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

[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.