Moparts
What's wrong with our Chassis?
Posted By: jyrki
What's wrong with our Chassis? - 08/21/09 05:42 AM
Last time out with our car we mainly made some damage. The car pulled the left front wheel up and in the next run the car pulled right hard making it undriveable. I has been pulling right for a while even in a good run, four link rear with 1/3 run preload on the right upper bar. The car also twists pretty bad mainly raising the left front. Last night we measured the body, it seems straight. The wheelbase was slightly off 0.15", but we fixed that and now the axle is straight in the car. Front end alignment was off a bit, very different from one side to another, we didn't get it very good but at least it's "symmetric" now. Is there any hints, shock adjustments, prelaod/torsion bar adjustment things that would help us? Here is a video of the wheelie launch:
http://www.youtube.com/watch?v=rBZjrkUn6jEAnd here of the last qualification run where it went right hard when the throttle was pressed:
http://www.youtube.com/watch?v=aEHELDeG6Lc Could it at least partly have been just a driving error? Sorry about the quality of the videos.
Before the race I tried to compensate wheel weights a little with a tighter right reas spring, 125 lbs on the left, 150 lbs on the right, is that a mistake? We also had a 40 lbs ballast in the very right rear corner, effect of that?
In this good quality video from 5:00 you can see the last qualification launch from both front and rear, the not so pretty elimnator trial can be seen at 8:34:
http://www.youtube.com/watch?v=SpG_-sDJ6EgWe have our national finals a week from now, and any help would be appreciated to get it sorted out.
Posted By: rebel
Re: What's wrong with our Chassis? - 08/21/09 07:57 AM
have you removed the differential from the suspension & checked all the welds? the ones where the tubes go into the housing & the ones where the spring perches are. i was doing similar but not as exagerated wheelstands last season. my problem was the tube on one side was going out of round making my ladder bar mounts become misalined. i even had a mother of a strongback brace & it still distorted. i'd be removing the rear end for an up close & personal inspection if i was you. before your next outting, that looks dangerous.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/21/09 08:10 AM
No we haven't, but the four corner laser measurements last night didn't reveal anything wrong at least when standing still. The rear axle is a Strange Dana 60 and the IC point is currently about 5.5" high and 44" long We tried longer but it didn't seem to work as well. With this set up (except the unpaired rear springs and the ballast in the right rear) the car has run succesfully. It has always pulled slightly right when I have driven it, and also always raised the left front corner more. I believe we have never run on a such good track before though.
Posted By: rebel
Re: What's wrong with our Chassis? - 08/21/09 10:43 AM
do you have a strongback on your rear end housing? if things are moving you could very well still have all the measurements right but you said in post 1 you've noted some variations on your previous settings. this could be due to twisting of your tubes.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/21/09 11:07 AM
It's a Dana with an LPW cast cover, can't really brace a Dana. We had never before checked the chassis with "pro equipment", but all the dimensions and angles were pretty close and now should be up to par. Rear shock broke? Or settings completely wrong? There is about 1/2" travel inwards and 4.5" our when standing still. The rear coiovers are Strange double adjustables and front suspension is rebuilt stock with Konis and hte travel limited to about 2".
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/21/09 11:12 AM
looks like you need an anti- roll system in that thing. what kind of shocks?
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/21/09 11:23 AM
Strange double adjustables in the rear, Koni "stock" in front. An anti roll bar would propably help the symptoms and we'll install one during hte winter, but does it cure the problem? Rear locator is a wishbone, all the rear suspension parts are from quartermax.
Posted By: WhiteB1Duster
Re: What's wrong with our Chassis? - 08/21/09 01:00 PM
i just had that same problem amonth ago. my duster went from picking the front end up even to justthe left front and a lot of body rol to the right. i checked all the suspension and thing was ok. then i pulled the coilovers in the rear off and found that the right ones shaft was bent. they were koni. i replaced both with a set strange double adj. iam hopefully going to nyirp sat. for tnt i hope the change fixes my problem. btw your car is awsome.
Posted By: VernMotor
Re: What's wrong with our Chassis? - 08/21/09 01:14 PM
What was the scale weights ?
