maybe it's just me. I have a 2000 Civic Si. stock shocks/ITR springs, and RE730's @40psi, are the only things I've done to the car suspension wise. Stock sway bars as well.

As I'm going through a turn at 50mph (offramp suggests 35mph), when I lift the throttle really quickly, the car has tendency to turn-in a bit more then when I'm on the gas. I'm guessing it's because the car is not pushing that hard.

Is this something that is inherit to FWD? I ask because this would help with my upcoming auto-x.

or...am I just crazy.

 

This is a generalization, but basically all cars do that to some extent or another. Basically, when you lift the throttle (or hit the brakes) it transfers weight off the rear wheels and onto the front, thereby increasing the available traction at the front of the car, and decreasing the available traction in the rear.

 

This is something that can easily get away form you. In some cases, I've borrowed FWD cars for autocrosses (while usually I autox my FD RX-7), and ended up spinning them because I had forgotten how easily they lift off oversteer.

Anyways, if you are TRYING to induce oversteer, this is the wrong way to go about it. Learn to left foot brake instead.

 

ugh....left footbraking!! I'd have to pratice that.

 

Why is lifting off the WRONG way to induce oversteer? Different yes, wrong? no...

 

its wrong because its slower. LFB transfers weight to the front and turns the car in without lowering rpms, cant beat that. youre not changing gears in a turn, so might as well use that other foot.

 

You know, several people have made that comment before and I don't get it.

If you lift, your rpms drop and the speed drops... fine. If you LFB, in order to get any meaningful weight transfer, your speed drops which forces your rpms to drop. Explain to me how that's different? What am I missing?

-Confused in VA



[Modified by maxQ, 1:28 PM 7/11/2002]

 

[QUOTE]LFB transfers weight to the front and turns the car in without lowering rpms, cant beat that.

You know, several people have made that comment before and I don't get it.

If you lift, your rpms drop and the speed drops... fine. If you LFB, in order to get any meaningful weight transfer, your speed drops which forces your rpms to drop. Explain to me how that's different? What am I missing?

-Confused in VA
[QUOTE]

It is just a quicker transition. Unless you are gassing it while you are breaking in which case you have a huge amount of money to blow on broken parts.

 

its easier to finesse a LFB than to lift the throttle. when im talking about LFB, i mean ~gently~ applying a little pressure to the brake. the guy who taught me described it as imagining an egg between your foot and pedal. you dont LFB so much your speed DROPS, its just transfering just a bit enough to achieve your goal without slowing down, so keep the right foot planted and modulate with the left, its a dynamic process and is what it takes to keep your car "on the edge".


let me reiterate, you are not stabbing the brakes, you are not trying to slow your car down, you use brakes to control your weight transfer, but you dont need that much. when youre full bore in a turn, you are trying to sense if the car is oversteering or understeering. when you feelit understeering or trying to push, thats when you respond by a little LFB. oversteer/understeer is a DYNAMIC process, it needs contant work to maintain the correct line. what they teach you at drivers school of looking at the apax, fixing your wheel to make a constant radius and smooth on, smooht off is to really just teach you BASIC car control. welcome to the next level. someone used to have a quote in their sig saying something like "its amazing, even professional drivers still think brakes are for slowing down" i believe techniques like this is what the commentator is alluding to. im done preaching... im just a novice anyway.


[Modified by Tyson, 10:45 AM 7/11/2002]

 

It isn't about weight transfer, which you correctly point out is dependent upon acceleration. It's about screwing with the rear traction circle - adding more to the job and reducing available lateral grip.

Scott, who doesn't think most of our cars have enough brakes to recommend this technique......

 

I think that's a matter of opinion. Set up right, my car rotates fairly nicely with the barest lift of the throttle. I have found the timing of a LFB to be more difficult than a "lift-n-go"... and I'll bet you "lift-n-go" is just as fast. YMMV.

My $.02

 

Ahh... it's about involving the rears with something else other than lateral traction. That makes more sense.

I still wonder if the rate of loss of traction is different enough between the front and rear to make it worthwhile...

-Less confused in VA



[Modified by maxQ, 1:45 PM 7/11/2002]

 

You're balancing the front braking with additional throttle (assuming you had any left - if not it makes for a slightly different problem) - net effect of brakes on front traction should to be nil....

Scott, who is tempted to try it in T3 at PIR....I'm that desperate....


