[Mistamike17]

Gentlemen, I've run upon a dilemma with my setup. As I type this, my car sits in the parking lot on KSport Kontrol Pro coilovers. They use a progressive rear rate and a linear front spring. Both rates are near 9 kg/mm (~500 lb/in). As such, I've had difficulty getting my car to rotate, and I'm incurring massive corner exit understeer.

To compliment the low rear rate, I'm running a Hotchkis competition rear bar (27mm, 202% stiffer than stock). My hope is that a stiff rear will help keep the inside front planted while throttling on through the turns. Yes, I'm aware that a large amount of corner exit understeer can be blamed on driving. I'll admit that I have a heavy foot, but in a class where I must compete against the nimblest of cars (STS), I have to exercise this car's advantages to the fullest. Hence, the understeer. As a direct comparison to the lighter, lower horsepower chassis of the EF Civic Si, I have a much heavier weight and nearly double the wheel horsepower. At this point, you should get what I'm saying. I have to make up ground somewhere and the horsepower number is where I believe it can be done, all other things equal (driving, tires, etc.).

That is problem number one. Problem number two also lies with the coilovers. In order to achieve negative camber, we have an inherent problem with running out of tie rod adjustment for the toe in caused by negative camber. This problem is especially terrible on the KSport coilovers. I'm guessing the steering arm is placed too far away from the center of the car, and even with -1.5* of camber, I'm running out of arm adjustment with them threaded fully in.

Now, my question to ClubRSX's finest, is what can I do to compensate for this. I've already realized that my weakest link in the competition setup is the coilover set. From here, where do I go? I run STS, so any shock combination is fair game. I've had Konis and Ground Controls on my car along with Hotchkis camber plates, but with the plates, in order to achieve any lowering at all, you have to shorten the stroke to nearly nil in the front.

Help me out, guys. I'm looking for around -2.25* of front camber and a small amount of toe out (probably 1/16* on each side) in the front. The rear rate needs to be up there so that I don't have to utilize this rear competition bar by itself (I have the front bar just sitting in my garage). I want to be able to plant what I have coming out of the turns, guys. So, help me out here with a new setup.

 

[justjim]

Sounds like you are on the right track.
Soften up the front spring rate
Soften up the front anti-roll bar rate
Possibly stiffen the rear spring rate
Leave the rear anti-roll rate stiff as is
1/16" toe out front
1/16" toe out rear
At least -2deg camber front
no more than -1deg camber rear
Less air pressure in rear tires (start with ~38psi front, ~33 psi rear)
Add LSD

 

[Mistamike17]

Sounds like you are on the right track.
Soften up the front spring rate
Soften up the front anti-roll bar rate
Possibly stiffen the rear spring rate
Leave the rear anti-roll rate stiff as is
1/16" toe out front **CHECK**
1/16" toe out rear **CHECK, 1/8* each side**
At least -2deg camber front
no more than -1deg camber rear
Less air pressure in rear tires (start with ~38psi front, ~33 psi rear)
Add LSD

Huh? I've always heard more in the rears, less in the front so that the fronts hook better and bring the rear around.

 

[dan_wheeler]

Sounds like you are on the right track.
Soften up the front spring rate
Soften up the front anti-roll bar rate
Possibly stiffen the rear spring rate
Leave the rear anti-roll rate stiff as is
1/16" toe out front
1/16" toe out rear
At least -2deg camber front
no more than -1deg camber rear
Less air pressure in rear tires (start with ~38psi front, ~33 psi rear)
Add LSD

=STX

Huh? I've always heard more in the rears, less in the front so that the fronts hook better and bring the rear around.

You can do it with both. In the RSX, many guys have to run higher than max recommended tire pressures to get rotation. Also, sxcessively high rear tends towards snap oversteer and some skitter. Excessively low pressures result in smoother rotation.

-Dan!!

