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grannyknot

Shock Tower Brace

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On ‎2‎/‎26‎/‎2015 at 6:17 PM, John Coffey said:

The second biggest bang for the buck is full length, welded subframe connectors that go from the TC rod mounts to the rear subframe combined with triangulated front strut tower bracing.

I have no experience with the Z chassis (yet).  But I can vouch for this reasoning on other cars.  I put welded-in subframe connectors on my Mustang, along with a triangulated front strut tower brace.  The STB tied into the firewall across its middle third, similar to the one pictured by grannyknot.  It made a very big difference in the consistency of the car in rapid transitions.  It made a noticeable difference even in normal driving over uneven pavement.  To be fair, that car never truly felt planted until I redid the whole rear suspension (torque arm and panhard bar).  But the SFC alone improved the stiffness enough that I could jack up one corner of the car and lift both wheels off the ground for rotating the tires.

Does anyone make a subframe connector for these cars?  There were a variety of kits for Mustangs, ranging from small rectangular tubing to add to the factory bracing, all the way to 2in x 3in tubing that had to be sectioned into the floorpan.  My floors are in good shape.  So I don't think I'd ever consider cutting them.  But if an add-on SFC exists, I'll definitely put them on my list.  BTW, don't forget that one of the largest masses in the car is the driver.  Any good SFC will provide bracing for the seat mounting points, as well.

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Bad Dog Parts makes weld in subframes.  Regarding the Fox body Mustang, I built an NASA AIX 1991 hatchback for a customer in Seattle.  You basically have to replace the rear suspension and the front K member and suspension to make those cars handle.  A lot of work.

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13 minutes ago, John Coffey said:

Regarding the Fox body Mustang, I built an NASA AIX 1991 hatchback for a customer in Seattle.  You basically have to replace the rear suspension and the front K member and suspension to make those cars handle.  A lot of work.

Yup.  But when you do, they handle pretty well.  Mine was a SN-95 chassis ('98 Cobra), but pretty much the same story.  By that measure, I should be ahead with the Z, lol.  Thanks for the source.

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FWIW, it looks like even his replacement rails are thicker, and fit over the existing ones.  That would stiffen things up over stock.

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On 2/26/2015 at 3:17 PM, John Coffey said:

 

Sorry, can't get rid of this box, even after starting over.  Once you put something in a Reply box it seems to be "cookied" forever.

 

Anyway, the Bad Dog rails don't connect the sub-frames, which is what the goal was I thought.  Just looking for the connectors connection.

 

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True.  But stiffer rails help to some degree.  We're getting into details here.  And I didn't attempt any rigorous analysis.  But for my Mustang, the SFCs probably only provided half their stiffness contribution due to stiffening the subframe attachment area.  The rest was due to adding more cross section to the floor.  Since I haven't studied the Z yet, and I haven't seen pics of Z SFCs, I may be completely wrong.  But even stiffening the floorpan has got to help.

As far as removing the quote box, I've found a workaround.  If you click the "Source" box above and to the left of the reply box, you can manually delete everything, including the HTML code for the quote box.  Then click again to restore the normal view and proceed as if nothing ever happened.

Edited by the_tool_man

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Since I helped pull this thread off topic, I'll try to help bring it back.

Grannyknot, have you considered whether or not you really need the near vertical tube on the passenger side connecting the two attachment points?  It would seem to be redundant since it's parallel to the passenger side strut tower.  Though as someone pointed out, you could mount a fire extinguisher to it.  Still, even in that case, it could be a piece of flat bar instead of tubing, and be a little lighter maybe (depending upon your tubing wall thickness).

Edited by the_tool_man

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On 2/26/2015 at 3:17 PM, John Coffey said:

The second biggest bang for the buck is full length, welded subframe connectors that go from the TC rod mounts to the rear subframe combined with triangulated front strut tower bracing.  

I'm just pointing out that Bad Dog does not appear to provide the solution that John Coffey, professional race car builder, suggested was the second best bang-for-the-buck.  That's all, not even debating whether it's truly worth doing or not, just saying that there's no sub-frame connector offered by Bad Dog.  I seem to recall seeing the actual connectors on Bad Dog's site in the past, but maybe he doesn't make them anymore.

gnosez (Gino says?) is Bad Dog.  I'll send him a message and maybe he'll get in here.  He already replied on the windshield question.

Edit - Sent him a message, let's see what happens.

Edited by Zed Head

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2 hours ago, Zed Head said:

Does he still?  He only shows replacement rails on his web site.

http://baddogparts.com/

http://baddogparts.com/index.php?main_page=index&cPath=2_5

Bad Dog has these rear frame rails/connectors, not sure if this was what John was referring to:

http://baddogparts.com/index.php?main_page=product_info&products_id=2

These are for a 240Z not sure about what they have for a 280.

240fullrear.thumb.jpg.f6cc6bcf9950938777

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That's probably the part.  Don't know why he calls them rear rails.  He mentions connecting in the description.  Apparently the 280Z sub-frames extend further than 240Z (edit - they don't, they're the same length.  The 280Z's just use thicker steel and are better braced in general), so maybe not as necessary.  OR maybe they're already connected.  To the garage...

