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Exessive body roll during AutoX?

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Exessive body roll during AutoX?

Postby Vipex » Fri Oct 24, 2014 10:42 pm

Recently I have been Autocrossing a lot. Its been a ton of fun, but my suspension is pretty soft since its stock. I get plenty of body roll, which is expected, but I want to know how much body roll is typical for a stock 88 Si? The only thing I've added to my car are a set of 15x7 Enkei RPF1's with 205/50R15 Potenza RE-11A Tires.

Here is an example of some body roll I experienced while tackling a 180°turn.

Image

Does any one else who races with a stock suspension get body roll similar to this? Does that seem excessive to you?


The reason I'm asking is because I have gotten a few comments about how much my car rolls during racing. Since I've never seen my car on the track, I decided to put together a g-force/Angle sensor to take some measurements. I mounted the sensor just in front of the hand brake. I figured its a pretty flat spot, and sorta close to the center of the car.

Image

Any way the sensor reported that the max amount of nose dip I got was -40°, and the maximum roll angle I got was 56°. Both those values seem a bit ridiculous to me. You can see for your self in my video.




I'm certain the sensor was reading accurately. I did plenty of testing with it before and after the race. I'm also pretty sure the sensor didn't come loose during the race. Do you think it is really possible my CRX has that much body roll?
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Re: Exessive body roll during AutoX?

Postby Baker » Sat Oct 25, 2014 6:23 am

On an old, stock suspension, which probably has a lot of miles on it, I would say this is likely pretty typical.
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Re: Exessive body roll during AutoX?

Postby tommy » Sat Oct 25, 2014 12:49 pm

I'd agree. The question should be what are you going to do about it.
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Re: Exessive body roll during AutoX?

Postby Meech » Sat Oct 25, 2014 4:04 pm

The angles given by the reader do seem very exaggerated when comparing to the picture. In the picture it looks like you're getting 15-20* MAX. 45* is insane. What I'm thinking is that the sensor was not calibrated properly? But yeah, even so, that is a lot of roll although common on the stock suspension as Baker and Tommy have mentioned.
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Re: Exessive body roll during AutoX?

Postby Vipex » Sat Oct 25, 2014 9:44 pm

I agree the angle readings during the race seem wrong. When I did my initial tests the readings were pretty dead on. I calculated the angles by using gravity as a normal vector. I wonder if the extra g's during the race some how threw off that calculation.

As for fixing up my suspension, I have been looking into upgrades for a little while now. I was thinking something along the lines of

Koni Yellow Shocks
Ground Control Coil overs, with 350f 450r spring rates
ST 22mm rear sway bar, and the adapter kit needed for 88 rear LCA's
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Re: Exessive body roll during AutoX?

Postby jfrolang » Sun Oct 26, 2014 12:38 am

I like the Tanabe rear sway bar better than the ST.
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Re: Exessive body roll during AutoX?

Postby KevinEF7 » Sun Oct 26, 2014 1:26 am

The fresh spring/shocks upgrade on its own would drastically reduce the roll, a good oppurtunity to buy fresh 89-91 LCA's (shocks would be 89-91 specific and easier to source) and the Tanabe bar really is a great performer for a low cost and very easy trouble free install on stock style oem endlinks
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Re: Exessive body roll during AutoX?

Postby Vipex » Sun Oct 26, 2014 10:09 pm

I wanted to avoid the hassle/cost of getting new LCA's. I already sourced the correct shocks, at least according the the website I found them on.

Front: http://store.redshiftmotorsports.com/ko ... 05367.aspx

Rear: http://store.redshiftmotorsports.com/ko ... 05366.aspx


I've also looked into Tanabe sway bars, and heard good things about them. I'm opting for the ST because its a 22 mm instead of a 20 mm. I remember reading some where that larger diameter sway bars are stiffer. I'm not sure if 2 mm would actually make much of a difference, but that the reasoning behind my preference.

Also, the ST sway bar is adjustable and I thought the Tanabe wasn't. I could be wrong about that though.
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Re: Exessive body roll during AutoX?

Postby tommy » Mon Oct 27, 2014 9:53 am

Well, the good thing would be that you'd be able to see what the impact of each item would be on your car independently, and then go further if you want. Yes, the thicker the bar, the stiffer it is. I've never had trouble with my ST bar, but I'll leave it up to those with Tanabes to say why they're better.
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Re: Exessive body roll during AutoX?

Postby Dave_Darling » Mon Oct 27, 2014 6:51 pm

You weren't measuring the body roll on the car. You were measuring the centrifugal force on the car. Guaranteed. If you got to 45 degrees of tilt, the car would be up on two wheels and you'd either be in the process of rolling over, or you'd be just about to start the process.

