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28m
06-07-2011, 12:06 PM
I bought a Jet (4 bar 4 bar) last year with three races left to go in the season. I won 1 out of the three and 2nd in the other and 3rd in a 8k to win after starting 24th with a provisional. Car was FAST. This is a Jet that a local guy updated to a 2010 rear 4 bar mounts. I re-clipped the rear of the car in the off season but did not change any pickup points of the suspension. I did change the under slung bars which happens to be how Jet centers the rearend. So I really don’t know for sure where the rearend should be aligned left to right.

I started the season with the tires inside each fender. I went out and the cars was tight tight tight. Made spring changes, add RR trail, raised Jbar on pinion and shocks to loosen it…it got tighter. It reacted the exact opposite of what it should have. Before the main I pushed the rearend over to the right hoping to stop it from planting the RR. It got so tight I pulled off. Again, acted the exact opposite of what it should.
That week I used logic and moved the rearend back to the left (further than what I started with originally) so that all my bars where lined up correctly. The pull bar straight, the driveline straight and the bars towed in slightly in the front. Now the RR tires is inside the fender 3 inch and the LR sticks out about 3 inches. The rearend visible looks too far to the left…but all my bars are in line and the drive line is straight. The car is now LOOSE loose loose. No side bite AT ALL. Even entering the turn OFF the GAS, it skates and will not catch. I wait on it and wait and wait and finally when I pick of the gas, it is instantly loose. I peddle it til the car is straight then it rockets forward. Last week the track was so hooked up, they were turning laps faster than the track record. I had to drive the track like dryslick because I was so loose and NO SIDEBITE.

So in a normal world, the rearend too far to the left would make you think it would be tight getting in. It should plant that RR so hard the car sticks and drag the front end over. Matter of fact, it was loose in the heat last weekend so I…
Dropped the J-bar to the bottom hole on the pinion, softened the RR spring, softened the RF spring, put and 8-2 on the LR and a 3-5 on the RR. This thing should have rolled over so hard and pinned that RR but no…I GOT LOOSER. I know this MIGHT make the car looser on the gas but it was even skatier with no side bite off the gas. The changes had the opposite reaction.

This week I moved the rearend over to the right…like 3 inches. Again, I am lined up RR to RF tires, the tires are under the fenders on each side and the car looks back to normal. HOWEVER, my pull bar is pushed over to the right, my driveline is pushed over to the right and my bars point to the left in the front. Im not worried about the bars pointing to the left as again, this was a conversion to upgrade to a 2010 rear. It is likely the bars are not lined up for that reason. It does concern me that the driveline is not straight. When the LR is hiked up, the driveline is close to straight tho. ?????
IS IT EVEN POSSIBLE…that the rearend was too far the left and caused a loose condition with no side bite? It doesn’t make sense to me but is it possible???? Can you explain the theory if so?

Side note. EVRYTHING in the car…springs, bar angles, shocks, scale numbers, etc are the exact same as last year. The only thing that is not the same is the placement of the rearend. Also, each time I have moved the rearend, I have adjusted my scale numbers back to my baseline setup.

powerslide
06-07-2011, 09:35 PM
question is not why is everything backwards... but why are you moving the rearend side to side 3inches at a time?!?!

Get the driveshaft lined up and work from that. its possible that changing track conditions could be throwing you a loop.

JAMESGANGRACING
06-07-2011, 09:46 PM
if you did not change the pick up points or bar that the j bar mounts to than the rear end should be in the same spot it was before. You can just find a point and make your own measuremet to use for referance. did you change where the springs/shocks mount in the car?

Mosidebite
06-07-2011, 10:20 PM
if all mounts are the same as before. Set rearend side to side by getting degree of angle on the shocks. Have Johnny tell ya what angle the left rear is and the right rear is at ride height and set it.

28m
06-08-2011, 11:28 AM
question is not why is everything backwards... but why are you moving the rearend side to side 3inches at a time?!?!

Get the driveshaft lined up and work from that. its possible that changing track conditions could be throwing you a loop.

I agree, and that is exactly what I did; I lined up the driveline BUT, the car is ridiculously loose. I pointed out the track last weekend was hooked up and track records were broken. This is my home track that I have raced for 15 years and 4 championships. I understand changing track conditions. When I do adjust, As I explained, it has the opposite reaction. I.e., drop the jbar on the pinion and it gets looser on entry. The reason for moving 3 inches is because, I didn’t change the top decking mounts. Last year the tires where both inside the fenders. When I line up the drive shaft, the LR tire sticks outside the fender 3 inches. When I move it to the right three inches, the tires are again under the fenders. YES, I know that aligning the rearend to the fenders is REDICULOUS but it is the only reference point I have

28m
06-08-2011, 11:43 AM
if you did not change the pick up points or bar that the j bar mounts to than the rear end should be in the same spot it was before. You can just find a point and make your own measuremet to use for referance. did you change where the springs/shocks mount in the car?

Well, thats the thing...lol. I had to reclip the rear because the last race of the season, I got hit in the rear and pushed my clip over. I then got hit in the rearend and it folded my j-bar.

No, I did not change the spring/shock mounting points.

28m
06-08-2011, 11:49 AM
if all mounts are the same as before. Set rearend side to side by getting degree of angle on the shocks. Have Johnny tell ya what angle the left rear is and the right rear is at ride height and set it.