" New 70-73 Datsun 240Z replacement under floor frame rails. Replace those rusty frame rails with these custom fabricated rails. These are two piece assemblies that connect the front frame rail section to the rear frame rail behind the seat. 

Great for high HP or V8 conversion "

Edited by Zed Head

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Guess I will jump in here too. As with The Tool Man, I am new to the z car, so trying to learn what I can here before tearing into the work that my car needs.

I installed weld-in subframe connectors on a '69 Camaro convertible. It was by far the best improvement I made to the car. Wrestled for a long while about cutting/welding in something so permanent, but eventually drivability won out for me. Once installed it was like driving a completely different car! I did not realize just how much flex that car had until the connectors were put in. Combined with some suspension tweaks and PU bushings, cornering and handling improved a ton. That thing drove like it was on rails.

The subframe connectors I used (and I assume The Tool Man also) were tube steel (1" x 3" if memory serves) members that were welded into grooves cut into the floor pan. They ran from the rear of the front subframe to the front mounting points of the rear one, and were also welded to each of these.

If there is something like this available for the 240z, I will be all over it. Have not found anything yet.

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Eyeballed my 280Z and the rear and front sub-frames aren't on the same line.  Not connected directly either, except through the bend of the floor pan (the bend would add rigidity), although almost overlapping.  The Bad Dog 240Z rear frame "connectors" would get someone close but I don't that they're a full direct connection.  It's an interesting engineering problem, load distribution/transfer, stress risers, and all that.

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The Bad Dog frame rails/subframe connectors are two parts as shown above.  Weld them together.

There are also John and Pete's pics of the extensive frame prep for the BRE cars.  One big thing that helps in front is a tubular brace going from the outside of the TC rod mount to the inner front of the rocker panel.  Its crosses the rear of the wheel well.  Another good reinforcement is to box the connection of the lower and upper frame rails behind the rear of the front fender.

If you guys go on Facebook and find the old Betamotorsports page you'll see a lot of reinforcement I just did for the Peking to Paris endurance rally car.

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Sorry, been travelling and I limit my internet usage while driving.

Okay, let's start with some basic info:

What Bad Dog Parts labels as 240 front rails (a poor choice on my part) start 9-inches in front of the firewall, cover about a bit more than a 1/3 of the TC rod box are and end where the stock rails ended. They are made from 13 gauge steel and are 2to 3 times thicker than stock rails. They can be used over existing stock rails or as stand-alone replacements and are sold as singles or as a set.

The optional rear 240 rails were designed for folks who wanted a stiffer unibody, had increased the HP or autocrossed/raced their Zs. These are butt welded to the aforementioned front rails and welded on the member cross member running in front of the rear wheel well. I showed them to Mr. Matsuo and his reaction was to slap his head, tell me they could have made these for $2.00 and gave me a pat on the back and a smile. They are sold in sets only.

To complete the circle so to speak we recommend a front triangular strut tower bar and a roll bar to hold the rear strut towers in place.

The 280 frame rails (the word front is not needed here) also are made from the same gauge steel and start around the same 9-inches in front of the firewall and end where the stock rails do. They are made as a complete replacement or as a cap over an existing rail. Sold in pairs and as a single piece. I would hazard a guesstimate and say that about a dozen people have bought and made modifications to allow the use of our 240 optional rears with the 280 rails (most I believe had installed LS/LT/RB motors).

Both the 240 and 280 rails are compatible with replacement floors sold by Zeddfindings. My street and 240 race car have Charlie's floors installed.

Bad Dog recommends that if your car will be kept stock and you need floor pans then get the best that's out there - Charlie's floors and his rails. If you need something stronger for whatever application then contact us and if you need something even stronger then you should search HybridZ.org for the means via box tubing welded half in and half under the floor pans that will allow you to build a bullet-proof subframe for really, really high HP Zs.

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As part of a nice treasure trove of left over BSR parts, I found a roll of undeveloped B&W 35mm film which turned out to be the photos of the BSR 260Z GTU car. Maybe at some point I'll strip the current BSR 240 CP clone, go all the way and make it into a clone GTU car. The only problem, setting aside the cost, would be the issue of having to run in vintage run groups with cars making nearly double the HP and the fact that I do not possess even a small portion of Bob's racing skills.

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I'd actually looked through the Hybridz thread before but how they fit didn't really sink in (or I forgot).  Didn't really think of the rear transverse-oriented sub frame (where the BD rails terminate and weld on) as the rear sub frame.  I've been looking at the arched piece that goes over the axles, thinking in terms of a  lengthwise frame rail, trying to connect two parallel rails in my head.  The rails should probably actually be called bracing, or stiffening ribs, or boxed sections, or boxed bracing.  The metalwork in front, where the engine bolts in, would be a sub-frame.  I think.  The 240Z rear "rail" might better be called a rail (brace) extension.  History prevails though.

Found another good BD rails thread, describing how to make them fit and weld them in.  http://forums.hybridz.org/topic/58497-installing-bad-dog-frame-rails/

I'm almost disappointed that I have a 280Z, with decent shape rails/boxed braces.  No good reason to modify yet.

Nissan shows where all of the sub-framework is in their Body chapter, as dotted lines.  Here's 1972.

1972 240Z.PNG

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