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I have an 08 GRT 4 bar car with the spring behind on the lr and in front of the rr. I'm really good on entry and going through I just can't get any drive off. I race on a pretty flat 3/8 mile track. We have the lr birdcage indexed into the spring 2 degrees. Springs areLf550Rf600Lr175Rr150Any help would be great thanks
Where is the left bottom bar on the chassis? What is your 5th coil spring and shock and it's location?
probably got a pullbar on it, and not a liftarm.
The bottom bar is 3 up from the bottom and we are on a pull bar. It's the bisquit one from quick car. GRT sold me a spacer to put in there so we only run 3 bisquits and they are all reds. Its 10 3/4 inches up from center and 2 inches forward.
what hole would you be in on the LR to have that bar level?
how much LR weight?
pullbar mounted in center of rearend?
rear weight %?
use a 1050 spring adjust preload to get 1 1/2 inches of travel
Pullbar is in the center and we have 45 lbs of lr and about 57.5% rear thought about taking some rebound out of the rf to help the weight transfer a little easier
Lowering the left bottom bar on the chassis adds drive from the center out while on the gas if it birdcage is floated. Adding angle by moving it up on the frame removes drive. I would also think about moving the bar to the left of centerline.
Adding LLB angle increases wheel loading, which increases drive. However, it also icreases roll steer which makes the car feel looser. The car will want to crab down the straight with more LLB angle.
the rear steer far outweights any drive raising the LLb adds. lowering the bar adds drive reduces rear steer and makes the car drive much straighter, it indexs the birdcage into the spring more when the car is on the bars.
When you start think and understanding thrust angles, then you will see how adding angle increases drive. Lowering the LLB DECREASES drive. Indexing does increase which increases the initial bite but not once the car is up on the bars. There is a point of diminishing return though. Just like any adjustment. Depending on the chassis, one or two holes should be enough to change a cars handling without having too many adverse reactions.
Lowering the LLB to a flat position lowers the thrust angle of the LR. This unloads the LR tire. Sure the indexing will load the spring more, but it's short lived. As the car starts to climb the bars, the top of the spring is moving away from the bottom faster than the indexing can keep up with.
This does not work for every driver. Some "feel" way to loose when they are not. If you don't like it, don't use it. How much angle is used also depends on the track. Is it a tight 1/4 mile or a sweeping 1/2 mile. Less angle would be needed for the 1/2 mile.
Try increasing angle and length of LLB. Increase in angle will increase drive, increase in length will take rear steer out, in turn tightening overall handling. May need to increase RF spring rate to loosen entry when doing so.
if your just wanting to add drive off the corner raise the LRT rod one hole. sure raising the LRB rod will add thrust angle but also adds rear steer which loosens the car more than the added drive tightens it up and lowering does add instant drive till the bars take over an the car gets off the spring, once the car is off the spring it still keeps the car straighter because of the reduced rearsteer. the top rod over rides the lower rod, if your just wanting to tighten exit lower the bottom rod, if your wanting to loosen exit raise bottom rod. but if you want to add drive an tighten up exit raise the top rod.
Tend to agree with 4banger , my drivers in crate and emods all agree lowering LRL adds drive and makes car come off corner harder and straighter.
hey 4banger, your inbox is full.
When he left rear bottom bar is at an upward angle the left rear spring acts digressive. As the suspension drops the birdcage rotates away form the base of the spring and unloads the spring. As you flatten the lower bar out the suspension drop reduced the loss of spring and can actually index the birdcage into the spring which adds drive. there is more to the equation that just the thrust angle of the bars. Once the car is on the bars the spring is unseated so if it was all about thrust angles of the bars you could remove the spring and the car would know no difference. Look under "To Tighten Corner Exit"
http://www.bryke.com/blog/tech-infor...nt-and-set-up/
There are drivers that can keep the car on the bars all the way around the track. The spring can be removed for all intensive purposes. But like I said before, if you don't like it, don't do it. If it didn't work many, many fast cars would have little to no roll steer under throttle. Again, if you don't like it, don't do it! I know what works for me and my cars.
Iv'e read more of those generic tech articles than I care to admit. When I quit following everybody else's iseads and gave the car what it wanted and what worked, it got faster.
The upward angel is better is antique thinking, many cars with full drop are only a few inches off of the spring and when the car goes into the corner it is on the spring even with trail braking. If you rotate the birdcage into the spring you can almost eliminate spring loss especially with the longer lower leverage lengths used on many birdcages. Don't believe it put a camera on it. You will be amazed at what you learn. This it the same type of information taught in any major chassis schools now so I guess that they are all "Generic" information. I do not have to believe in something for it to work, it is simple mathematics and movement ratios that can be seen in effect in the shop with the car on stands.
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