Posted By: MR_P_BODY
Re: What's wrong with our Chassis? - 08/21/09 01:23 PM
First put a anti roll bar on it... that will change
everything.... then your going to start all over
EDIT
check all the welds like others have said but put
the anti roll on it
Posted By: BobR
Re: What's wrong with our Chassis? - 08/21/09 01:25 PM
Has something changed or is this a new deal that you are just sorting out? Something is very wrong IMO but it's real hard to diagnose from looking at videos. It looks to me like your RR tire is lifting which could well indicate a shock problem on that corner. The anti-roll bar everyone is talking about is a good idea.
Posted By: moparacer
Re: What's wrong with our Chassis? - 08/21/09 01:26 PM
Dana's will break the tube loose on the passengers side.
You can see it if sometimes you look closely at the plug welds. Alot of times the very center will be busted out of them.
The car I have now had a axle tube broke loose and it had alot of other welds cracked from the continuous flexing.
Posted By: Hemiroid
Re: What's wrong with our Chassis? - 08/21/09 02:08 PM
As others mentioned, I'd be looking at the coilovers. Check the coils closely for breaks. We had a coil break, but you could hardly tell visually that it was broke as the two pieces stayed close together at rest. And another vote for the anti-roll, no chassis car should be without one.
Posted By: Craig
Re: What's wrong with our Chassis? - 08/21/09 02:12 PM
Quote:
It's a Dana with an LPW cast cover, can't really brace a Dana.
LPW makes a tube brace for their cover, I put one on my Dana... http://www.lpwracing.com/p_axletubebrace.asp
Quote:
Rear shock broke? Or settings completely wrong? There is about 1/2" travel inwards and 4.5" our when standing still. The rear coiovers are Strange double adjustables and front suspension is rebuilt stock with Konis and hte travel limited to about 2".
Are you saying the rear shocks only have 1/2" compression available at ride height? That seems like a big problem to me. Although my car is much slower, my 4-link setting is similar and I get over 1" compression on the launch. This is with a fair wheelie and best 60' of 1.26. You may be bottoming one or both rear shocks on the hardest launches. I think your rear shocks should be at mid-travel at rest.
And your car is really AWESOME! 
Posted By: bonefish
Re: What's wrong with our Chassis? - 08/21/09 03:08 PM
very interesting mine went from wheelsup straight to doing the same thing.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/21/09 03:17 PM
the shock settings have been 4 and 7, but I just can't remeber my logic now which one is which. We had the coilovers out during the laser measurements, replaced by solid bars, and the springs were ok. Didn't pull them apart though and check how they feel. Anyway, we currently have about 1.5" compression and perhaps 1/4" preload. I could add about an inch or so relatively easy, but that also changes the link settings, so perhaps I should alter them too? Or is it too many changes at once? As you can see, we are fairly virgin with the four links; I did put some preload in there, but was it in to right direction? Can't check it anymore because correcting the rear axle/wheelbase alignment we shortened the right lower bar without touching the upper. Now the upper bar is "free", so it seems there is no preload.
Posted By: demon440
Re: What's wrong with our Chassis? - 08/21/09 03:31 PM
Does that rear have a spool or sure-grip?
Check both axles.
Posted By: B G Racing
Re: What's wrong with our Chassis? - 08/21/09 03:36 PM
Usually you will find something binding,bending,flexing or broken.Find the problem before adding or changing anything.
Start at the front of the car and work back,don't overlook anything, mounts,alignment,suspension bolts....everything.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/21/09 04:24 PM
Yes, it has spool Haven't checked the axles yet, they are 40 spline solids. We had three chassis professionals with us yesterday, and they checked about everythin possible and also drew a map of hte chassis to later check dimesions easier.
Posted By: 440FISH
Re: What's wrong with our Chassis? - 08/21/09 05:11 PM
If you look at the last video at 5:00-5:10 the car loads the right rear a lot. You are asking a lot from the shocks with that car. I would take the shocks apart and check them?
Can you get a video of the passenger side rear tire to see if the rear end is moving around?
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/21/09 05:19 PM
it's really hard to tell anything with those videos. it has a tremendous amount of body roll for what ever reason. if everything is straight and nothing is broke. an ANTI-ROLL and maybe better shocks are the answer. didn't see how fast it was running but ti looks like it's making good HP. you may be beyond what the strange shocks can handle. you may have to step up in that area. mopars from what I have seen have a lot more body roll than other makles even with a chassis car, maybe it's all the torque a mopar makes
go full stiff on the right rear shock and see what it does.
