Can someone explain in simple terms what a j-bar does and what affects it has by lowering/raising it on both the frame and the pinion?
Printable View
Can someone explain in simple terms what a j-bar does and what affects it has by lowering/raising it on both the frame and the pinion?
Changes roll center of rear. Down pinion/up chassis "tighten car or stick rr harder. Opposite loosen. Pinion bigger adjustment then chassis typically. There's a point where have too much angle in j bar and then your really chasing your tail.
Afco used to it believe had good article explaining j bar in their tech section
Thanks for the reply... that’s what I thought but wanted verification on it...
Un j-bar related...any thoughts on being able to get the car up on the bars but car seems to unload and “slam” back down as soon as you get out of the throttle
Driver new to late models? If so, that’s usually driver induced. There’s things you can do to help. What car, springs, bar locations, track configuration/surface conditions etc?
Have a similar problem too, car sticks the rr good to the center. After that it feels like it looses the rr an skates just a little to much.
Before or after you pick the throttle upQuote:
Originally Posted by Roudy73
It would be on the throttle.
Typically slamming back down is Driver letting out of throttle to fast but with today's shock valving it should still hold car up on lr.
This would typically indicate that the car is too tight on the throttle. At that point you need to decide weather or not you could afford to be tighter in on decel because many of the adjustments that generally loosen accel generally tighten entry. You need to identify what is actual happening at initial throttle pick upQuote:
Originally Posted by Roudy73
It feels like when I get the car loose enough on entry the car just skates through the corner. It could be the way i drive too. I drive the car to straight people have said. If I enter sideways it will just keep sliding. By the time it catches everyone is a car length ahead.
How are you "loosening the car on entry"?Quote:
Originally Posted by Roudy73
We were taking lf spring out. But its almost like it took the drive out if it too. Thanks for the responses.
What would be a better to free up entry at the track?
lf spring for the most part is an entry only adjustmentQuote:
Originally Posted by Roudy73
heres what i recommend
go test and be honest with yourself (go pro looking at the steering wheel)
almost 99.9% of the time the car is too tight and breaking loose in the middle = killing drive off
I'm guessing this is when its slick and you will have to give out all info to help
but test when slick and drive straight, fix entry, then middle should almost fix itself (little tweak at most) then work on exit
if you trip at entry you'll fall at exit
What are you doing on the RF/LR/RR? single spring, bump stop/spring/etc.Quote:
Originally Posted by Roudy73
Rf 275 black penske bunp with one spring runber, Rr 225 with two spring rubbers, Lr 100 16 inch spring. It is a B/G rocket. No stacks can just run single springs. Grt74 is probably right about being to tight in. I have just never found a adjustment that has made the car comfortable getting in. When I get it free enough then it feels like the car is in top of the track.
spring rubbers come to mind (could take them out, with that said go up to 250 on rr but no rubbers) 250 will be less load with out the rubbersQuote:
Originally Posted by Roudy73
sometimes soft left rear springs are not always the answer, try 150-175 but you will have to learn not to let the car slam, but will be free in, more drive off, you would be surprised how many have gotten off the soft deal
soft springs for the top teams are so they can beat the body rules
bars
could go up on lr bottom
could lengthen rr bars 1/4 inch (leave car the same way you have it,tractioned up)
rr bottom level at ride height (slick)
I'm guessing your close and looking for just a little
Are you setting load or just put bump and rubber in RF/RR and run? Spring rates WITH rubbers don't mean much, so many different coil spacing and rubbers out there. BTW, you hijacked this guys post
I had a guy set them in a smasher. They are the blue rubbers like rocket recommends. Sorry for hijacking his post.
Grt74, how do you get around the body rules if you run a stiffer spring in the lr?
If your driver comes in an tells you it is to tight, like stuck on the rr. Would you loosen entry or loosen the car on the gas?
Fix entry to center and the exit generally fixes itselfQuote:
Originally Posted by Roudy73
i have argued till I'm blue in the face about this one with the drop rule (they are dip chits on this one)Quote:
Originally Posted by Roudy73
if you are going to jack it up and check it, with a total height measurement, why should it matter at ride height????? sure it gives the bars more angle to be gained and some will drag the frame rail going threw the pits but if you know what your doing with springs you can gain the same or better results cheaper (don't need all the crazy valving)
125-175 spring you should be ok, it will free the car up going in OFF THE GAS, then you have the added bar angle to be gain when you pick the gas back up (its not preloaded threw the roof) but you'll have to have the rf correct too so it will work
some will laugh at this and say it will never work, if there were not ride height rules, just a total height rule when jacked up, i would tell you to put a 300 on it, start at ride height and jack rounds in till comfortable
I started this year with a digressive stack, 55lb rate at ride height. I could not get the car to rotate on entry (off gas, I may not be the best driver...). This week a threw my 170lb barrel spring on and it was a night and day difference. Car rotated on entry so much better and I could get on the throttle much earlier. Now this track does no tech beyond weight, my deck was probably 41” at ride height. I’m going to dial it in a bit to be legal at other tracks. What did I learn? I need some LR spring to make the car turn.
What were your loads with the stack vs single spring. I 55 is to soft