SouthernSon

I have never seen this addressed but I would like some input from any of you guys that have experience in the behaviour of the two different engine layouts on response time to countersteer/ correction. I find myself instructing in rear engine layouts occasionally and don't have that much experience in driving them. I would think the correction after countersteer would be sooner with front engine as opposed to rear engine since the weight bias is towards the front. Correct?

sebdavid

I have a bit of experience with rear, mid and front engine layouts. Are you talking mid (Lotus) or rear-engine (911)? Rear-biased weight distribution will be exaggerated in a true rear-engined car compared with a mid-engined one.

With beginning students, you want to teach them to correct oversteer before a "slide" really develops. What I often find is that they wait too long to correct and from then on are always one step behind, which leads to tank-slappers and spins. This is valid for both front- and rear-engined cars.

When it comes to oversteer and over-the-limit control, the difference between the two layouts comes to one main factor: rear-engine, with the weight slung over the back axle, will have more momentum built in the slide, which means if you let it develop a bit too much, it will tend to go on and become a spin. If you catch it early and then modulate throttle and steering angle, however, you can use that momentum or inertia to drift to your heart's content.

So in a 911, for example, it's even more important for the driver to catch the slide before it develops into a spin, otherwise it'll be harder to catch. Similar as ice driving, when once the slide has really started, it's harder to gather things back up, due to the momentum effect being exaggerated.

It's not a huge difference, however: in both cases it's important to react very quickly before the slide develops too much, not only with proper countersteer, but also with proper throttle action (you want some throttle application to shift some weight to the back axle, but not too much to overpower the rear wheels).

I find the much bigger difference when dealing with the weight distribution of a 911 is in using that weight distribution to your advantage, for a medium-to-highly skilled driver. Many people will tell you "slow in, fast out" when driving a 911. That's wrong. In fact, the weight distribution allows you to brake much harder in a rear-engined car (because the rear brakes are working more since there's more weight over them), and then you want to enter the corner really fast, trail-braking much more and much later than you would in a front-engined car, to put some weight on that front axle and help the car turn in.

Then, if you're carrying anywhere close to maximum apex speed, you'll find a lot of understeer waiting for you when you try to apply the throttle at the exit of the turn. This is because you're transferring weight to the rear when there is already not much on the front wheels which are still trying to turn the car. You simply have to be a bit more patient than in your 'vette, and synchronize unwinding the steering wheel and applying more gas real carefully to tame the understeer.

In a 911, compared to a 'vette for example, you'll gain a lot under braking and entering a corner, and you'll lose some coming out of the corner, because of the peculiar weight distribution. It's a lot of fun because it really is a different experience.

In case you're talking Lotus, the trick with those cars is being extremely quick with your reaction time if oversteer develops. In fact you want to avoid it if you can, because the car has such a short wheelbase that things happen more quickly than in a 911, and waaaaay more quickly than in a 'vette.

I find that it is beneficial to students that are starting to go quickly to do one session provoking oversteer in safe spots on the track, just to get them used to the feeling and the reactions needed. Of course it needs to be clear that what you do with the throttle depends on why the slide started in the first place. If it's because you applied too much gas, then you have to let off a bit, if it's because you tried braking or lifting off mid-corner, then you'll have to apply some throttle to shift some weight backwards.

Ice driving and skidpad exercises help. Karting helps as well. Controlling oversteer is something that comes with practice.

ZoomFreakinZoom

^^^ what he said. With a rear engined car like a 911, it's more "snap" oversteer vs a corvette/front engined car where you have time to save the car during the slide and it is very gradual in its progression. If you don't start to correct almost immediately in a 911, you'll go around. You have to be on your toes much more in a rear engined car, because there is less room for error, and they don't tolerate fools very well, ask me how I know. That said, the biggest difference for me is that the rear engined car is much more unsettled in the braking zone, you have to balance the car with the pedals much more than you do in a front or mid engined car.

sebdavid

I don't necessarily agree that there is more "snap" oversteer in a rear-engined car. All else being equal, you'll feel it coming just as much and it will be progressive, but you need to catch it earlier before the angle gets too outrageous.

Snap oversteer, defined by a difficult to predict, very quick loss of grip in the rear and therefore insta-oversteer, in my experience, is more a function of suspension setup/alignment and wheelbase.

You do have that engine in the rear trying to move around a bit more in a read-engined car when braking HARD. And trail-braking becomes more important but also a bit more tricky due to the inertia.

ZoomFreakinZoom

Thats probably true, my experience has only been with GT3 Cup's, so there is no "oh look we're loosing it" feeling, it's your at the limit or you're over it and trying to hang on. That's a race car setup for "racing" though. A street going 911 or even a street car made into a race car will handle much differently. Trail braking has to be done right or you're going to end up facing the wrong direction, you're right about that one for sure.

sebdavid

Yeah, a GT3 Cup on slick is another ball game for sure. No give in the suspension + high grip = everything is sped up. Never driven one of those, I'd sure love to try though! One day.

ZoomFreakinZoom

I couldn't afford the tires much less the car . The perks of getting to drive for someone else, in their car.

SouthernSon

Good responses and confirmation of what I had thought. I have noticed on track and on video there seems to be, at times, a tendency to bring the steering back to neutral too soon resulting in another countersteer and then a tank slapper as it gets out of hand. Or, on the other hand, too much delay for initial countersteer resulting in spin. Indeed, I believe as you suggest, a good skid pad session would benefit one transitioning from front engine experience to rear engine as the timing and degree of inputs may differ in same circumstances.