I've managed to deal with this issue for the last 4 years that I've been tracking the car. Basically, if you're entering a turn at high speed and hit the brakes hard, the rear end of the car gets very twitchy. Although I'm somewhat used to it, I'd really like to find a way to either eliminate the nervous back end, or at least reduce it somewhat.

I think this year was the worst, maybe because I'm starting to really push the car hard. My friend Chris who drove the car several times also noticed this. I've thought of several things, I'll share them, but mostly I'd like some feedback here, and maybe over the winter, I can address the issue in time for the '05 track season.


1. More wing: Well, there's only one choice here, the Mugen adjustable wing. But at $1000 (wing + paint) it's a very costly option. I'm not even sure that this would help all that much under hard braking, but maybe the additional downforce would keep the car more planted on high speed corners. So, this may not be a solution at all.

2. Rear tower bar: Several choices here, including JDM and Mugen bars. Cost is under $300, but is it going to make a meaningful difference? The ITR's chassis is already solid, so again, I'm not sure if this will help with the nervous rear end under hard braking.

3. Thicker sway bar: Another low-cost option. Main purpose here would be to introduce a bit more oversteer, and my driving style would be OK with that. But are you also stiffening the rear, so the rear stays planted under threshold braking?

Did I miss anything? Is there even a solution to this issue? There has to be, I've watched the Realtime ITRs for years. And those guys, the racers who go 10/10s, they don't seem to have this problem. So if anyone knows what to do, let me know. I've got all winter to take care of it.

 

solution: don't hit the brakes mid corner....

 

Mugen trailing arm bushings.

Its twitchy because of the way the geometry is designed - the rear tires toe out under droop. Swaybars dont do anything under braking/acel if there's no lateral load.

 

adjustable brake bias.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Its_real&its_spectacular &raquo;</TD></TR><TR><TD CLASS="quote">adjustable brake bias.</TD></TR></TABLE>

No, more aggressive rear pads. But it still doesnt solve the root of the problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">Mugen trailing arm bushings.</TD></TR></TABLE>
How does this help?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AssPenny &raquo;</TD></TR><TR><TD CLASS="quote">
How does this help?</TD></TR></TABLE>

Reduces the toe out under droop. They retain the factory range of motion, unlike the solid poly replacements, but are stiffer. And they're $115 per pair - about the same price as the poly.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo &raquo;</TD></TR><TR><TD CLASS="quote">solution: don't hit the brakes mid corner....</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">Mugen trailing arm bushings.

Its twitchy because of the way the geometry is designed - the rear tires toe out under droop. Swaybars dont do anything under braking/acel if there's no lateral load.</TD></TR></TABLE>

I'd like to add, if you go with the bigger sway bar, you may be potentially setting yourself up for a lot of understeer.

Though if you tackle the flex characteristics of a uni-body and address them as best you can, your car will be much more predictable and you will have a better feeling of what it is going to do. To do this you need to understadn torsional flex. If you give your suspension a stiff base to work off of (chasis rigidity) your car will be easier to work with to make it perform better.

Before I blew my engine I was able to get some good corner time in the passenger seat while I let the SCCA National Champion and third place finisher drive my car. Needless to say, all three of us were thoroughly impressed of the cornering characteristics of my car due to the significant amount of chasis bracing. Before hand I was questioning my decisions. However, after they drove the car it became quickly known that it was a good decision.

Some people take my setup a step further and seam weld the unibody. Though this is very expensive and very timely. I don't feel this is needed unless I see you racing on Speed Vison or whatever it is they call it now.

I would suggest:
1) Make the chasis stiffer so your suspension is easier to tune and you get more feedback out of it instead of having that vital information absorbed by the flex of the chasis
2) Braking mid turn or too late into the turn causes the weigh the car to shift foward and to the outside of the turn making the car continue in a straight line instead of driving around the axis of the turn. Try:
--A) Braking sooner (before the turn)
--B) Left foot braking during your apex (left foot on brake, right on gas...modulation of both pedals)
--C) Brake sooner then use gas pedal modulation througth the apex
--D) Hoosiers

Hope this helps.

