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Author Topic:   Trick in 06, redux !
Kromulous
Dirt Forum Champ
Total posts: 856
posted November 10, 2005 08:33 AM  
Short panhard bars, behind the rear end.

Hydraulic pull bars, or a combo spring / oil deal.


The more i look at the rear mounted panhard bar i like it. It should tighten a car as you get on the gas, the panhard bar will gain angle as the rear end rotates.

This would be particularly good with a 4-2 set up i would think, and a progressive pull bar spring.

The rear mounted bar would help in a couple areas. One, you could run a little less intial angle in it and that would help with lossening entry, and you wouldnt have to run a ton of wedge to get it to turn off throttle.

Two, it gains angle as you apply the gas, already been over that.

Three, on the back of the housing if mounted right, there would be less swing of the bracket, since its closer to the CL of the axles. Out in front of the pinion support your really far away from the axle cl, so a couple inches of pull bar travel and the height of that pinion side pivot point is all over the place. On the back side it would be alot less.

Anyone currently running a short panhard bar behind?

Thats my thoughts.


Krom.

JT54
Dirt Maniac

Total posts: 184
posted November 10, 2005 09:02 AM  
been thinking along the same lines ,but not enough time to test it....anyone have practicle knowledge of this??

psycho47
Dirt Full Roller

Total posts: 63
posted November 10, 2005 09:12 AM  
I was wondering the same. I am converting my 2-link to a 4-2 and have the provisions to mount front or rear panhard. The rear mounted panhard loosens you under braking, correct? Could you get enough adjustment with preloading the brake biscuit on a pullbar a little more to control the upword movement of the panhard? When these cars run the chained torque arm there is no cushioning of the braking forces at all so I would think it would be ok. Am I wrong?

andykmod
Dirt Freak

Total posts: 379
posted November 10, 2005 01:15 PM  
I ran a 19in bar behind and loved it with a 4-z car. Yes it does tight'n exit and loosens entry.

[This message has been edited by andykmod (edited November 10, 2005).]

Kromulous
Dirt Forum Champ
Total posts: 856
posted November 10, 2005 01:53 PM  
This would be ideal for a swing arm / z link car, i cant get ours loose enough on entry.

Better than a front mounted bar Andy or just different?

It seems to me it would be better, becasue usually you are fighting just that. Pyscho i think your on the right track.

Krom.

Kromulous
Dirt Forum Champ
Total posts: 856
posted November 10, 2005 01:55 PM  
Another thing i think will be big, or bigger in 06, is front roll centers, and adjusting them from track to track.

I believe this is the key to Pierce's success in 05.

Krom.

leapinlizard
Dirt Freak

Total posts: 436
posted November 10, 2005 02:07 PM  
Short bar behind?

My car is ten years old and runs this. In fact I don't even have adjustment o nthe rear end. Just a bracket welded to the rear end. When I first bought it it had the panhard mount on the underslung bar. Still does. Works for me too.

I never thought J-bars were a good idea.

andykmod
Dirt Freak

Total posts: 379
posted November 10, 2005 02:29 PM  
Kromulous, It took a few nights to get it dialed in with the height and angle, as for the angle we use about 1.5in of rake at the most. My car was a 4-z swing arm. At first it was so throttle tight the second you picked up the gas it pulled the front over and car was very tight in the center. We were running the short LH mount bar about 14 inches long and used that height and angle as a starting point and we are far from that now some nights it was almost level. When the rearend wraps up under throttle and the chassis is lifting, it don't take long to get some major angle. As for the entry it did free it up alot and it took the rough tracks alot better when you took all angle out and leveled it at ride height. I sold that car a few weeks ago but plan on putting the mounts on the new car.

