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Author Topic:   J Bar question
Racer17V
Dirt Full Roller

Total posts: 34
posted June 09, 2005 01:01 PM  
I've been reading about J bars on slick tracks. Some people have said to lower it on both ends when it gets slick.

What do you do when you're on the bottom hole on the pinion bracket... do you keep or reduce the height/angle on the chassis end?

This is for a 1/2 mile high banked slick track. Thx.

Sweeney21
Dirt Roller

Total posts: 5
posted June 09, 2005 01:50 PM  
I would raise it on the frame side to get more body roll in the car on the slick tracks. What do you have for split in your j-bar?



Racer17V
Dirt Full Roller

Total posts: 34
posted June 09, 2005 01:55 PM  
I just measure it by chassis height, that is from center of the bolt to the chassis, around 6 1/4 inches. I continue to raise it and pull the LR over until it gets too tight in the middle.

I would guess that is a total rake of around 8 inches (since I can't measure the lower bolt right now at work)

Sound like I'm doing this right?

matty150
Dirt Newbie

Total posts: 3
posted June 09, 2005 05:43 PM  
wouldnt raising the j bar on the frame take body roll out of the car?

rocket36
Dirt Freak

Total posts: 209
posted June 10, 2005 02:40 AM  
i asked a similar question with the guys at rocket. their response was when the track gets rough, a lower roll centre and flatter angle is preferable to a large angle to induce side bite.

GRTmod
Dirt Full Roller

Total posts: 33
posted June 19, 2005 08:19 PM  
LOWER the J-bar-frame end to get MORE body roll.

holeshot
Dirt Maniac

Total posts: 119
posted June 19, 2005 09:52 PM  
would'nt a rubber biscuit j bar help him get more side bite without changing the roll center or would you stay away from those and stay with a solid one?

hamer36
Dirt Maniac

Total posts: 196
posted June 20, 2005 02:48 PM  
Do you string the left side tires every time you make a change?

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 21, 2005 05:58 PM  
Hi Holeshot, I run the rubber J-bar, has a little give when you brush the wall or other fellas!! As for my 2 cents regarding the other situation...Excessive angle in the J-bar or in a panhard bar will not increase body roll although that's the appearence. As a matter of fact, raisng the frame side will raise the roll center and increase the amount of Lateral Weight transfer AKA; sidebite...this is not what you want as a track goes dry. Lower both sides to increase body roll, this will load more downward weight transfer to the RR tire and contact patch. Cars getting up in the air on the left side are not transfering weight downward, its merely the mathmatics of leverage lifting the chassis caused by severe bar angle. Your car will be much easier to drive and bite just as hard if not harder than anything up on two wheels. The key words here are Excessive Angle. Experiment and see what works for you but try lowering both ends with about 4 to 5 inches of split, good luck.

holeshot
Dirt Maniac

Total posts: 119
posted June 21, 2005 11:36 PM  
hey lundin are you going to run the 750 to win this weekend? I just raised my j bar up one inch on the frame side and put a 175 on my lr had 200's x the back. I can't get my car to turn on the gas think this will help?

rpm20
Dirt Freak

Total posts: 338
posted June 22, 2005 05:30 AM  
i would think that with the 200 on the rr and the 175 on the lr that you will definitely loosen the car up but maybe too much, maybe thats what you need .......who knows, give the car what it wants.
if i did that on my dw8 , it would be loopy as all get out and too loose.
i run 225lr and 180-200rr 200 will loosen exit and 180 will tighten entry. at least on my car.

quote:
Originally posted by holeshot:
hey lundin are you going to run the 750 to win this weekend? I just raised my j bar up one inch on the frame side and put a 175 on my lr had 200's x the back. I can't get my car to turn on the gas think this will help?


Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 22, 2005 08:04 AM  
Nothing worse than that mid-turn throttle push, I've heard you have to wait on the gas but that dosen't fit my style and as a driver you should'nt have to be waiting for anything!! If the car is woking good else where and your happy with it, maybe try a wider arc IN on entry. You might also consider trailing the RR a little if the track is tacky. My car is temporarily DEAD. Had to replace the rear-end housing, birdcages, shocks and J-bar from the clip I received from the 21 car on the right rear after he hit the wall and tagged me. The engine also started laying down big time and it was time to freshen it. Unfortunately I'm going to miss this weekends event. It should be back together in about a week or two. Good-luck this weekend!!

holeshot
Dirt Maniac

Total posts: 119
posted June 22, 2005 09:31 PM  
doing the springs like this on my harris would do the same as your saying rpm that is why I want to try this on my pro thinking thats what it needs to turn. if I can run on my own the car is super fast because i can wait on the car point it and stand on it. problem is antioch is fast and small so not alot of room to drive like that.