 

[Zzyzx]

Step 1 = unbolt your front anti-roll bar.

step 2 = take the car back out on track and re-evaluate it.

 

[P40vic]

My $.02. You gotta have lots of front camber, and you've already identified the tie rod limitations for that. IMO for the RSX & Civic you have to get some/all of your camber at the knuckle via slot(s), undersize bolts or camber bolts, etc. Then you can fine tune the camber and get some caster via the plates. And this technique doesn't hose up the scrub radius like getting camber at the top via the plate. As far as the GC/Koni setup, it could work but I really think you need to shorten the shock to get the travel required, which is not cheap.

Rear spring rate vs front rate is definitely a problem too. The excessive toe and camber change of the rear (vs front) suspension calls for lots of rear spring. 500/500 is pretty strange. Seems counterproductive to lower your front rate but if you can't tolerate something like 1000lb/in springs for the rear, you'll probably have to lower the front as well as raise the rear rate to get a reasonable balance. For your open diff, I would think you need to get the rear tire about 1" up in the air mid-corner (once you have your front camber & grip optimized) to be able to put some power down on exit.

A controversial but potentially effective trick is to alter your corner balance to get near equal weight on the front tires and unequal weight on the rear. Used by nats winners for both prosolo and solo, it might help utilize the power advantage you have. Any small right/left corner imbalance could be corrected via assymetric rear camber or tire pressure. This trick won't help in mid-corner when a rear wheel is in the air, but it will help on launches and when the rear tire sets back down on corner exit.

I'm sure you'll get some more good suggetions from other STS guys.

 

[justjim]

Huh? I've always heard more in the rears, less in the front so that the fronts hook better and bring the rear around.

Dan Wheeler sums it up pretty well. The main problem with your understanding of tire air pressures is that you think running lower pressures up front will make the front stick better. Every tire has an optimum tire pressure for a given weight it has to support. A traction vs air pressure graph would look like a bell curve with maximum traction at the top of the bell curve falling off on either side as pressures rise or fall. However the bell curve is lop sided falling off faster on the high pressure side, so as Dan described higher pressures tend to result in a more touchy loss of traction and snap oversteer.

Find out through experimentation what the optimum tire pressure is for the front and leave it alone when you find it. Then you can reduce the rear within some reasonable range to help the rear come around.

Sorry about the LSD comment, I'm not really up on class requirements.

 

[Zzyzx]

Straight spring rates are not going to give you very good information, and Wheel rates can be very miss-leading if the front and rear are carrying signifigantly different amounts of weight.

we need to calculate out his suspension frequency to get a decent picture on how his chosen springs are trying to make the car handle.

so with a estimate on corner weights based on FR bias and total weight of the car...

A 500 LB spring on the nose will yeald about 2.3 hz and 500 Lb spring on the rear will yeald about 1.9hz.

and there's his problem.

If he wants both the front & rear to have about the same frequency then the rear spring would have to be about 750 lbs/inch. 1000 in the rear, would give about 2.7hz and then he'd be dealing with a potential oversteer machine.

So, if changing the spring rates isn't possible or desirable, the next proper tuning tool he's got for adjusting balance is his anti-roll bars. And since he's already running a fairly large front bar, then decreasing or removing his front bar should be a very high priority. and he's going to have to readdress his alignment issues to make best use of the softer nose.

 

[Mistamike17]

=STX



You can do it with both. In the RSX, many guys have to run higher than max recommended tire pressures to get rotation. Also, sxcessively high rear tends towards snap oversteer and some skitter. Excessively low pressures result in smoother rotation.

-Dan!!

Cool. I'll keep that in mind. I had some good luck this past weekend on my buddy's RE01Rs running like 27 or 28 psi in the front and around 38 in the rear. Now that I'm back on my 'kooks, it may be a different story for this weekend.

Step 1 = unbolt your front anti-roll bar.

step 2 = take the car back out on track and re-evaluate it.

