BODY ROLL, What to do Options

[wjpierce]

Hello 914World.
I recently purchased a '74 914 racer and had it on track at Buttonwillow raceway last weekend. There were issues in that the car was last raced in 2014 but these were overcome.

Here is the major problem with the car. Body roll. Transitioning from a right to left turn requires neutralizing the car mid cormer and then allowing it to set. If that isn't done, the car wants to break loose when it sets into the next turn. I don't have a rear sway bar on the car and that is the first order of business but it seems impossible to me that a sway bar could overcome this much roll by itself.

I was thinking of trying coilover shocks to help with this. This might also allow us to corner weight the car.

What are your thoughts on this. Any other strategies that have worked for others with 914 racers?

I appreciate your input. Bill Pierce

[stownsen914]

From what you describe, it sounds like something is loose somewhere. Or you have a deteriorating bushing somewhere in your suspension - could be rubber or poly, I've seen both wear out / break apart. Many times the "taking a set" and wanting to break loose is the result of having to take up slack from looseness. It's called snap oversteer when this happens. It can be scary to drive a car that has this issue. A few things to look at - you can jack the car to get each corner off the ground and give the wheel or suspension a good shake as a first test.
Worn bushings on swaybar droplinks (or something loose)
Side to side slack in front swaybar (make sure the droplinks are pressed up against the bushings, or even better have a clamp on the car just inboard of where the bushings mount to the body)
Worn bushings in front suspension (or something loose)
Worn bushings in rear suspension (or something loose)

Another possibility is the car is set up too stiff in the rear, springs and/or swaybar, or alignment is way off, causing the car to oversteer. It's different than what I describe above, but can feel similar - the rear will feel "loose." Tell us about your suspension setup, including torsion bar and swaybar sizes, shocks, and rear spring rates. Those things tell much of the story. Also alignment specs.

[Matt Romanowski]

We need all the details on your setup. What size torsion bars, what shocks, what spring in the rear, rear springs, ride height, alingment, etc.

I think Scott might be on a good path with something being worn/loose. Dynamic rear toe (worn bushings) makes for a very lively car.

[slivel]

We need all the details on your setup. What size torsion bars, what shocks, what spring in the rear, rear springs, ride height, alingment, etc.

I think Scott might be on a good path with something being worn/loose. Dynamic rear toe (worn bushings) makes for a very lively car.

x100 on the dynamic rear tow comment. I like a car to be sprung correctly and fine tune the handling with sway bar and tire pressure adjustment.

[brant]

What diameter is the current front anti sway bar?
That would be my first suspension change if nothing is broken or worn out in the bushings and the bar is stock.


What weight are your rear coil over springs currently?
Also a first address type of issue if they are street springs currently

Front coil overs are not necessary for corner balance.
Rear adjustable coil overs are. (But the stock is already a coil over… not adjustable)
So I wasn’t clear which end of the car you were referencing

[wjpierce]

Thanks everybody. I've obviously got a lot of homework and examination of the car to do. It is currently at a race shop elsewhere so I will gather all of the data and report back. I appreciate the feedback. The car has not been on track since 2014 and several other rubber (and metal) parts showed their age and wear. I'll get back when I can answer your questions. Thanks again. Bill

[infraredcalvin]

In addition to current setup (and pics of course). What’s your level of experience? If it’s the same car in your avatar, I think I remember this car from older posts.

[yeahmag]

All the requests for more info are definitely on target. One thing I would keep in mind is that car feel is almost as important as any other parameter. Don't be afraid to play with out of the box spring rates and the like to see what feels good to you. My setup for autocross is radically different than most others and the car is a proven winner.

[sixaddict]

I have never used a rear bar…..and don’t believe one is needed. A 100 years ago, I had a torsion bar fail…….I could always feel it ahead of the terminal oversteer (autocrossing bc it was a guaranteed spin).
Changed them out and it was fixed…..

