Discussion
You're quite right it needs some slip, I should have said "added slip". If anything you take front slip off by taking lock off.
I disagree about the understeer. How can it tend towards it if it never gets there ?
You're confusing a change of lat acceleration balance with the tractive elimination of rear slip. On a front driver you use traction to correct oversteer NOT lateral acceleration, so it does NOT affect front end lat grip, and the car therefore doesn't tend towards understeer although I can see why it may look like it to the untrained eye from the outside.
I disagree about the understeer. How can it tend towards it if it never gets there ?
You're confusing a change of lat acceleration balance with the tractive elimination of rear slip. On a front driver you use traction to correct oversteer NOT lateral acceleration, so it does NOT affect front end lat grip, and the car therefore doesn't tend towards understeer although I can see why it may look like it to the untrained eye from the outside.
Debaser said:
If the balance is shifting from oversteer to neutral, then it is tending towards understeer.
So if you've got the back end out under power in a rwd car and you feather the throttle to bring it back, is it under-steering?I understand the point you're trying to make - yes, fwd cars will ultimately tend towards under steer and rwd cars will tend towards oversteer. It's physics.
The simplest test would be to put one car of each type on a frozen lake, get them up to (say) 30mph and then turn whilst applying power. The fwd car will carry on in a straight line, the rwd will be facing the wrong way.
Others are also correct when they say that the tendency to understeer can be factored out with clever different and a good chassis, in the same way that rwd cars can be prevented from constantly pirouetting round corners
Just to drag the thread out a bit further, how can fwd cars be competitive in BTCC against their rwd opposition?
Nigel_O said:
LOL - I'll re-phrase - how can fwd cars in BTCC be competitive against their rwd opposition, even when they have ballast on board from winning the previous round? 
Because they can be just as fast if not faster, look at the supercar beating times of the latest crop of hot hatches on the ring for example, but that doesn't make them 'better, more fun' that's subjective based on opinion. 
Nigel_O said:
GravelBen said:
Penalty ballast
LOL - I'll re-phrase - how can fwd cars in BTCC be competitive against their rwd opposition, even when they have ballast on board from winning the previous round? http://www.btcc.net/2014/10/28/regulation-changes-...
SidewaysSi said:
Look my friend, the Fiesta ST is a fine car (I have driven one at some length). However, it is simply not as good as an Integra DC2 R by some considerable distance. That is a car I owned for many years and drove extensively on road and track, including Euro trips etc. And I don't think anyone who knows much about cars would argue against that.
I however think my BMW is the more challenging car than the Integra which became a bit too easy. So yes, overall I prefer the BMW. Of course the Fiesta is probably more interesting than a 118i for most people, most of the time.
But I don't have a boggo BMW and many on here do not either. Mine has roughly 200bhp and against a similarly powerful/focused FWD car, the RWD is preferable.
I wasn't actually replying to you, but okay then. Clearly i've hit a nerve with you somewhere with my own opinion. I'm not sure why or how that's happened but clearly you're upset.I however think my BMW is the more challenging car than the Integra which became a bit too easy. So yes, overall I prefer the BMW. Of course the Fiesta is probably more interesting than a 118i for most people, most of the time.
But I don't have a boggo BMW and many on here do not either. Mine has roughly 200bhp and against a similarly powerful/focused FWD car, the RWD is preferable.
I haven't even mentioned the ITR once on here so i've not got a clue what you're on about now. You appear to be arguing with yourself for some strange reason. I'm happy that you're happy with your purchase but similarly you need to respect other for their alternative choices.
I'll leave you to it buddy. You seem to take someone else's opinion on here so personally, especially when it comes to a car you own. Ironic really seeing as you're claiming that Fiesta ST fans think it's the best car in the world. The same can easily be said about the 1 Series that you are preaching to the world.
nickfrog said:
You're quite right it needs some slip, I should have said "added slip". If anything you take front slip off by taking lock off.
I disagree about the understeer. How can it tend towards it if it never gets there ?
