Car: 1993 Honda Civic DX fully gutted w/ 6pt Autopower cage

Brakes: ITR 5 lug full setup with GT sports (Front) and Axxis Ultimates (Rear) and Stoptech braded lines. I have the Integra RS Prop Valve and the RS Master Cylinder and reservoir.

Tires: Yokohama A032R 205/50/15 running 32lbs cold on all 4 corners. Hot pressures see approximately 40psi.

Suspension: Type R front/rear 22mm swaybar, GC/Koni OTS yellows almost full stiff on shock setting 400f/500r, A-Spec rear subframe kit. Front and rear camber kit. Settings are -2.5 deg camber in front and -1.5 deg camber in rear. 1/16th total toe out in front and zero toe in rear.

Corner weight #'s: DF: 796 PF: 732 DR: 487 PR: 415 50.1%

The car is well setup for cornering and it handles like it's on rails at this point. The problem I am having is under heavy braking. The car has done it two different times at two different tracks. Under heavy braking (120+mph down to 40-60mph give or take) the back end of the car comes out to my left and it is absolutely sudden under braking. I had an offtrack excursion on Roebling yesterday because of this and while it happened in T1 I wasn't too worried because there was plenty of runoff there and I ended up not having to use it.

I realize that under heavy braking the rear tire contact patch is next to nothing because the car is so light back there. I guess I am just not used to it. I am writing to the experts here for suggestions on what to try. I don't know exactly where to start. I guess some ideas ran around my head were to get more weight to the rear of the car, always fill up the gas tank after each session, get a completely different suspension, or just suck it up and get used to it.

I'll be quite honest. This brake setup is so good I haven't even began to touch what it can achieve but this back end being so squirmish has me worried to try and brake deeper into corners at this point. Let's have a good discussion and I am here to learn more about my passion for motorsports

 

sounds like you have everything sorted out pretty well.
assuming there's no problems like a kinked line or sticking caliper that would lead to this kind of problem,maybe try a milder rear pad.
i have the Ultimates on the rear of my car(GSR front/rear brakes.CT P+ pads up front),and have never had any problems like yours...but,i also have a "tighter" suspension setup-500f/400r springs and 24mm front bar with a 14mm rear bar.
many people run stock pads out back with no problems at all.maybe give that a try.also check over your hard lines to make sure none are kinked,check that the calipers are in good shape,and maybe try a new prop valve.
Chris

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EleanoR &raquo;</TD></TR><TR><TD CLASS="quote">Suspension: Type R front/rear 22mm swaybar, GC/Koni OTS yellows almost full stiff on shock setting 400f/500r, .... 1/16th total toe out in front and zero toe in rear.</TD></TR></TABLE>

First thing is I want to make absolutely sure that it kicks out the same way when using threshold braking from high speed on <u>several</u> tracks. Since you've had this happen on only two tracks, I think it's too early to think there's something radically wrong with your car.

Going into threshold braking from 120 is getting on up there. Your 400# springs are a good compromise for a street driven car, but it's possible your driving style and speed have advanced so much that it's just not enough anymore.

To keep the nose up in threshold braking from 140, Ichishima openly recommends 14K springs, for example.

Another thing to consider is stronger brake pads all the way around...and go stronger in the rear, especially. You want the rear to be doing its fair share of the braking, and this will also help keep the nose up a little bit. Personally I am using Spec VR on the front and Spec B on the rear, and this works well.

Now...one more thing...remember that when the rear end hikes up, you're going to go toe <u>out</u> and <u>positive</u> camber. The toe out, coupled with the hugely increased front contact patch when treshold braking from high speeds, makes the car very, very darty.

If you even THINK about turning or twitch the wheel slightly, you're going to go darting off in some direction.

As a minor aid to helping with this, most of us have learned that slight toe <u>in</u> on the rear is a good thing to have.

Now, one more question. How many miles on your car, and are you sure the bushings in the rear are in good shape?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TeamNextGenChris &raquo;</TD></TR><TR><TD CLASS="quote">and maybe try a new prop valve.
Chris</TD></TR></TABLE>


I thought about looking into an adjustable proportioning valve. I don't know how well this would help the setup and if many people are using them at all.

George~

The bushings looked to be fine when we installed the setup. The car has approx 130,000 miles. The entire suspension was gutted and replaced in favor of Type R everything i mean from front control arms to rear control arms to front forks, sway bars.....everything Type R if you get my drift (former R owner here).

I am not used to having the rear end of a car that light compared to the Type R so getting used to it will take some time. I like the idea of some slight toe in on the rear of the car. Right now it is zero toe in the rear.

With your suggestion of more aggressive compounds all around (at least on the rear side of things) do you think this will improve the feel of the car at threshold braking? The back end of the car hasn't done this under normal braking or tapping the brake to slightly lower speed. It is only when at higher speeds and threshold braking. Car does not have ABS brakes. I know I am not locking up the rear tires either.

