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Post by otiscampbell on Apr 4, 2013 18:41:17 GMT -6
I've set up modifieds, mostly, in my 7 years of working on race cars. (Prior to mods, we raced karts.) Now, we are running a division of cars that are older asphalt late models with a perimeter chassis--our car has both truck arm and 3-link mounts. On dirt, we are running a 3-link with a J-Bar and a pull-bar and considering I didn't do much but square the rear and scale the car, it didn't handle too bad last season.
Now that we are in the final stretch before our first race, I want to get a good baseline setup down and one of the things about this car that bugged me was the J-Bar--or the fact that I didn't have a starting measurement for a baseline like the modified had.
My question for all of you setup experts is actually 2:
1. What is the best way to determine the J-Bar angle if all you have is one of those cheap angle finders?
2. What is a good starting point for the J-Bar angle? And as a follow-up, where should I start on the pinion side of the bar?
My thought is to figure out a starting angle and then determine where that is on the chassis side and then move it up and down to get different angles and take measurements so I can make changes at the track, if needed.
The track is a 1/2-mile clay. One turn is a little tighter than the other... My driver drove (and was most-comfortable) in modifieds so he would rather have the car a little more free than tight.
Thanks for your help.
Otis
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Post by confused on Apr 4, 2013 20:34:27 GMT -6
The easy way is to measure the hieght differences between the heims om the j-bar. Not sure where to start but I would say around 6 to 6-1/2 inches of rake. The frame mount should be higher than the pinion mount. Start with the pinion side at the centerline of the pinion, based on a nine inch rearend.
The weight, track width, tires, and track surface will all play into the set-up.
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Post by otiscampbell on Apr 5, 2013 6:10:33 GMT -6
Thanks for the reply. I was going to post everything else about this car in a different thread because, like I said, I'm looking for some help on a good starting base-line.
Right now, the car weighs approx 3050# with driver (3000# minimum). I will likely take it up to 3100-3150# because when we hit the scales after the last race last year with 1/2 of a cell of fuel, we were at 3002#...which is a little too close to being DQed for comfort. The tires are Hoosier D35s on 10" rims. I don't have the track width on me...but the track surface usually has grip unless they run us at the end of the night. I expect our first race to go dry-slick, though, because of the wind this time of year and other factors.
One odd thing compared to what I know about the mods... Another racer who is familiar with these cars told me to only run "a few degrees" of J-Bar angle. It could be because the bar is mounted on the lowest hole on the pinion side (it is a Quck-Change, not a 9") so running less angle helps compensate for this.
My overall goal is to get the car good enough to qualify near the front and have some adjustability in the setup so I can compensate when the track slicks off.
Thanks, again, for your help!
Otis
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Post by flipflopoo1oo on Mar 3, 2014 16:54:16 GMT -6
J-bars come in many off-sets as well as bushed and quick adjustable and walking! One hole up and bolt to bolt measurements is best to give a base degree depending on offset bend! Pinion movement by twist and lift comes into play with all adjustments, so keep any in mind with other changes changing j-bar and pinion angle as well as rear end offset with movements and ajustments! A simple ride height change will change so much as to where you want to go with most things! A biscuit on a right trailing arm to allow for some controlled movement ( if legal) helps save many adjustments when its all where you want things! This allows for instant steer going in and closing more on exit! Adjustable fully with limits!
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Post by volksmech on May 8, 2015 9:57:51 GMT -6
Do you have a link to the right trailing arm buscit setup you are talking about. i can not seem to find them listed anywhere.
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Post by flipflopoo1oo on May 9, 2015 6:04:03 GMT -6
Some where in other post -- its there-- run a few more searches!!!-- It's a small caged biscuit bar and fully adjustable by just its design-- just remember to back grind the threads off the front joint as to it bumping as a stop limiter on forward push or it will damage the threads hammering it! Great way to cure most steer problems as roll is not needed any more! Stronger springs to change pounds and transfer faster!!! One more add-on is a upper adj-chain link from top of left rear bird cage that is welded, running it back down to the same point of ft. of left trailing arm!! This is used with a spring pull bar as the diff. has to twist to tighten chain to add left rear bite from hell to a 3 link -pan hard bar car that is so much more drivable and yet hooked to the max!!!-- Personal messaging if more info is needed but I have it all posted if you can find it with searches! You may have to change wording on your searches to get more info in your returns on a subject of interest!!! I hate the radical nature of short bars anywhere on any part of a set-up and use practical common sense to get around thing that give way to needs of change from track to track or turn to turn or speed or driver preferences car to car! Set your common ranges of compressed spring heights and les go racing to win safely and drivable!!!
