right rear overdriving

[vms]

The rr seems to want to over run the whole car. That last time i raced it. Plus myself is hard on the throttle on exit. If i lower top left bar would it help

[Matt49]

No, that will make it worse. On a 4-bar car, lower the top RIGHT bar to take drive out of the RR.

[vms]

ok thats what i thought. thank you

[Bcollins82]

If you have too much angle in the LR upper it will drive it up under the car instead of driving it forward. Don't go over 45* at full droop on the LRU. If your not above that angle, lowering it will take away drive, making your problem worse.

[Matt49]

That's a good point bcollins82. You should use something to limit your travel (besides your shocks) to keep the birdcage from over-indexing. We shoot for 45* in the slick, less when it's tacky.

[rubbinsracin]

correct me if im wrong, but on most underslung cars the underslung rail should not allow the bars to go much if at all past 45*? I'm going to measure the angle on mine, but it cant be much past 45* if at all

[mqdirtracer57]

What is the simplist way to check droop?

[racin29]

put a jack under the car right in front of the lr tire and jack it up till the tire is just barely touching the ground then use an angle finder on the top bar

[Bcollins82]

I get the car up in the air and level and let the rearend hang fully topped out on both sides, then measure the angle.

[anissa5]

I let the lr hang and jack the right rear up to ride height with out the spring then jack up 2 to 3 in when you do this the lr will index even more then just letting the right rear hang there.

[rubbinsracin]

i did some checking last night with tires and shock and spring off the LR and only a junk 7" shock on the RR (had to limit the RR travel somehow) and by moving the right rear way up until it bottomed out on the shock. beyond where it would travel with a shock/spring on and allowing the left rear to go all the way down to the underslung frame and i could only get right at 47* LU bar angle . this was with the bar all the way up on the frame and all the way down on my birdcage to achieve max angle possible.

in short our underslung will not let us go past the 47* mark, even under extreme circumstances. And 2* is about a 1/4" so if i get past 45* im probably going to be picking the LR up with the frame rail lol

[Bcollins82]

i did some checking last night with tires and shock and spring off the LR and only a junk 7" shock on the RR (had to limit the RR travel somehow) and by moving the right rear way up until it bottomed out on the shock. beyond where it would travel with a shock/spring on and allowing the left rear to go all the way down to the underslung frame and i could only get right at 47* LU bar angle . this was with the bar all the way up on the frame and all the way down on my birdcage to achieve max angle possible.

in short our underslung will not let us go past the 47* mark, even under extreme circumstances. And 2* is about a 1/4" so if i get past 45* im probably going to be picking the LR up with the frame rail lol




So how much can your LR drop in inches from ride height before it hits the underrail? Sounds like it's not going far enough. Measure from the top of the axle to the bottom of the frame, then let it droop and re-measure. Different cars like different amounts, but you should at least be in the 5 or 5 1/2" range.

[rubbinsracin]

you know, i didnt measure the amount of drop in inches. the previous owner had a camera on the LR before and when the car goes around the corner and the car is really up on the bars, it will still leave some room between the tube and the underrail. so i know that im not running out of travel and picking up the LR with the frame rail. i will get under and measure it. but how much drop should an underrail 01 shaw car have?

[Bcollins82]

you know, i didnt measure the amount of drop in inches. the previous owner had a camera on the LR before and when the car goes around the corner and the car is really up on the bars, it will still leave some room between the tube and the underrail. so i know that im not running out of travel and picking up the LR with the frame rail. i will get under and measure it. but how much drop should an underrail 01 shaw car have?




As a general rule it's between 5 and 6 inches from ride height to full droop, and you'll be able to feel a 1/4" adjustment.

[Egoracing]

When the chsssis is rolled over the angle gained on the bars will be more than you can get with it at drop unless you compress the RR to the limit it is on the track and then drop the LR.

[rubbinsracin]

measured tonight, 6 1/8" if the RR is tucked way up using a fully compressed 7" shock as a stop. so that is well beyond where any normal 9" RR shock with a spring would let it go. so i put the my normal RR shock/spring and tire on the ground and put the jack in front of the LR and took the tire off and jacked the car all the way up and then i had my dad, who weighs about 230 on the RR of the body above the tire and pushed down. I then put my brother. who weighs about 230 as well on the RF frame rail to cause it to simulate roll. i made took my measurement, 5 15/16 puts me right on the frame with just a glimmer of light in between the axle tube and the underslung rail. so im thinking the car is right in the ball park.

another question, my RR 4 bars with the car at ride height go straight back from the frame to the birdcage. and my left side bars run slightly out, meaning the frame side is further in than then birdcage mounts, in other words the bars are further towards the outside of the car on the birdcage side. i have never noticed this before. the driveshaft is completely straight, from tranny to pinion. so im thinking i need to just move the left side birdcage in just enough to bring it to straight. is this correct and i am just over thinking this or is there something i am actually missing?

[Bcollins82]

You have no way to repeat your measurements. This is the reason all chassis builders have you check droop with both sides hanging. I'm guessing when you check it like that your not dropping far enough. If your at the track, or even back at the shop it's not very likely you'll be getting consistent measurements by doing it like that. And on the LR bar toe, we've normally run the bars (left and right) toed in slightly, but Shaw should have a left to right measurement for you. It's usually a measurement from the lift arm to one of the frame rails.

[rubbinsracin]

im not so much worried about the drop, considering we are running good now and we only have 5 races left this year, its not worth making changes and chasing my tail for the remainder of the year.

we have the measurements for centering the rearend and it is centered correctly. and like i said the right side bars run straight back. but the left side moves toward the outside of the car as the bars go backwards to the birdcages. but what would moving the left side bird cage in towards the center of the car about 1/2" to 5/8"(not sure on the exact measurement it would take) do to the handling? i know it would stand the shock up maybe a degree or two which would make it react heavier right?

[Bcollins82]

Getting the drop correct is an essential part of making a spring behind setup work. It's overlooked too often and if you don't have it right can cause exactly the problem your describing. As for the LR birdcage being moved in to straighten up the bars or toe them out, I was told by Tader Masters to move ours inboard like that before to stand the shock up and actually slide it in far enough that the bars were pointing left so they straightened up when the car hiked and rolled. That adjustment was supposed to tighten the car up on throttle, but we noticed very little change by doing this.

[rubbinsracin]

im not sure what problem you are talking about. im not the OP and dont have problems with the RR over driving. i just got in the convo talking about ways to help with it. im fairly sure that my setup is pretty much spot on. if there is anything holding me back, its the fact im still learning to be more consistant with my driving. ive been a part of setting these cars up for about 10 years. but am still new to actually driving them.

[Bcollins82]

Lol my bad.... Got confused thinking u were OP.