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Old 03-22-2012, 01:57 AM   #1
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Default Chassis Rigidity beyond a roll bar...

I have been reading lately about "door bars". Preferably the Hard Dog door bars as seen here: http://www.gomiata.com/mim2dobaforh.html
I currently have a Hard Dog Xtreme Roll bar, which was the first thing I ever put in my car after I bought it. The Hard Dog door bars bolt right up to the lower mounts of my roll bar.
Questions:
Is this something that's going to be a real pain getting in and out of my car?
Am I going to wack my knees all day long and get pissed off?
Is it going to actually make a significant difference in chassis strength?
Is it going to interfere with my door panels or any other interior parts aside from maybe notching my carpet?

I also have been looking at the Frog Arms as pictured here: http://www.flyinmiata.com/index.php?...umber=13-71000
Questions:
Will these make a significant difference?
Seems like a lot of work (fender removal, looks like maybe some drilling, etc), but the cool thing is, you don't even see them.
I'm thinking door bars for sure, but frog arms???
Opinions/ suggestions...
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Old 03-22-2012, 02:12 AM   #2
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Door bars make the biggest difference in my 2000.
Next was the FM butterfly+rails.
Then the shock tower bar.
Then the door seam welding.
Rollbar hardly did anything.
I don't have frog arms.

Go to youtube and search for my video "miata door bars ingress".
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Old 03-22-2012, 02:14 AM   #3
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I have door bars in my track car and I am pretty sure they are low enough to not interfere with getting in the car. I never bang my legs on it. It's pretty much a no compromise mod.

Yes, they make an enormous difference, like change your sway bar set-up difference.
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Old 03-22-2012, 02:41 AM   #4
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I'm definately buying the door bars...probably no frame rails or strut bar. I'd like to hear more reviews on the frog arms though.
Looks like the door bars mount to the lower roll bar mount. I assume I drill the floor for the front of the bars?
My car is a very clean setup. My roll bar looks like it came factory, and I hope the door bars will end up the same way.
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Old 03-22-2012, 02:53 AM   #5
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why no frame rails? can't think of a single reason you wouldn't want them.
cheap, fairly easy to install, significant improvement, etc
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Old 03-22-2012, 03:47 AM   #6
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Not a huge improvement if your current rails aren't beat to ----. Mine aren't, and I'd love them for jack points, but from what I've heard they're not a huge benefit with an undamaged stock rails. I mean they're a layer of steel over a layer of steel. Door bars box up the...door.

All speculation and rumor though of course.
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Old 03-22-2012, 04:48 AM   #7
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It seems to me that the rails alone may not make a huge difference, by that the butterfly would make a significant change. Can anyone comment on that?
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Old 03-22-2012, 08:05 AM   #8
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frame rails made a huge difference to my Roadster (original rails were in good condition), could immediately feel the difference even just reversing out of my driveway.
I had 16 sets made up locally for people, everyone happy.
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Old 03-22-2012, 08:57 AM   #9
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miata.net has 2 great threads on Boss Frog "Frog Arms":

1. http://forum.miata.net/vb/showthread...ight=frog+arms and

2. http://forum.miata.net/vb/showthread...ight=frog+arms

I have an MSM which had more chassis stiffening than most NBs to start with and here's my progressive chassis stiffening mods and how I ranked them (0 = no difference, 5 = most difference):

- MX5 Plus Twin Hoop Roll Bar with intergrated torque box (5)
- FM Frame Rails (2)
- Boss Frog Frog Arms (3)
- Carbing 3-point Front Strut Brace (0) - the stock MSM front strut brace is quite good

Frog Arms made a bigger difference than the frame rails but the fact that I can easily get 2 wheels airbourne when jacking up a corner indicates that the frame rails are doing a pretty good job of chassis stiffening.
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Old 03-22-2012, 10:13 AM   #10
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I jacked up my car using the stock jack and the driver's side rear pinch point. Both back wheels came off the ground. I have no additional stiffening whatsoever, and both doors were open.

