rear sway bars?

[bryant]

i took my 71 maverick to that autocross today. it was my first time every driving an autocross. the car is a 71 maverick, with tcp upper and lower control arms varishock 2 way adjustable coil over in front and shocks in back. 4 leaf leaf springs and adco front and rear sway bars.
it was suggested to me that i should try to remove the rear sway bar. this makes sense in that i should let the rear axle rotate and let the tire stay flatter on the ground.
here are 2 videos from today. the first one is my first run with 2 spins that came from too much throttle. the second one was clean in that no cones were killed.

https://www.youtube.com/watch?v=xk4EQpO6i68

https://www.youtube.com/watch?v=YmziDoc8-9s

so am i on the right track to ditch the rear sway bar?

i also know i need better tires. these are nitto 555s (300 tread wear) but anything that is as simple as removing a rear sway bar will help then im all fort it. one thing im bummed about is that their is no real opportunity to test and tune or make adjustments on the suspension at the autocross events.

[71RS/SS396]

Disconnect the link on one side and give it a try, you don't need to completely remove it from the car.

[High Plains Mopars]

Watching these vids it does appear that your car is a bit tail happy which means you have too much rear bias on the roll rate. Yes, disconnecting the rear sway bar may make it more neutral. Or you could add more front sway bar if you want to keep the rear in place.

Best cheap available test method, find an empty parking lot and drive it right and left around a 100' circle. Have someone time the laps, make changes, run and time again. Repeat as necessary.

[Rod]

don't remove it! I think Tim stated remove a link on one side...some tracks with more traction will require the sway bar to be hooked back up......a rear sway bar is one more tuning tool just like adjustable shocks

[1967marti]

I agree with keeping the rear sway bar. It looks like it was keeping your body roll under control. When I took the rear sway off my 68 mustang I noticed a big increase it the way the rear of the car wanted to tip when I was doing sharp turns.
I do miss the qualcom stadium :-(

[rustomatic]

Consider keeping it, with better tires. The tires will make all the difference . . . I avoided this reality for a long time, but also avoided a rear sway bar, as I crashed on the freeway with a tail-happy '68 Mustang many years ago (had the combined crap BFG TAs and a 3/4 rear bar). With 200-treadwear tires, all parts of your suspension will speak to you much more clearly, and mostly likely favorably...

[bryant]

i do have a bigger set of front and rear sway bars that i can install. from what im getting here, it sounds like i should put the bigger front sway bar on and try it. i will also work on getting better tires.

i would say the car is very tail happy.

[JLMounce]

i do have a bigger set of front and rear sway bars that i can install. from what im getting here, it sounds like i should put the bigger front sway bar on and try it. i will also work on getting better tires.

i would say the car is very tail happy.

I'd listen to Rod on this one. The suspension isn't a pick one and leave it type deal. Especially if you're trying to be competitive. This particular track that you were filmed on, with your current tire setup does look like you may have a bit too much rate in the back. Other venues may be different for you in which case having some added rate back there could be benefitial. Especially if you find yourself in a situation where you need to be able to throttle steer.

What might be a good bet is to try and find an adjustable bar. That way based on your runs you can make adjustments before the next run. Too much rate? Dial it back, or even unhook it temporarily. Car won't rotate? Add in some rear rate as needed.

For comparison sake, the setup you have on there right now might be pretty decent on a big bore style road track where you don't see the types of quick transitions that you do on a tight autocross.

[hotrodalex]

I take it your current rear bar isn't adjustable?

Mine is 3 way adjustable, I've run it on all three settings at various different autocrosses depending on rear grip.

[bryant]

the current front and rear bars are not adjustable. the front is a 7/8s bar and the rear is a 3/4. i do have another set of bars. 1 1/8 3 way adjustable front and a 7/8s 3 way adjustable rear bar. im planning on installing the front one tomorrow. i could install the rear also but i dont know if the thicker rear bar is the way to go right now.

[hotrodalex]

Do you have the anti-roll rates for the bars? It's possible that the lowest setting on the new rear bar is the same as (or less than) your current bar.

For example, the DSE A-body rear bar drops from 739 ln/in to 597 lb/in when you switch the outer hole.

[bryant]

i dont know the rates of these bars. they were from a group buy on a maverick forum board. addco did a custom run on these bigger bars and messed up on the design twice on the front ones before they said they cant do the adjustable ends right and just sent out a standard end bar. the adjustable end rear bars took 2 trys and the second one requires custom frame mount to be able to work. addco never released the rates on these bars and from the poor level of engineering they demonstrated on the design failures, i would not expect them to be able to give them.

[High Plains Mopars]

the current front and rear bars are not adjustable. the front is a 7/8s bar and the rear is a 3/4. i do have another set of bars.

Well crap, no wonder. 7/8 is way too small of a front bar for a serious auto-x effort.


