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Just replied to a PM and it got a bit long winded talking of lift off oversteer and camber. It took me so long to write I'm going to post it up here so I can reference to it again.
It was in reply to a question as to whether a person should just get front camber bolts fitted and not bother with rear adjustment. Specifically it was regarding the FN2 but applies to all cars really as the theory is the same.
It was in reply to a question as to whether a person should just get front camber bolts fitted and not bother with rear adjustment. Specifically it was regarding the FN2 but applies to all cars really as the theory is the same.
Not a problem.
It really does depend on if you are going to track the car and/or how hard you would ever drive on a public road.
I'll explain the benefits of the rear settings on the Fast Road Set-up.
All FN2 Type Rs came out of the factory with geometry within Honda tolerances, i.e. if camber or alignment is too great then the car will go back to 'finishing' and the suspension fettled with to try and achieve the the specified tolerances.
No car will be released where they do not meet that specification, however since there is no camber adjustment on the front and the rear suspension is a torsion beam, which ordinarily would not allow camber adjustment, the specifications are quite wide and easy for the production line to produce.
Specifically looking at the rear, the car can come from Honda with positive camber, where the top of the wheels are further apart than the bottom. That means that in a straight line the outside of the tyres has more pressure on the tarmac. Now for example, introduce a right hand corner into the equation, the suspension loads up and compresses on the left as the weight of the car shifts to the left. Due to the lean of the car, the positive camber is exaggerated on the left hand side of the car, the side that is doing all of the gripping and the outside tyre now only has a very small contact patch with which to grip.
If the car had negative camber to start with, you don't need lots of grip in a straight line, just enough to braking and accelerating (drive wheels obviously), in the same scenario, the car goes into the bend. The tops of the wheels are now closer together than the bottom. The car leans into the bend, effectively adding positive camber to the left hand side of the car. Now, because the camber is already negative, the left tyre will now be flat on the tarmac, have the biggest contact patch and give the best grip when you need it.
Obviously this is a good as it will add more grip and increase the speed you can carry through a corner. My car now grips well enough on the rear that it can lift the inside rear wheel in a corner.
What Jeremy Clarkson found so appealing in the EP3 but lacking in the FN2.
Now the next bit is slightly harder to understand and unless you drive on the limit, even harder to use on the open road.
The toe of the rear wheels ideally would be set to be toed in, where the fronts of the tyres are closer together than the rear, and this is all to do with lift off oversteer and controlling it.
You go into the right hand bend and you are carrying a bit too much speed into the corner and you start to drift wide. The front is scrabbling for grip and you let off the throttle but don't touch the brakes. The weight of the car now shifts to the front and the back should go 'light'.
Now from the factory the characteristic of the FN2 is that the car will continue to run wide until the front eventually get enough grip to turn as tightly as you are wanting and if you've done it early enough you make it round the bend. If you think of it, it is all about getting the nose of the car pointing out of the bend and then you can put the power back on.
Setting the toe in on the rear, means that when the car goes light on the rear as the weight shifts, the left hand rear tyre can be used to break traction and 'tuck in' the nose of the car in the bend.
This is called light off oversteer. Now the reason why it is controllable with toe in, is that the right hand tyre is not pointing into the corner as much as the fronts or the left ear and does not break traction to the same extent. The rear end is now turning faster than the front, and the front end should now have gripped, where previously it had lost traction. When the angle of the car is pointing through the corner, you can apply a little more throttle and the back end will now grip as the weight transfers. The right hand tyre can grip easily and then gives the left hand one the ability to find grip.
Now this all is happening in split seconds and to do this you need the reactions of a cat, but I've made it sound more dramatic than it really is. If you are doing it properly it is the fastest was to get a car round a corner as you can get all four wheels breaking traction and you get a four wheel drift, but it is also desirable if you have carried too much entry speed into a corner. It is the front wheel drive equivalent of balancing a car on the throttle.
This does seem to counter the effect of camber I described above, but it is complementary, as if you cannot get good grip in the first place, you will just end up sliding off the road backwards.
An easy way to see it in action is to find a quiet, big roundabout. If you go round the roundabout, gradually increasing speed you will start to drift wide. In a car that has not been set-up properly when to start to go wide, all you can do is lift off and wait for the front to grip. In a car that has been set-up properly the rear end will start to come round and you can start playing with the throttle to balance the front and rear.
Like I said, you might not ever get into a situation on the road, or you may depending how you drive.
Still, you can appreciate just adding grip to the front is not the full story in setting up the geometry of the car.
Hope this helps.
John