I welded up my PHB mounts yesterday, I thought I would share....I'll post better pics with the bar attached when the new one (don't ask) shows up in a few days.

axle mount (http://www.onrails.us/images/rearpanhardaxle.JPG)

frame mount (http://www.onrails.us/images/rearpanhardframe.JPG)

VERY COOL!!! Is that the start of your three link you have talk about?

Ooooooohhhh! Aaaaaaaaaahhhhh! :)

Nice shocks too :)

I presume that they lay over like that when the rear end is lowered? I note that your coils look much closer together than mine do. So I guess you figured out some rear springs to switch to?

cool! that area is a bitch to weld in, is it not!?! the frame mount Looks somewhat familar from when I installed my HTH kit, I remember it being a royal pain to get to with the welding gun, plus half of it is vertical or inverted.

Yeah Steve, that's what they look like at 5" of drop. :D
I need to do some relocating of the upper mount...it's on the list.

A bitch to weld??? Yeah, it sucked. Penetration is great but appearance sucks. I wound up making 3 passes on the frame mount just to make sure it stays there.

BTW, for those interested I'll have seat of the pants results in a week and actual track numbers with and without PHB by the end of the month.

I'm confused... what do you need a panhard bar for in a C4L setup??? Won't it bind against the uppers? Seems redundant to have a panhard bar :confused:

(I'm assuming you won't have the 3-link done within a week :) )

I'm confused... what do you need a panhard bar for in a C4L setup??? Won't it bind against the uppers? Seems redundant to have a panhard bar :confused:

(I'm assuming you won't have the 3-link done within a week :) )
The panhard bar determines the roll center height. Since the factory C4L configuration has a RRCH of between 20-26" and the PHB as I have installed it has a RRCH of 11" that is over a foot of difference. :eek: Moving roll centers has an enormous affect on how the vehicle handles (which the track results will confirm). This is why the aftermarket spends thousands of dollars on R&D to develop products for the front (spindles) that will raise the roll center. Moving the rear roll center is not so easy, especially in a weekend end bolt-on package so it is usually left to fabrication shops.

Will the upper links and the PHB fight for control of the roll center...to an extent but only after quite a bit of travel which I do not have. With the spring rate/ride height/shock combo I run the overall axle travel is limited to a couple inches either side of neutral; not enough to cause a conflict between the two.

I would not worry about the C4L and PHB fighting each other in suspension travel at all. After all that is supposed to be vertical and your PHB is long enough that it will not diverge very much from vertical.

I would be concerned about the battle during body roll. In this case you are asking the C4L to move sideways proportional to body roll and lever arm from C4L RC to PHB RC. Can you say "bind"? Knew you could ;-)

Still the lower RC should be easy to feel and an improvement. You will need to increase rear roll stiffness to rebalance with the lower RC though. Got plans for that change in the next week too?

Increased rear roll stiffness....can you say 175 lbs springs? Thought you could :D

Actually as I think about it... you will have lots of roll stiffness due to the resistance of the C4L to move laterally with body roll.

Are you going to run the PHB with the Edelbrock uppers or are you swapping back to stock rubber bushed uppers? I would think the rubber bushed uppers would work better by providing enough give for the range of body roll you need. Presuming that you have limited body roll in other ways (like springs and AR bars).

I would expect your improved UCAs to work with the PHB as a set of lateral parallel links. Both providing total lateral axle location against the other. Probably an effective RC in between the two.

I think you may have strange affects, especially in light of recent 1/8" inch comments. But we are a bit into the theory zone so I'm curious to see what really happens.

We'll see very shortly....stay tuned

Dennis where are you going to get lap times? have you raced thier before? If so what were the times and what are your perdictions on the new set up?

Going to BuRP, haven't been before with this car. I will run half the day with the bar and half the without so it will be very scientific. Same track, same day, same tires, same conditions, same driver, etc....

No predictions, we'll just have to see what happens, I'm hoping for a noticeable improvement. I'll post a "best of lap times" with the other cars and the mods just for comparisons as well.


BuRP-Buttonwillow Raceway Park in Buttonwillow, CA. It's an hour north of Los Angeles.

