Roll Bar

Why do we need a roll bar in an MGB? In the event of the unthinkable accident where the car rolls, that’s why! When an MGB rolls, the front windshield will collapse, and chances are your three-point seat belts will lock up and prevent you from ducking down. Your imagination can complete the rest of this scenario.

Of course, this is not a scenario that we would like to imagine but, there is always that slight possibility the car may roll. So, roll bar it is… right?

The roll bar will certainly help by providing added rigidity and safety when the car rolls. If it is a well-designed roll bar, it will also help with side collisions by supplying added steel and rigidity between the two doors.  Beware however, not all roll bars are designed for the ultimate unthinkable scenario. Some roll bars are designed more for show (sex appeal) rather than protection. Additionally, padding is needed, and I will discuss this later.

If you have a roll bar or want to install a roll bar, these are some of the features your roll bar should have:

  • The bar should be re-enforced horizontally to better distribute the forces of a roll across all the attachment plates and help prevent bending or collapsing.
  • The roll bar plates should be metal on metal and never have other materials such as carpeting in between (carpet should be cut).
  • The roll bar should have 3/8” thick steel plates cut to the same size as the mounting plates on the roll bar to be placed on the opposite side of the attachment steel (under the car Figure 2 – A) unless you are drilling through solid steel and the position does not allow for more than a large grade 8 washer (Figure 2 – B). Two plates with two bolts sandwiching the metal of the car will distribute the shear forces over the entire plate surface and the two bolts as opposed to the individual bolts and a washer. Without a plate, when one individual bolt fails, the others will not be far behind.
  • The roll bar should be attached in the X, Y and Z direction and not just the Y and Z direction like many I have seen.
  • The roll bar should be heavy to lift meaning it is made of substantial steel and should have a diameter greater than 1.50” but preferably between 1.75”-2.00”.
  • The bolts used should be grade 8 or higher and the torque values of the bolts should be the recommended torque for the bolt size and grade (consult a bolt torque table).
  • There should be no air gaps in between the roll bar mounting plate and the back plate. Gaps like this weaken the bolt and it is in this area that the bolt will shear more quickly under stress. An example of this is when the roll bar may not fit perfectly (to be expected) and one mounting plate has a gap that will not close (squeeze together) when tightening the bolt to torque. See Figure 1 as an example of how I created a steel plate to go between the inside body steel and roll bar mounting plate to fill the gap.
  • Spray rust oil where you drill the holes from the inside and rust protect the plates and bolts on the bottom of the car. I use a wax oil type rust protection for the outside and Krown spray for the inside holes.

If you have a roll bar installed already, you may want to inspect it and then plan to take corrective actions when you have the time. Below is an example of two different roll bar installations, mine on the right and another on the left. You can click on the picture to enlarge it to understand my comments.

  1. Consider the diameters of the bars. 2.00” is better than 1.5” providing the steel is similar.
  2. The black roll bar has a second bar on the bottom adding horizontal support and rigidity helping to prevent collapse of the roll bar itself and better distributes the forces among the mounting plates. Racing roll bars will also have a third bar angled to the front for even more protection and rigidity (Figure 3).
  3. Have a look at the bolt directions and locations. The red roll bar has bolts in the Y and Z directions, in other words, bolted down and towards the front. No bolts towards the side, X position.  This is important because of the forces that the roll bar will have to endure in the case of a roll. The first impact normally is on the corner when the car rolls. This force will be in the X direction to push the roll bar right or left, depending on the direction of the roll. Additionally, the red roll bar is bolted high up and through more sheet metal while the black roll bar is bolted in the X, Y and Z positions and low down over the frame of the car. The back mounting plate bolts into the X direction but also has a plate sitting on the Y axis for added support. These two bolts help on the first impact when the roll bar is pushed sideways and for later for rolling, such as down a hill.
  4. The mounting bolts on the red include only washers. Of greater concern is that the washers are one on top of the other, allowing for tiny gaps (Figure 2 – C).

Roll Bar Padding

It is vitally important to pad the roll bar because your head WILL hit the roll bar in any type of accident, even if another car hits you from behind. When struck by another car or hitting an object, the energy from the impact will go to collapsing the metal, pushing the car and the passenger will be thrown up and out if not wearing a seat belt. If you wear a seat belt, you will be held in, but your upper torso will go up, back and forward causing your head to hit the roll bar one or more times. The skull versus a 2-inch-thick steel rollbar will surely result in a major concussion and/or permanent brain damage.

Not all padding is the same either. For example, the padding you see on jeeps is designed to protect your head if you go over a big bump when your head may gently bump the bar. The soft sponge like padding will help in these scenarios. But, in a roll over at higher speeds, or an impact of any kind, the soft sponge compresses so easily and quickly, it does not supply any real protection from the steel bars. That is why there are standards for roll bar padding. Please note that pool noodles do not meet these standards.