1 1/8 3 way adjustable front and a 7/8s 3 way adjustable rear bar. im planning on installing the front one tomorrow. i could install the rear also but i dont know if the thicker rear bar is the way to go right now.

That 1.125 front bar is more like it. Although I'm surprised they made the front adjustable. I'd definetly do the front bar, and drive it around for some feel on its response. Try a psuedo auto-x in an empty parking lot to compare the feel to what you had pn teh weekend taped above. I'm betting it helps out a lot.

I'd compare the layout of the adjustable end link section of the larger rear bar against the one you have now before attempting an install. If the layout is nearly identical and you can see that the adjustment points allow you to create a greater length in the links and mounts on the new bar, you may be able to adjust it to be as soft as your current bar. The best option would be the ability to make it softer and firmer than your current rear bar to better dial in the combined set up. At this point, you don't necessarily want to step up the rear rate until you see what the increased front rate does for you in the existing combo. Change one thing at a time, measure and compare, then make another change.

[bryant]

thank you every body for the great advice. ive put the front bar on and am going to the autocross this sunday. i also took off the rear traction bar links. i know i will have lots of fun and learn a lot more.

[Carl @ Chassisworks]

Hey Bryant, I watched that front bar shenanigans unfold. Glad you were able to get one finally. Also, thanks for running TCP Suspension!

Just a couple quick things to add. With the double adjustable VariShocks you have a HUGE advantage. The VariShocks have a wider dampening range than the other shocks in the market; this flexibility can help overcome difficulty with ARB rates. Don't be afraid to turn the knobs in both directions, one click at a time, to see how this effects the handling.

Also, if you're going to do a lot of performance driving events, I would suggest picking up Carrol Smith's pocket tuning guide. You can get it on Amazon or, if you click on the image below, you can get it through our e-store.

https://static1.pt-content.com/images/pt/2014/12/8630-1.jpg (http://www.cachassisworks.com/p-2793-road-race-chassis-tuning-guide.aspx)

[GrabberGT]

I run my front bar on its stiffest setting at all times. The rear is 3/4 and stays connected as well. I use the shocks to tune. I thought I had the car set too stiff until the last GG autocross. Rod (above) came over and set my shocks at almost full stiff as well and I picked up all kinds of traction. This makes the tires do the job their supposed to.

[Rod]

I run my front bar on its stiffest setting at all times. The rear is 3/4 and stays connected as well. I use the shocks to tune. I thought I had the car set too stiff until the last GG autocross. Rod (above) came over and set my shocks at almost full stiff as well and I picked up all kinds of traction. This makes the tires do the job their supposed to.

basic shock adjusting

Bump-

During bump, the dampers and springs absorb the upward movement from cornering or road irregularities (the springs store some of it), the dampers then goes into rebound. If there isn't enough damping then the cycle begins again until the car returns to the original ride height, with a bouncing motion to the car. Another trait of under damping is that loads go into tire and suspension relatively slowly, this combined with the bouncing effect means a constant varying download force. Acceleration, braking or cornering in this state with also vary due to the various download rates, so it is important to have enough bump stiffness to be able to deal with uneven surfaces.

If there is too much damping, then it is effectively like running no suspension and any upward motion will be transmitted directly to the chassis. Over damping will result in a increase in the loads acting on the suspension and the tires. The handling will feel very harsh and hard, this will effect street driving in terms of comfort levels, so might not be desired for a daily drive.

This is undesirable in both under and over damping settings as it will reduce the handling of the car and will affect acceleration, braking and cornering loads.

Rebound-

During rebound (following the bump compression phase) the dampers extend back to their original positions, using up the stored energy from the springs. The rebound stiffness needs to be set at a higher value then the bump setting as the stored energy is being released. If there is not effect damping on the rebound, the wheel will quickly return through the static level and start to bump again, with the bouncing effect unsettling the suspension with little control.

If there is too much rebound stiffness, then the wheel could hold longer in the wheel arch then needed, effectively losing contact with the road as the force to push the wheel back down is slower to respond to the changing surface level. This state is again far from ideal and it is best to make sure a good level is set for optimal tire contact with the road.

Damping Effect On Cornering:

Bump

Front Bump Increase= Understeer.

Front Bump Decrease= Oversteer.

Rear Bump Increase= Oversteer.

Rear Bump Decrease= Understeer.


Rebound

Front Rebound Increase= Understeer.

Front Rebound Decrease= Oversteer.

Rear Rebound Increase= Oversteer.

Rear Rebound Decrease= Understeer.

NONE OF THIS IS A GOLDEN RULE......here's were the tuning magic comes into play....sway bars, vehicle weight, coil spring rates, roll center, CG, wheel base, control arm jacking effects, shock compression and rebound curves,,,,and so on,,,so sometimes the adjustment on one car is not what makes sense for the next car

[bryant]

great info. ill save that and start testing the different settings. this turning thing is pretty complicated, but lots of fun!