E Brake and autox

2106 Views 23 Replies 5 Participants Last post by SUPRAT, Oct 20, 2001

463supra

Discussion Starter · Sep 3, 2001

Has anybody used their e brake while autox ing? I never have but I read somewhere that this is a fairly common practice to hit the tight corners better..What do you all think?

Jeff

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Grant

· #2 · Sep 3, 2001

Our E-brake is attached to a drum brake in the back, not the discs brakes like most cars, I don't know if its strong enough to lock the wheels up, but it might be. I was scared I might break it

I've found it easy to just trail off the brake coming into a corner. The more braking force, the less the car understeers. Its the only way to get the damn thing to turn with stock 97 suspension....

Andi

· #3 · Sep 3, 2001

Grant said:
Our E-brake is attached to a drum brake in the back, not the discs brakes like most cars, I don't know if its strong enough to lock the wheels up, but it might be. I was scared I might break it I've found it easy to just trail off the brake coming into a corner. The more braking force, the less the car understeers. Its the only way to get the damn thing to turn with stock 97 suspension....

Unless you need new e-brake shoes like I do, the e-brake can lock the rear brakes with aplomb. I've done quite a few e-brake U-turns on the street using this method, although not in autox because I found it slower than simple trailbraking.

Andi

463supra

Discussion Starter · #4 · Sep 3, 2001

OK please explain trailbraking so I know if I am doing it correctly. I know it causes some oversteer which is what I am looking for.
Jeff

G

· #5 · Sep 5, 2001

463supra said:
OK please explain trailbraking so I know if I am doing it correctly. I know it causes some oversteer which is what I am looking for.
Jeff

Simply enough, braking after entering a turn. Theoretically, you can brake all the way to your apex. Practically, you will shift so much weight forward that your rear will be too light to grip.

This is for road courses, not parking lot autox. I don't know if you can build up enough speed in a parking lot autox to manifest this on a Supra.

Grant

· #6 · Sep 5, 2001

Of course you can. And in the low-speed parking lot autocrosses its the only way to get the damn car to turn.

In many parts of an autocross you want to get through the corner as fast as possible - exit speed doesn't matter as much since most of the time there isn't a straight after the turn. Oftentimes there is another corner of equal or lesser speed, so I find myself trailbraking a lot. I wish there were more road courses that are as technical as a good autocross (I wish I lived closer to VIR).

Try to think of it this way, if you want the car to turn more, apply some brake (smoothly), if you want it to understeer more, apply throttle.

463supra

Discussion Starter · #7 · Sep 5, 2001

So if I got this right braking while turning will cause my rear to get loose and make the corner easier..?

G

· #8 · Sep 5, 2001

463supra said:
So if I got this right braking while turning will cause my rear to get loose and make the corner easier..?

It will make you loose. Whether that makes the corner easier is another matter entirely.

You ARE only doing this in a parking lot, right?

Grant

· #9 · Sep 5, 2001

In low speed corners I have found it helps out quite a bit. The rear already has plenty of grip, its the front that looses traction first (at least my car does) so applying some brakes shifts some weight to the front for more traction. Too much braking shifts too much weight off the rears causing them to loose traction, hence you spin out. As Oolan said, try it in a parking lot first

I don't find it as necissary in higher speed corners, or maybe I'm just too chicken with walls around

OTOH hand you could just get the 54% stiffer rear sway bar from Dusty, and not ever worry about understeer

I'd put mine on now, but with the stock front one I think it would get a little excessive.

bwill

· #10 · Sep 8, 2001

As to the e-brake manuver yeah, you can do that. I do SCCA Solo 2 events and some track events but I don't do the e-brake. If I am coming up to a tight slow (say a 120 degree turn) I lift off the throttle suddenly on purpose to unweight the rear, turn and many times hit the brakes at the same time. What you do is get your rear to overotate (turning a lot quicker than the front). Instead of slogging though a tight turn trying not to scrub too much with understeer and lose time you can get the car turning fast. Many times during this process I am also going for a gear change (heel toe) and when the rear overotates like I want, then I let the clutch out, applly throttle which throws the weight back to the rear for grip and you squirt out the turn like a wet bar of soap. That is if you do all of those things right in very short order. Not only can it be the fastest way through a very tight and slow corner (15mph type) hell, it is FUN!!!
Barry H. 94ttSupra Super Stock

SUPRAT

· #11 · Sep 12, 2001

Grant, what are the mm widths of your tires stock? I found Toyota under-tired the fronts. I have a set of 255/45ZR17 on the fronts with 17'x10' rims and my car doesn't understeer almost at all at autoX's now. I also have coilovers too. Feels like a different car. I enjoy roasting this highly modded RX-7 TT on slicks and I am on street tires at BPU++ e-TTC at my local autoX. I just rub my Supra's shit all in his face(he says he'd smoke me cause lighter this ,mods and tires that...

) beat him by almost 2 sec!