[Modified by RR98ITR, 10:53 AM 7/11/2002]

 

Useful for keeping FWD cars from oversteering in some slaloms and slow turns, and turbo cars from falling off boost. It does put a hurtin' on brake pads if you get aggressive enough with it.

 

not that im starting an argument, just to discuss this further. i dont like your explaination. first, why would you want to reduce overall lateral grip? the goal is to maximize overal grip. if the front is over worked, you reduce the front and allow the rear to grip more. secondly, how is this achieved solely in the rear by using the pedal which brakes both the front and rear wheels, especially with a general front bias in all racecars. it is about weight transfer.

enough brakes? LFB only requires a gentle push of the brakes. what car doesnt have enough brakes for this?

do as you guys please. i have experienced my lap times drop because of this. top Honda winner in ITA in my region preaches LFB, he sets new records with every car he drives.

 

But see, I wouldn't even consider using LFB unless I was at WOT. I have much more coordination with my right foot to accomplish a modulation of the throttle than to take my left foot on AND off a new pedal with a much less sensitive touch.

The risk/reward is not high enough for me to consider it if I'm not "givin' it all she's got".

Andy - who practices LFB on a few corners on his trip home in the hopes that it will be of some benefit someday...

 

LFB is a technique with which to combat understeer - by reducing rear lateral grip (not overall lateral grip - which I never said).

Read the next post, and rethink it all. LFB isn't about weight transfer, which depends on acceleration as I said. If LFB was about weight transfer, why bother? Just come off the throttle.

Yes, most of these Honda's don't have enough front brake to take heavy LFB - if a driver finds this to be no problem they aren't going fast enough or using their brakes hard enough. Mind you, any driver is entitled to their own opinion about their own skill and the validity of any technique, I would simply respond that laptimes provide an objective view.

Maybe an ITA CRX is better off than most in this regard and your local winner can get away with it - I'm glad you cited a good example. Neither Bob Endicott or Pierre Klienubing can be observed using the technique, and I'm advised that they don't.

Scott, who isn't dogmatically opposed to LFB...

 

Whoah.. I'm getting confused now.. Braking and lift throttle oversteer are primarily about weight transfer and it's effects on the radius of the traction circle front and rear, as I understand it.. Scott, it sounds like you're talking about using the brakes and then applying enough throttle to overcome the braking at the front, and not slow down, almost similar in theory to making a handbrake turn, right? I really don't think this is the dominant mechanism in the LFB I see at autocross (and it certainly isn't the way I'm using it)..

but then again, maybe you are far more advanced than I at this..

..but if so, why is LFB a technique for not just FWD but also RWD and AWD, where as the LFB/throttle-> handbrake effect would be unique to FWD?

Regarding "enough brakes", I think the comment refers to the extra heat that LFB tends to cause, especially if you are overzealous about it and in a track situation, as opposed to conservative use in an 60 second autocross run..

Edit: Scott, you posted while I was typing.. as for why LFB instead of coming off the throttle, because it's smoother and quicker for transitions.. (for me)
Edit2: my experience is autocross based (thus so are my comments).. I don't have experience with open tracking.


[Modified by MechE00, 11:21 AM 7/11/2002]


[Modified by MechE00, 11:23 AM 7/11/2002]

 

I shouldn't have to say this but I'd better.

LFB as discussed by me here is the technique of simultaneous application of gas and brake commonly used to combat understeer on front wheel drive.

Not to be confused with the simple use of the left foot on the brake pedal ala karts, F1, shiftless turns, and sequential gearbox equipped cars.

Scott, who can barely push the clutch pedal with his left foot....

 

No, I'm talking about a cornering sequence wherein you apply a little brake, and compensate with a little more throttle to deal with understeer. That's what LFB most properly is.

I don't know what your input sequence is, or anything about autocross. Tell me more detail.

LFB would be closely akin to an E-brake scheme - same thing done a different way. (edit - I would never let go of the wheel mid corner and use the e-brake for such a purpose - yikes!)

Your question with respect to FWD vs RWD application requires a little thought - I don't think about RWD much. Obviously on FWD the only thing the rear wheels do besides hold the car up and roll, is generate braking thrust when called upon, and genrerate lateral thrust. On a RWD the rears channel both forward and rearward thrust. If I apply the brakes in a corner without balancing out that force with gas on the drive wheels I will decelerate and get what I would expect to get - duh. If I balance brake against gas, I will reduce available front lateral grip. So, I might use LFB to push the front out mid corner, or saying it another way I might use LFB to combat oversteer. That would then beg the question of what kind of oversteer that was. Chassis setup induced neutral throttle oversteer at a point in the corner - ok maybe. To much gas induced oversteer at any point in the corner - not so ok.