[This message has been edited by andykmod (edited November 10, 2005).]

rpm20
Dirt Freak

Total posts: 350
posted November 11, 2005 02:54 AM  
hey krom,
i looked at andys short bar behind and liked it so much that i will use it on both cars this season.
its really simple and i made my own serrated brackets.
i can see that the closer centerline mount would cause less change on accel. than the j bar in front.
also, you know the trouble i had being tight getting in , so i think it should help that too.

happy
Dirt Forum Racer

Total posts: 83
posted November 11, 2005 05:29 AM  
Krom,

The bar behind is how the "J" car from Specialty Fab is being made and they have dominated up here in Wissota land.
Wish somebody could post you some pictures of one.

Kromulous
Dirt Forum Champ
Total posts: 856
posted November 11, 2005 06:28 AM  
Same here RPM, our car is always tight in, always. Its a constant battle really, in particularly at the big Tri oval we race at.

Happy, i thought J-Cars run these, what rear suspension do they run mainly?

I remember seeing Andy and a couple guys talking about it thru the year, the short bar behind. Seems like the answer to me. The kicker is its not new, just drug up from the past. Maybe used differently now, a combonation thing.

Anyone know any down sides to it? There has to be, usually is any way.

Less angle, better in thru the rough stuff, going in. Looser in, so i dont have to run 200lbs of LR bite and 54% wedge. Should be looser in on the gas, out at our tri oval track. I cant really see a downside right now. Unless its so tight coming out you cant clear the wall. Then i guess you can crank some more bar angle in for rear steer.

I'm excited about trying it next year. Plus the packaging should be alot better, at least on our car.

Got pics? post em please.

Krom.

happy
Dirt Forum Racer

Total posts: 83
posted November 11, 2005 08:02 AM  
Every thing I have seen is a 4-Z, but I think they will build them anyway you want. The cars that I help on are a 4-Z's also ( something like the Skyrockets ) with the shorty in front, our main track is a high banked 1\4 that gets rough at time but always slicks over. The short bar had to go due too them not going through the rough stuff too well but we sacrificed a lot of forward and side bite when we did it.
We talked about trying the bar mounted in the back on one of them next year to see how well it works.

mayhem
Dirt Roller

Total posts: 18
posted November 11, 2005 12:13 PM  
Sounds like a good idea! Just trying to picture how to make the bracket? The one thing on my mind is these new Hoosier tires!

chickenlittle
Dirt Full Roller

Total posts: 75
posted November 11, 2005 02:59 PM  
JR motorsport sells a slotted piece that you can weld onto you housing. It is designed to be used with a slotted block. You can adjust it in 1/4 inch increments. Would be great for fine tuning. I will try this set up on my new car too. I think it would make the car more consistent and easier to drive with the roll center not changing as much under dynamic loading. I will have to go with 19+ inch bar to be IMCA legal though. Still looking forward to trying it out.

andykmod
Dirt Freak

Total posts: 379
posted November 13, 2005 12:42 AM  
Chickenlittle, That is the same bracket i used for mine.

JT54
Dirt Maniac

Total posts: 184
posted November 14, 2005 10:13 AM  
I know people have posted photos in the past ,but could someone please post some more ?

rpm20
Dirt Freak

Total posts: 350
posted November 14, 2005 10:39 AM  

 
heres a picture of andys that he sent me if a picture helps.

chickenlittle
Dirt Full Roller

Total posts: 75
posted November 14, 2005 04:20 PM  
Thanks for the pic. That is kind of what I had in mine. Was unsure of how far over to put it and how high to mount it. This gives me a good idea as to where to start.

wissota3x
Dirt Forum Racer

Total posts: 93
posted November 14, 2005 07:04 PM  
That picture is of my car that I posted last spring. It is an Elite chassis out of Fargo ND. It has the same panhard mount as J car. The rearend in that picture is actually out of a J car. I have installed quite a few of these surrated mounts myself and I can give you guys some pointers.The surrated pieces can be purchased at DRW in Billings MT. ( 1-800-379-9902 )The bottom of the surrated bracket should be welded about 1 inch below the bottom of the rearend housing. Jay uses 2 inch square tubing (.120 wall )on the left frame panhard mount . Make sure that the panhard itself is pointed slightly forward to the rearend when everything is in place.Most of the time when the rearend is in place in the proper location in the chassis there is 8 inchs between the back of the 3 inch housing tube and the square tube for the panhard. We weld a square washer right to the head on the 3/4 inch bolt that holds the panhard to the surrated bracket.We make it so that it just fits inside the bracket so the bolt can slide up and down but not spin.This eliminates having to put a wrench on the bolt when adjusting up and down.(You will only need one wrench ).Hope this helps !!

