body roll

[hasben]

Our car will not roll over as much as it should. We have checked ride heights, j-bar has 5" of rake. Car has Q/C and jbar located appx 1 " below pinion. Shocks are not binding nor birdcages - what are some additional areas to check?

[js11]

What kind of rear suspension, front clip, springs, etc are you working with?

[johnny v]

Tear drop tank or regular rectangle or Square? Alcohol or gas?......... RR spring?

I am right in the middle of a winter refurbish on a 09 harris , pulling a 32gal tear drop cell and putting in a 16gal rectangular cell..... previous owner ran on alky, we are on gas.... we are only putting in 8 to 12 gal of gas..... Weight way down low in the tear drop.....

Going to raise the CG..... been looking at lots of cars.... probably put the bottom of the cell 2" below main frame rail ( looking at it from the rear)..... might even make a couple of sets of mounts to raise or lower it easily .....

[hasben]

Johnny you know the car. 4bar chevelle clip kk704 tires

[hasben]

springs 650/600 front and 200/225 rear. i think - book not here

[johnny v]

Johnny you know the car. 4bar chevelle clip kk704 tires

I'm old and forgetful, refresh all our memories with details...

[js11]

I'm assuming you're running the spring behind on the LR.

For what it's worth...

My experience has been that if the car is not binding though suspension parts, the slip yoke at the tranny or through the shocks, you might have too stiff of a RR spring, or too still a RF spring, or both. You don't want to go too soft at the RR corner though, because that will decrease side-bite...even if you do increase body roll. You can also hang ballast high and to the RR side of the chassis to help things along (above and just behind the tire).

Further to that point, if you already have the softer spring on the RF, and the 225 is on the RR, try putting the 200 on the RR ( I would also run a 200 or 175 on the LR). Also, make sure your LR shock is not topping out. All this assumes you have the correct offset on the QC, and that you've strung the car to make sure things are square-up.

Also from past experience, I'm thinking that 5" static rake (and 1" lower than the QC pinion at the QC plate) is a bit too much. I've often found that too much rake at the J-bar makes corner exit too skaty and erratic. Try 4' from static, and a little higher than the yoke at the QC. Then lower both ends if you feel you need to lower the RC.

...Just my immediate thoughts on the question. Good luck.

[hasben]

johnnyv you are on target with the fuel cell. When you set that little cell, mount it as close to the decking as you can.

Our fuel cell is rectangular.

We have been having trouble with the rear seal and thought it was possibly the yoke bottoming out. We cannot duplicate that in the shop. That is one of the things we have checked. We have debated about decreasing the angle in the jbar. In fact upon checking we have 6.5" of rake. That could be some of our problem. But the chassis mfr recommended that setting on the rear end.

[js11]

If your damaging the rear seal of the tranny, then that is not helping. It could very well be affecting the other aspects of the suspension. I would try to get at least 2.5" of barrel sticking out the the back of the transmission seal, and at about 2" in (that's assuming it's a Bert or some other aftermarket tranny). I have experienced this in the past. Once I ironed that out, it was amazing the difference in how the car responded.

I don't know how you are simulating this in the shop, but on the track there is a lot of movement that can be hard to replicate in the shop. If you go on Youtube you can find some Mods with suspension camera footage that will be very helpful to see.

[hasben]

we have about 2" of the yoke in the transmission at ride height. It is the long yoke. Transmission is only 3 years old and will accept long yoke. Only getting about 1 1/2 " travel on pull bar. It is a new yoke and not distorted.

[oldtrackchamp4x]

Is the car getting on the RF? How much shock travel do you have left on RF? If there is over 3/4 to 1 in left i would soften the RF spring to 500-525 and LF to 550-575. Can also add lead up high on RR side over rear end. Also agree with js11 on changing rear springs. Works for me. JMO

[HEAVY DUTY]

I have not seen the LR drop mentioned. If the LR tops out too quick, it will keep the car from getting on the right side. Too much causes worse problems though.

[hasben]

we have chain limiter on car which stops roll before topping out lr shock. We have even put a 2" extention on shock and lengthened chain. No change in rf travel still 1 1/2" to 2". Cannot find any binds in shocks or birdcages.

[HEAVY DUTY]

we have chain limiter on car which stops roll before topping out lr shock. We have even put a 2" extention on shock and lengthened chain. No change in rf travel still 1 1/2" to 2". Cannot find any binds in shocks or birdcages.

