ITRCA

Went to an Autocross a month ago with the R. The Lot is small so it is fairly low speed. Course was tight and I kept getting LOTS of Understeer. I have Zeal B6's (554/335), camber adjusted and I run on Azenis. I had the rear shocks set full stiff. The Front Shocks I tried at the softest and next to softest setting with the Front tires at 39 psi and the Rear tires at 32 psi. Nothing worked and all I did was push.

To hopefully improve this problem I had an alignment checked and tweacked. I have -2 degrees of camber in the front and -1.4 degrees in the rear. I have 1/4" total toe out in the front and zero toe in the rear.

I raced this past weekend after the new alignment and even ran full stiff rear/full soft front with 39 psi Front/28 psi rear (Azenis). I still had a lot of push on an even faster course. I was not sure , other than driver, what to blame my woes on. I had decided maybe the suspension rates were an issue. Or maybe the parking lot surface and size was the issue.

A Freind (ohtheguilt) stopped by the event just in time for my last 3 runs. I was 2.5 seconds behind STS while running in street mod. I was complaining to my friend about the push that would just not go away. Since the problem began this year we thought and thought what coudl have been the problem. He says, "when did you add the harness bar and rear strut bar"? I had added them for the Type-R Expo. The car was fine at the Expo but it was MUCH higher speeds.

We scrambled to take the bars out just as an experiment. I also got one of the Regions best drivers to ride with me (He weighs 275 pounds). With him in the car and no bars I gained 1.3 seconds. He gave me a few tips and I was feeling better cause the car had just bahaved more normally. By the end of my 3rd run I had improved by 2.1 seconds over my runs with the bars.

We didn't test to see if it was one bar or the other. The rear strut bar took all my usable storage space so i was not sad to see it go. The Camera bar was a beautiful piece but i think it was the biggest culprit. That said everyone should choose their mods wisely (Not just suspension mods). Just cause everyone else is buying them or doing it, doesn't make it a good modification or idea.

All that said even with the bars out I don't feel I have enough rotation so i am chaning my rear springs to 8 kg/mm (447lb/in). Will let everyone know how they do.

Trey

This really was a pretty strange phenomenon...I would have never thought that a harness bar could cause that much stiffness, but I guess the proof is there...2.1 seconds is alot of time.
It is always possible that the placebo effect was running full force, but when I ran the car, it DEFINITELY wasn't pushing like Trey said it was with the bars in it...the rotation was very nice (I hope I get to drive it again with the new springs)...its a shame I showed up late; Trey would have had an even better day had I been there to tell him to take the bars out sooner!!

Nathan

Glad to hear you're solving your handling woes. Always puts a smile on your face to drop 2 seconds

And you'll probably want a stiffer rear bar (if you're not already running a Mugen 26mm). Last year, Sean Lousin, the gracious car owner allowed me to co-drive his R. He was running 400F/550R on Zeal B6's and a 23mm JDM bar. The car didn't rotate well enough at last years nats (still good enough to win though). He started with a 400F/450R and a stock rear bar and the car pushed even worse.

He's since added the 26mm rear bar and loves the balance the car now has and is perfectly comfortable on track (not too much oversteer)

Trey: Real spring rates would have worked or just pumping up the pressure in the rear instead of lowering it..

Try putting the bars back in and running 39 psi in the front and 44 psi in the rear.

i was really thinkin in getting that mugen rear bar and a cb harness bar, are they worth the bang for the buck as far as stability? mugen is a bit expensive but im mugenizing my car anyways, so it's not as much of an issue, i do wonder about the harness bar though! thanks guys...

Logic would say that if you stiffened the car with bracing and it goes slower, then there is something wrong with the suspension setup. Removing the harness bar and rear strut bar made the car softer in terms of chassis twist and you went faster. If the chassis was now twisting more than before and you are getting more speed, then the setup with the strut and harness bars needed to be adjusted. A change in the tire pressures, roll-bars or springs to change the understeer/oversteer balance with the bars installed would seem to be the better choice. Or perhaps the chassis twist was giving a better camber for the tire on the course, giving the rear end more grip. Maybe an experiment with camber is in order.
I have an Autopower 4 point roll bar installed in my car, with the removable belt and harness bar option. It has made the car noticeably stiffer (and 58 lbs heavier). It was a fair bit of work to put it in but well worth the effort and money. I could not imagine driving without it. I do not autocross, I only drive on the track. Learning to drive faster and tweaking the suspension are the entertaining parts, since in HPDE events there are no prizes, only bragging rights. Now if I could just go faster up the straights!

descartesfool wrote:Logic would say that if you stiffened the car with bracing and it goes slower, then there is something wrong with the suspension setup. Removing the harness bar and rear strut bar made the car softer in terms of chassis twist and you went faster. If the chassis was now twisting more than before and you are getting more speed, then the setup with the strut and harness bars needed to be adjusted. A change in the tire pressures, roll-bars or springs to change the understeer/oversteer balance with the bars installed would seem to be the better choice. Or perhaps the chassis twist was giving a better camber for the tire on the course, giving the rear end more grip. Maybe an experiment with camber is in order.
I have an Autopower 4 point roll bar installed in my car, with the removable belt and harness bar option. It has made the car noticeably stiffer (and 58 lbs heavier). It was a fair bit of work to put it in but well worth the effort and money. I could not imagine driving without it. I do not autocross, I only drive on the track. Learning to drive faster and tweaking the suspension are the entertaining parts, since in HPDE events there are no prizes, only bragging rights. Now if I could just go faster up the straights!