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Post by flipflopoo1oo on May 9, 2015 6:24:05 GMT -6
I HAVE SEVERAL CARS TO KEEP GOING AND A FEW OLD ONES TO PLAY AROUND WITH! SPENT 6 HOURS ON THE SCALES YESTERDAY TRYING TO FIND A HAPPY POINT W/WO PASENGER ON A CRUISER CLASS CAR JUST HAVING TO BE REVAMPED AFTER A 6 INCH BENDER--- REAR RECLIP WAS NEEDED AND A TOTAL UPGRADE TO FIT THE RULE CHANGES IN BODIES!! IT WOULD HAVE BEEN SO EASY TO USE THIS SLOTTED STEER WONDER BUT NO CHEATING IN OUR SHOP ALOWED! WHAT WOULD BE THE POINT OF WINNING THAT WAY IF THE REST CAN'T CHEATING ALL THEY CAN!!! B- MODS HERE ARE THE NEW CHALLENGE ON SLICK TIRES AND PLENTY OF HORSES! only ONE WIN SO FAR BUT TONIGHTS ANOTHER NITE! GOOD LUCK WITH YOUR UPGRADES AFTER YOU DOWNGRADE BACK TO DRIVABILITY!!!
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Post by flipflopoo1oo on May 9, 2015 7:57:18 GMT -6
QRP66-500 REMOVE FRONT THREADED SHAFT AND REPLACE WITH ROD END AFTER GRINDING THREADS BACK A BIT TO KEEP FROM STOP LIMITER FROM DAMAGING THEM WHEN BUMPING! a LONGER END IF NEEDING ROOM FOR A NUT TO LOCK IT THERE! YOU USE IT AS A FORWARD STOP AND ADJ BISCUITS AS TO AMOUNT OF TRAVEL NEEDED AND THE LAST ONE AS WHEN BREAKING A BIT TO PULL OPEN EVEN MORE! CLOSED 3/8 AGAINST STOP AND ABOUT A 1/4 OF FREE TRAVEL AND ANOTHE ON THE BISCUITS WHEN OFF THE GAS AND ANOTHER 18 ADDED TO IT IF BRAKING GOING IN WORKS GREAT TO ADD DRIVABILITY!!! I run a cross switching set-up that plants right rear just by lifting the throttle as it noses easily sending pounds to the left ft. and then to right rear as-to be planted before you turn or roll! Of coarse the left rear has to be maintained by the cross by the 150 = pounds of lead placed there low and rear as possible! The action hinges at the left rear axle and never lifts at all loosing pounds there as to the left drag pulling the car left into the turn when lifting! Once shifted weight of the roll or rather right down-force is in place the right has equal pounds applied by using more right rear bar angle to make up the lack of pounds there in transfer! The left rear always has more until on the throttle switching drive to the right side as-to turning the car left with drive-- this lessens the need for roll out, being sideways to use left rear drive to correct a sideways car and the need of hiking to get bite or transfer! This to keeps spoiler down-force from loading your wagon of the corner with more air weight to tote! 1/2 inch roll out lets the tires stay hooked and little heat is made to change your perfected set-up! One tire does not have to break traction when going straight and this too frees horses to be faster around and off the corner! The higher right bar angle pushes the car back over to stop rear steer off the corner to be able to stay lower on the track or drive right under anyone else at any time you have room to get by as the drift out with their rear still steering and having to turn right to keep up with their rear!!! Most all of you have had trouble if close in traffic getting off the turn low if hiking and over-steering in the process of not being able to stand fully on the throttle or getting it up on the bars in traffic or God forbid having to drop in traffic and the time it takes to get it back up and in control!!! Good for Goose and Gander as it can even out the rear while hiked if you please!!! Nothing new as seen in use by a few 35 years ago!!! Best fix all I've seen for some older three link cars!!!
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