How much does it drop? 4 to 4 1/2 " from ride height to chain tight is about right. Different ways to measure changes it a little. I would measure with all 4 wheels on ground and jack up under seat to simulate roll. Measure between thecaliper brkt and bircage straight up to the deck. That or the Center of gravity height. If they are ok, you have a front end geometry problem ( too much antidive)

[hasben]

we measure from bottom of top overrail to top of top of axle tube and it measures 4.25" from ride height to full travel that is allowed. we run usra kk704

[JustAddDirt]

we measure from bottom of top overrail to top of top of axle tube and it measures 4.25" from ride height to full travel that is allowed. we run usra kk704

Depending on how far in the framerail away from tire, that could be 6" of drop at the contact patch of tire. May be too much.
just an observation.

[thfleshman]

if the car is not rolling over (assuming all binding issues if any) are fixed in suspension get a long yoke and try to bury it in the trans we had issues and the yoke actually was binding on the shaft(not the housing) because the yoke was hitting the shaft where the output shaft splines ended. we took the output shaft out and had it relief cut about .010 and its perfectly fine now. I believe the new trans may even be doing this from factory now?? thats just hear say

[hasben]

we have checked the yoke travel into the transmission. No problems.

[JustAddDirt]

If you are on a 225 on the RR with a KK 704 tire you may be too stiff depending on tracks ran. I run UMP tires, and that 225 RR spring works well on our tires. But we have a softer sidewall.
What are your shock valvings?
If you have some stiff valving, or alot of low speed in the RF you may need to soften the RF spring 50# at a time till you get some movment. 1.5-2" is not alot of travel. Are you on a bumpstop on the RF?
Chassis roll, or hike does not always promote forward traction or sidebite.
What is the car doing, or doing wrong?
Is it skating across track on entry or through middle?
No forward traction?

[MM90]

Body roll doens't create sidebite, sidebite creates body roll.

[hasben]

If you are on a 225 on the RR with a KK 704 tire you may be too stiff depending on tracks ran. I run UMP tires, and that 225 RR spring works well on our tires. But we have a softer sidewall.
What are your shock valvings?
If you have some stiff valving, or alot of low speed in the RF you may need to soften the RF spring 50# at a time till you get some movment. 1.5-2" is not alot of travel. Are you on a bumpstop on the RF?
Chassis roll, or hike does not always promote forward traction or sidebite.
What is the car doing, or doing wrong?
Is it skating across track on entry or through middle?
No forward traction?

Car does not skate on entry or middle. Driver say that you just have to wait on the car to turn. So it could be skating to a degree. It does not appear that they are taking too much speed into the turn. This was with about 60# lr bite. Also we run WAR shocks ( I do not know the valving). We have lowered front springs to 500/550 and are considering lowering rear to 175 to promote forward bite and to help car getting over onto right side. We do not run bumpstops as car won't roll over far enough for them to work.

[JustAddDirt]

Body roll doens't create sidebite, sidebite creates body roll.

Jackpot!!!

Hasben,
Have a some questions:

What kind of chassis?

If you have to wait on the car to turn, is it too tight on entry and threw middle?
If car is understeering on corner entry, then it will just scoot RF tire across track and never scotch it up and get on the RF.


How long has your driver been driving?

How long has, or has he ever driven a 4 link modified?

Does he trailbrake?

Do you have a brake floater on LR?

Does car set down on corner entry, or stay up on the bars?

Does he arc the car into the corners, or drive straight into the corner, and try to turn car quick with brakes?

Is he driving into the corners as hard as the frontrunners?

[Dirtrunner35]

Great questions above. Why do you think the car isn't rolling enough ??

[johnny v]

I have worked on a couple of different cars at the same tracks that "hasben" races on.... and all at one time or the other experienced the "wait" on the car......

I call it a failure to rotate.....

Its real hard to "arc" cars into the corner around here because I would classify the tracks as almost "Paper clip" type .....

Cars that are Real Fast every week seem to turn in "on there own" and stay up on the bars all the way through the entry, center and exit...you never seem to be able to tell or see that wait on it or hesitation.....they never loose much momentum......

Lots of MY Chassis issues are really Driver issues... but I do run about 3.5" of stagger, High Left Side %, about 3 degrees of castor stagger and around 40#s of bite to help the car turn and rotate... and harp at my drivers to brake straight, let off the gas slow, arc it in, let it rotate and then roll back into the gas slow........

[hasben]

so in essence we don't have the needed amount of side bite & car is slipping?

[hasben]

too many questions! can't remember them to answer. Car is an Impressive has floater on lr. car sets down on lr but does not slam down too hard, driver experienced in 4 bar mod & late model, driver goes into turn with competitor and they drive away on exit. Frontrunners are at the front and we aren't (LOL). Driver has tried all angle of entry.

