RE: Seat Leon Cupra R: Driven

[Onehp]

nickfrog said:

Nanook said:

You sure about that? Consider your traction circle for a front wheel on the 4WD Golf, and the front wheel on the FWD Leon.

All other things being equal (power applied, speed, steering angle) the front wheel on which car is going to run out of grip first?

Good point. The answer is "it depends" IME. If you're off the throttle when you turn in then the lighter car will run out of outside front wheel friction after the heavier 4wd car (because of the effect of the higher centrifugal/centripetal forces exerted, assuming it's set up to understeer like 99% of road cars).

If you're on the throttle before the point where you start unwinding the lock then the FWD car will probably lose friction first (assuming you haven't taken any mitigating measures like trail braking), but that's because you're relying on traction rather than lateral grip.

So yes the traction circle is only showing us the total amount of friction (lat grip + longitudinal adhesion) so taking something away from one does indirectly favour the other.

If at the apex all of the friction is used up by lat grip, then it doesn't matter how many wheels are driven as there is nothing left on the table for traction, hence the fallacy of thinking you can use all the power all of the time. All you're actually doing is turning in slower than the outright max apex speed so that you can use more traction by freeing up friction to the detriment of lat grip, which is a great strategy too btw.

Edited by nickfrog on Wednesday 29th November 16:20

Good points. To add, the difference for me is feeling where this limit lies. The 4wd haldex car will actually loose traction on the inside wheels first, if this happens it triggers the electronic systems, further risking the car bogging down to keep composure. Getting a feel of when this is about to happen is not easy. On the FWD Cupra the VAQ differential will prevent the inner wheel from spinning, instead you get a good feel through the wheel of how much grip that front wheel has, and you get a fairly good idea of how much throttle it will take before braking the traction circle. So while AWD ulitmately should have the best traction, in reality the FWD will be easier to judge and enjoy... this is valid for most 2wd vs 4wd setups, the latter usually more complicated and more difficult to judge when total grip (lat+traction) actually runs out. Although when it does and the 4wd is properly diffed, that tends to be less demanding on the reactions of the driver. All in all, I enjoy proper 2wd more than 4wd, perhaps just because it is easier to play a bit with traction as an element in the driving. And especially in more treacherous circumstances, traction problems are a better forwarner of slippery conditions than noticing the lack of grip in descelleration or mid-corner...

[rainmakerraw]

IanCress said:

rainmakerraw said:

The Skoda Superb 2.0 TSI 280ps DSG AWD is a tenth faster than this, with 30hp less and 100KG more weight. That can't be right, even with AWD, surely?

AWD and DSG gearbox, versus FWD and manual box. I'd say the Cupra does well to only be a tenth down to 60mph. Once the Cupra can put its power down it will start to pull away. Throw a few corners in to the mix and the Superb wouldn't stand a chance.

But then you wouldn't expect it to, it's a very different type of car.

No, I compared times from the Superb DSG to the Cupra DSG...

[nickfrog]

Onehp said:

Good points. To add, the difference for me is feeling where this limit lies. The 4wd haldex car will actually loose traction on the inside wheels first, if this happens it triggers the electronic systems, further risking the car bogging down to keep composure. Getting a feel of when this is about to happen is not easy. On the FWD Cupra the VAQ differential will prevent the inner wheel from spinning, instead you get a good feel through the wheel of how much grip that front wheel has, and you get a fairly good idea of how much throttle it will take before braking the traction circle. So while AWD ulitmately should have the best traction, in reality the FWD will be easier to judge and enjoy... this is valid for most 2wd vs 4wd setups, the latter usually more complicated and more difficult to judge when total grip (lat+traction) actually runs out. Although when it does and the 4wd is properly diffed, that tends to be less demanding on the reactions of the driver. All in all, I enjoy proper 2wd more than 4wd, perhaps just because it is easier to play a bit with traction as an element in the driving. And especially in more treacherous circumstances, traction problems are a better forwarner of slippery conditions than noticing the lack of grip in descelleration or mid-corner...

I agree that 2wd offers more clarity as to which axle will let go first, which is a massive help in the rain in particular.

I disliked the Haldex setups for that reason but I understand the FRS is pretty transparent at the slight detriment of rear outright friction as the rear wheels are oversped.