[brant]

I run an aftermarket (larger diameter) rear bar with adjustable drop links
Really like it although I don’t run it very tight

The problem becomes the need for a limited slip

I Like street cars with stock bars also

But driver style probably plays a role in rear bar applications

[wjpierce]

I have the information many have requested.
The car has:
Turbo tie rods
23 mm front torsion bars
Bilstein shocks/ struts with 225 lb. rear springs
19mm front sway bar
Purchased, but not installed 16mm Weltmeister sway bar
Toyo R888r tires

I have heard the concern about the need for a limited slip diff with the addition of the rear sway bar but hopefully I won't unload a corner sufficiently to lose traction

Any other advice? Thanks, everybody. Bill Pierce

[brilliantrot]

The 914 Aaron (yeahmag) has and I autocross seems to be pretty happy with the same setup except we have gone to 550lb-in rear springs to keep out of the bump stops on the rear shocks. We have since upgraded to some fancy Penske shocks that might allow us to drop down to a 450lb-in spring and add some compression valving to help keep it off the bump stops but running low, on Hoosier with data showing we have sustained 1.3G with peaks to 1.7G, and low friction bearing’s trailing arm pivots, we need a LOT of rear spring.

[wjpierce]

Thank you. I was thinking that heavier springs would help as well. Our next outing is Willow Springs and I'm going to try the sway bar but I think I'll also buy some springs if the car still rolls like it does. I am coming from a formula car and perhaps my expectations are unrealistic. Severe direction changes require treating the change as if there are two turns. One to settle the car and another to negotiate the turn. Simply changing direction rapidly will certainly cause the car to spin unless I sort of make it neutral as I change direction. I am explaining this badly, but perhaps you know what I mean. I am certain that setting the car is really allowing it to settle on the stops.
Thanks again, for your feedback.

[stownsen914]

What you are describing is the car "taking a set" i.e. loading the suspension in preparation for navigating a turn. Ideally the car should exhibit the same attitude as the transition happens. Sounds like yours isn't. Lots of reasons it could happen, including the looseness / snap oversteer I mentioned in the earlier post.

Can't remember if I mentioned, but is there a possibility your rear shocks are hitting the bump stops? If so and it's the stock rubber type, that can ruin handling in a hurry.

As for stiffening the rear springs, if you are looking to dial out oversteer tendencies, going to stiffer rear springs is almost certainly the wrong answer. Going stiffer in the rear (springs or swaybar) will promote oversteer, not reduce it.

[brilliantrot]

Can't remember if I mentioned, but is there a possibility your rear shocks are hitting the bump stops? If so and it's the stock rubber type, that can ruin handling in a hurry.

As for stiffening the rear springs, if you are looking to dial out oversteer tendencies, going to stiffer rear springs is almost certainly the wrong answer. Going stiffer in the rear (springs or swaybar) will promote oversteer, not reduce it.

I think he is hitting the bump stops, we fought the same issue for a long time with 225lb-in rear springs. Car was nice and balanced until you really got aggressive with it on turn in and the rear would instantly go to snap oversteer after a slow weight transfer as we were hitting the bump stops. The rear roll center on lowered cars seems to be so low there is almost a digressive affect to the spring rate.

In any case, the car has only gotten easier to drive and better behaved after doubling the rear spring rate. You can hold it in a controlled power slide drift if you want which I was never able to do in my 914.

[campbellcj]

I went from 200's or 225's to 350's along with revalved Bilsteins and the car behaves way better. Has 22mm hollow t-bars and F+R swaybars.

[yeahmag]

What Evan said... It seems counter productive, but it needs to stay off the bump stops. Running a small o-ring or ziptie on the shock can give you valuable information. Even with 300lb springs were were burying the tell tail. Quick transitions are effortless now. Car still will take a nice set in a long turn and most importantly for Evan, will drift all day long ;-)

[brilliantrot]

The ability to hold the car at angle really helps when you want to rearrange the course when someone through the corner should be tighter than you do!

[Brett W]

Here is the major problem with the car. Body roll. Transitioning from a right to left turn requires neutralizing the car mid cormer and then allowing it to set.

Need to address the shock valving. All of what you are describing occurs in the phase of cornering most affected by the dampers. I have to bet the dampers either are street dampers or are valved for comfort more than racing. Get those dampers out and have them valved by someone who understands race dampers.