 

To me it is just normal. When I race and under hard braking the car wiggles (sometimes a lot). All I do is counter steer when necessary and when finally at the speed I desire, get back on the gas, which settles the rear end and I keep going.

You'll get used to it. If not, then I think RJ's solution of the bushings might help.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">I'd like to add, if you go with the bigger sway bar, you may be potentially setting yourself up for a lot of understeer.</TD></TR></TABLE>

Not a bigger rear bar.........

Anyways, further discussion about the trailing arm bushings - https://honda-tech.com/zerothread?id=493789

I had ordered a set from King, but I guess they forgot about me, I was never charged.... and been to busy to install a set, so I havent followed up.

 

How much trail braking are you doing?
Suspension set-up?

All the sugguestions above are on the right track, however to fully understand whats going on, we need to know about the car and your driving style.

 

Even though I had no where near the amount of chassis stiffening equipment that Brando had, I had the JDM Rear strut tower bar on and the EM racing c-pillar bar.

I was using these for about six months and recently took them both off and sold them due to financial issues.

After removing these parts and going for a spirited drive through the canyon I felt the rear end was a lot more "twitchy" during heavy braking compared to when I had the strut bar and c-pillar bar installed.

Granted I believe the strut bar did the most of this and If I had to do it all again I would probably pass on the c-pillar bar.

Start small, try different things and see what works.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">



I'd like to add, if you go with the bigger sway bar, you may be potentially setting yourself up for a lot of understeer.

Though if you tackle the flex characteristics of a uni-body and address them as best you can, your car will be much more predictable and you will have a better feeling of what it is going to do. To do this you need to understadn torsional flex. If you give your suspension a stiff base to work off of (chasis rigidity) your car will be easier to work with to make it perform better.

Before I blew my engine I was able to get some good corner time in the passenger seat while I let the SCCA National Champion and third place finisher drive my car. Needless to say, all three of us were thoroughly impressed of the cornering characteristics of my car due to the significant amount of chasis bracing. Before hand I was questioning my decisions. However, after they drove the car it became quickly known that it was a good decision.

Some people take my setup a step further and seam weld the unibody. Though this is very expensive and very timely. I don't feel this is needed unless I see you racing on Speed Vison or whatever it is they call it now.

I would suggest:
1) Make the chasis stiffer so your suspension is easier to tune and you get more feedback out of it instead of having that vital information absorbed by the flex of the chasis
2) Braking mid turn or too late into the turn causes the weigh the car to shift foward and to the outside of the turn making the car continue in a straight line instead of driving around the axis of the turn. Try:
--A) Braking sooner (before the turn)
--B) Left foot braking during your apex (left foot on brake, right on gas...modulation of both pedals)
--C) Brake sooner then use gas pedal modulation througth the apex
--D) Hoosiers

Hope this helps.</TD></TR></TABLE>

Where do j00 come up with this stuff?

Do you even know what the purpose of left f00t braking is?

H00siers have nothing to do with this.

ITRs come with plenty of braces already.

braking mid corner shifts the weight forward, true, but it does NOT make the car go in a straight line...after all the front wheels are turned, aren't they?


RJ advice is the best (assuming you're driving the car correctly), the mugen trailing arm bushings make a fair amount of difference in straight-line braking stability.


-Matt, who aparently forgot to take his daily dose of the stupid-pill this morning



Modified by El Pollo Diablo at 3:51 PM 10/18/2004

 

A person asks a simple question and someone belts out a thesis on something totally unrelated to the subject at hand plus gives out some god awful advice.

I concur, RJ gave the best (and correct) advice so far.

 

I think the wiggling is normal. I would take advantage of that and swing the tail out to get the desired rotation at turn in (read: trail brake). So my apex and track out line can be as straight as possible.

If the wiggling is too much to your liking, I would try more aggressive rear pads, and/or lowering the rear if you have height adjustability, and/or add a slight rear toe-in. Try these options first before spending $$ on more expensive parts.

 

Ya all just need some big a$$ wing on the back to stabilize the biotch

 

Here is my experience with tail wiggling since I'm not a racer and just a HPDE driver.