[johnny v]

so in essence we don't have the needed amount of side bite & car is slipping?

I would go the other way..... with 0 #'s of LR, you should have sidebite out the ball park... It seems like you might be too tight on entry.....

IMHO and with notes from Shane C off the old dirt forum: If you going to run 0 bite.....

550 LF 450 RF 200 LR 225 RR, 0 bite, 56% rear, 55.5% left , all with driver....

Also from Shane C blog post:
I typically don't do much to tighten entry from the baseline as the track slicks off, as the driver has a brake adjuster and 2 pedals that he should be able to adjust entry with as needed. It is better to error on the loose side on entry for than to get the car too tight to turn in most cases, and some good footwork from the driver should usually do the trick.

[bittight]

Sounds as tho your to stiff on rr spring, lr #'s are maybe a little high but not bad the bite in lr should actually help it turn into corner. If it was me I think I'd try to soften the rr spring 25# at a time. Tight paper clip tracks I've saw guys go from 200# to 150# at places such as haubstadt, putnamville ect. If your track has banking you really don't need all the side bite the heavy rr spring promotes on entry. But if u get to soft on rf with banking the car won't want to stay down it'll want to dig into surface and push up from the experience I've had working on these cars for the past few yrs. also if you have to much rake in J bar it will top out n not let the car roll up onto the right side as far, it'll roll faster, make quick side bite then done so you'll be tight entering then the rear will run out early middle and want to scotch out late center and exit. Another thing that can cause it not to lay over on right side is to much angle in the pull bar, to much angle seems to hold the car off the rr spring. Do you run a 90-10 dampener on top the housing if so I'd try to leave it off, soften rr and I bet it will help you turn into and rotate a lot better.. Good luck

[hasben]

bittight you have described some of our problems we had with a different car. The angle of the jbar intrigues me. I have been thinking that we have too much angle and the driver described what you were saying - except they called it loose. So we worked on that. Jbar angle could possibly be a part of our issue.

What do you think we could do to enhance our forward drive?

[bittight]

Less rake in j bar should help with that some also. If u get the entry working to where u can trail brake it into the corner and the car wants to go left on its own then that will help your traction off the corner cause your carrying more momentum through the center and by trail braking roll into gas sooner and easier which in turn keeps your rear tires hooked up cause your not sliding the thing early center to get it turned if that makes sense. Id be sure to also go thru the bump steer and caster/camber before you even mess with any of it, bad front end settings will kill a cars entry if its not naturally set to turn down the track, its not going to turn well if there pointing towing in or out from one another.. Keep in mind I've never driven a 4bar car only crewed for one of the better mod drivers in the Midwest and we had pretty good success.. Watch the car if your not the driver, and I like to stand on the fence at corner exit so you can see if the nose pushes, or is he's back steering it hard thru the center and on exit. Shock valving If bump, j bar and rr spring aren't helping. also u can soften lf some to help entry but that's not going to help exit.

[oldtrackchamp4x]

In reading Johnny v's post that he has been at the same tracks as Hasben, and that the cars never seem to come all the way down, turn in on their own, and they don't lose momentum. Leads me to think, without seeing for myself, that they are backing up the corner. There was discussion on this driving style in other posts. I've started driving this way myself and when i get it right the car is very fast. To back up the corner you SLOWLY back off throttle, about 1/3 to 1/2 of full while still in the straightaway, 2-3 car lengths sooner then you normally would. You also apply a LITTLE brake. Upon turning into corner you are able to get right back on throttle, without losing any momentum and not coming off the bars. Watch and listen to the fast cars and see if this is what they are doing. Like i said, i'm not that good at it on a consistent basis, and as always this is JMO.

[hasben]

Thanks everyone for your input. Bench racing is nearly over for us. Hopefully by using some of your ideas we will get this car working better.

[JustAddDirt]

Sounds like the car needs to be loosened up on entry.
That can be done with a softer RR and a softer LF. and less j-bar angle.
I have found that if you car is a bit loose on entry, you can back the corner up a bit, trailbrake and keep the car up on bars, and pullbar loaded, and you will have a greater corner speed through center and exit.
That is alot for a driver to learn, perfect, and remember to do each lap though.

[juice87]

sounds like you need to spend a couple days on the scales playing with lead and writing down all your results... plus how about your rr spring table is it even ? also maybe put some angle in rr bottom bar to loosen on entry when heavy play with wedge then take some angle out of bottom bar for feature? without seeing its a crap shoot!!