread starter olithebad
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Diogo
(Banned)
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- No, thanks
- 174
- Iriquois
well terminal velocity basically means the maximum speed an object can go at due to drag(air resistance) and friction. A bulkier car(size wise) would mean it would have a lower top speed.
Yes that is correct, an object that weighs more will fall/drive faster down a slope(downhill) but that would also mean it would have difficulty going up slope.
Also, a lighter car only has an effect on the acceleration not top speed
- 104
- Georgiesbest
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- GTP_Famine
It's irrelevant, beyond a very low level.
In terms of straight line speed, friction coefficient of the tyre is also only relevant to how much torque - not power - can be transmitted by the car to the road surface. Since, at top speed, the car is producing just about as little torque as it can manage (gearboxes multiply torque; high gear = low multiplier), what torque the tyre can cope with is irrelevant so long as it can maintain the paltry 2,000lbft or so the Veyron generates at the wheels in 7th gear.
Moreover, the friction of a tyre that isn't loaded is zero, regardless of the friction coefficient. The loading is what generates friction - this is, in part, why downforce and lift change this calculation.
However it's an irrelevance since the tyre on the 4150lb car doing its top speed run is the same as the tyre on the 3950lb car doing the same top speed run - it's a factor that can be normalised because it is effectively constant between the two tests.
In general, as I said, rolling resistance can be calculated by multiplying the vehicle mass by about 1.35%, though it can be changed by downforce or lift.
Just for reference, "100kg" is a mass, not a weight. "1000N" is both a weight and a force - since weight is force (mass multiplied by acceleration; in this case a mass of 100kg accelerated downwards by gravity to generate a weight).
That aside, you said that weight does not affect a car's top speed. If it has the gearing to exploit it then it does - just not by very much. Even a Veyron that weighed half as much as it does wouldn't be able to go that much faster than a normal one (I worked it out - 1.74mph!), without invoking relativistic speeds...
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- 104
- Georgiesbest
I apologise haha, bad habit calling a cars mass "weight". No need to inform me of the physics, all of my lecturers make the same mistake and no one feels the need to point it out
. I will be more careful with my diction so as to not confuse you and complicate matters.My point was was that when weight increases, tyre friction increases. This means that the force put down by the tyre increases by the same amount as the rolling resistance force increases. This is regardless of how much of the tyres available grip is in use, as long as it is less than the maximum. So the net force put down on the road by the tyres is the same regardless of weight.
At least this is what it says in my physics text book. There might be a difference in the real world physics, but if it is it would be marginal and due to something we have not taken into consideration, and something that GT5 certainly wouldn't take into account in its physics calculations.
So for the purpose of this discussion in the game, it doesn't matter
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- GTP_Famine
Yes and no. Yes, to a limit. But no, you're applying it to the whole car.
If you increased the mass of, say, a Mazda MX-5 by 10lb - big Christmas dinner - you don't increase the load on every tyre by 10lb. You increase the load on each tyre by 2.5lb. If you increase the mass of a Ford Focus RS by 10lb, you increase the load on each front (drive) tyre by 3.2lb and the load on each rear tyre by 1.8lb.
The amount of available grip on a drive tyre isn't coefficient of friction x vehicle weight, it's coefficient of friction x corner weight. More to the point here, it's coefficient of friction x instant corner weight as this weight can change wildly according to what you're doing at the time - a 50:50 (MX-5) or 63:37 (Focus) static weight distribution isn't very relevant when you're standing the car on its nose. Ultimately, adding 10lb to the mass of a car does not increase the mass on any one tyre by 10lb. Unless you're in the middle of a colossal crash and only one wheel is on the ground.
Which it won't do. The weight (or normal force) of the vehicle changes according to the overall vehicle loading, while the weight of an individual tyre changes according to the corner loading. The friction coefficient of the tyre on the road surface changes only according to the corner loading (and can be affected by other factors such as footprint, inflation and, amusingly, even the tread pattern).
But it's only relevant to the amount of torque and to a static vehicle. Notice how it's quite hard to get a car moving by pushing/pulling it, but quite easy to keep it moving once it's started?
- 104
- Georgiesbest
Ahh, that's a very good point.
I was, quite wrongly, assuming we had an even weight distribution, and that all wheels were driven.
Weight transfer isn't really too much of a problem, because when at top speed you are effectively at equilibrium, and the weight isn't shifting about over the wheels. But the distribution due to the uneven load/suspension settings gives us cool results.
This would suggest that a car could increase its top speed merely by changing its distribution so that more is over the driven wheels. This would cause there to be less weight on the non-driven wheels, reducing the rolling resistance force.
Although again, it very much is unlikely that GT5 takes these physics into account, and even if it did, we would be talking about an almost unnoticeable difference.
Glad we've got to the bottom of it
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- slashfan7964
My truck is a AWD and when it had 780hp the launch was insane but top end blew.
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- IceManPJN
- IceMan PJN
That isn't how gravity works. As an illustration, a light-weight object falls just as fast as a heavier one. The only reason that a sheet of paper or feather falls slower than a rock is air resistance, which has absolutely nothing to do with weight or gravity. If you take a ten-pound box and a hundred-pound box of equal size and drop them at the same time from the same height, they will hit the ground at exactly the same time.