Posted By: Irun5snd8th
Re: What's wrong with our Chassis? - 08/21/09 07:35 PM
Take a real good look at everything. Get up there with some brake clean so you can find a crack if its there. Take the shocks off and inspect them or just swap them from one side to the other. If the shock is the problem it should do something very different switching sides although I would not think thats the safest method of testing. Anti roll bar will definitely help but there is no substitute for tying the chassis together with a cage.
Posted By: 11secondC
Re: What's wrong with our Chassis? - 08/21/09 10:53 PM
Quote:
didn't see how fast it was running but ti looks like it's making good HP.
8.0's @ 170+ @ 3400 lbs, I think its making some steam... 
Posted By: gregsdart
Re: What's wrong with our Chassis? - 08/21/09 11:45 PM
One more vote for the antiroll. I had my car leaving on the right rear, it was twisting so violently it would rip the left rear off the track. Anti-roll, with some preload, much better! Picked up about .02 in the 60 fts as well.
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/22/09 12:12 AM
Quote:
Quote:
didn't see how fast it was running but ti looks like it's making good HP.
8.0's @ 170+ @ 3400 lbs, I think its making some steam...
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/22/09 12:14 AM
Quote:
Quote:
didn't see how fast it was running but ti looks like it's making good HP.
8.0's @ 170+ @ 3400 lbs, I think its making some steam...
he's way over powering the poor strange shocks I bet.
Posted By: MR_P_BODY
Re: What's wrong with our Chassis? - 08/22/09 01:44 AM
Quote:
Quote:
Quote:
didn't see how fast it was running but ti looks like it's making good HP.
8.0's @ 170+ @ 3400 lbs, I think its making some steam...
he's way over powering the poor strange shocks I bet.
First thing ...it should have a anti-roll on any
4-link.... thats a must have
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/22/09 01:48 AM
Quote:
Quote:
Quote:
Quote:
didn't see how fast it was running but ti looks like it's making good HP.
8.0's @ 170+ @ 3400 lbs, I think its making some steam...
he's way over powering the poor strange shocks I bet.
First thing ...it should have a anti-roll on any
4-link.... thats a must have
but I need you to come down and show me where I can put them on my challenger 
there is no room anywhere 
Posted By: MR_P_BODY
Re: What's wrong with our Chassis? - 08/22/09 01:54 AM
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/22/09 02:10 AM
Quote:
but I need you to come down and show me where I can put them on my challenger there is no room anywhere
Can you turn it around and run it on the rear(doesnt
matter)
tried everywhere at every angle, the huge truck rear (dana) takes all the room 
Posted By: bigdad
Re: What's wrong with our Chassis? - 08/22/09 02:13 AM
Awesome car, always has been !!
In the other Vids you posted..It never did that ?
I will vote that something is broke, My friend here with a low 10-2nd 63 Dodge recently turned a Dana 60 tube and it acted kinda like that but, he is not working the kind of HP you are putting down !!
Please get it right before it scrapes the wall !!
Posted By: TS3303
Re: What's wrong with our Chassis? - 08/22/09 02:19 AM
an anti roll bar is not the answer only a bandaid for a chassis that is not rigid enough. There is something seriously wrong with the rear, shock, or chassis. on the video at 5:00 it is turning right before the tire makes one revolution and at 8:30 every time he got on the gas it drove right. The rear is moving in the car, the 4 link brackets are moving, the chassis is cracked, or an axle/spool problem, who knows maybe the right rear caliper is stuck (doubt it based on the down track actions). It should be going left with that much extra load on the right.
Posted By: Hemiroid
Re: What's wrong with our Chassis? - 08/22/09 02:22 AM
Quote:
an anti roll bar is not the answer only a bandaid for a chassis that is not rigid enough. There is something seriously wrong with the rear, shock, or chassis. on the video at 5:00 it is turning right before the tire makes one revolution and at 8:30 every time he got on the gas it drove right. The rear is moving in the car, the 4 link brackets are moving, the chassis is cracked, or an axle/spool problem, who knows maybe the right rear caliper is stuck (doubt it based on the down track actions). It should be going left with that much extra load on the right.
