Accuracy of Lateral G meter.
- Thread starter JRizEJ6
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NOPE! I just pulled like 1.4 G's regularly in the Mazda Kimchi or Karachi or whatever it is that I won in the B license test. The Kusabi, that's it. 1.4 in a flat corner (no extra downforce to help me grip). I know it can vary based on the radius of the turn, speed, etc, but I think everything I've driven so far shows a lot more grip than I think the cars really have. (I'm almost done golding the A license test)
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- swift-bass
Well, I don't use it for accurate reading. I use it more for the stability of the car.
There are times when you flying down a straight, you twitch the steering wheel and the meter starts to look like a game of Pong. That let's me know I'm getting ready to spin, period. Now, that's an extreme case, but I hope you see where I'm coming from. I use it to show me how the wieght is sitting over the tires, not so much to measure actual G-forces.
There are times when you flying down a straight, you twitch the steering wheel and the meter starts to look like a game of Pong. That let's me know I'm getting ready to spin, period. Now, that's an extreme case, but I hope you see where I'm coming from. I use it to show me how the wieght is sitting over the tires, not so much to measure actual G-forces.
Yeti you are wrong in your theroy. There is 1G acting on us in a vertical sense but when you talk about cornering forces you are talking about lateral G forces, or loads acting sideways. The ability of a car to maintain a lateral G load of over about .8-1.0 is difficult for a street car. Some race cars however will do much higher.
A far a the G meter in the game goes I think it is definately a bit liberal in its readings. I have not had a chance to test it in a steady state stuation so i cannot be sure, but I am pretty sure it is. It is possible for a street car to hit 1.5 G or above but that is in a transitional situation where weight shift comes into play.
A far a the G meter in the game goes I think it is definately a bit liberal in its readings. I have not had a chance to test it in a steady state stuation so i cannot be sure, but I am pretty sure it is. It is possible for a street car to hit 1.5 G or above but that is in a transitional situation where weight shift comes into play.
Tires, tires, tires!
The maximum G force is dictated by tires mostly. Racing tires can easily give up to 2 G. Street tires will max out at 1G often below. In license tests they don't tell you what kind of tires you have but you can guess by the max G you reach.
Experiment with it yourself. Go to any track with a car that has all 3 types available and see how far you can get the meter to go.
The maximum G force is dictated by tires mostly. Racing tires can easily give up to 2 G. Street tires will max out at 1G often below. In license tests they don't tell you what kind of tires you have but you can guess by the max G you reach.
Experiment with it yourself. Go to any track with a car that has all 3 types available and see how far you can get the meter to go.
any crappy car can pull over a g of lateral force. they just can't sustain it. when you read in magazines and whatnot that a sports car did "1.02 g's on the skidpad" it means that it can sustain that many g's. i could hop in a geo metro, swerve side to side and probably get 1.5g's of lateral force. there's just no way in hell it could sustain that much.
to calculating lateral force is just a simple physics equation: a = (V^2)/r
to calculating lateral force is just a simple physics equation: a = (V^2)/r
not realy gvan... all lat g are done on a flat skidpad, so its kinda cheating to add verticle G's into it... so far ive found the meter to be fairly accurate, street cars on slicks tend to pull about 1.5 ish which is about right, race cars with low CG and slicks should pull over 2 which they do.
Scaff
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The single biggest thing that will effect lateral G in GT4 would be the tyres fitted to the car.
Its not the only factor, but it is a major one. The racing tyres offer grip levels far higher than IRL as a result the peak lateral G that is shown is very high.
Colorado S14 is quite right that the cars weight, centre of gravity and polar moment of inertia will all play a part, but the biggest factor at play in GT (and by that I mean all the games) are the tyres.
The following may help out
http://www.miata.net/sport/Physics/07-Circle.html
http://www.miata.net/sport/Physics/13-Transients.html
The level of mechanical grip offered by tyres is one of the reasons why I dislike the reliance some people place on skidpan results. Its a very big mistake to equate skidpan figures with a cars ability to handle; the lateral G figures offer by skidpan testing will allow you to figure the level of absolute grip that the cars tyres offer. Not its ability to handle.
For example here a few examples of 200-ft skidpan figures
Ford GT - 0.99g
Z06 - 0.94g
Mustang Mach 1 '03 - 0.83g
Z4 - 0.92g
Boxter - 0.91g
Enzo - 1.01g
Saleen S7 - 0.99g
RX-8 - 0.88g
Crossfire - 0.89g
Pontiac GTO - 0.81g
As you can see not a huge difference in the figures and in no way an indication of how well the cars will handle, particularly when in comes to knowing when you are going to exceed maximum grip or how the car will react when you need to change direction quickly, for example traveling through a chicane. You should also be aware that a cars skidpan figures are not compariable with the max lateral G a car can pull in a corner, the surfaces are very different in term of grip levels.
Just to give you an idea of how high real world lateral G figures can get, when the Radical SR3T set a time of 7mins 18secs on the Nurburgring, its telemetary showed a peak lateral G of 2.10 at 122mph through the Schwedenkreuz corner, and this was on Dunlop Formula R road tyres!