[This message has been edited by wissota3x (edited November 14, 2005).]

[This message has been edited by wissota3x (edited November 14, 2005).]

andykmod
Dirt Freak

Total posts: 379
posted November 14, 2005 07:41 PM  
Yea, i got that pic off your post, mine is alittle different then that but not much. I sent it to Ron so he could get the idea on what i was doing. Sorry for the confussion guys.

wissota3x
Dirt Forum Racer

Total posts: 93
posted November 15, 2005 07:38 AM  
Andykmod,
Could you post the other pic that shows the top looking down. I tried but failed twice. Thanks!

Kromulous
Dirt Forum Champ
Total posts: 856
posted November 15, 2005 08:27 AM  
What about an offset rear end housing (offset to the RR) with a Whart-hog on the tube on the left side, with a panhard bar about 12" or less long.

That may be interesting.

The thing about this bracket is that i would like to see it fitted closer to the axles CL, as close as possable. That way i can run a whart-hog on the right side tube sometimes to run a long panhard behind, for big sweepy tracks.


Any other thoughts and ideas for 06?

Krom.

oldfordmod
Dirt Full Roller

Total posts: 54
posted November 15, 2005 09:32 AM  
Please let me ask you guys a couple of questions about this mount. 1) Couldn't you angle the mount top toward the right to lessen the amount of movement of the RE to the right when you raise the bar? 2) Or do you want the RE to move to the right when you move the bar up and to the left when you move down? Thanks

Kromulous
Dirt Forum Champ
Total posts: 856
posted November 15, 2005 11:11 AM  
You could, dont see why not.

As well you could cut the bracket on a radius once you figured out your length. Like a 19" for IMCA, bar length / radius.

Use a BSB radiused mount on the frame side as well, so you dont have to play with the length so much on small adjustments.

Krom.

wissota3x
Dirt Forum Racer

Total posts: 93
posted November 17, 2005 07:38 AM  
andyK,
I forgot to mention that Jay does do what your talking about,but only a little bit.
I haven't had one of his cars for 2 years but he only suggested moving the rearend side of the panhard for adjustment and leave the frame side alone. Seemed to work good at the time .

racer19x
Dirt Full Roller

Total posts: 28
posted November 17, 2005 08:55 PM  
3x, couldn't the serated mount be closer to the rear housing? It looks like it is about 2 inches behind the rear. Just thinking it would take flex out of it, and make it a little tougher.

wissota3x
Dirt Forum Racer

Total posts: 93
posted November 19, 2005 08:15 AM  
racer19x,
You could make it closer as long as the bolt can slide in and out without problems.There are alot of these cars out here with this mount and it takes a big bad crash to bend them.

GRTmod
Dirt Full Roller

Total posts: 37
posted November 23, 2005 04:59 PM  
With a two link i always liked the panhard bar in back, but i've never done anything with a four bar behind. One thing im gunna try is bringing the right rear top four bar down to the axle. Towards the end of the year i had it like that on the left and i've never had a car bite so much off the corner.*cant wait till next season*

qwikguy42
Dirt Roller

Total posts: 6
posted December 01, 2005 08:23 PM  
I run UMP so I dont have a bar rule, I am getting a new uni-mount car that I think I am going to run 4 link z link with, i am also getting a braking bar installed, cant wait to try it out. I think this panhard bar on the rear of the housing is a awesome idea, i have seen this done on old model HOT cars with long long bars, but what would happen if you put a clamp on the left rear axle tube close to the housing with a bsb radiused frame mount, and run about a 11 or 12 inch bar, i need a very short bar because i run a very tight turned 3/8 mile track.