Dman
Dirt Freak

Total posts: 270
posted June 23, 2005 08:08 AM  
You also need to consider that more j-bar angle will move the rear end to the left as the car rolls which increases side bite or right side loading by pulling the RR closer to the center of the car. Too much angle will make the car erratic on rough tracks and beat the Cr*p out of your mounts.Change your RR offset instead if you have room.On rough tracks like Antioch and Watsonville can be you might be better off with a longer panhard bar. We always carried a long bar and left the mount on the rear end in case we needed it. We run the biscuit j-bar with about a 4 in. split normally with good results (if we can escape the carnage).
(Larry ,you could sure use a little good luck!)

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 23, 2005 09:27 AM  
Thanks DMAN, I couldn't agree more. Hopefully that will change in the near future, I've been close to winning a couple of times but just can't seem to stay out of trouble. Seems I'm in the wrong place at the wrong time but that's racing and I'm not complaining. Anybody here going to Cottage Grove in July for the 2 day race. Curious as to what gear they run. I'm told the track is very tight with hardly any straightaway at all. Sounds like a 5.67 or 5.83?

holeshot
Dirt Maniac

Total posts: 119
posted June 23, 2005 02:50 PM  
taking the 3 off set off the rr and put a 2 off on the rr will do what to the car?

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 23, 2005 05:50 PM  
Holeshot, putting the 2" off on the RR will loosen you up. When Antioch is wet and tacky, I'll run the 2 but not very often. If you want to tighten your car, leave the 3 on the RR and put a 2" off on the left rear provide you're already using a 3 or 4 off on the LR...

foxracin11
Dirt Full Roller

Total posts: 26
posted June 23, 2005 05:56 PM  
ok heres a new question.. when raising the j- bar on the drivers side, it pulls the rearend to the left, should you try to keep rear centered under car or should you let it come over? and how much is to much for it to be pulled under?

viper3244
Dirt Full Roller

Total posts: 57
posted June 23, 2005 07:30 PM  
I AM NOT AN EXPERT,BUT here is my experience with them. I usually start at level to 3 degrees up on the frame side with the j-bar. I like to start with it as close to the center of the pinion on the rear end. This is where I set it for initial set up and scaling, and then we don't check or adjust length until next time we do pre-rsce set-up.. If the track starts to slick move it up on the frame side only, and usually not more than 1 to 2 inches. (similar to a pole vaulter using a longer pole) We have tried crazy things like way below the pinion on rear end and way up on the frame, but the drive usually complains the car is to irratic. Hard to drive smooth. What I was told was shortening makes it quicker and angle makes more roll. good luck


holeshot
Dirt Maniac

Total posts: 119
posted June 23, 2005 08:59 PM  
thanks everyone, but one more ? when you check angle do you put a strait edge on the c enter of the bolt to the center of the bolt and check the angle or do you put it on the flat side of the j bar before it curves down?

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 24, 2005 08:33 AM  
Fox11, try to keep the RR in-line with the RF, if you get the entire rear end moved over to far, it will tighten your car. You might have to lengthen your J-bar alittle bit to acomplish this. Its another reason not to go overboard with excessive angle.

Holeshot, forget about checking the jbar angle, just take measurements from each locating point to the groun. This will give you "split" which is the difference between the two measurements. Once you dial in your split, raise and lower your J-bar a corresponding amount on each end and you'll always maintain the proper split. You can then check the angle if your car happens to be sitting on level ground. I took steel tape measure (just the reel inside w/ the numbers) and rivited it to the square tube that my J-bar slider mounts to. Now I just note the location by reading the measure ment on the tape ! I don't need to use an angle finder or measure to the ground any longer. Us old guys have to be crafty, I don't like crawling under my car all night!!

foxracin11
Dirt Full Roller

Total posts: 26
posted June 25, 2005 06:02 AM  
thanks im gonna make sure right sides are in line and give it a try tonite see how it goes we race on a track that always goes slick by the time first race somtimes befor practice is done so i need the side bite to get it to sit down gettin in but she wants to skate and i have to wait and the are eating me up from that point out

jws
Dirt Maniac

Total posts: 115
posted June 26, 2005 07:37 AM  
One thing that may not agree with what everyone else has said is that a lot of j-bar angle will loosen up a car getting in if it has a lot of rear steer. By getting the car to roll away from the lr quicker, the rear steer kicks in and bring the back end out faster on entry. This is offset somewhat by the fact that you are sticking the RR into the track faster. I suppose it depends on how much rear steer your suspension set up uses.

