Why do some cars spin on grass? why other cars do not?

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alfredchiwai

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amigo8833
I understand why a car spins when one of its wheels is on grass. It is owing to the difference of friction between them. For instance, one rear wheel on road gives frictions for pushing forward and the other rear wheel on grass can't give enough friction to go forward, an imbalance that makes the car spins because one side goes forward and the other side goes slower.
However, I don't know why some cars spin (e.g. NSX Type R, Evora) and some other cars don't (e.g. CLK touring car) in such situation. Please explain and state how to tune to avoid them. Thanks!
 
Its power and downforce mostly. If you have a 900 HP car it will spin a lot easier than a 200 HP car since you have one wheel using 900 HP and the other wheel is spinning without any grip.
 
Another factor is the grip level in the race... if you're online with the "Real" setting active then those white lines are tremendously unforgiving!
 
Sandy106
Its power and downforce mostly. If you have a 900 HP car it will spin a lot easier than a 200 HP car since you have one wheel using 900 HP and the other wheel is spinning without any grip.
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So, why my Evora (450 hp) spinned on Nurburgring with one wheel on grass and my CLK touring car (490 hp) did not? Could you elaborate on the downforce which makes the car spins? Thanks for your reply anyway.
 
alfredchiwai
So, why my Evora (450 hp) spinned on Nurburgring with one wheel on grass and my CLK touring car (490 hp) did not? Could you elaborate on the downforce which makes the car spins? Thanks for your reply anyway.
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There are a million reasons one car would spin and another wouldn't. Angle you went into the grass, amount of throttle input, braking, steering, suspension settings, etc.

Offhand, in that situation, it could have been the higher downforce on the touring car keeping it more planted compared to the Lotus. Though, as I said, it could also be that the lotus went off in the grass just right and spun while the CLK got lucky.


alfredchiwai
You mean LSD? Higher initial torque and acceleration to avoid spinning? Thanks for your reply!
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Not my post, but yes, LSD=Limited Slip Differential
 
alfredchiwai
So, why my Evora (450 hp) spinned on Nurburgring with one wheel on grass and my CLK touring car (490 hp) did not? Could you elaborate on the downforce which makes the car spins? Thanks for your reply anyway.
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The Evora has less downforce than a DTM car. Higher downforce will give the tires more grip off the track since it pushes the tires into the ground. Theres other factors that affect it too like speed and whether or not you are cornering, but power and downforce are the 2 biggest factors.
 
A primary feature of ABS on modern cars is the ability to break on such situations without sending the car to a spin. Unfortunately, GT5 doesn't implement ABS that way. Sure, it makes your breaking distance much longer, but at least you can still keep it under control.

If you do that with ABS set to a high value in GT5, you will still go in to a violent spin.
 
  • Drivetrain layout
  • Tires
  • Speed
  • Angle at which your going into the grass(coming out of a turn and hitting the grass on the outside/slowly merging into the grass on a straightaway/etc
  • LSD Settings
  • Downforce
  • Whether you are accelerating, braking, or cruising when you come in contact with the grass.
 
sam_i_am
A primary feature of ABS on modern cars is the ability to break on such situations without sending the car to a spin.
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Complete nonsense.

sam_i_am
Unfortunately, GT5 doesn't implement ABS that way. Sure, it makes your breaking distance much longer, but at least you can still keep it under control.

If you do that with ABS set to a high value in GT5, you will still go in to a violent spin.
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That's realistic. ABS works per-wheel.

If you brake heavily with one side of the car on a high grip surface and the other side on a low grip surface then the car will spin... either in real-life or in GT5.

The brake system extracts the maximum possible retardation potential of each tyre... it'll brake 'softly' on the low grip side and 'strongly' on the high grip side.

Many people today think of ABS as some kind of braking cure-all, but it isn't. You have to know when/how to use it.

A system that WOULD help in the conditions you describe is auto-stability management... but it has its limits too.
 
speedy_2
  • Drivetrain layout
  • Tires
  • Speed
  • Angle at which your going into the grass(coming out of a turn and hitting the grass on the outside/slowly merging into the grass on a straightaway/etc
  • LSD Settings
  • Downforce
  • Whether you are accelerating, braking, or cruising when you come in contact with the grass.
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Great to see the points and I would like to know any link which explains each of them in detail. Thanks.
 
TenEightyOne
Complete nonsense.


That's realistic. ABS works per-wheel.
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Er... Is that not contradicting yourself? If ABS works on individual wheels, then by braking one wheel more than another, it would stop a car spinning if one side of the car was on a low-friction surface and the other side had more grip. If it applied the same amount of braking on the right and left wheel, then there would be a yaw effect which would spin the car. I therefore conclude that by ABS braking each wheel according to the grip it has, it stops cars from spinning.


As for the list of points:
Drivetrain layout: A mid engined car is easier to spin than an FR car because the centre of mass in the car is in the middle (engine being the heaviest part), but in an FR it's in the front... It's a lot harder to explain than I've just realised, but the order of ease of control (in a basic sense) goes like this:
Front engine, front wheel drive
Front engine, all wheel drive
Front engine, rear wheel drive
Mid engine, all wheel drive
Rear engine, all wheel drive
Mid engine, rear wheel drive
Rear engine, rear wheel drive.

At least that's the way I see it. I put mid-all under FR because of the lift-off oversteer being greatly magnified by the mid engine placement.