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 02, 2005 08:04 AM  
The shorter the bar, faster reaction.

Only thing is the length will be critical because if its to short the swing may be to large.

Example, a 10" bar. Mounted level, but upon full throttle with the housing rotates 3" at the pull bar. Then the panhard bar gains 3" of rake or so, that will pull the rear end to the left, and tighten the car. So the length, due to the swing in pivot points will be critical.

Krom.

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 02, 2005 09:49 AM  
The only thing I would add to this discussion is this......

where you put the mount on the rear housing makes changes work different. We have two cars with this pan bar location. One car has a centered rear housing, the mount is welded on the back of the center section, the other car has a offset rear housing, with the mount welded onto the rear of the center section the same way....... one car has a 15 inch bar, on car has a 17 inch bar. because of the 2 inch offset in the housing...... When you locate the center of the tire contact patches if the housing mount is right of center(of the contact patches) when you raise the mount on the frame you RAISE the rear roll center........if the mount on the housing is left of the centerline of the contact patches as you raise the mount on the frame you LOWER the rear roll center....

This is very hard to explain, and I will try to put a couple dots and line for you to draw it out.....

.-----l
------l-.

draw out this line then raise the
dot on the left and draw again. you can see where this line crosses the centerline to locate the rear roll center. this example rasies roll center.


.-----l
-----.l

draw this out and connect the dots then raise the dot on the left and draw again......you will see where the line cross will be lower ......this will lower the roll center.......

so, the adjustments you make to the car may not respond the way you believe. The adjustments made to the housing side will always be the same........as you lower the mount it will lower the roll center, and as you raise the mount it will raise the roll center......

I'm just trying to help all these people wanting to run the SHORT pan bars, the location on the rear housing is VERY, VERY important......

I hope all this makes sense and is easy for people to draw out and understand.

the differance is huge, one will give you a raising roll center as the chassis rolls, the other way you will have a falling roll center.......... with the falling roll center as it rolls it becomes easier for the chassis to continueing to roll..... the other way the chassis will start to roll and as the roll center raises it gets harder to roll......and tends to limit the amount of roll.... I have found the raising roll center tends to help on heavy tracks, to help settle the chassis down, on a dry slick track the falling roll center helps by getting more side bite and allowing the chassis to get on the bars already before you are in the gas.......smooth drivers needed for this set-up, no throttle stompers.

[This message has been edited by awkwardjeff (edited December 02, 2005).]

[This message has been edited by awkwardjeff (edited December 02, 2005).]

[This message has been edited by awkwardjeff (edited December 02, 2005).]

Chad
Dirt Freak

Total posts: 276
posted December 02, 2005 10:49 AM  
I agree Awkwardjeff, you explained this very well. Many don't understand the effects of adjusting the frame side of the panhard/j-bar and miss the effects to the roll center. Same goes for your explanation on front vs. rear location of the panhard bar with the rising and lowering RC.

I would not recommend running the panhard bar behind the housing on a 4-bar car, because the suspension is very sensitive to chassis/body roll, and it requires the dropping RC to keep it working correctly, especially when running the LR spring behing the axle. That's my opinion, but interested in hearing if others have run the a panhard behind the axle on a 4-bar car.

wissota3x
Dirt Forum Racer

Total posts: 93
posted December 02, 2005 11:25 AM  
J cars typically use panhards behind.11 out of 12 top wissota cars.Florida Speedweeks champ.

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 02, 2005 11:25 AM  
According to that theory, with a centered rear end. The rear mounted panhard bar would be ideal with a 4 bar.