I was really thinking about doing this, and I've read the several times that you've suggested it, but I'm worried that the 27mm bar in the rear will be too much for no front bar. How do you think it will behave with no front and a 27mm rear bar?

My $.02. You gotta have lots of front camber, and you've already identified the tie rod limitations for that. IMO for the RSX & Civic you have to get some/all of your camber at the knuckle via slot(s), undersize bolts or camber bolts, etc. Then you can fine tune the camber and get some caster via the plates. And this technique doesn't hose up the scrub radius like getting camber at the top via the plate. As far as the GC/Koni setup, it could work but I really think you need to shorten the shock to get the travel required, which is not cheap.

Rear spring rate vs front rate is definitely a problem too. The excessive toe and camber change of the rear (vs front) suspension calls for lots of rear spring. 500/500 is pretty strange. Seems counterproductive to lower your front rate but if you can't tolerate something like 1000lb/in springs for the rear, you'll probably have to lower the front as well as raise the rear rate to get a reasonable balance. For your open diff, I would think you need to get the rear tire about 1" up in the air mid-corner (once you have your front camber & grip optimized) to be able to put some power down on exit.

A controversial but potentially effective trick is to alter your corner balance to get near equal weight on the front tires and unequal weight on the rear. Used by nats winners for both prosolo and solo, it might help utilize the power advantage you have. Any small right/left corner imbalance could be corrected via assymetric rear camber or tire pressure. This trick won't help in mid-corner when a rear wheel is in the air, but it will help on launches and when the rear tire sets back down on corner exit.

I'm sure you'll get some more good suggetions from other STS guys.

Wow, great info.

Do you have any other suggested reading for the last thing you mentioned there? I didn't follow it very well. You corner balance to setup the car equal from left to right in the front and unequal from left to right in the rear? Is that right? You basically unbalance the rear of the car so it gets crazy loose?

Also, maybe I understand it wrong, but won't any camber gained at the knuckle with camber bolts also cause toe problems that I already can't correct? Maybe there's a difference that I'm not seeing from altering the top and the bottom of the strut assembly.

 

[Mistamike17]

Straight spring rates are not going to give you very good information, and Wheel rates can be very miss-leading if the front and rear are carrying signifigantly different amounts of weight.

we need to calculate out his suspension frequency to get a decent picture on how his chosen springs are trying to make the car handle.

so with a estimate on corner weights based on FR bias and total weight of the car...

A 500 LB spring on the nose will yeald about 2.3 hz and 500 Lb spring on the rear will yeald about 1.9hz.

and there's his problem.

If he wants both the front & rear to have about the same frequency then the rear spring would have to be about 750 lbs/inch. 1000 in the rear, would give about 2.7hz and then he'd be dealing with a potential oversteer machine.

So, if changing the spring rates isn't possible or desirable, the next proper tuning tool he's got for adjusting balance is his anti-roll bars. And since he's already running a fairly large front bar, then decreasing or removing his front bar should be a very high priority. and he's going to have to readdress his alignment issues to make best use of the softer nose.

<3, Awesome info man. Link me to those formulas so I can have them for the future, please.

Keep in mind that the rear spring is slightly progressive. I say 500 lbs all the way around, but in reality, it does increase a bit with load in the rear, however I cannot seem to get an exact number from KSport on it. I would may assume around a 550 or so rear with a bit of load on it. I'll see if I can probe more with them to get that exact rate of increase.

I see what you're saying here with tuning with the bars. I can go to the stiff setting in the rear also, but it's only 18% more stiff, and I don't see it really making a big difference from there.

 

[P40vic]

No, you won't find "creative" corner balance ideas discussed much. Basically you just corner balance to get the fronts as close to equal as possible, and put a greater imbalance across the rears. Will it make the car crazy loose? No. Is it perfect? No, but you have an open diff and lots of power and a nose heavy car. It's about finding the best compromise for your situation.

