I'm a big fan of roll cages in cars but what I heard recently shocked me.A supposedly top car engine builder in this country gave someone I know this advice.He said that having a roll cage in a car was not a good idea as you need the car to twist to get a good launch at the dragstrip.The safety aspect aside and the fact that I'll not be doing much drag racing,this advice seems to be totally alien to me.What do you all think,is he talking crap or is there any truth in it.Thanks

 

i suspose to a certian extent that is true but you don't want the chassis to flex excessively either, especially drag racing, and the cage is a safety item more so that structural support, even if it does double in that respect. SFCs control flex and a cage would help. you can use all sorts of trick to preload the suspension to control flex and get a good launch.

 

Chassis flex, for all intensive purposes for us, is uncontrollable and not necessary constant from one situation to another no matter how similar. So the idea is to make the chassis more rigid to remove that "variable" and use the suspension to control your launch since it is actually tunable by us. Same goes for handling.... You want the suspension to control your handling. Of course tires play a big role in both situations and should be considered in how you design the overall package. And there is that whole safety thing if you plan on putting it on its roof now and than .

 

First lets get the terminology straight. Everyone thinks they need a cage.

The word cage refers to a full cage that fills the entire car. It has a roof bar that goes around the top of the windshield and has a-piller bars. Good cages also have bars going forward from the a-piller bars to the front of the car's frame.

A "roll bar" is simply a main hoop behind the driver with 2 bars going back and 2 forward door bars.

Very few cars, especially street cars will ever need a cage. Yes it will make the chassis very stiff and driving on the street will be very noticable. A roll bar is a better choice. It will stiffen the chassis up a bit but still allow a bit of flex.

For the dragstrip you don't want any flex or very little. A properly set up car should NOT just pull the driver side front wheel up off the ground. Both front wheels should rise together. If only one wheel is lifting then the chassis is twisting too much. Don't forget that when the left front wheel is coming off the ground, the right rear is trying to also. That's how bad chassis flex can be.

Drag racers don't want flex but they want weight transfer. When you launch, the front end rises and transfers weight to the rear where it's needed.

I still only use a 6 point roll bar. I need some video of my car launching to determine if a full cage should be installed. Legaly I don't need the full cage until I run quicker than 10.0 in the 1/4. I know of a couple of mid 12 second cars with a full cage.

 

yeah what he said

i would just go with a roll cage, so in an event of an accident the roof wont cave in that much if you roll over..

i have seen mostly convertible cars with roll bars, they need them real bad.

 

So from what you have all said I can come to the following conclusion.That the cage will take away the unwanted flex in a launch allowing the suspension to be fine tuned without any unwanted behaviour from the bodyshell? So he was probably talking ****e after all.Thanks people.