Reason being the the mount on the frame would be stationary, the mount on the rear end would rotate down. Lowering the RC, more roll as you apply more throttle.


awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 03, 2005 01:40 AM  
Kromulous, I assume you were replying to my post, first what I posted isn't theory, it's fact base math for locating rear roll center........I think what you aren't taking into account is the frame mount doesn't stay stationary.....the chassis rolls.....it rotates around the roll center.........so as the right rear compresses the left rear raises, this raises the frame the only thing that stays level is the rear end housing.......or at least that is suppose to stay level to keep both tires on the ground, in the shop lots of people try to figure things out, and they say this side raises, so they jack up that side of the rear end,,,,,,that would be backwards, if the chassis raises you need to jack up the chassis. to try and figure things out in the shop put some hold downs in the shop floor and tie the wheels down, just like they would be on the track then start without springs a jack under each side set at ride height, start raising and lower the jacks to see the affects.....the dynamic change in the turn is moving your roll center.

I love both our cars, both are fast, but are set-up different for a reason.

quote:
Originally posted by Kromulous:
According to that theory, with a centered rear end. The rear mounted panhard bar would be ideal with a 4 bar.

Reason being the the mount on the frame would be stationary, the mount on the rear end would rotate down. Lowering the RC, more roll as you apply more throttle.



dirtrace54
Dirt Freak

Total posts: 220
posted December 03, 2005 11:10 PM  
how would you suggest trying this on a swingarm/zlink mod. this sounds like something we would be interested in trying. could you give me some starting points. this is one area i have no knowledge is the rear mounted panhard bar.

PS. Krom gets around. Seen your replies in the 4m.net front roll center thread. really good info

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 05, 2005 08:36 AM  
Locating rear RC's static and effective would require quite abit of math. The true effective RC would have to account the spring locations, and rate. Along with many other variables.

My post above was in reference to Chad's post about 4 bar cars and rear mounted panhard bar.

Your post above said:

When you locate the center of the tire contact patches if the housing mount is right of center(of the contact patches) when you raise the mount on the frame you RAISE the rear roll center

If the mount on the housing is left of the centerline of the contact patches as you raise the mount on the frame you LOWER the rear roll center


Most cars are left of center, at least mine is. So thats where i'll base my point of view one, as well when you say left of center, i assume this is a AFT looking FWD view point.

Left of center housing, you could start with flat bar. As the chassis rolls over it would lower the RC in two ways, housing rotation and the frame mount would be rising.

Plus as the panhard bar begins to loose length as it swings thru its radius the rear end housing is going to migrate left, this should have an effect on whats happening as well.

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 05, 2005 10:21 AM  
Krom,

This is why I stopped posting for the most part, this site has gotten so big with many helpful people and things tend to be debated.......

I was going to use the words "rear roll axis" instead of roll center....and maybe I should have......

let me try and explain a few things, springs don't locate roll center, or roll axis......springs determine the AMOUNT of roll on one side of the roll axis, there are MANY things that determine the AMOUNT of roll.

also, just because you raise the frame mount doesn't LOWER your roll center or roll axis. That was my point of my orignal post.

If you draw a line up and down in the center of of your contact patches, then draw a line along your pan par........where these to lines intersect is your roll axis. If the rear housing mount is left of the vertical line you draw for your contact patches as the chassis rolls.....yes you will lower your rear roll axis as the chassis rolls. if the rear housing mount is right of vertical line which is center of contact patches as the frame mount raises in roll you will have a rasing roll axis...... try it, draw it out...........

That is the reason guys are running the short pan bars........The problem is people know it works good on a dry slick track, and they BELIEVE it's because the bar reacts faster, and gains sooooo much angle, and for other reasons.........but the truth of the matter is it's beause of a falling roll axis.

You could start with the pan bar 2 inch higher on both sides.......then just run softer springs to get the same amount of roll..........right?????? if that makes good sense to you.....then you are correct, springs locate roll center. If that doesn't make good sense, then springs only control the amount of roll .....

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 05, 2005 11:30 AM  
Debate is what makes things fun, for me anyway.

While i'm not trying to argue with you, i am trying to debate some things.