You're confusing a change of lat acceleration balance with the tractive elimination of rear slip. On a front driver you use traction to correct oversteer NOT lateral acceleration, so it does NOT affect front end lat grip, and the car therefore doesn't tend towards understeer although I can see why it may look like it to the untrained eye from the outside.
I'm not talking about how it looks to the untrained eye from the outside. I'm talking about the physics of what happens in a FWD car when accelerating out a corner. I disagree about the understeer. How can it tend towards it if it never gets there ?
You're confusing a change of lat acceleration balance with the tractive elimination of rear slip. On a front driver you use traction to correct oversteer NOT lateral acceleration, so it does NOT affect front end lat grip, and the car therefore doesn't tend towards understeer although I can see why it may look like it to the untrained eye from the outside.
Most cars will corner with some understeer. In a FWD car this will increase when accelerating out a corner. If you're oversteering at the point you get on the power the oversteer will reduce, and the balance will eventually shift to understeer. From the moment you get on the power the vehicle balance is shifting (or tending) towards understeer.
This happens every time you accelerate your Megane out of a corner.
Nigel_O said:
So if you've got the back end out under power in a rwd car and you feather the throttle to bring it back, is it under-steering?
As you're bringing the back into line it will be oversteering, but the oversteer is reducing. The vehicle balance is tending away from oversteer and towards understeer. Debaser said:
If the balance is shifting from oversteer to neutral, then it is tending towards understeer.
So if you've got the back end out under power in a rwd car and you feather the throttle to bring it back, is it under-steering?I understand the point you're trying to make - yes, fwd cars will ultimately tend towards under steer and rwd cars will tend towards oversteer. It's physics.
The simplest test would be to put one car of each type on a frozen lake, get them up to (say) 30mph and then turn whilst applying power. The fwd car will carry on in a straight line, the rwd will be facing the wrong way.
Others are also correct when they say that the tendency to understeer can be factored out with clever different and a good chassis, in the same way that rwd cars can be prevented from constantly pirouetting round corners
Just to drag the thread out a bit further, how can fwd cars be competitive in BTCC against their rwd opposition?
Nigel_O said:
Just to drag the thread out a bit further, how can fwd cars be competitive in BTCC against their rwd opposition?
I haven't followed for years but in the old days IIRC the BMW carried extra weight.I'm unsure how much (if any) disadvantage the FWD are with the smooth tracks and sticky slicks - certainly they are easier to recover from a nudge mid corner.
DELETED: Comment made by a member who's account has been deleted.
I'm talking about the public road. Of course Grip round a corner isn't dependent on power, but debaser was talking about coming out of the corner.I'm more than happy for you to show me though of course, but it'll have to be with somebody else's car.
nickfrog said:
Again, it neutralises itself, CRUCIALLY without any loss of front lat grip (the very definition of understeer).
It is possible to reduce and eliminate rear slip without losing front lateral friction. It has nothing to do with understeer. It is simply because the (tractive) front wheels happen to be in front of the car. They pull the entire car without needing to generate slip themselves.
That's not the definition of understeer, though it is one behaviour that is commonly used to describe understeer.It is possible to reduce and eliminate rear slip without losing front lateral friction. It has nothing to do with understeer. It is simply because the (tractive) front wheels happen to be in front of the car. They pull the entire car without needing to generate slip themselves.
Pretty much all cars understeer under the limit, and the ones that don't are plain bad to drive.
The most important understeer in not limit understeer, but understeer in normal driving, otherwise known an linear range understeer. Understeer in the linear range means the car always corners less harder than the steering wheel angle suggests it should. The car develops less lateral acceleration than a neutral car would give you for the same steering wheel angle. Linear range understeer makes the car predictable to drive. Typical numbers for a road car are 1.6 to 3 degrees of "lost" steering wheel angle for a g of lateral force. Big SUVs are maybe in the range 2.5 to 3.5 deg/g. Anything under 1.3 is tricky to drive. This is the reason why Porsche 911s have skinny front tyres and wide rear tyres, it has nothing to do with traction, it has all to do with fighting the powerful linear oversteer effects of the rearward weight distribution. The skinnier/more flexible the front tyres are compared to the rears the more linear understeer.
