Left-foot braking

[gangajas]

Interesting vid:

http://www.autocar.co.uk/VideosWallp...=224464&Mode=B

I've tried left-foot braking, but when I drive 'fast' (relatively) I feel safer with right-foot braking, because I haven't really mastered the technique yet. Same with heel&toeing.

[ViperASR]

I left foot brake in the mini-van just because I'm used to always using my left foot for something and it reminds me of driving a cart as it is an automatic.

When I'm driving quickly in the 944 I heel&toe. The pedals are set up beyond perfectly for it, making it really easy to learn.

Intersting video about the Torsion front diff though

[ARMAN]

dont really understand how much it will add you in control other than you have your left foot ready to break rightaway... just higher fuel consumption and brake disks wearoff?
maybe in focus rs with its cool differential it can make a difference but what it does for normal fwd or rwd?

btw brilliant idea from Autocar to make such vids, i always loved reading Chris Harris's articles in czech Autocar in the pre-JW age LOL

thanx for linky Gangajas

[graywolf624]

Completely useless technique on a track or road despite what he says. The only reason to left foot brake is to unsettle the car for things like slides. Its not the best way to get around a corner. It might help you if you've already screwed up to correct understeer or oversteer, but its not what you should be doing.
Go karts.. good for keeping the revs up..
Rally cars, good for forcing the proper amount of rotation.
But other wise not worth it.

Hell my Iroc had a torsen differential. Left foot breaking does nothing for it. Hes essentially trying to argue that by braking while accelerating he keeps the cars weight from shifting rearward. The problem with that arguement is that you can do the same damn thing by moderating your gas correctly rather then hitting it hard.

[TopGearNL]

Reminds me of the Walther Rohrl vid

Anyway pretty interesting, would like to master that technique one day!

[coombsie66]

Originally Posted by graywolf624 Completely useless technique on a track or road despite what he says. The only reason to left foot brake is to unsettle the car for things like slides. Its not the best way to get around a corner. It might help you if you've already screwed up to correct understeer or oversteer, but its not what you should be doing. Go karts.. good for keeping the revs up.. Rally cars, good for forcing the proper amount of rotation. But other wise not worth it. Hell my Iroc had a torsen differential. Left foot breaking does nothing for it. Hes essentially trying to argue that by braking while accelerating he keeps the cars weight from shifting rearward. The problem with that arguement is that you can do the same damn thing by moderating your gas correctly rather then hitting it hard.

He is not trying to argue that braking whilst accelerating keeps the weight transfer forward at all, that is just stupid as it means that the car is not accelerating if you are increasing the weight transfer to the front of the car.
What he is saying, which is actually correct is all to do with the quaife ATB differential in the front of the focus RS, i know about this as we fitted one to the rear of our formula student car at university and spent quite a bit of time altering suspension set ups and driving techniques to get the best out of it traction wise.
The torsen or quaife ATB are essentially the same in function (not neccesarily design). Both are not limited slip, therefore they do not work at 100% slip, as chris harris stated. The reason for this is in the design, in a limited slip diff you have a series of clutch plates (or viscous plates, or cones etc depends on design) that try to equalise the speeds of the two outputs of the diff when there is a certain amount of speed differential between the two outputs. The ATB or torsen does not have these plates, it depends upon the friction force on the end of the planetary gears inside it which are thrown in a particular direction depending on the torque varience across the diff and its outputs. Its a bloody difficult thing to understand when you have the pieces in your hands let alone to explain!
Anyway, the only time the ATB doesnt bias the torque across the diff is when there is too much slip on the inside wheel (we found this as we were picking up the inside rear on the apex and exit of corners) when this happens, the only thing limiting the slip of the inside wheel are a few sprung washers in the middle of the diff, and they do very very little and are not going to hold the torque produced by the engine which is soley trying to spin the inside airborne wheel!! It just acts like an open diff.
So (i eventually get onto the left foot thing!) by left foot braking on the apex and exit of the corner, you are applying a braking torque to the inside wheel, this means that there is less slip on that inside wheel and therefore the diff is sending more torque to the outside front wheel (in the Rs's case) meaning better acceleration out of the corner. This is mostly the case on uphill exit, slippy, gravelly, tight corners, where your typical ope diff'd FWD car would be sat there spinning the inside front for half an hour before you get anywhere!!
You are effectively using the brakes to act as a clutch pack to lock the differential when the slip of the inside wheel becomes too much, and you keep the accelerator buried so that you are overcoming the braking torque you are applying with the extra engine torque.

