[sacklunch]

Hey all,
Some of you may have seen my posts about ordering the MRC roll bar, which can be purchased here.

So I just received the bar and it looks good; came with 8.8 metric bolts and nuts, and back plates.

But I have some concerns about adherence to SCCA and NASA.

1. firstly the plate thickness isn’t up to spec per SCCA. They require 3/16 inch, whereas the MRC is about 3.2 mm (NASA lists 1/8 inch, so I'm good there). NASA also says plates should have "a minimum dimension on any side of 2.5 [in]". I'm also good there. For the plate thickness, what I’m thinking is I can weld on thicker plates to the existing plates. Can anyone confirm this is allowed? I can’t seem to find anything online about adding thickness via welding.
2. unlike in the photos on the website, the back section of the bar is bolt in. I don’t think this matters, as I’ve seen other bars do this (no doubt to reduce shipping costs). Can anyone confirm this is okay per rules?

*Edit. So I spoke with someone at SCCA in their road racing division. He directed me to their rule book for March 2023 (link here).

Regarding thickness of plates on p. 99:

"The thickness of mounting plates bolted or riveted to the structure of the car must not be less than the thickness of the roll hoop or brace that they attach to the chassis, and must be backed up with a plate of equal size and thickness on the opposite side of the chassis panel."

And on p. 100 SCCA says (1701 - 2699 lbs) tubing should be at least 1.500 x .095 (outer diameter x wall thickness).

In my case the MRC bar is mild steel. I just measured the diameter at 1.75 in (4.4 cm) and the thickness should be c. 0.120 in (3 mm). So I should be good with the current diameter (1.75 in or 4.4 cm), tube thickness (0.120 or 3 mm), and plate thickness (1/8 in or 3.1 mm).

Regarding the bolt-on rear braces, I'm a bit fuzzy still. SCCA says on pp. 100-101:

"Removable bracing may incorporate connectors of the double-lug, double ear-type, tapered, or muff-type as shown in figures 14 and 15. The double-lug type must include a doubler, gusset, or capping arrangement to avoid distortion or excessive strain caused by welding. Double eartype joints must be fully welded at all the mating surfaces."

Figures 14 and 15 given below. Compare the MRC after.

The MRC exceeds the size for the double ear thickness at 1/4 in (6.6 mm). But the MRC does not have a "capping plate," i.e. the double ears are welded onto the side of the tube, rather than forming part of the "cap" as in Figure 14.



TLDR (for now): The MRC here meets SCCA standards except for one part of the bolt-on rear braces. I will need to add/weld a "cap" around the mainhoop. This isn't a huge hassle and should only take a few hours.

Open questions:
1. Unlike in Figure 14 above with the rear brace maintaining the same diameter up to the mainhoop, the MRC uses a clevis slide style mounting (male). I need to figure out if this is allowed per SCCA.
a. I'm considering just buying some 1.75 DOM tubing and making my own rear braces, or at least modifying the MRC ones (use a 1 7/8 in hole saw as here). But this may get me into another problem - I don't know the rules on welding pipes when not close to the joints (e.g. if I cut the end off of the clevis on the MRC and welded a 1 3/4 in tube on to butt up to the main hoop).





edited - to be finished tomorrow, along with NASA comparandum
As a point of comparison, Virginia International Raceway (VIR - the closest racetrack to me) gives (see here):
Cars over 1500 lbs using mild steel roll bars require 1.75 in x .120 in. So the MRC bar qualifies. BUT, per VIR rules, you must use 3/16 in (4.7 mm) plates. Oddly, their rule book does not mention different regs for weld-in cages, while other rule books allow you to use thinner plates if welded (usually 0.08 in or 2 mm).





some initial pics; I’ll post more when I install!

 

[sacklunch]

 

[firebert]

Which series are you competing in? Typically roll bars (without front and side protection) does not fall under the rules where it pertains to roll cages.

There seem to be a lot of questions here so I'll try my best to not miss any of them
1. Typically it is acceptable to add to the thickness or area of the spreader plate by welding but the tech inspector may not be salified with the sum of the two thicknesses so you might have to weld your thinner plate to a full thickness plate. However if you are going through that type of trouble you might as well just cut off the old spreader plate and weld a new one in to avoid any scrutiny.
2. The tab and bolt style of connection for your rear diagonals place the fastener in sheer if your car rolls over. This type of connection is typically seen on cusco cages does not pass tech in any sanctioning body.
3. If you want to modify the rear diagonal mounting style it is best to simply remake them with DOM and notch them into the main hoop

Some of my observations are
1. your harness bar should be welded to the main hoop, not the rear diagonals
2. I don't see reinforcing plates? Assuming they're simply not pictured
3. It is sometimes necessary to drill a inspection hole to verify tube thickness.

