250 Sport Roll Bar

[BugMan]

Just going through my boxes of bits I have yest to fit to the chassis, and I literally tripped over the roll bar, so thought I'd take a look at it, as to where/how its fixed to the car.

The fixing looks very simple, just a large M12'ish size bolt in the end of the roll bar, which I assume you need to drill a new pair of holes in the small square plate on the back of the car then then screw up through.

Now I have seen pretty  much everybody fit the bar once the body is on the chassis, which I understand as you need to drill through the fiberglass, and then into the steel chassis below, but is there any reason not the drill the mounting hole now, and then when the body is fitted be able to drill up through the fiberglass from underneath?

 

[Nick Mace]

There are some benefits in that route because it’s tricky to measure the right location with the bodywork on. I nearly made mine too far forward and struggled to get the bolt in.

Possible problems I can see are (a) it might be hard to drill up from underneath (not much room); and (b) you may want to fine tune the position when the bodywork is on. If the bodywork doesn’t end up being perfectly central, you may need to compromise on the position of the bar a little bit. You can measure it all, but sometimes you need to stand back and see what looks right (which might not be completely central). 

[Thrustyjust]

I would wait until the body is on. If you drill the hole now, then you wont be using an M12 drill in your holesaw, so you wont get a perfect body cut. If you pilot it 6mm ( or whatever your pilot drill is) then you 'could' drill through the body from underneath when fitted. Then hole saw from the top, but the body isnt 'exactly' square and it could look a bit out. Also be aware of it not being a rollbar , as it wouldnt support the car if it did unfortunately roll at speed, but a hood hoop is a better name. With that in mind, it also needs to be square with the windscreen to keep the hood taught.

[TAFKARM]

Referred to as a "style bar" in the MX5 fraternity