1.) Wiggling was extremely pronounced when I was using Cobalt VRs in the front and stock pads in the rear. Switched up to Cobalt GT Sports for the rear and it reduced it somewhat. This is the first thing I'd look into before anything else.

2.) Biggest fix was the driver. Instead of gorilla stomping on the brakes at the end of a high speed straight (only place where wiggling was noticable), I learned how to be a bit smoother with the pedal itself. Instead of slamming it, I rolled into the brakes in a more progressive manner so that weight transfer wasn't sent forward suddenly.

If I kept my car, the next step was going to be the Mugen bushings after reading and doing research on the RR/AX forum. But I held off on the bushings anyway since 1) I'm not racing the car (w2w or tt) and 2) I figured out how to compensate by adjusting my driving style a bit (since I'm not doing w2w/tt).

R compounds doesn't help with the wiggling. Neither will a bigger rear bar. Bushings and possibly the rear wing should stablize the rear. But for me, the nut behind the wheel needed the biggest adjustment.

 

Try running equal compounds on the front and rear. If this doesn't make things more "comfortable" to you, go with the bushings as they will help.

FYI, I run XP1108 compound on both the front and the rear. She feels nice and stable, and I'm not one to brake early, either.

Hope this helps, and good luck.

 

First of all, it's normal and isn't going to go away.

I found that more aggressive rear pads helped the overall feel of the car under braking. Going too aggressive can lead to the rears locking up first, which makes it more unsafe at the limit.

 

I was told that the more one can wiggle their ***, the cooler they are

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yoshi234 &raquo;</TD></TR><TR><TD CLASS="quote">I was told that the more one can wiggle their ***, the cooler they are </TD></TR></TABLE>

says w.ho. boi...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by yoshi234 &raquo;</TD></TR><TR><TD CLASS="quote">I was told that the more one can wiggle their ***, the cooler they are </TD></TR></TABLE>

There is a Renault commercial for the Megane that basically says this. It is kind of funny. A little risky for US television, but very normal for European TV.

 

Okay?

This I think is the most important thing and I couldn't agree more. I personally didn't or don't analyze what I do on the track when I do it. It's not reflex but more feel.

Best way to explain this was when David instructed me recently, he made a few comments, either while I was doing particular things like; "nice trailbraking through turn#1" or of course my nemesis "hold off on the brake till 2 1/2 marker this time, Woop's ok maybe next time".

I already was aware of some spots I wanted to improve but he pointed out things I did that I NEED to concentrate on to be smoother and faster. Braking zones have not been my strong point since my first failure.

But, my point really is, I was not really aware when I was trailbraking. I knew what I was doing to get the car to rotate but I wasn't really thinking about it.

In turn when I got in his car and rode with him for a few sessions, I'd ask where he was deciding his braking points, and he responded similarly that he was driving more for/with feel and not trying to label or nail one spot every time. Of course this all in an HPDE, but the experience I hope illustrates a point.

Agreed and once I was able to balance the front/rear bias with more even pad compounds the wiggle lessened.


Exactly what I did and exactly the same results.


Ya just can't stress this enough. Heck I'm still guilty sometimes.

I think the biggest most pronounced times I've experienced wiggle in my car and Dave's as a passenger (his has the BC RS suspension, mine is totally stock) were in the uphill before the front straight at Beaverun, turn #7 and #9, again uphills at Watkin's Glen and again but not as much into turn #1 at Limerock. My experience is limited as well as the tracks I've driven but the first things that worked for me was changing pad compounds, then working on smoother brake application.

 

So, based on the responses, it looks like there isn't really a fix here, just a combination of things to do to minimize the problem.

I look forward to working some more on my braking technique next year on the track, and see what happens.

In terms of mechnical solutions, I'm already running a pair of Cobalt pads (I forgot the name) in the rear, so we're good there. I might consider getting the Mugen Rear Tower bar. And how hard is it to install the TA bushings? Any pointers to some DIY instructions?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fso_BamBam &raquo;</TD></TR><TR><TD CLASS="quote">And how hard is it to install the TA bushings? Any pointers to some DIY instructions? </TD></TR></TABLE>

Press in, press out.