That is a sweet track!! Looks ideal testing. http://www.buttonwillowraceway.com/ if that is the place. You can test all aspects of your car there. CA must be the motorsports capital. I live in the wrong state.

good luck, are you going to have someone else drive the car, are you going to risk it and pilot it yourself? What did you do when going over the welds with another pass? Can't wait to see it in action! First time on the track! should be fun, I'll probably be in a porsche, lets you see beat that!

Yes, it's a very nice track. We actually have 6 nice tracks within about 3 hours of here. Buttonwillow, Willows, Thunderhill, Cal Speedway, Infineon, and Laguna seca. All great road courses. C'mon out, I have 2 harness'. :D

Don't tempt me, last year I went CA and played in the dunes in Glamis.

Dennis, are they allowing ride-a-longs?

I beleive so...Katz was coming out without his car.I would be pretty boring to drive 20 hours and sit and watch.

are you going to have someone else drive the car, are you going to risk it and pilot it yourself?

BURN!!! :D (gotta admit, that's funny! :) )

This is one thing about my project. I wanna race it, but I don't know if I'll have the cajones to push it through a turn after spending 4 years building it. :eek:

good luck, are you going to have someone else drive the car, are you going to risk it and pilot it yourself? What did you do when going over the welds with another pass? Can't wait to see it in action! First time on the track! should be fun, I'll probably be in a porsche, lets you see beat that!
Missed this post somehow...coming from a guy who doesn't even have a car on the road...start slinging it when yours actually drives. Or bettrer yet runs a faster lap time than me.

Not sure I understand the weld question.


This is one thing about my project. I wanna race it, but I don't know if I'll have the cajones to push it through a turn after spending 4 years building it. :eek:
What's the point in the build if you don't have some fun with it afterwards?

Yes, it's a very nice track. We actually have 6 nice tracks within about 3 hours of here. Buttonwillow, Willows, Thunderhill, Cal Speedway, Infineon, and Laguna seca. All great road courses. C'mon out, I have 2 harness'. :D
You Cali guys can really get to someone :D

Very nice work. What spring were you running before the 175s? and are you changes sway bars?

Thanks,

I was running 150's previously, I may go back to them. I liked the ride height better before. No rear bar and I just picked up a 15/16" for the front today, I still need to see if it will bolt up. Steering linkage has been an issue thus far.


Ok, I got ambitious tonight and spent some time figuring out the dang sta-bar situation. Wound at the hardware store for some steel tubing to make my own spacers. I got it all hooked up and went for a ride....oversteer city. I have LOTS of work to do in the rear now. Corners that I used to roll right through I now slide right through. Fun but not the fast way around. Here is a pic (http://www.onrails.us/images/stabar0001.JPG) of the link and spacer....oh wait I have polyurethane (http://www.onrails.us/images/stabar0003.JPG) bushings now. LOL

Lemme guess: you are still running the Edelbrock UCAs?

Why don't you try the stock rubber bushed UCAs and see if that oversteer goes away. That would confirm my theory about the competing RCs.

Lemme guess: you are still running the Edelbrock UCAs?

Why don't you try the stock rubber bushed UCAs and see if that oversteer goes away. That would confirm my theory about the competing RCs.
I haven't bolted the PHB up yet so thats not it. Just the fact that I have increased front roll stiffness so much now that ass end is loose, time for new springs.....again.

what was that post about then, if the PHB isn't done??? a little confusing? what suddenly made you have oversteer then?

cody, your car is so f 'n sweet!! I hate you so much :)

what was that post about then, if the PHB isn't done??? a little confusing? what suddenly made you have oversteer then?Read the posts meatball. Up 5 posts I explained that I had installed a front bar in response to 93Polo.

I have to admit that I am not exactly sure what setup you are on now myself...

You talked about goibng to a 15/16" front bar but not what you ran previously, so this is a smaller bar than you were running?

So if I am following along, you are trying to achieve roll control through higher rate springs with smaller bars, rather than the more typical softer spring and bigger bar?