Its not the only factor, but it is a major one. The racing tyres offer grip levels far higher than IRL as a result the peak lateral G that is shown is very high.
Colorado S14 is quite right that the cars weight, centre of gravity and polar moment of inertia will all play a part, but the biggest factor at play in GT (and by that I mean all the games) are the tyres.
The following may help out
http://www.miata.net/sport/Physics/07-Circle.html
http://www.miata.net/sport/Physics/13-Transients.html
The level of mechanical grip offered by tyres is one of the reasons why I dislike the reliance some people place on skidpan results. Its a very big mistake to equate skidpan figures with a cars ability to handle; the lateral G figures offer by skidpan testing will allow you to figure the level of absolute grip that the cars tyres offer. Not its ability to handle.
For example here a few examples of 200-ft skidpan figures
Ford GT - 0.99g
Z06 - 0.94g
Mustang Mach 1 '03 - 0.83g
Z4 - 0.92g
Boxter - 0.91g
Enzo - 1.01g
Saleen S7 - 0.99g
RX-8 - 0.88g
Crossfire - 0.89g
Pontiac GTO - 0.81g
As you can see not a huge difference in the figures and in no way an indication of how well the cars will handle, particularly when in comes to knowing when you are going to exceed maximum grip or how the car will react when you need to change direction quickly, for example traveling through a chicane. You should also be aware that a cars skidpan figures are not compariable with the max lateral G a car can pull in a corner, the surfaces are very different in term of grip levels.
Just to give you an idea of how high real world lateral G figures can get, when the Radical SR3T set a time of 7mins 18secs on the Nurburgring, its telemetary showed a peak lateral G of 2.10 at 122mph through the Schwedenkreuz corner, and this was on Dunlop Formula R road tyres!
I agree that it's inaccurate. If you want to try a simple test, do this. Go to GT3 (yeah, pull it off the shelf), and do the license test with the Corvette on the wet skid pad. Very simple math, now just simply obtain your average speed around the skidpad, get the radius (it's given on the license test description), and calculate the amount of lateral G's you are pulling. I think you'll be surprised at what you obtain.
m*a = m*(v^2)/r
Divide the acceleration you obtain by the constant for gravity, and you will find your lateral G number. I calculated G's in excess of 1.2 on wet pavement in a stock Z06. That's inaccurate pertaining to real life. The Z06 would not be able to sustain this kind of grip even on dry pavement let alone wet pavement.
By the way, tires partially determine the maximum lateral grip. It's really dependent upon the amount of friction developed between the tire and the road, and downforce makes a huge difference to this aspect. Your want to increase the normal force between the road tire and the surface, and by adding more "weight" via downforce, you increase the normal force the road generates on the tire. Since friction is dependent upon the normal force, thus more normal force means a higher friction force. A higher friction force means you can sustain greater speeds through a turn.
Anyway, I have found a lot of their values in the game to be a little too high.
m*a = m*(v^2)/r
Divide the acceleration you obtain by the constant for gravity, and you will find your lateral G number. I calculated G's in excess of 1.2 on wet pavement in a stock Z06. That's inaccurate pertaining to real life. The Z06 would not be able to sustain this kind of grip even on dry pavement let alone wet pavement.
By the way, tires partially determine the maximum lateral grip. It's really dependent upon the amount of friction developed between the tire and the road, and downforce makes a huge difference to this aspect. Your want to increase the normal force between the road tire and the surface, and by adding more "weight" via downforce, you increase the normal force the road generates on the tire. Since friction is dependent upon the normal force, thus more normal force means a higher friction force. A higher friction force means you can sustain greater speeds through a turn.
Anyway, I have found a lot of their values in the game to be a little too high.
Scaff
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basmasta7
Your formula can be used to give a very basic guide, but you need to take into accound that a tyre is not a solid non-deformable object, if it was your calculation would hold true.
However tyres are very deformable, and as such are subject to radial, circumferential, axial and torsional deformation. All of which must be taken into account when you look at grip levels and maximum lateral forces.
http://www.miata.net/sport/Physics/10-GripAngle.html
Scaff
Right, but how do axial loads apply to this? Also, the tire does deform therefore creating a larger surface area of contact for the tire applied to the pavement. If the tire was non-deformable, it would only have one point of contact on the road at all times. I suppose it doesn't matter since the equation does not take in any distributed forces or pressures (stresses) into matter. How would you go about calculating it then? It's a very simple test, but the above mentioned forces will not dramatically alter the tire's performance unless a yield point is reached for the wheel or the rubber (which is the yield point is incredibly high for rubber). Anyway, I will read over your that site you gave me, though. Thanks for the extra information.
Scaff
nooo, i'm sorry but my equation is right in all cases. all the aspects of the tire affect the max average speed a car can travel in a constant radius circle, and hence are factored into the "V" part of the equation. i'm a mechanical engineer. this is the stuff i do all day.
you guys are still stuck on the magazine numbers of lateral g forces around a 200 ft skid pad. like i said before - those are not MAX numbers of lateral g's a car can withstand. they are the max lateral g's that a car can sustain for an indefinite amount of time. there's a huge difference.
i don't doubt that the high levels of grip are unrealistic, but when you have 1.5g's on the meter when you're driving a civic it's not quite as unrealistic as you guys are making it out to be. i have an accelerometer in my integra and i can attest that i have achieved well over 1 g.