On the camber, it doesn't take much change in angle at the knuckle to get lots of camber, so it doesn't eat up much of the tie rod threads. Takes lots of motion to get camber from the plate, which uses more tie rod up. I had -2.7* on my civic with just a lower bolt change, and still had lots of tie rod to adjust toe in/out.

 

[Zzyzx]

In competition, even a 1% change in will be noticeable.

 

[Mistamike17]

No, you won't find "creative" corner balance ideas discussed much. Basically you just corner balance to get the fronts as close to equal as possible, and put a greater imbalance across the rears. Will it make the car crazy loose? No. Is it perfect? No, but you have an open diff and lots of power and a nose heavy car. It's about finding the best compromise for your situation.

On the camber, it doesn't take much change in angle at the knuckle to get lots of camber, so it doesn't eat up much of the tie rod threads. Takes lots of motion to get camber from the plate, which uses more tie rod up. I had -2.7* on my civic with just a lower bolt change, and still had lots of tie rod to adjust toe in/out.

Awesome. I may have to stop by my dad's house tomorrow and see about a little front corner balancing. I believe he has some scales laying around in his garage. I'm sure the rears are already way off, though.

In competition, even a 1% change in will be noticeable.

With that said, I guess I'll try the stiffer settings on the rear bar this weekend and leave the front bar on. If the car still doesn't behave how I want it to, I'll pull off the front bar next weekend and throw my rear ITR bar back on or something.

 

[P40vic]

BTW, the only coilover set that gets camber at the knuckle that I'm aware of is KW. IIRC the RSX that SCC mag set up worked this way, and they also increased the caster with the top plate, not sure if it was a KW plate or not.

 

[Zzyzx]

With that said, I guess I'll try the stiffer settings on the rear bar this weekend and leave the front bar on. If the car still doesn't behave how I want it to, I'll pull off the front bar next weekend and throw my rear ITR bar back on or something.

Remember, anti-roll bars increase lateral load transfered in a turn. Meaning they reduce the maximum potential traction that end can make. So stiffening the rear bar is going to mess with your oversteer/understeer balance, where as softening the nose will effect both the oversteer/understeer balance of the car as well as reduce inside wheel spin on corner exits.

 

[P40vic]

Awesome. I may have to stop by my dad's house tomorrow and see about a little front corner balancing. I believe he has some scales laying around in his garage. I'm sure the rears are already way off, though.



With that said, I guess I'll try the stiffer settings on the rear bar this weekend and leave the front bar on. If the car still doesn't behave how I want it to, I'll pull off the front bar next weekend and throw my rear ITR bar back on or something.

I wouldn't go too crazy with the corner balance thing, the spring/bar/camber stuff is going to be far more important.

 

[Mistamike17]

BTW, the only coilover set that gets camber at the knuckle that I'm aware of is KW. IIRC the RSX that SCC mag set up worked this way, and they also increased the caster with the top plate, not sure if it was a KW plate or not.

Interesting. Any more details on this?

Edit, nvm, I found it.

 

[P40vic]

Not sure if they have all their project car articles online at sportcompactcarweb.com, they built up a turbo RSX and the suspension article was quite good, summed up a lot of the problems we've all run into with the RSX/Civic. I don't have a copy of it but maybe someone else on the forum does?

 

[Mistamike17]

Front bar is disconnected for the weekend. I forsee an RSX pointed backwards on the course a time or two.

 

[jmercado567]

You wont be pointing backwards... your rear spring rate wont allow it unless you make driving mistakes.

850 is a minimum rear spring. front at least 650. With Linear springs.

as for the tie rods, have a smart mechanic drill the other side of the strut steering arm so that you can bolt the tie rod on the other side.

very safew, cheap and almost free if you do it. You will regain lots of steering response and you will not have to turn the wheel as much during quick turns such as slaloms.

Remove the front bar as many experienced men have expressed. Sounds like you have done...

By the way... driving mistakes will cause understeer.