- 174
- Iriquois
Yes...in a vacuum, but we arent talking about in a vacuum, are we? Bottom-line, a heavier car will reach the bottom of a slope faster than a light car
- 11,660
- GTP_Orido
Weight affects directly into the load generated on tires and suspension, more load usually means less speed in a given corner compared to an identical lighter car. Acceleration depends on torque + good gearing, top speed depends on many things, aerodynamic drag, car size, horse power, etc. That's what i know.
- 1,019
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- yzfmike
- yzfmike
How high are we talking about the boxes being dropped? This is talking about acceleration of horizontal proportions not vertical. A vehicle's speed is limited by gearing, power, aerodynamics, and how much distance it has to reach max speed. The longer the road, the more speed it can gain. The only way it can gain more speed is by how much power it makes, the more the faster. How well the car can cut thru the air makes a difference as well. A coefficient of drag .25 is better than .27 (2009 Nissan GT-R Aero Package to 2011 Nissan GT-R Aero Package).
the true answer is maybe. it depends on what is limiting the top speed. is it gear related? or is it weight related? is the track flat? but you need to compare the SAME car, not two different cars, bc then you have aerodynamic differences and gearing and a different motor specs, blah, blah, the list goes on.
just test it in the game. buy a car, make sure it has full power, and go top end it. then go and lighten the car and see if it goes faster. simple. same track, same car )except for the second run it weighed less), same gears, same tires, same frontal area, same coefficient of drag number, etc. make sure it just doesnt run up on the rev limiter in top gear, bc then the answer will be no.
just test it in the game. buy a car, make sure it has full power, and go top end it. then go and lighten the car and see if it goes faster. simple. same track, same car )except for the second run it weighed less), same gears, same tires, same frontal area, same coefficient of drag number, etc. make sure it just doesnt run up on the rev limiter in top gear, bc then the answer will be no.
- 2,073
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- mrvajj
Once a vehicle has overcome it's inertia it doesn't matter (to a point) how heavy it is. Top speed is all about torque/gearing vs aerodynamic drag.
- 104
- Georgiesbest
No this is incorrect.
Two balls the same shape. One with a mass of 10kg, the other with 100kg.
Drop from 500ft in the air.
They will both accelerate towards the ground at the same speed.
However, the heavier ball will accelerate for longer and to a greater speed than the lighter one because it weighs more.
Both balls have the exact same drag coefficient, but one weighs twice as much as the other, so it will find equilibrium at a larger terminal velocity.
This is why a heavier person falls faster when at terminal velocity than a lighter one.
If people would just read all of the posts by me and famine it basically explains it all and includes some numbers.
see my post above. IT depends on the conditions. if you want to compare apples to oranges.....
thats the problem with most researchers is they try to mold their (evidence they believe in) and prove their theory. whether its correct or wrong. evidence should shape the theory and not the theory shaping the evidence. fyi. good luck to all/.
not proper or accurate lot.
thats the problem with most researchers is they try to mold their (evidence they believe in) and prove their theory. whether its correct or wrong. evidence should shape the theory and not the theory shaping the evidence. fyi. good luck to all/.
not proper or accurate lot.
- 6,392
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- wat3rm370n
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- yzfmike
- yzfmike
Lets take two different cars. Lets use a NASCAR Sprint Cup car. It has over 800 HP at non restircter place races. Weighs about 3200 pounds. It can go up to and over 200 MPH depending on the track. Now lets use a NISMO 350Z GT500 car. It has approx. 500 HP. Weighs about 2400 pounds. It can also go to 200MPH as well (You can use V8 Supercars as well). This shows that being lighter and with less power it can go just as fast as a car that is heavier with more power as well. Now also, Nissan is running the Deltawing at Le Mans. Nissan and the ACO are working to make this car have times between the LMP1 and LMP2 cars. This car uses a 1.6 Liter 
Turbocharged motor, putting out about 300HP. It will go faster than the GT1 and GT2 cars that have more power and weight. The Deltawing is a very good example of a low horsepower, lighter car, going as fast as a top LMP2 car witch has more power and weight. I am curious too see how the Deltawing cuts its chops in Frace in 3 1/2 months.
Turbocharged motor, putting out about 300HP. It will go faster than the GT1 and GT2 cars that have more power and weight. The Deltawing is a very good example of a low horsepower, lighter car, going as fast as a top LMP2 car witch has more power and weight. I am curious too see how the Deltawing cuts its chops in Frace in 3 1/2 months.
It's rather funny... this all started with a simple question from olithebad, and has ended in a quite complicated discussion (at least for me who isn't that into science). I'm wondering whether olithebad has managed to filter out a concluding answer. Personally I learned a lot from this post (though I'm not sure if what I've learned is correct), but I think lav01 gave the most practical answer to help out olithebad.
my 2 cents
my 2 cents
Rotary Junkie
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- RJs_RX-7
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mjm_98
If you been eating sprouts, then quite a lot I would imagine.
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- GTP_Famine
Sorry, but weight has no impact at all on ultimate top speed, if the road is flat and veery long
So long as there is sufficient gearing, yes it does, just not by very much.