So, the way you figure rear RC, just so i got it right. Draw line, vertical, thru the center or the tire, center of contact patches, two lines one for LR and one for RR, right?

Then locate each end of the panhard bar and connect the dots. After that you loose me, continue the line on over to each line for the contact patches and find where they intersect?

Then what? take the mid point on that line, between the two contact patches?

Confused, Krom.

WPP
Dirt Freak

Total posts: 468
posted December 05, 2005 01:32 PM  
Interesting guys i think i can see whats happening here too me rear spring rate would make a big differce the way i see it you better know what happening when your on the throttle and the car rolling you could be springing you car wrong good post guys i think i will reread it again

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 07, 2005 12:41 AM  
dear confused,

Please report all abuse to a friends parents, school teacher, or other close family member.

seriously Krom, if a vertical line and a horizonal line cross, and that intersection represents something........how far do you draw the line....... my guess would be draw the line until they intersect. I think you have been reading way too many Steve Smith chassis building books. In another post you stated spring location was one factor in figuring roll center/roll axis.....why would it matter where you put your springs.??? for this debate let us azzume the roll center is dead center in the chassis, if the springs were both 2 inches from center or 4 inches of "spring base" ......what would be the differance if they were 4 feet apart, 2 feet of center on each side????? just use a stiffer spring again correct?????? and because all those Steve Smith books say we want to run as soft a spring as we can we put the spring base as wide as we can....while I agree with the last part of the statement, it has NOTHING to do with roll center/roll axis It has to do with making changes and being able to feel the changes..............

Everything you think that locates the rear roll axis is ONLY controling the amount of roll on one side of that axis, but because it's a solid axle if you stiffen the spring on the right side it will roll less but the left will raise more, unless you raise the roll center INTSTEAD of making a spring change. If you put a stiffer right rear spring in the chassis did you move the roll center/roll axis?? you must have moved it to the right because the right side will roll less?? is that what you are telling me??? Have you ever heard of a balanced set-up?? that is where the right compresses and the left side lifts the right amount without affecting each other. It is truely rotating, a unbalanced set-up is like this...too stiff a right rear spring, so the chassis starts out rotating around the axis then because the spring is too stiff it now starts to affect the left side.... or how about this example........chassis is hiking too high on the left rear, you and I are at the track and both agree.......you can make one change and one change only, what change are you going to make??? stiffen right rear? raise pan bar? if you raise the pan bar is that both ends? or which end? or maybe you are going to stiffen the right front to keep the left rear from unloading, I hear guys do that too.....

My final statement on this subject is this......you came on here looking for help, I tried to give you some EXTRA input. You are the only person who has questioned or debated anything I have posted, you want to debate this now.......that would seem like you NOW feel you have enough knowledge on the subject matter to put on a good arguement, so you have all the answers but you asked the questions........i'm sure all the knowledge you have gained over the last month or so is all correct and you now know exactly how it all works and no longer need any other outside assistance, .........

ever heard this quote? Man, when I was 19 years old I couldn't believe how stupid my father was......then when I was 24 I was surprised at how much my father had learned in 5 years........now that i'm 34 I understand how stupid I realy was in my 20's

[This message has been edited by awkwardjeff (edited December 07, 2005).]

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 07, 2005 07:12 AM  
To be perfectly honest, and trying to remain calm, i was confused on how you were drawing your lines. Thru where, the vertical lines, the line thru the panhard bar is a no brainer.

I assumed you got your info from the AFCO tech pages. So i went there and had a look at there Panhard bar tech. A vertical line from the top of your spring base, down until it intersects the panhard bar line.

As for all the other personal attacks, i dont care what you think, i was just asking questions so i could try to understnad your point of view better. No where in the above posts did i say that my opinions were the gospel.

And the thread was started about what was going to be the new trend in 2006, i was not looking for help, but rather a disscussion, which is obvously above you.

Good luck with your life, your gonna need it.

Krom.