That would work but, the car began life as a 2000 Swingarm car. In 2010, the mounts were replaced with new 4 link brackets. Not only that, I can’t expect Johnny to know the location of the birdcages on the rearend.

This problem is because I was too dumb to make a measuring point to reference the rearend position. I don’t have a way to get it back to where it was last year. I guess I am looking more for input on the way the car is reacting to adjustments.

Has anyone ever, or can you imagine, how or why my car is sooooo loose if the rearend was too far to the left??? I have a test and tune tonight so I imagine Ill know soon if it is fixed. I just hate making a change without understanding why it does what it does.

Mosidebite
06-08-2011, 04:13 PM
There is generally a measurement from the rotor to the birdcage. That measurement would set your instant centers. If the reclip was done back to johnny's specs then the measurements should work.

Dirtrunner35
06-08-2011, 07:20 PM
When you are moving the rear end left and right, are you squaring it up?

28m
06-09-2011, 01:10 PM
Update after 4 hour Test and Tune...

No change by moving the rearend over. The car was the exact same with no side bite. Car slides and skates, off the gas entering the turn.

I made HUGE swings at the car to get it to react...Dropped J bar to bottom hole on pinion...no changes. Raised j-bar on the frame 2 inches...no change just super twitchy. Dropped RR lower bar one hole...no change. Raise LR upper 1 hole...no change. Put a 225 RR spring from a 200...no change (yes I know this will loosen the car on the gas but I was trying to get the car to stick off the gas entering). Added 60 of LR bite from 40 to 100...no change. Went to 60 RR bite...No change.

I had many people watching me make laps and they know the issues I am fighting. Every one of them said the same thing..."the car looks great. It gets up on the bars, it doesn’t slam down but if I didn’t know you were changing things I would never know you even touched the car. The car looks the exact same." Most of the time I was on the track by myself so they could hear my motor...Let’s just say everyone is stumped because they could her how little gas I was giving the car and at times all but stopped/spun out when OFF THE GAS.

AS far as I can tell, nothing is binding. In my shop I have jacks under it going thru the entire range of movement. It all looks great.




When you are moving the rear end left and right, are you squaring it up?

Yes, but I have not played with it to close the rearend up (trail LR). Would the rearend opened up cause the skating off the gas entering? Please say yes :)

mbaker76
06-10-2011, 12:49 PM
I think it would cause the same 'feeling' as a drift even if not actually drifting. How much trail are you talking in the RR?

28m
06-10-2011, 02:55 PM
I think it would cause the same 'feeling' as a drift even if not actually drifting. How much trail are you talking in the RR?


OOpppps. Yeah I'm a dumb a$$. I normally squared the rearend to the trailing arm brackers. When I bought the car, it was on a frame maching to ensure it was straight from the frame and lower ball joint to the trailing arm brackets...it was. Last nite I strung...strang...stringed...the car out and the RR trailing arm bracket is back 1.25 inchs. Needless to say, when I got hit in the rear and bent the clip, it must have twisted the main frame as well.

I am adjusting it to be square and trying it out tomorrow. Fingers crossed.

LM14
06-10-2011, 05:25 PM
Go to Jet's web site and download his setup book. It tells how to square the rearend for a 2000. I realize mounts have been changed but it doesn't effect how that rear should be squared.

Next, allign your left side tires to get close. 3" back space wheels everywhere but the right front. The RF is a 2" bs wheel. According to Jet, cars older than #532 (yours) should use a 23" j-bar and mount to the outside of the bracket on the 1.5" square sliding mount (closer to the tire) IF you didn't change the j-bar mount and it is still original to the 2000 build. The newer cars use a 19-1/4" j-bar and mount to the inside of the bracket on the 1.5" square sliding mount (closer to the driveshaft). Center of the pinion (on a 9" rear) and 5" from the bottom of the 1.5" square tube on the frame to the bottom of the sliding clamp the j-bar bolts to.

If he actually used the 2010 Jet 4 bar mounts (16" upper and 14" lower bars?), you should be able to use the Jet measurements listed in the book. If they don't work the mounts were put in wrong.

Your pull bar should be centered on the rearend between the hubs. It should run basically straight to the frame mount. Is your pull bar mount on the frame the welded solid or left to right sliding style?

That all being said, if you are making these huge changes and nothing changes....it's either bent someplace or in a bind. Get your shocks on a dyno, springs rated, birdcages free?, check the rearend housing for straight, bent ball joints/a-frames binding, bent spindles, etc.

Huge changes are not your friend. Get everything checked for binds and straight, set the rearend square as per the book, set your left side tires in line and put it back to baseline setup.

PM me if you have questions.
SPark

rubbinsracin
06-10-2011, 05:41 PM
one time when i was pitting for a guy that had a wreck we went to another competitor who was driving really close to the same year as ours that was "straight" and asked him if we could come over to his shop sometime and take some measurements and such. he was happy to help someone. and this guy is a top guy at a few local tracks. we just brought a case of beer with us and paid his entry fee the next week. best money we ever spent. found out he just makes adjustments like we do....guesses lol

28m
06-16-2011, 01:13 PM
Problem solved the RR was back 1.5 inches on because the frame was bent up front. Here is the car with more sidebite…LOL
Thank you all.


http://www.smugmug.com/gallery/17531261_NcKBLw#1336483309_JvPxG52-A-LB

nlnmmnto123
06-19-2011, 08:54 AM
thank you everbody