Roll bar

The main hoop in my 92 civic's roll bar has been extended about 1.5" using the same DOM tubing. Is this safe , or should I just cut the whole thing out?

by safe I mean safe..and legal.

By extended do you mean a taller hoop has been welded to the top of the old hoop or do you mean they cut the tube and spliced in another section of tube?

The latter is usually a no-no and the former is questionable. Rules usually state the main hoop must be a continuous tube.

spliced in 1.5" of pipe at the bottom.

Since you don't know how it was done I would replace it. A proper splice would require a smaller tube inserted inside the two outer tubes and then roset welded. And most racing bodies do require the main roll bar hoop to be one piece so on this point alone I would replace it.

Adding tubing to the top of a roll bar hoop is common practice on older open race cars. The rules say that the top of the drivers helmet must be 2 inches below the top of the hoop. If a taller driver buys a car from someone who was short then more then likely he would need to extend the roll bar hoop.This is not required in closed cars if the current hoop is already up the the underside of the roof. You can't raise it any higher and if the driver can sit in the car then he's good to go.

SCCA's rules (and I believe NASA's as well) do spec a 1 piece main hoop for Club Racing. Autocross rules do not specify such a thing (since roll bars are not required) but they do recommend it. As jimbbski mentioned, there are allowances for extending a hoop under certain circumstances. If it was done properly (and you need to consult the GCR to see if it was), you won't have any legality problems.

Now on to my concerns: you mention it was 'extended using the same DOM tubing'. That tells me it probably wasn't rosette welded as per SCCA specifications but was rather circle welded, meaning it won't pass tech at a Club Race or Solo I (TT or hillclimb) event. Putting that aside, any time you weld two pieces of tubing it's very difficult to verify that you have truly full penetration. Meaning that's a place where a failure is more likely to occur just when you need it least.

If you are AXing only, drive it and have fun. OTOH, if you are headed for higher speed events, replacement with a one piece hoop is an excellent idea.