2 things to reply here. I am sure the handling could have been sorted out while leaving the bars in but at what cost and hair pulling? Seems more logical to remove the bars and go from there is more needs to be done. I am going to up the rear spring rates slightly but testing camber settings is hardly financially feasible.

That said when i consulted 2 different auto-x and road racers they confirmed that in FWD cars atdding a roll cage had often caused understeer due to stiffness than then had to be worked out through spring rates and rear swaybars along with alignment so i don't think the blame is solely on the suspension.

Also, Driving a track vs auto-x is so VERY different IMO. Track being higher speed and typically (Everything I have done) unofficially timed leaves you with inaccurate data on handling impropvements. Also with a track size and traffic times vary to a degree that auto-x doesn't see. Very valid points just pointing out that putting this in for things sake isn't always a good idea.

On the tire pressure note I will try higher rear tire pressure rates but I have ALWAYS had a noticable change by lowering the rear pressures. Both work in theory and I have always gone down for the more controllable of the oversteer options.

Trey - I don't think your slower times were due to your strut brace & camera bar. I would have played with the tire pressure, rather than take off your strut bar & camera bar.

ATL region's Pro (DS) driver told me once to have the tire pressure vary by no more than 3psi in either direction. I typically run 1psi higher up front than the rear. The reasoning being (from Ken Rupp) that you want to get a feedback from the front tire, rather than from the rear. Stiffer front will communicate to you before it breaks the contact with the pavement. You don't want the ass-end to be telling you that you've overcooked the corner, 'cuz you're pretty much screwed by the time you realize this from your rear tire feedback.

I would have to say that adding in a Mugen front strut bar did cause a severe understeer. I had to remedy it with matcing rear bar + 23mm jdm sway bar.

Sean I played with Tire Pressure AND Shock settings before removing the bars and nothing made a noticable difference. Once the bar came out the feel and times showed a significant change was made.

I have talked to many different racers (From your region as well as all sorts of places) and there are dozens of tire pressure theories. The only one that makes sense is that there is the one perfect pressure for grip and anything above or below that will reduce grip so you can raise or lower your rear pressure to help with oversteer but the behavciors will vary based on whether you raise or lower the pressure.

I am opting to leave the bars out (Why not if the car does better and I can sell the parts). I have also decided to increase the rear spring rates slightly (Still staying front weight biased, due to lack of info on what the B6 valving can handle) and plan to get a 23 mm JDM bar.

I can get the springs and rear bar anbd still have enough $ to pay for an HPDE by selling the other 2 bars.

Trey

Trey - I know you're faster than I on an autocross, but I gotta say, I will vote for the tire pressure issue also. Going lower on the back end will normally cause additional grip (to a point) not less grip. I would definately have been running at a minimum, the same pressure as the fronts. In fact hot pressure=40-42 max when I run. Rear hot pressure 42-46.

Then again... I do like to spin!

BudMan (aka...dnfjeff)

I PROMISE and am not debating this as I know it not thinking it that lowering tire pressure as well as raising it in the rear causes oversteer. Not the point I was putting up for debate.

Do i need to put the bars back in run 50 psi in the rear and still get understeer to prove this point to everyone?

Azenis on a 2500 lb car seems to have the most grip at about 38-39 psi. Lowering or raising it will cause the tire to slip but in different ways.

I ran 39/38 and went down 2-3 psi until i started getting SOME oversteer. The car began to increase in oversteer behavior as the pressures went down. This is caused by the tire rolling over and losing contact patch. Raising the rear pressures will cause there to be a lack of patch from the get go and will let go more suddenly and less controllably IMO.

I prefer some understeer and that is how I have chosen to lower rates vs raising them.

I ran an entire auto-x previously with the tires at 39/37 to 40/36 at most and the car was MUCH MUCH worse than the bars in and the presures at 38/28. I am not advocating those as good pressure but that lowering can induce oversteer and the extreme at which i had to go to with the bars in seems to point to something (The bars).

I shoudl be able to run pressure everyone seems to be more comfortable with at the next event with no bars in. That said pressure numbers mean nothing it is even heat and roll over that matters.

Hmmmm - although it's tempting, you'd kick my ass either way...

Note: we need to be in the same group next expo

sorry - not trying to work you up **as I look for my beer icon**

jeff

Only worked up because the primary concern everyone seems to have is tire pressure. I have taken 18 runs with the bars in and the tire pressure have been just about anything you can think of and they all sucked.

The whole point was don't get too crazy just buying parts. If the car does what you want (Which mine did prior to the bars) why spend the money on them. I think the issue I had with the handling was mostly induced by the camera bar and I didn't independedntly test each bar so there is still more to be learned here.

On that note, I'm selling my B-pillar bar, because I don't like taking it in&out when my son is going to ride with me

$75 obo for custom made steel bar available for delivery at the next Expo!