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Author Topic:   J-bar vs. Short bar vs. roll center
tilley88
Dirt Forum Champ
Total posts: 879
posted August 07, 2004 03:08 PM  
I'd like to run my j-bar in the heat and my short bar in the feature. My question is where should I place each of them? Should I mount the j-bar 1" higher on both ends for the heat(tacky), then drop the short bar down 1" for the feature(dry)? This is on a DW8 w/short 2-link.

xhubby
Dirt Freak

Total posts: 376
posted August 08, 2004 07:53 AM  
Tilley 88, We did that last week, & didn't change the location at all. Simply took off the j-bar & put on the shorty. Car was fast!! DW-8 short 2-link also.

tilley88
Dirt Forum Champ
Total posts: 879
posted August 11, 2004 12:27 AM  
xhubby, how high on the frame side is your mount? And which hole on the pinion?

xhubby
Dirt Freak

Total posts: 376
posted August 11, 2004 04:46 AM  
tilley88, we are at 8" up on the frame,(bottom of the brkt.), & second hole from the bottom on the pinion plate. We are using the pinion plate from Dirt Works. The one we had on the car early in the season was from our local race shop, & the position of the holes was very different. Messed us up for quite awhile,(waaay too much angle in our j-bar/short-bar).

WPP
Dirt Freak

Total posts: 451
posted August 11, 2004 05:34 AM  
Is the pinion mount holes lower on the dirt works mount if so what is the height from the ground on the pinion and the chassis on the mounting points thanks

xhubby
Dirt Freak

Total posts: 376
posted August 11, 2004 05:38 PM  
WWP, No, the holes on the DW plate were higher than the first one we were running. The second hole fron the bottom on the DW plate matched up with the top hole on the old one. That's when we figured out we had been running waaay too much angle in our panhard bar. As far as the measurements from the ground, I couldn't tell you. That would all depend on the ride heights.

tilley88
Dirt Forum Champ
Total posts: 879
posted August 11, 2004 09:06 PM  
xhubby, I believe WPP was askin the same thing I'd like to know. Could you measure from the floor the distance to your pinion mounting bolt & the floor to the frame mounting bolt & let us know the difference between the two?

WPP
Dirt Freak

Total posts: 451
posted August 12, 2004 05:51 AM  
You said it tilley i have also just change pinion mounts on my dw but i got the one from afco and it has a extra hole in the bottom for lower placement i always measure mine from the ground to the mounting points i don't go from holes there are too many differt ones out there and ride heights do make a differce thanks

mod70
unregistered Total posts: 451
posted August 12, 2004 11:45 AM           send a private message to WPP   Edit/Delete Message   Reply w/QuoteBBBBBB
Really the best way to measure any bar "rake" is with an angle finder. To say that you have 3" of rake in a bar does not take into account the length of that bar and the difference of the length of the other guy's bar. The longer the bar is, the less true angle 3" of rake will give you. That is why I will allways try to give my answers in terms of degrees of angle. Of course I reallize not everyone has an angle finder in the box, but I would highly recomend getting one.

WPP
Dirt Freak

Total posts: 451
posted August 12, 2004 01:25 PM  
I am not worried what the rake is what tilley and me is asking how far off the ground the pinion mount and the chasiss mount is with the bar hooked up on each end to give us a idea. I was not aware dws sells a differt mount i am just trying to campare mine with theirs

xhubby
Dirt Freak

Total posts: 376
posted August 12, 2004 05:24 PM  
I'm heading to the shop tonight, & I'll try to remember, (getting old you know) to get the measurements, & the angle. I don't think it's the DW plate that is different, so much as the one I bought from our local race shop. The plates were made locally, more than likely to fit his cars. You might want to check the placement of the holes if you do buy another brand.

xhubby
Dirt Freak

Total posts: 376
posted August 12, 2004 09:04 PM  
tilley88 & WPP, Here's what I got. These are not exact (we didn't have the air pressures set exactly) but is real close. Measurments are to the center of the heims.
Floor to pinion mounting point- 8.5"
Floor to chassis mounting point- 14"
Angle was between 20 & 22*(hard to see the gauge laying on my back looking through bifocals) lol.
We have the j-bar on now so I hope I did the angle correctly. I set the angle finder on the threaded rod part of the j-bar so it was in line with the pinion mounting point. Hope this helps & good luck.

tilley88
Dirt Forum Champ
Total posts: 879
posted August 12, 2004 09:26 PM  
Wow, sounds like I need to raise my chassis side. If it's too low, will that cause a push? BTW mod70, good info on the degree thing. But I believe I have a very similiar set-up to xhubby's and possibly WPP's, so that's why I asked in terms of inches. Thanks for goin' thru all the trouble, xhubby!