Right, LFB probably not a threat to the brakes of an autocrosser - I'm always thinking road course.

Scott, who doesn't think this should be so hard....


[Modified by RR98ITR, 11:37 AM 7/11/2002]

 

I think this is a big one - you said "LFB instead of coming off the throttle"

You're just talking about "braking with your left foot" - what I was referring to in the other post ("shiftless turns").

Scott,....grumble, grumble,......damned autocrossers......

 

yeah, you know, i think we are all talking about using the LFB in different circumstances, turn-in, middle of the turn, sharp turns (as in autox)and so forth, where LFB is definately viable in many different situations, but not all. so i guess we should all just be open to trying what makes us go faster.

hey, whadaya know... googles got the answers.
http://www.google.com/search?sourcei...t+foot+braking


[Modified by Tyson, 11:51 AM 7/11/2002]

 

Umm.. yeah, I guess this might be a semantics problem.. left foot braking is using left foot for braking in most uses I've heard, however a quick google search reveals the technique you are talking about (as primarily a FWD Rally technique..

btw Scott, a RWD LFB application explanation can be found: http://freeweb.telco4u.net/hostage/leftfoot.html

It looks like I got bitten by my own sloppy use of terminology.. of course, I'd like to play the "I think the terminology is poorly chosen" card, please.

I now know that I don't "LFB".. I "brake with my left foot" on autocrosses.. weight transfer is what's tightening up my line, not ebrake style rear grip modulation.

Thanks Scott, I nearly always learn something from following your posts..

 

It's so great to see a good ole competition forum discussion. These are the topics that make this place great.


I see two separate issues here, if I'm not too confused.

1. LFB in general, as in used to slow the car down and/or used to trail brake. There are very fast drivers who both use and don't use LFB, I think we all know that. Personally I only use it on the track while in traffic and at the starts for the first couple of laps. Normal mode for me is to brake with the right foot. At the autox, I only LFB (unless there is a need for a downshift, which is rare in the Talon). With the ITR I did it everywhere where there was no need for a downshift (but ITRs do like a lot of downshifts). Not sure of the true theoretical benefits, but the reason why I LFB is because at least in my head it seems to cut down on response time. Also having control of both gas and brake at the tips of your feet is a good "reassuring" feeling in my book anyway. A lot of great drivers either do way more LFB than others or none at all, so it's hard to take sides on what is better. Some people also use LFB for trail braking on the track very effectively. I do it quite a few times, but I'm sure it's not as effective as it can be, so I'm still practicing. It's good to see that Bob Endicott has already been mentioned. As far as I know he is a master of LFB trail braking. (Wait, actually he is a master of any FWD racecars. ) I've talked before to a friend who is also a Panoz school instructor and who co-drove with Endicott at road atlanta a few years ago in a CRX. He was very impressed at how well Endicott could rotate the car in T7 with LFB trail braking. This is something that many other FWD people (including me) have been trying to do right because it really pays off to rotate the car well in T7. I'm sure Bob also has many other places on other tracks where he uses some of his LFB tricks. That guy is unbelievable.


2. LFB in the middle of a turn to get the car to rotate (if I got it right?). If the turn is not a decreasing radius turn (T5 at roebling is first to come to mind), I do not think a well setup car should require any kind of braking or forward weight transfer to get the car to stick on the line. If this is the case, then the car is handling bad because it is making you do something *else* other than being on the gas in the middle of a turn. If for some reason I go in too hot in a turn or I'm a little too optimistic and get on the gas too early, breathing off the gas is all that should be required to get things back on line. This isn't even a full lift by any means. Fully lifting while in a turn at least in the crxs I drove will most of the time results in a cool drift that is definitely not good for lap times. In the rain usually I've seen some drivers, including my co-driver (who is an ex-rally driver) go through turns with the brake lights lit up all the way. He says he likes it better like this because he can better effectively keep the rear end doing what he wants. I tried it for the heck of it a few times and just breathing of the gas to get the same weight transfer works just as well for me. So I guess it's whatever works best for you.

 

I'm probably guilty of terminological impropriety myself. We need some precise distinctive words or phrases that don't exist.

Scott, who's left foot works in a kart, but not in a car.....it knows...