LGS_18

Is it at all possible to bolt in a harness bar in a 90 Firebird? I see that some people say its unsafe, but i would like a little explanation if possible. And if is, would i just have to weld a roll cage in?
Thanks!

AlkyIROC

Unsafe is a vague term. Technically, if you're going fast enough to require a 5 point harness, you should also have at least a 6 point roll bar. A full cage is not required until you get into the 9 second range.

If you're not going fast enough to need a roll bar, the factory seatbelt will work just fine. Putting in a 5 point harness will only be for show. Although not recommended, you could install shoulder straps over the seat and back to the shock tower mounting area. This means the shoulder straps are very long and when they're cinched down, they should in no way be able to come off you shoulders.

A 5 point harness is also not technically street legal plus when you use the shoulder straps and are tightened down to hold you into the seat, you can not lean forward to reach anything.

Tibo

iTrader: (15)

I mostly agree with AlkylIROC. I'm not sure if a drag strip will allow you to run with a harness bar. Even if it was a roll bar with the top hoop cut off they still might not let you run the harness' to it. As far as Autocross and daily driving go I don't see a problem with it provided it makes sense. I believe the bar needs to be not more than 15° down from your shoulders. If you can weld you could make one that bolted to where the rear seats' shoulder belts go and either the bolt that holds the rear seats in or the bolt that the rear seats' belt bolts to. Even if you are not on a dragstrip if you are going to be moving fast enough to need a 5 point harness (ie seriously breaking the law) then you need a proper roll cage.

I made a harness bar in my convertible. I won't ever be going to a dragstrip because my trunk mounted battery does not follow their diagram and I have shaved door handles. My car will probably not be going over 80 and is just for shows, driving and autocross.

Alky also brought up the inability to move much with a harness. One of the arguments against a harness and harness bar combo on the street is in the case of a roll over your torso cannot slide to the side to avoid being crushed. However in my case with a convertible, anybody with a slight bit of knowledge of a thirdgen convertible knows that in the event of a convertible roll over without a NHRA spec roll bar--your dead.

LGS_18

Awesome. Thank you for your input. I am on my way to 10's now so it would probably just be smart to put in a cage anyway. Lol

Tibo

iTrader: (15)

If you want to be driving on the street with a harness and your state is picky then the schroth rallye 3 and 4 are DOT approved 4 point harnesses.

AlkyIROC

If you're on your way into the 10's you should be fast enough that a roll bar is already mandatory. If you don't have the cross bar so passengers can get into the back seat then the roll bar wouldn't be legal anyway.

Going with a full cage adds some weight but it is nicer than trying to convert a roll bar into a full cage. The basic 6 point roll bar requires tubing to be 1-3/4" diameter. A full cage only requires the tubes to be 1-5/8" diameter. Converting a roll bar into a full cage means you'll have a bunch of tubes that are larger and heavier than they need to be.

A very basic 8 point cage will certify to 8.50. Main hoop with cross bar. 2 tubes going to the back. A halo tube around the roof. 2 A-pillar tubes and door bars. All the tubes after that are specialty tubes. They're not really required but all serve a purpose.

I also installed a knee tube. X-ed my door bars. Sill bars. Cross tube across the roof and there's a lot of extra tubing at the rear mainly because my car is back halved.

There are a lot of good cage kits available. S&W probably makes one of the better kits. Price of the kits is cheap. Cost to install can get expensive. A typical chassis shop could charge $100-$150 or more per point depending on how much interior they need to remove to weld it all in. Mild steel is fine but should be DOM tubing with a minimum wall thickness of 0.118". If it's thinner, it won't pass a chassis certification and all that money invested will limit you to a 10.0 timeslip.

Tibo

iTrader: (15)

I was under the impression that if it wasn't the correct thickness it wouldn't even be recognized as a cage or roll bar and if you ran fast enough to require a roll bar you would be asked to leave. Is that not correct?

AlkyIROC

Tech at the track generally have no idea how thick the wall thickness is. A 0.095" thick tube looks the same as a 0.134" wall thickness when all you can measure is the tube diameter.

It's only when you get a chassis certification that the wall thickness is measured with a sonic tester.

If there's a chassis certification sticker on the cage then it's been tested and will pass a tech inspection.

Jaysz28

iTrader: (30)

I debated a harness bar for my 'bird. It is no where near a 10 sec car in the 1/4, but I wanted an option for a 5 point harness for driving events at PBIR, Sebring, Homestead and Daytona speedways. If you pull any g's into a corner or brake hard, its nice to not have to worry about keeping yourself in the seat.