[This message has been edited by Kromulous (edited December 07, 2005).]

[This message has been edited by Kromulous (edited December 07, 2005).]

leapinlizard
Dirt Freak

Total posts: 437
posted December 07, 2005 07:39 AM  
I wanna fight too!!


Akwardjeff, You said,


where you put the mount on the rear housing makes changes work different. We have two cars with this pan bar location. One car has a centered rear housing, the mount is welded on the back of the center section, the other car has a offset rear housing, with the mount welded onto the rear of the center section the same way....... one car has a 15 inch bar, on car has a 17 inch bar. because of the 2 inch offset in the housing...... When you locate the center of the tire contact patches if the housing mount is right of center(of the contact patches) when you raise the mount on the frame you RAISE the rear roll center........if the mount on the housing is left of the centerline of the contact patches as you raise the mount on the frame you LOWER the rear roll center....

AFCO says on the web site that if the RC is located outside the Panhard Bar mounts the raising and lowering of the panhard bar becomes opposite of the reaction when the RC is within the bar mounts. So, Wouldn't you have to decide where the RC is first before deciding what adjustment is needed?

AFCO says nothing about which side of the "center of the contact patchs" the bar is mounted too.

While I have my theory's, I'm not so attached to them I can't be more open to others idea's.


PEwaste
Dirt Full Roller

Total posts: 67
posted December 07, 2005 08:13 AM  
Roll center has nothing to do with contact patches of the tires. Krom asked a simple question, and you choose to rip on him.

An easy, not real accurate, but easy way to get in the ball park is measure your Panhard heim to heim and go to the middle. It isn't the right way but it gets you a lot closer than drawing lines here to here, up to there and down that way, across the tire to the pinion to here to there. Don't make it too hard, thats my point.

To keep it simple... Do what you know and what is best. What adjustments do you make?

If your car sits flat, doesn't get much LR "Action" as we say, to increase side bite raise the panhard on the frame. If the car gets a lot of action on the left rear, lower it on the pinion. When you make things too difficult you end up making the wrong decision in the end. You'll adjust the panhard the same front to rear reguardless of where it is placed at.

With the panhard in the rear, the effects are going to be about the same but the car will be initially tighter going in if you are r unning a spring or busciut bar because of the wrap up from the inital setting.

It's not hard, don't overthink it... but the personal attacks from awkwardjeff were uncalled for.

Kromulous
Dirt Forum Champ
Total posts: 856
posted December 07, 2005 08:40 AM  
Here is something i wanted to share as well. The thing that got me wondering about effective RC locations, was on a thread about front RC's on 4m.net.

A poster over there said if you had a 5000lb spring on the right sides, where would the RC's be? He replied the right side springs. This from a R&D guy for a major LM chassis company so i trust his opnions.

It went on to say that springs have alot of effect on RC's, not static but effective. Thus the reason some LM's run the front RC to towards the RF tire, and then run a stiffer LF spring. There trying to control the RC under movement, or dynamicly.

Same would happen with the rear suspension. You run a RC thats biased to the LR, and run a stiffer rate RR spring to bring it back more to center.

I dont know all i need to know about, but trying to learn. There isnt alot of info out there about effective, and dynamic RC locations, but i'll keep trying.

Maybe i am in left field here, and am all wrong, but i aint above admitting that. Although i will say i believe BPRC's success this year is because of better understanding this phenenoms.

Krom.

[This message has been edited by Kromulous (edited December 07, 2005).]

Greggie
Dirt Freak

Total posts: 300
posted December 07, 2005 09:25 AM  
Actually, PE Waste, tire contact patches have everything to do with roll center... That is one of the first things to locate when you find true roll center and center of gravity. You say do what works, well, what Awkward Jeff said was that raising one type of bar does the opposite of another type.