Watching the vids, as soon as he hits the throttle the right rear immediately dives. If you watch the first vid, you can see how extreme the movement is.
Posted By: TRENDZ
Re: What's wrong with our Chassis? - 08/22/09 02:45 AM
Put a sway bar back there. You are getting "roll steer" from the massive torque you're engine makes fighting the weight of the car and the rear gear. Turbos will do that. Roll steer occurs because of unequal length upper/ lower bars on the 4lnk. As long as you allow the rear to roll(no sway bar) it will turn like that. On a car that heavy, with that much torque, no shock/spring adjustment will ever be enough. My car was not as extreme as yours in power, but it was heavier (3700lbs)with a 3.50 gear, and would do the EXACT same thing. The car would corkscrew and turn on the launch and on gear changes until I put a rear bar in it. After the bar the car was almost boring to drive, as it was extremely predictable and controlled. see a poor vid at
HTTP://www.YOUTUBE.COM/WATCH?v=IR2DrlHDjeY
Posted By: JoWeTu_6
Re: What's wrong with our Chassis? - 08/22/09 02:52 AM
If all your welds are ok and all your chassis points are met. check your springs and make sure they are the values you think they are.
Also read these.
http://www.hotrod.com/techarticles/chassis_tuning_tire_traction/index.htmlhttp://racingarticles.com/article_racing-50.html They will help you in providing abit more tunning detail.
John T.
Posted By: JoWeTu_6
Re: What's wrong with our Chassis? - 08/22/09 03:00 AM
Quote:
an anti roll bar is not the answer only a bandaid for a chassis that is not rigid enough. There is something seriously wrong with the rear, shock, or chassis. on the video at 5:00 it is turning right before the tire makes one revolution and at 8:30 every time he got on the gas it drove right. The rear is moving in the car, the 4 link brackets are moving, the chassis is cracked, or an axle/spool problem, who knows maybe the right rear caliper is stuck (doubt it based on the down track actions). It should be going left with that much extra load on the right.
Movement to the right is immediate.
Posted By: TRENDZ
Re: What's wrong with our Chassis? - 08/22/09 03:21 AM
It's turning right because the wheel base on the right is getting shorter from unequal length 4 link bars combined with roll rotation. A sway bar will correct the problem, assuming the bar length difference isn't to extreme.
Take the spring/shock out of the car, and set the housing roll angle where you see it in the video. I gaurantee you that the wheelbase on the right will get sorter when compared to the left. Nothing has to be broke for this to occur.
You could lengthen the upper bars to match the bottom, and it would steer much less, but it will still roll rotate without a sway bar.
Posted By: bigdad
Re: What's wrong with our Chassis? - 08/22/09 03:31 AM
Ok, I'll buy that but.. the car DID work before and has put down some serious numbers earlier so, why now has things changed without something breaking ?
Posted By: TS3303
Re: What's wrong with our Chassis? - 08/22/09 03:32 AM
as much as it is pitch rotating I can see that happening.
Posted By: TRENDZ
Re: What's wrong with our Chassis? - 08/22/09 12:46 PM
Good point about the car working before, although I don't think it ever was working as they hoped. There is a good chance that a shock is not functioning correctly. Like others have said, the shocks are being asked to do more than they can handle on this monster. I still say put a bar in it. I would definetly remove the springs and at the very least hand check the shocks. I would also put the same rate springs in the car, let the sway bar handle the twisting, and let the shocks and springs support the car and control the speed of reaction.
This is one of the coolest cars out there, it would be a shame to see it wrecked.
Posted By: Al_Alguire
Re: What's wrong with our Chassis? - 08/22/09 02:59 PM
Well if it worked ok before and now it is not seems the only logical answer is something is BROKE! Be it shock, weld, or axle/spool something is not working as it used to. Find out what that is first THEN ad an antiroll before someone gets hurt! Just my humble opinion.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/24/09 05:56 AM
Thanks for the suggestions. Will check everything once more, take the coils off and check the shocks, both front & rear I'll also scale the car and try to figure if the problem is there. Should be racing on friday and haven't got much time to spend on the car before that, but we'll see wether it works or not. The four link bars are equal length, 22" each. Hopefully I'll find something really wrong, won't be easy to go driving unless I do.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/28/09 05:14 AM
Quote:
Dana's will break the tube loose on the passengers side.