Or were you reducing front lateral weight transfer through the smaller bar in anticipation of the lower RRC reduction to lateral weight transfer from weight jacking?

My apologies...I thought most had been following my saga and knew that I have been without any bars front or rear since the beginning of the year. I happened to meet up with a freind who had a 15/16 bar for me to try, I already knew the 1.125 bar I have in the garage was going to be too much.

Partly my fault for letting this hijack get off on a tangent.

You are correct Steve. I don't subscribe to the soft spring/big bar theroy, hence the 150% increase in front rate and 40% in the rear.

Not anticipating any weight jacking effects form the lower RRC, we'll have to see though.

Good info. As you can prolly tell I lurk more than I post ;) I've been lurking Pro-Touring longer than I've been here.

oh, well you confused me, this post was about installing a panhard bar, and then you said you took it out for a drive and had huge oversteer? so i figured your phb did it? sorry "Meatball" not everyone is following along your bumpy ride of suspension engifeering. So are you going to take the swaybar back off? and was the bar on the front or rear, i am taking it the front?

I thought I had been trying to follow along Dennis...

I am still feeling a little slow though. What I think I have read does not quite make sense, so I must have missed something or am making a bad assumption. You went from no bars to a bar on the front, and you went from balanced to significant oversteer?

oh, well you confused me, this post was about installing a panhard bar, and then you said you took it out for a drive and had huge oversteer? so i figured your phb did it? Until Lamar hi-jacked it(It's OK Lamar :D )

So are you going to take the sway bar back off? and was the bar on the front or rear, i am taking it the front?The bar I added yesterday was to the front, no I am not taking it off. Premature judgment on my part. I do not have an over steer condition, (it's an extremely sensitive to throttle rear). I just have to re-learn how to drive it now.

I am still feeling a little slow though. What I think I have read does not quite make sense, so I must have missed something or am making a bad assumption. You went from no bars to a bar on the front, and you went from balanced to significant over steer? I went from no bars and a slight push condition to a front bar only and a much better balanced car with incredible throttle steer....I like it.

I went form no bars and a slight push condition to a front bar only and a much better balanced car with incredible throttle steer....I like it.


*A hint of jealousy comes over him as he reads this statement*

Mmmm, throttle steer. Acceleratorial bliss.

So, how much would it take to get you to do the same to my car?

if you buy the bondo..he will come! Dennis i think the seat of your pants expirementing isn't working for you too good. So when you are going to get that PHB on, and what are your expectations/changes?

I went from no bars and a slight push condition to a front bar only and a much better balanced car with incredible throttle steer....I like it.
Thanks for the patience Dennis, I think I'm catching up here finally :)

Do you have any explanation why your results are backwards of all generally accepted practice? I mean you push, suggesting a bit more weight transfer in the front than the rear. You add a front bar thereby adding even more weight transfer in the front. Should push like a pig. I doubt you have significant body lean differences without/with the bar. Why is the front now sticking?

Actually Steve, it had significantly more body roll than I was aware of. I had the opportunity to do a little cornering while a friend was in front of me ...he said it rolled quite a bit more than he would have expected for those springs.

I suspect the push, or what the driver perceived as such was a result said roll. The bar eliminated the roll and gave the car a much more balanced feel. I also suspect the PHB will add to the balanced feel as it will give the illusion of the back being much lower. How will actually turn when pushed to the limits...I don't know yet.

What does your camber do with body roll? Your tire/wheel combo would not tolerate camber errors well. Could you be keeping the camber more in control by limitting body roll and thus getting more traction in the front?

I went from rubber bushed C4L to IRS in the Mustang Bullitt (or laterally flexy to not flexy). There are two major things I noticed:

First the car is much groovier in the turns, meaning you can put it on a line and it stays there without constant correction. This is very cool and by itself made the conversion well worth the effort and $$$. You may not notice this so much since you are coming from a hard bushing setup.

Second is the change to RRC was balanced by an increase in rear anti-roll to maintain balance. I suspect I corner flatter, but cannot truly say I notice that as a difference. I already had stiffer springs (600 front/250 rear versus a generic GT with 450 front/210 rear) and a lower ride height so body roll has never been much. But I do feel the suspension working more, the body is displaced not just by the front but also by the back as it goes over the bumps. On some back roads it can get just a bit busy as things rock and roll side to side.