Scaff
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basmasta7
Well the Physics PHD and racer who wrote the highly regarded article I linked to appears to disagree with you.
As for the rest, I'm sorry if my original post was not clear, but I did say that skidpan tests are not a realistic indication of max lateral G (and why I find them unrealistic) and also gave a link to a site that documents a road tyre (Dunlop Formula R) generating a max lateral G reading of over 2g.
Road/track surface also obviously plays a big part here.. For example, G readings quoted by different magazines for the same cars may differ 10-15 percent easily.
Car&Driver vs. Road&Track is the easiest comparo, as they often have the same cars tested pretty much the same time.. Then compare those readings to the ones recorded by Evo for example, the difference caused by the track surface is huge...
But obviously it's wrong to compare the highest G reached to the readings magazines quote; like said before, highlights are highlights, but magazine G measurements are for constant lateral force.
Car&Driver vs. Road&Track is the easiest comparo, as they often have the same cars tested pretty much the same time.. Then compare those readings to the ones recorded by Evo for example, the difference caused by the track surface is huge...
But obviously it's wrong to compare the highest G reached to the readings magazines quote; like said before, highlights are highlights, but magazine G measurements are for constant lateral force.
Scaff
i just read the entire article, and i don't see anything that contradicts what i've said. i'm well aware that the tire and road relationship is not a simple friction problem. if it were that way, then a lateral force of over 1g would be impossible. really all i'm saying is that a = (V^2)/r no matter what so i'm sure the g's on the meter in the game correspond to the exact speed and radius you're turning at. however, the game could be allowing unrealistic speeds (V) which would in turn make the lateral g level unrealistic. so far the only argument i've seen so far that would void the validity of the game's physics in this respect is the corvette on the wet skidpad.
Well, I lost my original post due to computer freeze.
Anyway, I did skidpad results, and I did not do momentary maximum lateral G testing. The testing I tried in GT3 should be somewhat accurate and related to real world values. The radially acceleration (normal acceleration) is an approximate value that should be close to real world values. No temperature involved in these processes either which affects the tire's cohesion (warmer tires, more free roaming electrons to momentarily bond with the free electrons on the ground).
By the way, I totally goofed. The lateral G's were in excess of 1 G, but I meant to say the coefficient of friction for the tires was greater than 1.0. That was the very strange part of the Z06 wet skidpad test. I'm trying to find my old post in another forum where I tested this with a fellow member. If I find it soon, I will be sure to post it in here for everyone to read over and scrutinize.
And most axially and torsional stresses induced on a rigid body are typically considered internal forces that do not have a very noticeable effect on any of the external forces until the internal stresses reach the yield or fracture point.
To finalize, I just wanted to add this: it's a game. It's possible that PD had to tinker with the physics a little to get the cars to perform realistically. What equation do you think PD is having our little PS2 calculate while we're turning? They certainly can't do integration, and series will eat up the PS2's memory fast. There has to be a quick and dirty way to generate physics without so much involved math. I believe the game is simulation in terms of feel, but to me, the numbers are a little off.
Take for example, on Mission Hall 23, my Skyline was pulling 1.2G + with slight steering input on the banked turn. That doesn't add up. You'd be feeling the G's in your ass more than your side.
Anyway, I did skidpad results, and I did not do momentary maximum lateral G testing. The testing I tried in GT3 should be somewhat accurate and related to real world values. The radially acceleration (normal acceleration) is an approximate value that should be close to real world values. No temperature involved in these processes either which affects the tire's cohesion (warmer tires, more free roaming electrons to momentarily bond with the free electrons on the ground).
By the way, I totally goofed. The lateral G's were in excess of 1 G, but I meant to say the coefficient of friction for the tires was greater than 1.0. That was the very strange part of the Z06 wet skidpad test. I'm trying to find my old post in another forum where I tested this with a fellow member. If I find it soon, I will be sure to post it in here for everyone to read over and scrutinize.
And most axially and torsional stresses induced on a rigid body are typically considered internal forces that do not have a very noticeable effect on any of the external forces until the internal stresses reach the yield or fracture point.
To finalize, I just wanted to add this: it's a game. It's possible that PD had to tinker with the physics a little to get the cars to perform realistically. What equation do you think PD is having our little PS2 calculate while we're turning? They certainly can't do integration, and series will eat up the PS2's memory fast. There has to be a quick and dirty way to generate physics without so much involved math. I believe the game is simulation in terms of feel, but to me, the numbers are a little off.
Take for example, on Mission Hall 23, my Skyline was pulling 1.2G + with slight steering input on the banked turn. That doesn't add up. You'd be feeling the G's in your ass more than your side.
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You can sayt hat race cars can easily hit 2gs, but I know F1 cars can sustain 4 and a 550GTO will supposedly pull a 4.5 on a switch back...
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