You can see it if sometimes you look closely at the plug welds. Alot of times the very center will be busted out of them.
The car I have now had a axle tube broke loose and it had alot of other welds cracked from the continuous flexing.
And we have a WINNER!!!
I was getting kind of worried because had checked everything and didn't find anything really wrong. but yesterday I noticed paint had came off from one plug weld, more light and a small punch with a hammer and the plugweld came off. Then looking closer, the weld around the passanger side axle tube was loose all around, pretty unnoticable since there was 4 years dirt on it. No wonder it had been leaking some oil for a while...
Anyway, now it's fixed, although I didn't have time or material to properly reinforce it. Three hours and I will start a journey in to our national finals, and we'll see wether it works or not. Once again, thanks all for the suggestions and help!
Posted By: 1_WILD_RT
Re: What's wrong with our Chassis? - 08/28/09 05:20 AM
Quote:
Quote:
Dana's will break the tube loose on the passengers side.
You can see it if sometimes you look closely at the plug welds. Alot of times the very center will be busted out of them.
The car I have now had a axle tube broke loose and it had alot of other welds cracked from the continuous flexing.
And we have a WINNER!!!
I was getting kind of worried because had checked everything and didn't find anything really wrong. but yesterday I noticed paint had came off from one plug weld, more light and a small punch with a hammer and the plugweld came off. Then looking closer, the weld around the passanger side axle tube was loose all around, pretty unnoticable since there was 4 years dirt on it. No wonder it had been leaking some oil for a while...
Anyway, now it's fixed, although I didn't have time or material to properly reinforce it. Three hours and I will start a journey in to our national finals, and we'll see wether it works or not. Once again, thanks all for the suggestions and help!
Rebel had it even sooner.. Glad you found it.. Before things got ugly!!
Posted By: Comp Chassis 2
Re: What's wrong with our Chassis? - 08/28/09 05:29 AM
If the tube has moved, how did you fix it? Might want to scale it and see what the corner weights are. Once they twist almost impossible to fix without cutting brackets and rotating around housing & rewelding. A real pain, I,ve had to fix a few. If tube has twisted suspension points are going to out of whack. Likely no weight on right rear.
Posted By: jyrki
Re: What's wrong with our Chassis? - 08/28/09 05:32 AM
Checked the corner weights, with two flats of preload the rear wheel weights are even with me in the car, the front left is 80 lbs heavier than FR. Seemed to me that the tube hadn't moved or turned, but it just flexed when force was applied. I pulled the axle forward from each side of the center section, and the drivers side was solid while the pass. side clearly flexed. At the moment it isnät that important that everything there is up to par, but at least it should now follow some logic.
Posted By: Comp Chassis 2
Re: What's wrong with our Chassis? - 08/28/09 05:47 AM
If it didnt take a permant twist, and has returned to normal spot, you should be fine. normaly once they move they stay there. and the amount of force it took to twist it is almost impossible to duplicate in reverse. First indicator is usually dropped ride hieght on the right rear. hope its fixed good luck at the national open!
Posted By: Quicktree
Re: What's wrong with our Chassis? - 08/28/09 09:48 AM
Quote:
If it didnt take a permant twist, and has returned to normal spot, you should be fine. normaly once they move they stay there. and the amount of force it took to twist it is almost impossible to duplicate in reverse. First indicator is usually dropped ride hieght on the right rear. hope its fixed good luck at the national open!
glad to see you back and posting I presume you are the original compchassis?
Posted By: 1Fast340
Re: What's wrong with our Chassis? - 08/28/09 02:54 PM
Jyrki:
good that you found it! and good luck at the finals!
BTW saw a pic of your big bad car in Street and strip magazine!
Posted By: MR_P_BODY
Re: What's wrong with our Chassis? - 08/28/09 03:14 PM
I had the same issue with my brothers altered, he
wanted to use the Olds rear and I never checked it
when I build the car and about a year later the right
tube started to move... one time the wheelie bar
whould be in the right place... next pass it would
be 3" higher than the left(this was at Norwalk) and
he was in the money... we finally took the wheelie
bars off so he could finish the race... bad mistake,
next pass he put it right up on to the chute mount,
he finished 2nd that night... after looking closely
at it when we got home the right tube was moving,
so I went through the whole thing... been fine since