I have not really had the car anywhere that I can push it to and beyond it's limits. No track time. But I've driven highway 16 through the Rumsey Canyon and highway 20 a fair amount. In that environment it is very smooth and confidence inspiring and the car feels as though it's limits are higher than my limits. There is one particular hairpin on 20 that, while marked 35, I've taken at 55-60 without the car feeling like it is working too hard. I would attribute this solid feel to little body roll and the lower RRC.

What does your camber do with body roll? Your tire/wheel combo would not tolerate camber errors well. Could you be keeping the camber more in control by limitting body roll and thus getting more traction in the front?Interseting thought, that may be it.
On some back roads it can get just a bit busy as things rock and roll side to side. I've been noticing the same effect just since installing the front bar.

...I've been noticing the same effect just since installing the front bar.
Trust me, you have not seen anything yet ;-)

Try the one sided speed bump test.

The front goes over and the car body tilts to one side and comes back down.

The back goes over and the car body tilts equivalently to one side and comes back down (this is with the balanced IRS setup).

On original C4L with front and rear bars the body stayed level when the back went over the speed bump, pretty much no tilt at all. With no tilt from the rear, the rock and roll frequency and displacements were half what they are now. This is close to where you are right now. Lower the RRC with the PHB and re-balance the rear weight transfer with a bar and you will start to really see what I am talking about :)

BTW there are only a few roads that are bothersome this way and the effect diminishes with speed. So if it's rockin and rollin you just aren't going fast enough yet!

Our recent discussion regarding tuning weight transfer through spring rates has caused me to think a bit more about spring rates and their affects. As you have been trying different spring rates, have you done the natural frequency calcs and tried to sync them up? I am starting to figure out that there is a lot of room for improvement in ride and handling on the El Camino here. Basically the original rear spring rates are compromised stiffer, and thus to a higher NF, for load hauling. Makes for a bouncy feeling ride that I have always noticed but just figured out why. (Yeah I know, I'm slow :) but in my defense there have been other higher priority mechanical issues on my '68).

I went through the calcs when I did my IRS conversion and switched from the longer/softer '99 IRS springs to the shorter/stiffer '03 IRS springs based on the results. With my stiffer fronts the '03 springs matched up better and I have been very happy with the result. I'll never know how far off the '99 springs might have been though since I never ran them.

This experience has suggested to me that, for me at least, it is best to tune springs to a NF number first. Then tune desired additional roll control (and I will likely always want more than the springs give alone) second using just the bars. I think the NF is the best predictor of what to expect with stiffer/softer springs.

But my $$$ says you already know all this :)

No Steve, I haven't run through the natural frequency numbers yet. I wanted to wait and get the ride height finalized and build the new front control arms first (they are longer and will change the lever action ratio).

Back to the panhard bar.... ;)

Actually a rear roll-center question: Where can I find a diagram to figure rear roll center with the 4-link?

Thanks

K

The rear roll center height when using a converging four link is determined by several sets of imaginary lines that will intersect at the the centerline of the axle. I'll do my best to explain;

From the top looking down you need to to find the point where the two upper arms would meet and the lower arms would meet if they were extended, then in side view plot the lower arm point in-line with the lower control arm to determine the height, then do the same for the upper links, next draw a line to connect those 2 points and measure up form the ground at the point that the final line intersects with the axle centerline.

Until Lamar hi-jacked it(It's OK Lamar :D )

Geesh next time I'll just ask if you're going to use poly bushings in the PHB. Just kidding... Just kidding... ;)

I would think that the PHB would keep things more predictable as the rear will remain centered. I know changing from a stamped steel PHG in my 94 Z28 to a heim jointed LG unit did.

Maybr It has been posted but are you using more parts from circle track cars or is this a kit for the a-body?

The bar and axle bracket are Speedway parts. The frame bracket is my own design.