 

Check your alignment in the back. I'm guessing you have some toe out...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EleanoR &raquo;</TD></TR><TR><TD CLASS="quote">
The bushings looked to be fine when we installed the setup. The car has approx 130,000 miles. </TD></TR></TABLE>
Well... OK.... My ITR's bushings didn't look too bad but there's a world of difference now w/the new bushings.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">I like the idea of some slight toe in on the rear of the car. Right now it is zero toe in the rear.</TD></TR></TABLE>
You can ask anybody from the old N1 racers to the budding H1 champion...it helps.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">With your suggestion of more aggressive compounds all around (at least on the rear side of things) do you think this will improve the feel of the car at threshold braking? </TD></TR></TABLE>
It helped me a couple of years ago when I first started reaching higher speeds at the ends of straights. You don't want to lock up the rears, but you want a compound aggressive enough that the rear is doing its job and helping to keep the nose up.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> I know I am not locking up the rear tires either.</TD></TR></TABLE>
Are you absolutely sure you're not locking up one rear wheel?

 

passenger rear is locking most likely. it happens on my STS car.

brake dive is not reduced with a more aggressive rear pad unless you aren't generating as many braking g's.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by George Knighton &raquo;</TD></TR><TR><TD CLASS="quote">You can ask anybody from the old N1 racers to the budding H1 champion...it helps.</TD></TR></TABLE>

That's interesting. I too have zero toe in the rear along with 1/8 total toe out in the front (1/16th at both corners). I don't have any instability problems under braking. Then again, it could be time on the car and me just being used to it. I dunno.

Agreed on the bushings, though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Back in Black &raquo;</TD></TR><TR><TD CLASS="quote">
That's interesting. I too have zero toe in the rear along with 1/8 total toe out in the front (1/16th at both corners). I don't have any instability problems under braking. Then again, it could be time on the car and me just being used to it.</TD></TR></TABLE>
You're just a better driver than we are.

Are you still on 14/16 or have you gone heavier?

 

I can't imagine going to a stronger pad compound for the rear "helping". All I've found with stronger rear pads is the rear locking up under highspeed braking.

Personally... I'd say to stay away from a strong compound in the rear. I have similar issues, but found that the stronger pad had me locking the rears up constantly while the front end had no issues what-so-ever.

This was on 400/500 spring setup and also for a 16k/14k setup. (gutted 4pt kirk civic VX).

I've attributed a bunch of it to lack of weight in the hatch. I was actually looking into applying some more downforce to the car to help compensate the initial braking at high speeds. Hoping to stabilize the rear.

Unfortuantly... car is being sold... so I can't test it out and tell u the results

 

Just skimming down through this, I'm liking the idea of stiffer fronts. With the rear light, nearly all cars will nose dive under that kind of braking. The trick is to minimize it without sacrificing too much other places.
That said, racing is all about compromises. With a stiff front, the rear won't lift as bad the rear brakes should do there job.
Another option that comes to mind is aerodynamics. At that kind of speed, spoilers, splitters, and skirts come into play. I don't know if you're following a rulebook in your build, but maybe it's another area to look at. In theory, a rear spoiler could help stick the rear or a splitter could help suck the car down to the track.

FWIW.

Tim

 

Yes i thought about a wing setup to induce downforce but am I at a high enough speed to where this wing will cure the problem? I highly doubt it but it could help out a little. I am inclined to try the stock pads for the next event in my setup to see if this would help along with a little toe in like George said.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EleanoR &raquo;</TD></TR><TR><TD CLASS="quote">Yes i thought about a wing setup to induce downforce but am I at a high enough speed to where this wing will cure the problem? I highly doubt it but it could help out a little. I am inclined to try the stock pads for the next event in my setup to see if this would help along with a little toe in like George said.</TD></TR></TABLE>

I found my favorite brake setup was napa ceramic junk in the rear and cobalt spec VR+s in the front. Worked great in my hatch. I never did get into good toe adjustments though, 0 all around since I was driving the car distances to all events.

Having just actually reread your setup list... I'd say goto stockers in the rear. The brake pads you are running (front/rear) are extremely similar and I'd suspect some minimal lockup in the rear.

full setup just in case it helps:
kyb super special gyhmkhanas
16k front, 14k rear (swift/hypercoil)
23mm jdm itr rear swaybar
22mm LS front swaybar
Kirk 4pt bar
-2.5deg camber front
-1.8deg camber rear
Toyo RA-1s
Gsr brakes all around
SS brake lines
15/16th brake MC (loved this for pedal feel and modulation)
Cobalt SpecVR fronts
Napa junk rear
Autozone blanks all around (love cheapies)

Car was corner weighted and setup with 0 toe all around.
~2144lbs without driver.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EleanoR &raquo;</TD></TR><TR><TD CLASS="quote">"no locking in rear".</TD></TR></TABLE>
How are you absolutely sure you're not locking one wheel a little?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by George Knighton &raquo;</TD></TR><TR><TD CLASS="quote">
How are you absolutely sure you're not locking one wheel a little?</TD></TR></TABLE>

I run xp10 front, xp8 rear... if the steering wheel is turned at all, the inside rear tire will lock up. If i'm going straight ahead, the fronts lock first. I like the way the car feels with the aggressive rear pads, but thats just my preference, and i'd rather the rears lock first anyways with any sort of steering input.

Edit: Even if the trailing arm bushings look good, with a lot of miles on them they're likely trashed. They're cheap to replace, might as well just do it.