 

[sacklunch]

Thanks for replying! I know what you mean about Cusco style cages using similar bolt styles. But the scca rules are clear that they are fine so long as you meet thickness requirements, 6 in from the top horizontal, and use the cap as in Figure 14. The guy I spoke with at scca verified this. Yes I agree with you that it would be better to cut off plates and reweld, though I don’t think that’s an issue as the thickness is in spec per scca. I need to drill a hole for inspection, saw that in the rule book. Lastly, I just want to run in track day events, hpde, etc. So I don’t have crazy standards, but as far as I can tell these are the minimum standards to get on track at most tracks in the states. Thanks again! /on my phone forgive errors

 

[sacklunch]

Thinking on this more it may best best to just buy some tubing and make my own rear braces. It’s a pain in the rear that I have to do this just to get on the dang track for hpde but what can I do. In the end I guess I don’t know if I would have gone with a different bar. I can’t run the hard dog because the mounting points on the firewall side are compromised beside kswap mods; and the only other option I know of is that one guy in CA who wants like 2k for a dang roll bar.

 

[MidwestManiac]

I've been taking my sweet time with doing a harddog rollbar install... I have heard it's more intensive than doing an engine swap and after having to take a Tonya to places, modifying brackets, and just swearing up and down the car, now I can firmly say the amount of effort that one has to put in to get the harddog rollbar in correctly is about the same as an engine swap.

I went with a hard dog as I wanted to retain use of the hardtop side striker latches and not have the rollbar in the way of being able to remove the hardtop. But the next rollbar I do I may just go custom.

 

[firebert]

For HPDE, typically roll bars are not required on most cars unless they're convertibles (like on our spyders) so they will not be scrutinized as closely as a roll cage which is used in road racing. The rule book that you shared in your first post pertains to roll cages used in wheel to wheel racing or higher level time trail events. Realistically unless you start competing in those types of events you are fine as is.

If you have any concerns I suggest you contact the organizer of the HPDE event as they have the final say on who is allowed on-track. You mentioned VIR being your home track. I see HPDE events being held by Track Advantage, Track Daze, Apex Driving Events, etc. They will be the ones doing the tech inspection on your car at the event.

As far as HPDE with VIR Club it looks like for touring groups, roll bars are not even required....

 

[sacklunch]

Thanks for the link to event. Yes, I see that some amateur events at VIR (and no doubt others) do not require a roll bar, but my experience is that most do (e.g. see here at VIR, requiring bar). And yes, I agree with you that I will not be scrutinized at the level of wheel-to-wheel racing events. But I want to make sure I don't have to pull the bar off later and make adjustments. It's relatively easy to make my own rear braces and weld them to the mainhoop. Then I don't have to worry about what events I can/can't attend. Make sense? Or am I being crazy?

 

[sacklunch]

I've been taking my sweet time with doing a harddog rollbar install... I have heard it's more intensive than doing an engine swap and after having to take a Tonya to places, modifying brackets, and just swearing up and down the car, now I can firmly say the amount of effort that one has to put in to get the harddog rollbar in correctly is about the same as an engine swap.

I went with a hard dog as I wanted to retain use of the hardtop side striker latches and not have the rollbar in the way of being able to remove the hardtop. But the next rollbar I do I may just go custom.

View attachment 95953

It's funny how much easier it is to take the gas tank out with the softtop gutted. I recently had to have my gas tank repaired and was dreading removing it, after reading tons of posts about how awful it is. With the softtop gutted, it seriously took me an hour, or less, to pull the tank. One of the easier tanks I've pulled!

 

[MidwestManiac]

It's funny how much easier it is to take the gas tank out with the softtop gutted. I recently had to have my gas tank repaired and was dreading removing it, after reading tons of posts about how awful it is. With the softtop gutted, it seriously took me an hour, or less, to pull the tank. One of the easier tanks I've pulled!

Definitely so, installing the rollbar is probably way easier without the soft top in the way too. The tank drop isn't even the hardest part as I've dropped the fuel tank out of this car alone 3 times

 

[firebert]

Thanks for the link to event. Yes, I see that some amateur events at VIR (and no doubt others) do not require a roll bar, but my experience is that most do (e.g. see here at VIR, requiring bar). And yes, I agree with you that I will not be scrutinized at the level of wheel-to-wheel racing events. But I want to make sure I don't have to pull the bar off later and make adjustments. It's relatively easy to make my own rear braces and weld them to the mainhoop. Then I don't have to worry about what events I can/can't attend. Make sense? Or am I being crazy?

It make sense. I believe people who are running a roll bar should have the safest one possible. What you have now can be improved upon but is not inherently dangerous.

As for the event you linked. TrackAdvantage only list roll bar is being a requirement with convertibles however they don't go into specifics. I'm willing to bet they don't have any requirements for size/thickness of spreader plates, one piece vs two piece roll bar, etc.

 

[sacklunch]

True! Well, I contacted them and they said they go by VIR rules, which are actually more stringent than SCCA. But will they actually be out there measuring with a micrometer? Maybe. I don’t know. I called SCCA back today and spoke with them about the clevis style bolt together rear braces. They said I shouldn’t have a problem, even though technically the MRC bar doesn’t have the style of supported double ear outlined in the manual. Anyways sounds like I’m good. Worst case scenario I will weld on a support U bracket and be good per scca spec.

 

[sacklunch]

Installed the bar yesterday. Pics below. Overall I'm very pleased with the quality. Retains factory seat belt mounts. Bar fits perfectly under oem hardtop with oem headliner (does not touch, but very close). Kit came with all bolts (8.8 metric, so SCCA/NASA spec) and plates. No need to drop the gas tank, though obviously for this version you need to have your softtop gutted (they sell a softtop version).

 

[Asskicker32]

Love it! Thanks for posting