SUPRAT

· #12 · Sep 12, 2001

Oh, and sorry if I sounded arrogant on my last post, I didn't mean it that way. I read my post and it sounded like I knew more about autoX than you. Probably not even close to the truth.

Anyway take care and have fun.

Grant

· #13 · Sep 13, 2001

I have the largest 17" tires I could fit under the car, 275/40/17s in front and 315/35/17s in rear. I'm going to fix the problem with suspension, not tire. Bigass sway bars and coilovers should do the trick. Right now I have to trail off the brakes to get it to turn, and take a late apex in order to stay on the track while applying throttle out of the turn. I have stock suspsion now, the 97+ suspension might be set for more understeer.

2 seconds??? I think that guy in the rx7 couldn't drive

There is a guy here who has a BPU +FMIC rx7 with coilovers and A032Rs who was always beating me pretty bad (has a lot more experience). This last time to the Ocala Speedway (its a small road race track) I got within .3 seconds of his best time. I know I'll do better next time, all I have to do is ditch the 250lb passenger

Plus I'm sure I could shave another 2 seconds off just from driving it better. Unfortunately his car blew an apex seal, but he should be back with a T78

in a 2800lb car

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SUPRAT

· #14 · Sep 14, 2001

actually, it was 1.633seconds. I rounded up naturally.

This was on a road course also. He had hoosiers

. I guess he couldn't drive AS WELL as I could, but he looked pretty damn good if you asked me. I have had some pro instruction at big tracks, so maybe that was the diff.

Sounds like you're going to have a handful when he comes back.

I'm hearing all sorts of mess you get into when you change the anti-roll bars, the coilovers, and the strut tower braces changing the suspention geometry~having to recalibrate this and that. Is this true? I think it was Andi saying he lost some exiting speed due to power-oversteer when he put on a stiffer rear sway bar. I have also heard that the anti-roll bars don't help much on this car anyway, especially if you already have coilovers. Is any of this true? Sorry for the questions.

I just worried I'll screw up my car slapping on parts that say they do this and that, wasting money and time.

Have any of you put test equipment on your cars with your suspentions and tires upgraded? Lateral G's and slalom? just wondering.

Do your 275's rub at all? you must have rolled the fenders.

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Grant

· #15 · Sep 14, 2001

As I said I have stock lexus suspension now, it really sucks. As soon as I'm not poor I'll get some coilovers

If you increase the roll stiffness of one end of the car, there will be more weight transfer at that end and less grip. With the stock suspension, corning and corner exit and turn in is more limited by the front end (as you found out) slipping, so bigass sway bars have a slightly stiffer rear bar than stock. Most coilovers come with more bias towards oversteer as well. Of course if you put the bigass sway bar in back and a smaller one up front you will get too much oversteer as Andi has show. Hopefully bigass bars + Teins will be neutral. None of that changes suspension geometry, although you do need to get your car realigned after lowering it. The best way to find out how much negative camber you need is probably a pyrometer. Mine just came in the mail this week and I haven't gotten a chance to use it. You should probably just get the car aligned to Lance's specs until you figure it out. I don't know too much about this stuff, Eric or Andi could probably help you more.

I heard the 275s rub for the first time yestday, I've actually had more trouble with the rears (where I cut the inside fender lip). All I really had to do for the fronts was remove 3 bolts on the inside of each wheel well.

IMO strut tower braces don't do shit. Since our cars don't have struts, there really shouldn't be any lateral forces on the shock. Some people say they feel the car is stiffer all around with them, I can't notice anything.

Unfortunately me GTech meter is broken, so I can't do lateral G testing.

I think any rx7 with Hoosiers should do better. The ones on street tires are cake though

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Andi

· #16 · Sep 14, 2001

Grant said:
IMO strut tower braces don't do shit. Since our cars don't have struts, there really shouldn't be any lateral forces on the shock. Some people say they feel the car is stiffer all around with them, I can't notice anything.

Agreed.

G

· #17 · Sep 16, 2001

The rear strut tower brace makes a nice $200 shoulder harness bar. Jeff

G

· #18 · Oct 7, 2001

I hardly ever post on here

being an avid solo 2 autocrosser in local events, For the supra and it's size ebraking is very helpful. I rode in a 95 NA Supra and he had to ebrake to make it around a couple turns where my rx was just a good hard stab at the brake.

G

· #19 · Oct 11, 2001

Andi said:
Agreed.

While I don't notice much difference with the targa top on, there is a huge difference with it off, which leads me to believe strut tower braces substantially improve chassis rigidity. I drove a Supra before and after a front brace, not expecting it to change much. Before the brace, steering response was terrible and there was a lot more body roll. After the brace the situation was much improved, though still not as good as with the targa top on.

rapture

G

· #20 · Oct 19, 2001

SUPRAT said:
I have a set of 255/45ZR17

"255/45ZR17" what do these numbers mean? is it the thickness or the softness? never was quite sure as to the meaning of them

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