WPP
Dirt Freak

Total posts: 451
posted August 13, 2004 05:14 AM  
THANKS ALOT I checked mine and in the the bottom hole it was 6 1/4 then every hole after that add a 1 inch . I have mine mounted in the second hole at 7 1/4 .The chassis mount is at 11 1/4 from the ground and on the chassis tube i think it about 5inches Tilley if you need to tighten car move the whole bar down to loosen move the whole bar up on both ends.

xhubby
Dirt Freak

Total posts: 376
posted August 13, 2004 08:16 AM  
No trouble at all. I've always had trouble trying to get accurate measurements with the car on the ground. Just never could get in to where I needed be to read the tapemeasure, or the angle guage. I built four boxes the same height,( as high as my jack will lift the car, 8.25") to set the car on. Now I can set ride heights, & tire pressures, then set the car on the boxes, & scoot right under the car & actually see what the readings are. Works pretty good.
Good luck this weekend guys.

mod70
unregistered Total posts: 376
posted August 13, 2004 10:11 AM           send a private message to xhubby   Edit/Delete Message   Reply w/QuoteBBBBBB
The main reason I added my post was not as much for you guys (88, hubby, WPP) as I have gotten lots of good info from y'all, but for others who read it. Realizing that you were talking more about the mount, I've seen a number of questions and responses about angle refered to in terms of inches of rake and inches from the frame or ground. I just wanted others to know that it's not really the best way to measure angle, because it's too inconsistant from car to car and bar to bar. Degrees are the only true way of describing angle. (too preachy?)



tilley88
Dirt Forum Champ
Total posts: 879
posted August 13, 2004 10:33 AM  
Not at all. I was just lookin' for a reference point to go by on my short 2-link DW8. I have a problem measuring the angle of my j-bar because of the style it is(rubber bushed). The solid part of it and the threaded part of it are at two different angles. Once I put on my short bar, then measuring the angle will be a breeze.

WPP
Dirt Freak

Total posts: 451
posted August 13, 2004 01:22 PM  
MOD 70 Like Tilley said you had some good points. ALL i was trying to do is stay on the same track. Since you are this topic how much differce in a straight bar say 17 inches with 18 degree i normally run i have been thinking about going to the short straight bar 12 to 13 inches and try that would you say keep the angle say half of the longer bar at 9 degrees mounted the the same hole on the pinion thanks

mod70
unregistered Total posts: 451
posted August 13, 2004 03:03 PM           send a private message to WPP   Edit/Delete Message   Reply w/QuoteBBBBBB
I ran a J-bar to start, then went to a shorty after I broke the J-bar. This was mainly because it was cheaper than a new J-bar, but low and behold, I liked it better. I kept the same angle in both, 17*. The shorty reacted quicker, of course, but the overall feel between the two was about the same. The major difference was that it seemed to load the LR more than the J-bar.

88 - The best way to measure the angle of your J-bar is with a 2 foot level (or any straight edge), one end on the frame bolt, the other on the pinion bolt. Of course this involves removing the driveshaft, but regardless of the shape of the bend of the bar, that is where the immangined "straight line" would be.

tilley88
Dirt Forum Champ
Total posts: 879
posted August 13, 2004 03:52 PM  
Thanks for the info, mod70. I'll try that next time I'm at the shop. Sounds like 17*-22* is where I need to be. The angle on the short bar will probably be a little more because the overall length will be shorter than the j-bar, especially both sides being mounted at the same height as the j-bar. Am I correct in assuming this?

[This message has been edited by tilley88 (edited August 13, 2004).]

dluna
Dirt Freak

Total posts: 334
posted August 13, 2004 05:51 PM  
xhubby,

grain scales work PERFECT for that. you can creep around under the car, making adjustments while the car is on the scales. then you recheck the weight, etc. in a flash. grain scales are my friend (may not be as accurate as the digital scales, but a pound or two shouldn't make that much of a difference on a dirt track)

mod70
unregistered Total posts: 334
posted August 13, 2004 06:05 PM           send a private message to dluna   Edit/Delete Message   Reply w/QuoteBBBBBB
88 - You are correct, if you use the same mounting points the shorter bar will take a steeper angle than the J-bar had. I kept the same hole on the pinion, first hole below the yoke, and lowered the frame mount to keep my angle at 17*. I'm using a 7" tube and overall length center to center of 11".

WPP
Dirt Freak

Total posts: 451
posted August 13, 2004 06:48 PM  
Were did that shorty have the most effect on entry or off the corner thanks mod 70

mod70
unregistered Total posts: 451
posted August 13, 2004 10:56 PM           send a private message to WPP   Edit/Delete Message   Reply w/QuoteBBBBBB
The most noticeable to me was on entry. The car seemed to want to plant harder when it rolled over, and allowed me to pick up the throttle earlier.

RACEFAN33
Dirt Forum Racer

Total posts: 98
posted August 22, 2004 09:01 PM  
The shorty bar is it mounted on the inside or outside of the frame? I have ran the straight bar on the outside of the frame and inside of the frame. The straight bar react quicker but it seems to heat the tires up more.

mod70
unregistered Total posts: 98
posted August 22, 2004 09:46 PM           send a private message to RACEFAN33   Edit/Delete Message   Reply w/QuoteBBBBBB
Mine is inside the frame. I have a double mount, but have not tried it outside.

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