STICK01
Dirt Maniac

Total posts: 164
posted June 27, 2005 07:25 AM  
Well,

For what it is worth...this weekend i raced on a slick track and tried lowering the frame side of the j-bar and thought that lowering it overall would tighten the car, well it sucked...was loose in, loose off...thank god there was somewhat of a cushion to lean against! next time I will try lowering it all together on both ends...

STICK

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 27, 2005 08:30 AM  
You lowered the frame side and it lost some sidebite? In & out? How was your FWD bite?

I did pretty much the same thing, lowered it on the frame side 1/2" and it free-ed the car up a little. Were running very little split right now, 4" max (gotta remeasure).



STICK01
Dirt Maniac

Total posts: 164
posted June 27, 2005 01:53 PM  
Krom,

yeah it was definitely not what i was looking for...i think it really hurt the car in the middle and off more than anything.

fwd bite went out when it was way loose in the middle...

rpm20
Dirt Freak

Total posts: 338
posted June 27, 2005 02:00 PM  
it got loose because by lowering just one end, what you did was to actually raise the roll center and loosen the car.
in order to tighten the car you need to either add angle (which i think makes it too tight) or lower the whole bar equally. which is lowering it less but eqally.

quote:
Originally posted by STICK01:
Krom,

yeah it was definitely not what i was looking for...i think it really hurt the car in the middle and off more than anything.

fwd bite went out when it was way loose in the middle...



Kromulous
Dirt Forum Champ
Total posts: 796
posted June 27, 2005 02:39 PM  
Thats what i was looking for thou, i lowered the frame side a 1/2" just to shed off some side bite and free the car up a little.

Or am i making the wrong adjustment there?

holeshot
Dirt Maniac

Total posts: 119
posted June 27, 2005 11:22 PM  
here is my update......... won the heat race on greasy track with the 200 on rr and 175 lr j bar up 1" on frame side. car was a little tight to the middle and a little loose off but not to bad. main I drew a 5 made one change (raised the left rear arm up one hole) and was bad tight. if I did not gas it hard in the center i would push. passed 2 cars running good and then i got in the turn a little fast and got to close to the car in front of me did not bump but i eased in to the gas and pushed bad (got passed by 3 cars ) ended up 6th with a fast crowd of shoes. so it is getting closer thanks for the help

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 28, 2005 06:26 PM  
Holeshot, Saw the track but left early. I think you should have raised both sides of your J-bar an equal amount and which would have raised your RC since the track was slippery. This would have helped you getting in (loosened ya-up a bit) and there would have been an increase in side bite comming off. Looked like a 2" raise on both ends would have been the call from what I saw but it sounds like your going in the right direction.

holeshot
Dirt Maniac

Total posts: 119
posted June 28, 2005 09:49 PM  
I only have 1 more hole on the rear end to go up. I was thinking of putting a long bar on the back of the rear end like my harris had. that might be better for me.

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 29, 2005 10:21 AM  
I didn't realize you were already that high up on the pinion. Sounds like you have an issue somewhere else. Your car should have been plenty loose getting in. Maybe it was the track being unusually heavy but from all indications, it sounds like the J-bar was high enough on the pinion side. Do you know how much split there is between the two ends (mounting height)? Is the car a little heavy on the LS% ? If so, that would tend to make it push. The loose off might well be a result of the push going in or especially during a center-turn push... If you get the push out, you'll most likely reduse or eliminate the loose off condition. Good luck with whatever you decide

holeshot
Dirt Maniac

Total posts: 119
posted June 29, 2005 11:42 AM  
last time out 52.7 left 56 rear with 26 gal of fuel 49.2 cross 49 lr bite j bar 14" on frame 10" on rear end 5 deg up on bolth bars (3 link) 17 deg on pull bar thats what it stared with.

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 29, 2005 06:22 PM  
Those numbers all look good to me. Something else going on here but I'm not sure what it is. What spring to do have on the RR? What kind of travel do the shock indicators give and are you bottoming out the chassis anywhere on the frame particularily the RF lower a-frame?

holeshot
Dirt Maniac

Total posts: 119
posted June 29, 2005 09:43 PM  
travel on shocks 3 to 4 on rf ....2.5 to 3.5 rr.... 3 to 4 on lr . spring on lr 175 200 rr 700 rf 750 lf with nova lowers.nothing seems to be hitting.

Larry Lundin
Dirt Full Roller

Total posts: 45
posted June 30, 2005 09:31 PM  
Holeshot, swap the rear springs and don't do anything else, go give that a try....175RR, 200LR

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