What's wrong with our Chassis?
#444795
08/21/09 01:42 AM
08/21/09 01:42 AM
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jyrki
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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.
Last edited by jyrki; 08/21/09 02:13 AM.
Plynouth VIP '67 TT IC EFI
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Re: What's wrong with our Chassis?
[Re: jyrki]
#444796
08/21/09 03:57 AM
08/21/09 03:57 AM
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Joined: Dec 2006
Posts: 4,647 aotearoa
rebel
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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.
Last edited by rebel; 08/21/09 06:44 AM.
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Re: What's wrong with our Chassis?
[Re: rebel]
#444797
08/21/09 04:10 AM
08/21/09 04:10 AM
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jyrki
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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.
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Re: What's wrong with our Chassis?
[Re: rebel]
#444799
08/21/09 07:07 AM
08/21/09 07:07 AM
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jyrki
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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".
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Re: What's wrong with our Chassis?
[Re: Quicktree]
#444801
08/21/09 07:23 AM
08/21/09 07:23 AM
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jyrki
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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.
Last edited by jyrki; 08/21/09 07:26 AM.
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Re: What's wrong with our Chassis?
[Re: jyrki]
#444804
08/21/09 09:23 AM
08/21/09 09:23 AM
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MR_P_BODY
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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
Last edited by MR_P_BODY; 08/21/09 09:38 AM.
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Re: What's wrong with our Chassis?
[Re: VernMotor]
#444806
08/21/09 09:26 AM
08/21/09 09:26 AM
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moparacer
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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.
67 Barracuda street/bracket car 11.27-119 68 Dart 502 BB 8.70s-152 414 cid SB Dragster 7.65-174
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Re: What's wrong with our Chassis?
[Re: bonefish]
#444810
08/21/09 11:17 AM
08/21/09 11:17 AM
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jyrki
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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.
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Re: What's wrong with our Chassis?
[Re: jyrki]
#444812
08/21/09 11:36 AM
08/21/09 11:36 AM
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B G Racing
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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.
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Re: What's wrong with our Chassis?
[Re: B G Racing]
#444813
08/21/09 12:24 PM
08/21/09 12:24 PM
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jyrki
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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.
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