The rear roll center height when using a converging four link is determined by several sets of imaginary lines that will intersect at the the centerline of the axle. I'll do my best to explain;

From the top looking down you need to to find the point where the two upper arms would meet and the lower arms would meet if they were extended, then in side view plot the lower arm point in-line with the lower control arm to determine the height, then do the same for the upper links, next draw a line to connect those 2 points and measure up form the ground at the point that the final line intersects with the axle centerline.
Thanks :thumbsup:

K

OK, tubing showed up today and I just couldn't wait to get it installed. Driving impressions; the lowered roll center makes the car feel much lower. Just driving in a straight line down the street it almost feels like it sits lower in the rear. Hard cornering is much more secure feeling, the car just feels planted firmly all the way through the corner. A pleasant side effect is that it is also quieter in the back...go figure. I add two more rod ends and it makes less noise. I attribute that to removing what little lateral movement was present before therefore tightening up the forward links. I can't wait for next month....

I wonder if I shouldn't remove the bar for the next month to prevent any bias from the results. If I run for a month with the bar and then remove it at the track I will be unaccustomed to the feel and might not drive as well. Then the addition of the bar would actually result in a biased report toward no bar and the increase in lap time would be all the more evidence of the improvement.


Don't ask why it's not level, it will be tommorrow. Note to self, don't use aircraft locking hardware on fasteners you want to readily be able to remove.
http://onrails.us/panhard0003.JPG

Wahoo!

Methinks that one bracket needs to be -l-o-n-g-e-r- so the bar can be not only level but lower.

Now how long until you have the C4L uppers converted into the 3rd link?

Now how long until you have the C4L uppers converted into the 3rd link?
Who knows....maybe soon, maybe not.

Ah yes, the honest answer of a family man :)
I can relate, Elky projects always seem to take longer on the calendar than I think or expect.

OK, the long awaited update....

I just got back from BuRP and had a blast, the car is VERY flat. Note to self, worn out street tires do not stick on 150* tracks after running all day (the video will explain it). I did not get to run the test evaluation I had hoped, time deadlines and work schedules conflicted and I didn’t any of the things done I had wanted but didn’t want to miss the chance to get the car on the track. I haven’t even aligned it since the new front springs were installed; I know for a fact the front camber is at least zero if not positive.

My impression of the chassis, it is very flat. I had a buddy follow me a while and he said it rolls very little. No push whatsoever, I tried like hell but it goes where you point it….to a point, then it just comes around (there’s that video again). Towards the end of the day the track got very slick and my tires started to go away very quickly, within 2 or 3 laps. The last clean corner you can the engine rev as the tires are just spinning on corner exit, then the next corner they decided they had enough for the day.

The lowered RRCH is very apparent during cornering; it “feels” very low and is very smooth. Almost too easy to get comfortable with. I got passed by a brand new 911, but not without a fight and he didn’t walk away if that’s any indication of the cars ability. I had trouble with gearing. Running the Tremec and a 3.08 made for a very difficult acceleration down the front stretch. You come out of the esses into a tight left hander, 2nd is way too low and 3rd lugs the motor. Looks like it’s time for a gear swap, maybe 3.55’s.

Thanks for following my adventure, I’ll try and get the small stuff sorted out before I head out again, I’m setting the PHB up with hitch pins for easy removal next time, so maybe we’ll get that evaluation after all.

Bryce....I did the math, I was hitting about 125MPH on the back stretch, not enough track to use 5th.

Dennis, sounds like you had some fun.. Do you have any testing data to share with us?

125? i kinda doubt you were going that fast, everyone else was doing like 115, the porsche did "walk" right past you, but in your defense it was on a straight away, you either need a heavier foot or different gearing. I believe it was a twin turbo porsche. Glad you finally got out there and raced, even if you ended up with a face full of dirt!!

the porsche did "walk" right past you, but in your defense it was on a straight away, you either need a heavier foot or different gearing. I believe it was a twin turbo porsche.
On the back stretch??? I had to wave him by, we were side by side for most of the straight.

125 was based on 4800RPM, 26" tire, 3.08 gears and 1.00:1 trans ratio. If others were only claiming 115MPH, then maybe it was.