If you want to measure body lean, the photos are probably the best way to do it. Either that, or you have to instrument all four shocks and compare their extension or compression at the same time. (Comparing their max or min over the course of a run only shows you total suspension travel, not lean.)

It looks like you've got a fairly typical amount of body lean in that photo above. To flatten it out, you can make the suspension stiffer in at least four ways:

1- Stiffer springs. They will reduce the roll lean and also pitch. They will tend to make the ride harsher.
2- Stiffer shock valving. This will only really affect the lean in transient cases; the car will lean over slower but it will still lean if there are side forces on it for long enough. In some classes, where shocks are "free", this is the way you have to go. The ride will generally get much harsher on imperfect surfaces.
3- Stiffer anti-roll bars. These will link the two wheels at one end of the car together somewhat, making that end of the car resist leaning. The downside is that it places more load on the outside tire, and that can overwhelm the grip there. But you can tune them for oversteer/understeer balance by changing the effective lever lengths from the wheels to the bar on each end.
4- Lower the car. Even if the spring rates and other suspension bits are equal (they just about have to be changed to lower the car) there will be less lean per amount of force because of the shorter "lever arm" between the roll center of the car and the CG. (This assumes the roll center does not move much when the car's CG is lowered. Which is a reasonable assumption for a CRX up to a point.)

When allowed by class rules, usually a mix of all of these is done. The car is lowered using stiffer springs while replacing the shocks with ones valved more for the new spring rates, and stiffer sway bars (anti-roll bars) are added and used to tune the balance of the car.

Other possibilities include using less-grippy tires (they don't stick so there isn't as much side force) or driving around the corner slower. Neither one of which is much fun... ;)

--DD
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VTEC is Honda's "select a cam profile on the fly" system; VTECH is a crappy phone.
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Re: Exessive body roll during AutoX?

Postby solorex » Fri Oct 31, 2014 11:39 am

If you are going the Koni route, I would spend the extra $$ and get the SPSS valved ones from the get go, if you are enjoying autox now and plan to do more you will just want to upgrade anyways. The SPSS shocks are already shortened so you don't have to spend extra $$ on tophats for the front.
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Re: Exessive body roll during AutoX?

Postby AJC » Tue Nov 04, 2014 9:35 pm

You got body roll? I got body roll!

Image
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Re: Exessive body roll during AutoX?

Postby EF RaceRR » Tue Nov 11, 2014 1:04 pm

I would start with anti-roll bars, as others have said. Pick up a 22mm rear bar, or larger if you desire.

For the front, source all four OEM bars to tune your roll stiffness.

From there, you could do shocks. If you want to retain some comfort, I'd try OEM springs with Koni yellows with the snap ring on the lowest setting.

Getting the 89-91 rear lower control arms isn't that much of a hassle. I picked up a great pair of Si LCA for $40 shipped on here a few years ago. And for what it's worth, EG rear lower control arms will work as well.
http://crxcommunity.com/viewtopic.php?t=41148

On a side note, how do you like the RE-11A so far?
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Re: Exessive body roll during AutoX?

Postby Vipex » Tue Nov 25, 2014 7:41 pm

Hey, sorry of the delayed replay, school has been keeping me really busy.

Dave, Thanks for the feedback. Your break down of the suspension upgrades gave me a better intuitive understanding of how each will effect performance.

Solorex, I thought the only difference betweent the Koni Sports, and the Koni Race (SPSS Valved), was that the Race model can handle spring rates over 600 lbs, unlike the sport model. I am not planning on getting spring rates over 500 lbs, since this car will be mostly DD with some part time autoX/Road Course.
Until recently I was planning on using my stock top hats, since I don’t want to lower my car too much. However, I talked to the guys at Ground Control about their coil over conversion kit and they recommended I buy their full package instead which includes top hats.

Link: http://www.ground-control-store.com/pro ... 681/CA=167\

I might be able to save some money, if I order the shocks separately but that package from GC comes fully assembled. I figure the extra $$ for the package is the worth convenience since I won’t have mess with sketchy spring compressors or pay a shop to assemble the struts.


AJC, Nice MGB. I never knew you could get them to roll like that. The only one that ever shows up at events in my area has a really slow driver. I always wanted to see what his MGB could really do!
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Re: Exessive body roll during AutoX?

Postby Vipex » Tue Nov 25, 2014 7:49 pm

EF RaceRR, I am definitely picking up an ST rear sway bar. After reading this thread you posted in, I figured I’d just leave my OEM front sway bar alone for now.