Tyres can't generate a force without slipping, they are rubber, so under load they deflect quite a bit.
When a fwd car is in oversteer and the driver accelerates the load transfer to the rear tyres causes the rear tyres to have less slip angle and the front tyres to have more, the front tyres may not be saturated in grip, so you don't go straight over the lateral grip limit of the front tyres, so you don't suddenly limit understeer off line. Why? Because the car was never really at the limit. If you Barrel into a corner with lift off oversteer, carrying waaaay too much speed, and then get on the throttle, the oversteer corrects, but then the reduced load on the front tyres causes you massive understeer. The car shifts attitude from sliding sideways off the path to limit understeering off the path.
Anyway it is nice to discuss this stuff.
heebeegeetee said:
I'm talking about the public road. Of course Grip round a corner isn't dependent on power, but debaser was talking about coming out of the corner.
I'm more than happy for you to show me though of course, but it'll have to be with somebody else's car.
I don't think I've been in a RWD car that doesn't.I'm more than happy for you to show me though of course, but it'll have to be with somebody else's car.
I'm unsure that a passenger would even know it was happening.
Kawasicki said:
nickfrog said:
Again, it neutralises itself, CRUCIALLY without any loss of front lat grip (the very definition of understeer).
It is possible to reduce and eliminate rear slip without losing front lateral friction. It has nothing to do with understeer. It is simply because the (tractive) front wheels happen to be in front of the car. They pull the entire car without needing to generate slip themselves.
That's not the definition of understeer, though it is one behaviour that is commonly used to describe understeer.It is possible to reduce and eliminate rear slip without losing front lateral friction. It has nothing to do with understeer. It is simply because the (tractive) front wheels happen to be in front of the car. They pull the entire car without needing to generate slip themselves.
Pretty much all cars understeer under the limit, and the ones that don't are plain bad to drive.
The most important understeer in not limit understeer, but understeer in normal driving, otherwise known an linear range understeer. Understeer in the linear range means the car always corners less harder than the steering wheel angle suggests it should. The car develops less lateral acceleration than a neutral car would give you for the same steering wheel angle. Linear range understeer makes the car predictable to drive. Typical numbers for a road car are 1.6 to 3 degrees of "lost" steering wheel angle for a g of lateral force. Big SUVs are maybe in the range 2.5 to 3.5 deg/g. Anything under 1.3 is tricky to drive. This is the reason why Porsche 911s have skinny front tyres and wide rear tyres, it has nothing to do with traction, it has all to do with fighting the powerful linear oversteer effects of the rearward weight distribution. The skinnier/more flexible the front tyres are compared to the rears the more linear understeer.
Tyres can't generate a force without slipping, they are rubber, so under load they deflect quite a bit.
When a fwd car is in oversteer and the driver accelerates the load transfer to the rear tyres causes the rear tyres to have less slip angle and the front tyres to have more, the front tyres may not be saturated in grip, so you don't go straight over the lateral grip limit of the front tyres, so you don't suddenly limit understeer off line. Why? Because the car was never really at the limit. If you Barrel into a corner with lift off oversteer, carrying waaaay too much speed, and then get on the throttle, the oversteer corrects, but then the reduced load on the front tyres causes you massive understeer. The car shifts attitude from sliding sideways off the path to limit understeering off the path.
Anyway it is nice to discuss this stuff.
At least you showed me some (fascinating) workings as opposed to dogmatically proclaim stuff without any or resorting to insults like others...
Edited by nickfrog on Tuesday 20th December 10:02
DELETED: Comment made by a member who's account has been deleted.
Not sure where this thread is up to (getting hard to follow) but my car (RWD) at the limit of grip will slide into understeer if you're gentle on the throttle. I have tested this on a skidpan. If you boot it of course the back end will spin round like a top. 
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