How much more do you need?
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Old 03-22-2012, 10:42 AM   #11
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Anyone try the Frog Ribs? Second item in this link:

http://www.bossfrog.biz/Miata_Performance.html

Wondering how they compare to the Hard Dog door bars.
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Old 03-22-2012, 10:53 AM   #12
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I've been wondering if anyone has tried a 'through-the-floor' subframe connector type set-up in these cars?
One could tie them in to the rollbar mounts and into the front frame-rails.
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Old 03-22-2012, 03:13 PM   #13
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I like where the Blackbird rollbar mounts. (9th picture down)
I would think that it would be a better mounting place than the thinner metal of the floorboards.

http://blogs.insideline.com/roadtest...-roll-bar.html
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Old 03-22-2012, 07:45 PM   #14
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Quote:
Originally Posted by Lokiel View Post
I have an MSM which had more chassis stiffening than most NBs to start with and here's my progressive chassis stiffening mods and how I ranked them (0 = no difference, 5 = most difference):


- FM Frame Rails (2)
Rails only, or butterfly as well?

Quote:
Originally Posted by rleete
I jacked up my car using the stock jack and the driver's side rear pinch point. Both back wheels came off the ground. I have no additional stiffening whatsoever, and both doors were open.

How much more do you need?
I'm interested in adding stiffness for the times my hardtop is off, which is pretty much from April to October. I can get both wheels on one side off the ground from one jacking point with the roof off, so there's a decent amount of fore/aft stiffness in my car, but twisting flex is more noticable topless. That's why I'm curious about the butterfly itself (as opposed to just the rails), as it seems as though that piece would eliminate some/most? of the torsional flex.

Last edited by matthewdesigns; 03-22-2012 at 08:08 PM.
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Old 03-22-2012, 09:25 PM   #15
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How about stitch/tack welding the rest of the car? I did my door jams last weekend and want to do more. Such as the shock mount areas and behind the seat areas.
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Old 03-22-2012, 11:52 PM   #16
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Quote:
Originally Posted by matthewdesigns View Post
Rails only, or butterfly as well?.
I only have the FM frame rails - MSMs have a lot of underbody stiffening and plates that would need to be removed to accommodate the butterfly brace.

Quote:
Originally Posted by matthewdesigns View Post
I'm interested in adding stiffness for the times my hardtop is off, which is pretty much from April to October. I can get both wheels on one side off the ground from one jacking point with the roof off, so there's a decent amount of fore/aft stiffness in my car, but twisting flex is more noticable topless. That's why I'm curious about the butterfly itself (as opposed to just the rails), as it seems as though that piece would eliminate some/most? of the torsional flex.
With the frame rails in place, I don't have to jack the car up as high as I used to get both wheels off the ground so I know that they definitely add stiffness..

NAs and NBs in stock form have very little chassis twist prevention and was something that was addressed in the NC.

The biggest difference maker for me was the roll bar which addressed chassis-twist in a BIG way, I noticed the difference immediately when slowly turning right to exit the parking lot of the garage onto the street, the car felt completely different. I'd recommend a roll bar to anyone these days just for its chassis stiffening effects - the safety aspect and "cool factor" are secondary benefits as far as I'm concerned.

With my roll bar, frame rails, Frog Arms and Carbing 3pt front strut brace, I reckon I'm about as stiff as I can get without resorting to a roll cage. I can't fit the door bars though since I have MAZDASPEED seats which are wider than stock.
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Old 03-23-2012, 12:02 PM   #17
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Quote:
Originally Posted by Lokiel View Post
I reckon I'm about as stiff as I can get
Good to know.
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Old 03-23-2012, 12:59 PM   #18
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Quote:
Originally Posted by rleete View Post
I jacked up my car using the stock jack and the driver's side rear pinch point. Both back wheels came off the ground. I have no additional stiffening whatsoever, and both doors were open.

How much more do you need?
If I lift my 01 at one of the rear points, it will pick up 3 wheels. My rollbar is welded in, and the rear uprights go all the way to the frame rails in the trunk. It has sport bracing, but no aftermarket rails or door bars.
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Old 03-23-2012, 01:40 PM   #19
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Your RB is obviously adding quite a bit, then. I do have a HT on mine, and all 4 latches are snugged down pretty tight. I'm sure it would twist/flex more without the HT.
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Old 03-23-2012, 05:49 PM   #20
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Quote:
Originally Posted by hustler View Post
I have door bars in my track car and I am pretty sure they are low enough to not interfere with getting in the car. I never bang my legs on it. It's pretty much a no compromise mod.

Yes, they make an enormous difference, like change your sway bar set-up difference.
Hustler, change them which way? Stiffer front/softer rear, or vice versa.
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