As for the LCA’s I’m reconsidering the possibility of getting new ones, for a few reasons.
1. I wouldn’t have to buy this $50 adapter kit for my sway bar http://www.summitracing.com/parts/stq-5 ... MgodpGoArQ

2. My current LCA’s probably need new bushings, which I hear can be more costly to replace than getting new LCA’s. (I’m including labor in that cost)

3. If I ever want to do rear disc sawp, I would need 89+ LCA’s anyway.


On the topic of tires, I absolutely love my RE-11A’s! I can’t really compare them to any other sport tires since they are my first pair, but they have TONS of grip compared to my all seasons. On a wet street they seem to stay pretty grippe, however I haven’t had a chance to test their limits on a wet track yet.

I thought they made decent daily driving. They are a bit louder in terms of road noise, and there is a noticeable decrease in ride quality compared to my all seasons. Considering how they performed these two drawbacks are easily overlooked.

As for durability, when I autocrossed with them down in Boise they held up in the 100 degree heat pretty well. Everyone else was spraying down their tires, but mine never seemed to get soft between runs. They have been through about 2660 miles of daily driving, and 10 full autocross days. There is definitely noticeable ware on them, but they look like they have plenty of life left.
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Re: Exessive body roll during AutoX?

Postby LowFlyin » Wed Dec 03, 2014 11:31 am

Adding a stiffer rear bar is only going to exaggerate the rear inside lift you pictured.

What are you goals for autoX? Are you wanting to stay in the stock class?

For the stock class, you do get to change 1 of the sway bars. I would recommend changing the front before the rear.

I used to run a big bar on the back of my CRX

Image

...but now that we've put several 10s of hours of seat time in the Si Hatch racecar with NO rear bar...I'm beginning to change my philosophy on 4th Gen suspension setups.
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Re: Exessive body roll during AutoX?

Postby jaerodeck » Thu Dec 04, 2014 7:05 pm

shouldnt roll not be that bad, because of double wishbone suspension? yeah decreasing it is better but you still have full tire contact right?
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Re: Exessive body roll during AutoX?

Postby budget_crx » Fri Dec 05, 2014 11:00 am

You mentioned your LCA bushings need to be replaced, how about your other bushings? I would replace all your bushings with new units before looking into stiffer springs or sways, it will make a huge difference in the way the car feels. Shouldn't help with that crazy body roll though lol
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Re: Exessive body roll during AutoX?

Postby Vipex » Fri Dec 05, 2014 5:02 pm

I’m not super concerned with classing in autoX as I do it mostly for fun. For now I’m shooting for STS or a similar class.

My main objective for the suspension is to have it be adaptable. I would like to be able to tune it to do the following.

1. Tune it to perform pretty well in autoX with some predictable overseer
2. Tune it to be balanced/neutral on the track
3. Tune it to be safely driven in poor weather, after some practice

As for rear wheel lift, I haven’t noticed any problems in that area. I’ll keep it in mind when talking to the guys at ground control about picking spring rates. I'm more concerned about oversteer like this



I’m afraid of too much overstreer because, once I graduate and move back to the Seattle area, I may be tracking the car more often than autoXing. Most of the autocross events are about a two hour drive away, whereas the race tracks are a lot closer.
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Re: Exessive body roll during AutoX?

Postby Vipex » Fri Dec 05, 2014 5:02 pm

I’m holding off on new bushings for now, but I do eventually want to replace them. My buddy said it look like my new wheels had slightly positive camber. He suggested I get new springs and lower the car to get some natural negative camber, before I mess with the bushings.
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Re: Exessive body roll during AutoX?

Postby solorex » Wed Dec 10, 2014 2:03 pm

Bushings should actually be your first order of business. If they are original, some or all are likely very worn out.

The difference between the SPSS valved is not simply that it can handle higher spring rates, the rod is also shortened so that you do not need the extended top hats. Koni Sports are designed to be an OEM replacement shock, hence when you lower the car you are moving the piston away from where it was designed to be, hence the solution of an extended top hat which raises the piston back up. Make sense?

Even if you are running 500lb-in springs, the SPSS will do better and if you are getting into autox its the way to go.
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Re: Exessive body roll during AutoX?

Postby razordave » Sun Dec 14, 2014 8:53 pm

Bushings are most definitely the first order of business. No matter what springs/shocks/tires you run, you're not going to do anything right if you can't keep suspension components and wheels where they need to be.

Make sure to read about rta bushings before you decide to buy a full poly kit. If this vehicle is track only, then try to incorporate spherical bearings wherever possible.
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Re: Exessive body roll during AutoX?

Postby EF RaceRR » Sun Mar 08, 2015 1:53 pm

I agree about bushings.
I replaced every single one on my crx and it makes a world of difference.
This is my first crx that I have done all the bushings on. Steering response is crisp and it handles great.

I used all OEM bushings, with polyurethane and spherical bearings in select areas.
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