Tires, it's reasonable to believe that the hardness of the compound doesn't really matter, but the type of tire does; slicks only work on tarmac. Not sure how well PD have modelled the different tread types, though.


Speed is obvious, but also torque; the higher the torque the car has, the easier the wheels will spin on a low-friction surface. If you put a high torque car on grass it'll be pretty difficult to control... That said, if you have a high torque car with massive turbo lag, it'll probably be relatively easy because the engine will have no shove at 'oh no, I'm on the grass' speeds.


Angle; the higher your angle, the harder it will be to control, same as being on tarmac. Accelerating in a straight line is easier than accelerating around a corner, same rules apply to grass.


LSD settings are something I know very little about.


Downforce matters in that it effectively increases the weight of your car, so if you leave the road at high speed you'll be pushed into the grass much harder than if you have no downforce. This increases the grip you have. Pretty straightforward, really. However, downforce only really makes a difference at speed, if you come off the track and stop, it'll be just as bad as a car with low downforce.


Finally, the accelerating/braking/neither thing. If you're making the tyres stop or accelerate the car, they will struggle on a low grip surface. If you're braking they'll lock up and lose grip, if you're accelerating they'll spin and you'll lose grip. Best thing to do if you know you're heading for the grass is probably to brake, but stop braking before you hit the grass otherwise you'll have absolutely no control. By touching neither 'pedal', your tyres will only be trying to turn the car, not accelerate/brake it as well, and will therefore cope better at not making you spin... Ish.
 
My Tuscan modded seems to have a love affair with the grass, it never spins out but sticks to the grass like glue.

Same happens with a lot of other understeery cars.
 
Yes wether the off track grip settings are set to low or real makes a huge difference, as well as the drivetrain.
 
neema_t
Er... Is that not contradicting yourself? If ABS works on individual wheels, then by braking one wheel more than another, it would stop a car spinning if one side of the car was on a low-friction surface and the other side had more grip. If it applied the same amount of braking on the right and left wheel, then there would be a yaw effect which would spin the car. I therefore conclude that by ABS braking each wheel according to the grip it has, it stops cars from spinning.


As for the list of points:
Drivetrain layout: A mid engined car is easier to spin than an FR car because the centre of mass in the car is in the middle (engine being the heaviest part), but in an FR it's in the front... It's a lot harder to explain than I've just realised, but the order of ease of control (in a basic sense) goes like this:
Front engine, front wheel drive
Front engine, all wheel drive
Front engine, rear wheel drive
Mid engine, all wheel drive
Rear engine, all wheel drive
Mid engine, rear wheel drive
Rear engine, rear wheel drive.

At least that's the way I see it. I put mid-all under FR because of the lift-off oversteer being greatly magnified by the mid engine placement.


Tires, it's reasonable to believe that the hardness of the compound doesn't really matter, but the type of tire does; slicks only work on tarmac. Not sure how well PD have modelled the different tread types, though.


Speed is obvious, but also torque; the higher the torque the car has, the easier the wheels will spin on a low-friction surface. If you put a high torque car on grass it'll be pretty difficult to control... That said, if you have a high torque car with massive turbo lag, it'll probably be relatively easy because the engine will have no shove at 'oh no, I'm on the grass' speeds.


Angle; the higher your angle, the harder it will be to control, same as being on tarmac. Accelerating in a straight line is easier than accelerating around a corner, same rules apply to grass.


LSD settings are something I know very little about.


Downforce matters in that it effectively increases the weight of your car, so if you leave the road at high speed you'll be pushed into the grass much harder than if you have no downforce. This increases the grip you have. Pretty straightforward, really. However, downforce only really makes a difference at speed, if you come off the track and stop, it'll be just as bad as a car with low downforce.


Finally, the accelerating/braking/neither thing. If you're making the tyres stop or accelerate the car, they will struggle on a low grip surface. If you're braking they'll lock up and lose grip, if you're accelerating they'll spin and you'll lose grip. Best thing to do if you know you're heading for the grass is probably to brake, but stop braking before you hit the grass otherwise you'll have absolutely no control. By touching neither 'pedal', your tyres will only be trying to turn the car, not accelerate/brake it as well, and will therefore cope better at not making you spin... Ish.
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Wow, I'm very grateful!
 
this happens alot if you try to cut the corners on le mans. however if you dont accelerate on that gravel you should be ok
 
sam_i_am
I'm afraid not. See http://www.youtube.com/watch?v=xd5KDvXbE3M At 2:15, you will see exactly this. How ABS allows you to stop with one wheel on dry road and one on wet.
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That's completely different to braking a car with one wheel on tarmac and one wheel on grass though... so not a relative example.

ABS works per-wheel, as I said. Neema_t feels that's a contradiction, it's not.

Every wheel will gain the maximum retardation possible INDEPENDENTLY of the other wheels. The side of the car on tarmac will be able to stop sharply. The side of the car on grass will not.

Why not have a system that tries to stop yaw under braking? Ah, we have one... it's called ASM. ASM uses (partly) ABS systems to achieve its ends... because ABS is useless at controlling yaw (excessive yaw=spins) on greatly differing surfaces.

If you were going to try a half-grass-half-tarmac experiment then you might as well turn the ABS off because it would be safer to lock the grass wheels and skid thme.
 

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