I have to adjust my car, apparently, the opposite of yours to get the same effects. I used the old center of the bar theory like you said. When, after some testing and some learning, I found that that was not what to do... Had I known the lines to draw to do it the right way, I wouldn't have had to test and spend so much time trying to find the correct way... I would have found it in the shop in the off-season and not out on the track wasting tires and fuel for top ten finishes and would have been running up front like I did after I got it figured out.

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 07, 2005 10:09 AM  
[QUOTE]Originally posted by PEwaste:
[B]Roll center has nothing to do with contact patches of the tires. Krom asked a simple question, and you choose to rip on him.

I'm soooo sorry for continueing to post on this thread. Now, I'll make a personal attack on YOU......when you start a post with such mis-information the rest of your post can't be taken serioiusly. Anything you say after that statement comes from someone that has no clue......

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 07, 2005 10:16 AM  
[QUOTE

AFCO says on the web site that if the RC is located outside the Panhard Bar mounts the raising and lowering of the panhard bar becomes opposite of the reaction when the RC is within the bar mounts. So, Wouldn't you have to decide where the RC is first before deciding what adjustment is needed?

AFCO says nothing about which side of the "center of the contact patchs" the bar is mounted too.

This is great, you and Krom go to AFCO's web-site then come here to discuss things...LOL I guess the person that wrote that agrees with me......and that was the point if the roll center is OUTSIDE the bar.. what about if the bar is located on the right side of the rear housing? then attached to the right side of the frame......the roll center is OUTSIDE THE BAR.....but does that statement still hold true?????

I guess you brought the last statement in, "THEY DON'T SAY ANYTHING ABOUT TIRE CONTACT PATCHES" how do they say to locate the rear roll center??????

awkwardjeff
Dirt Forum Champ
Total posts: 589
posted December 07, 2005 10:33 AM  
Okay Krom,

everything you have posted in this post I agree with......when I started posting on this thread you stated that spring rates, and locations help locate the rear roll center.....now you tell me the it's "THE EFFECTIVE ROLL CENTER" I think that is EXACTLY what I stated, it controls the amount of roll. because you never posted static roll center that is what I assumed we were discussing. I'm NOT doing the back stroke, everything I posted is true, and agrees with what this R&D guy stated so far. let me ask you, with a 5000 spring in the right side is that a balanced set-up? that was my point in the last few posts. there is only one roll center, and it moves, yes that is dynamic, and that can be controled with mounts and angles, the springs, spring location center of gravity are all things that control roll or have a effect on roll........my point of adding ANYTHING to this post was to show adjustment can be backward if the roll center is outside the pan bar....and I guess that is what it says at AFCO, and it seems to be true as Greg states. I was just trying to help someone like Greg save some time and frustration.

I'm sorry I don't go to the 4m/AFCO site, there was just tooooo much fighting going on there for me, I left 4 years ago and haven't been back.

quote:
Originally posted by Kromulous:
Here is something i wanted to share as well. The thing that got me wondering about effective RC locations, was on a thread about front RC's on 4m.net.

A poster over there said if you had a 5000lb spring on the right sides, where would the RC's be? He replied the right side springs. This from a R&D guy for a major LM chassis company so i trust his opnions.

It went on to say that springs have alot of effect on RC's, not static but effective. Thus the reason some LM's run the front RC to towards the RF tire, and then run a stiffer LF spring. There trying to control the RC under movement, or dynamicly.

Same would happen with the rear suspension. You run a RC thats biased to the LR, and run a stiffer rate RR spring to bring it back more to center.

I dont know all i need to know about, but trying to learn. There isnt alot of info out there about effective, and dynamic RC locations, but i'll keep trying.

Maybe i am in left field here, and am all wrong, but i aint above admitting that. Although i will say i believe BPRC's success this year is because of better understanding this phenenoms.

Krom.

[This message has been edited by Kromulous (edited December 07, 2005).]



Kromulous
Dirt Forum Champ
Total posts: 856
posted December 07, 2005 10:45 AM  

 
From AFCO's site.

There panhard bar theory.

[This message has been edited by Kromulous (edited December 07, 2005).]

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