I'm looking at bolt-in door bars (BF or HD) for my upcoming Winter suspension upgrade project. Both brands bolt to the floorpan adjacent to the side sill verticals. I was looking at ways to reinforce the mounting and help transfer load into the sills. I was mainly considering using welded or bonded gussets made from steel or aluminum angle. While sniffing around, I came across these:

http://www.good-win-racing.com/Mazda...t/61-0725.html

Seems like it might be a good way to reinforce the sill and transfer door bar loads. Has anybody used these? I can't find much on the internet regarding actual field experience.

 

I haven't, but its a good idea. A lot of our "chassis" is in the rockers and side sills. I think you would get some benefit from making your own side sill reinforcements and working with that. Also, A friend of mine did a write-up for his own backing plate on the BF door bars.

Perhaps the side sills in combination with the backing plate reinforcement, you will find a nice happy medium:
http://s15.zetaboards.com/GearheadsM...7068194/1/#new

Lastly, the idea played around with is to try and extend the door bar (or just have a new one made locally) to reach the rocker panels, and weld it on. Kinda like Moti's design, but I really like the BF door bars which attach to the seatbelt bolt and in two locations in the floor pan. So perhaps some combination of these ideas will be the "ideal" setup for you.

 

eh, yes it's strengthing in a decent direction, but its like trying to make a piece of paper stiff by gluing another piece of paper to it. You'll have to add a lot of weight to make the same difference as door bars.

 

I think he is planning to use them in conjunction with the door bars? or are you referring to cage style door bars?

 

That's correct. I'm just evaluating methods to help transfer the door bar loads from the floor into the door sill vertical sides. Basically, enhancing a bolt-in door bar installation.

 

I saw that write-up. That's what got me thinking that there could be some easy ways to enhance a door bar installation. I like the general concept of your friend's idea, but it looks to me like his reinforcement is on the wrong side. In general, our big loads consist of shocks that move a wheel in an upward direction (i.e., compress the suspension). This would tend to "fold" the car with the center of the car moving down and the ends of the car moving up. That's what a door bar would resist. However, when it does so, it will be pushing down hard against the floorpan. In that case, the side that your friend reinforced doesn't help much.

Now that I look at it, I think these particular door sill reinforcements go at the top of the sill (where people normally seam weld). So, they wouldn't help with transferring door bar loads. I'm back to looking at homemade angle iron gussets I think.

 

Well, the idea is there. Figure out a way to spread the load that fits your image of how the loads will go. but remember, the key is to connect the "rear" and "front" chassis together. so work out whatever you like. We had a really indepth discussion and one guy had the idea of using the metal cross bar behind the dash and connecting that to transmission tunnel, then add in conjunction a butterfly brace.

So rather than focusing on the outsides (ie. using the already existing side sills), his idea was to create a whole new load path in the middle.

I am electrical, not mechanical so **** is pretty alien to me. I am just tossing out ideas I read while struggling with this issue previously. I will say, that you seem to be on the right path at least.

 

When I last installed my bolt in hard dog roll bar and door bars I welded in the backing plates on the inside rather than the outside. I also exdended the forward backing plate up the side of the sill and welded it. Its still bolt in but the connection is way stiffer than standard installation.

Bob

 

That's pretty much exactly what I want to do.

I've got a MIG and originally planned to weld. No concerns about the welds on the floor since I've got access below. But, I was worried about corrosion on the vertical part of the door sill as there is no access to the inside. Did you do anything to prevent corrosion on that surface?

I'm also looking into bonding with a high-strength epoxy mainly due to the corrosion concern.

 

It will probably rust inside of the sill tube where the coating gets burned off from welding. No different than welding in a cage though. I didn’t do anything to address the added corrosion potential.

It's interesting that cars don't rust much around here like they do in muggy climates.
Note: If you’re ever in the market for an old used car the Northwest typically avoids both rust and sun damage compared to other areas of the country and salt is not used on the roads. You might have to wash some moss off.

Bob

 

Damn right. The GTX I bought from you had loads of moss and weird **** growing in it lol. I found a little weed or tree or something sprouting in the bulkhead area under the windshield wipers.

Anyway, I noticed after installing my door bar (only had time to do the driver side) that I can grab it and wiggle it with a good deal of effort. Still, the movement is very noticable and seems to come from the floor pan area. I considered welding in reinforcement and seeing this thread confirms what i'm going to do.

 

how? what kind of door bar is this?

my BF never budged any. I used it as a fulcrum for wedging in my stock seat and aligning. On multiple occasions shook the car with it pretty hard. But yea, welded reinforcement is a good idea either way.

 

Hmmm . . . . From the Pacific NW. "Weed or tree or something." Wonder what it could have been? Occupy GTX!

My car has spent its life in TX with about a 3 year stint in ID. Rustwise, it is pristine.

I was born in Cleveland and spent a fair amount of time in the rust belt. Hence my paranoia.

The more I research, the more structural bonding looks feasible. It's being used more and more these days. It can also join dissimilar metals (i.e., could gusset with AL angle). Bonding (correctly) takes quite a bit more time than welding, but has some advantages. Hmmm . . . .

 

They are HD door bars. The problem is likely due to the fact that i'm not running mine in conjunction with a harddog roll bar. I'm using an autopower so that probably has a lot to do with the flexing. It takes a lot of effort, but I can definitely make the bar move and it definitely feels like its moving at the front foot (floor pan).

 

My car spent the first 7 years of its life in Texas DFW area. The dash cracked apart and lots of plastic bits and interior were having a tough time due to Heat and Ozone, all the crystal white paint came off at the car wash, forget about a plastic rear window. It seems to be happier with moss growing on it.

Bob

 

The hard dog roll bar really reinforces where the door bars attach at the rear bulkhead.

Bob

 

Ya I may make myself plates like the feet of a hard dog roll bar and some day bend up a main hoop and build myself a copy of one.