Its all about transfering torque to the wheel that has the most weight on it, which the torsen differential fails to do beyond a certain slip point. Anyone remember the video of the audi quattro vs the bmw X drive trying to drive the car off of some rollers with the front wheels on the ground and the rears free to spin on the rollers. The audi which had a torsen centre differential failed to get off for the same reason, too much slip across the diff, if the driver applied the brakes to the rear wheels then it would send torque to the fronts and drag the car off the rollers (as they eventually did). 8)

[Vansquish]

Originally Posted by graywolf624 Completely useless technique on a track or road despite what he says. The only reason to left foot brake is to unsettle the car for things like slides. Its not the best way to get around a corner. It might help you if you've already screwed up to correct understeer or oversteer, but its not what you should be doing. Go karts.. good for keeping the revs up.. Rally cars, good for forcing the proper amount of rotation. But other wise not worth it. Hell my Iroc had a torsen differential. Left foot breaking does nothing for it. Hes essentially trying to argue that by braking while accelerating he keeps the cars weight from shifting rearward. The problem with that arguement is that you can do the same damn thing by moderating your gas correctly rather then hitting it hard.

Edit: Coombsie's got it, I just rehashed it.

On the contrary, he's not suggesting that left-foot braking keeps the weight shifted to the front of the car, he's suggesting that the way that the differential works in the Focus RS (Renaultsport Megane F1 etc...) is that it apportions torque rather than limiting slippage. Therefore, when accelerating in a sharp turn, it can be used to the advantage of acceleration by slowing the inside wheel a bit and allowing the torque to transfer to the outside wheel and provide more drive through the corner, countering understeer. This way that he's describing the technique, it ONLY applies to FWD and AWD cars. A rear-wheel drive car like the IROC Camaro would not achieve the same handling benefit by left-foot braking during acceleration. The only time it would be useful is entering a corner and making the transition from braking to accelerating out of the corner a bit smoother.

[andreadebi]

Originally Posted by TopGearNL Reminds me of the Walther Rohrl vid Anyway pretty interesting, would like to master that technique one day!

which video please?

[pitfield]

I feel educated, thank-you for that. This is what JWis all about.
I often blip the throttle on downshifts in my MINI while braking with my right foot, is this heel and toeing?

[pitfield]

Oh great, it's piece of cake in the MINI, tried it in dad's Alfa 156 and the offset pedals make it difficult. Learnt to do this in the old C4S ex demo car at Porsche, not for the performance side of things but just with the sports-exhaust it sounded bloody brilliant.

[Stoopie]

With my previous job I had to drive a forklift truck pretty much, and then I used the brake with left foot too, it's just way easier IMO

[dutchmasterflex]

Heal and toe shifting is easy.. but when you throw in some left-foot breaking a long with it you need Walter Rohrl like powers.

I try to practice left foot breaking in my car just so I can have a better feel for the pedel with my left foot. Driving the shifter kart I don't really notice how bad my braking is since I'm using my left foot, but it definitely has an effect on my lap times.

[graywolf624]

With fwd cars, the left foot braking does improve the times, at least when driving on gravel or snow. Rally drivers generally use the left foot braking to "tie" the car in the corners. SKilled use of the left foot keeps the car from understeering and oversteering, improving the traction of both front and rear wheels. I'm not sure how much does it help of asphalt with good traction. And ofcourse it is very rough to the brakes.

As per above I certainly believe it could help you to unsettle the car on a rally course. A bit of a different beast then track driving.

I stand corrected on the reason. It only applies to fwd cars, which don't belong on a race track. So I defend my statement that its useless on a race track.

[TopGearNL]

Originally Posted by andreadebi Originally Posted by TopGearNL Reminds me of the Walther Rohrl vid Anyway pretty interesting, would like to master that technique one day! which video please?

walter röhrl rally audi S1 - YouTube

walter röhrl rally audi S1 - YouTube

8)

[gangajas]

Originally Posted by graywolf624 It only applies to fwd cars, which don't belong on a race track.

What?