The most common standard is SFI 45. Padding meeting the SFI 45 standard is not a soft to the touch padding. In fact, it is quite rigid and will require heat to bend and form to your roll bar. Additionally, the padding does not drip or melt in case of fire and is self-extinguishing. The design is much like a motorcycle helmet, the material under severe impact will absorb the impact forces (to a degree) and help prevent concussion. It is also important to note that the SFI padding works better with a racing helmet. However, on a regular MGB driving the streets, a racing helmet would just look “un-cool.” Having this padding on your roll bar is a much safer choice that just the metal roll bar itself.

Yes, I grew up with the cool tiny British sports cars with chrome roll bars. Putting padding on these would just take away from that look. But if the car rolled, your head would fair much better with the padding than without.

My Installation

I came across the perfect roll bar by chance. It was sitting in the back yard of as Ottawa MG Club member’s house, and I bought it for $ 100.00. It was an odd design and was full of rust. I sent it to a local Powder Coating Paint shop, RLD Industries to have the rust removed and then powder coated. This cost me $ 425.00 so the total cost of this roll bar in “like new condition” was $ 525.00 CDN ($ 405.00 USD).

Once painted, the installation began. I first cut out of cardboard templates for the mounting plates that I needed to have manufactured for the bottom of the car. I drilled the proper size holes into the cardboard templates in the exact locations required. I brought these to a local machine shop, and they cut and drilled the holes from 3/8” steel for me at a cost of $ 25.00. I cleaned these plates, sprayed with self etching primer and then black truck paint. I then made a trip to the Ottawa Fastener store and purchased ¾” Grade 8 bolts, lock washers and nuts for the installation at a cost of $ 35.00.

I placed the roll bar into the MGB and fiddled with it until I managed to get it perfectly centered and positioned correctly. I used a sharp knife to cut the carpet around the mounting plates and removed the carpet cuts so that the mounting plates were metal on metal.

I decided to drill the first hole through the floor on the driver’s side to see where it would come out on the bottom. It was perfect. Right between the vertical plates holding the rear springs. I could not have positioned it more perfectly. I inserted a bolt with a lock washer and nut, hand tight.

I then drilled the matching hole on the passenger side and again, it was right in between the spring plates. These holes were hard to drill because they went though thick steel. Because of the location, the plates I had made for those bolts would not fit, so I used washers. As I drilled the holes, I lightly sprayed the hole and inside area with Krown rust protection.

I then drilled the two holes on the side of the same plate, on the bottom, one on the passenger and the other on the driver’s side. The plates I had made for these fit.

I completed the installation of these two bottom plates by drilling the final two holes on the bottom and inserting all the bolts, lock washers and nuts, hand tight.

I then tackled the top side attachments but noticed a gap on the passenger side between the roll bar plate and the side wall of the car. I had to return to the machine shop and have another plate made to go in between to eliminate the gap. Of course, I applied etching primer and paint to match. As mentioned earlier, a gap of this size would severely weaken the attachment of the roll bar and risk bolt shearing.

Some Pictures of Installation

Once all the bolts, lock washers and nuts were in place and hand tight, I torqued all of them to 37 Foot Pounds as per the recommended torque on Grade 8 ¾” bolts.

I torqued them in a rotating fashion. One on one side then the next on the other and I went back and forth, up, and down, like torquing the lug nuts on a wheel.

Once torqued, I sprayed the outside plates and bolts with Cosmoline RP-342 Heavy Rust Preventative Spray (Military-Grade) 3 which you can purchase from Amazon.

At this point the roll bar was officially installed. Next was the roll bar padding. I choose Moroso 80944 SFI Approved Rollbar Padding available at Amazon. This padding fits 1.56” to 2.00” roll bar diameters and has sticky paper inside to mount to hold the padding in place.

The areas of the roll bar that should be covered are all the areas where your head or shoulder can hit in a violent collision. Consider that your upper torso will be thrown around; up, down, left, and right. I sat in the seat and tried to duplicate these motions and decided to cover the following areas on my roll bar. It took two cut pieces joined in the middle.

The main challenge is bending the padding to fit the bends in your roll bar. I called the company Moroso and confirmed with their technical department that heating the padding with a heat gun would not have an affect on the capacity of the material to perform as expected in a crash. Therefore, I used a heat gun to heat both sides of the padding and stretched it onto the roll bar and it slowly bent with the roll bar. This is a step you need to do slowly. Take your time and re-heat often in areas that require more bending. I considered using added glue, but I decided that the look of the half roll bar with a joint in the middle and the two side ends, did not have the sex appeal expected. Therefore, I knew that I intended to wrap the roll bar with tape as I did not like the look.       

I ordered special “Racing Tape” to tape the complete upper part of the roll bar. This tape was very difficult to work with and left multiple creases. I removed it and decided to use the old faithful, Gorilla Tape. That did not work either. I considered a vinyl cover, but the upholstering company said that would not work either because of the half circle. By the time I returned home, the look had grown on me, and I find it fine. Furthermore, my next project is to design and attach a tinted Lexan wind screen that will reduce the cockpit wind and noise while also blocking much of the blinding lights of cars driving behind me at night.

Stay tuned for this project because I have already started it and have become very frustrated with the creation of the template needed to cut the Lexan wind screen.

The bottom line is that this roll bar is safer and will function better in the event of the unthinkable accident.