Back to this Roll Cage deal........

Post by **Mr. Foully** » Mon Dec 27, 2004 4:24 pm

........I bought my car because it's a convertible, not because a 240 is one of the best handling/dependable/easy to mod, bang's for the buck out there. But now I want that other stuff too.

I've done the struts, springs, swaybars, some bushings and a front strut bar but now the chassis's lack of structural integrity is the main problem in achieving cornering g's or general driving fun.

I think I need more than a hoop or a 4 point but a 6 point would take up a lot of front seat area---but most of all, lose that cool roadster look.

I was thinking of a modified 6 point, with the forward bars coming from a crossbar of the hoop, going between the front seats at shoulder level, angled down, going through the dash to tie into the firewall. They would only be an inch or two apart from the hoop to the dash, so they wouldn't provide as much torsional rigidity as a conventional 6 point, but they would add nearly as much forward-to-back integrity.

I can't hear the radio anymore anyway, the two bars would approximately go through the dash there. I know sooner or later I'll be losing the AC for weight, I'd then also have to consider jetisoning the heater too.

Bottom line, I think our cars need rigidity forward of the seatbacks/roll-hoop area.

Thoughts?

Mr. F

Post by **AZhitman** » Mon Dec 27, 2004 8:52 pm

Did you get a triangulated FSTB or just one that spans the towers?

The triangulated one that goes through the firewall really ties the front end together well, I noticed a night and day difference with mine.

I've driven a few coupes / fastbacks and my vert doesn't feel any "looser" than them.

Post by **Mr. Foully** » Tue Dec 28, 2004 5:59 am

Young Mr. Hitman, that is surprising to me. My car feels like a hinge, pivoting around my ***, yet most every review I read of the 240 touts it's structural integrity.

I have a conventional (cheap) FSTB. I am considering upgrading or fab'ng my own fender ties. After doing some research, I was going to put up a post about all available aftermarket chassis braces.

Post by **Hijacker** » Tue Dec 28, 2004 9:26 am

I agree with AZHitman on the torsional rigitidy of the vert. Forward to rear, the car is sound, it's the lateral torsion that the lack of a roof has affected the car. I have said this many times, and will say it again: I can jack my car up by the nose, and the doors still open and close as if the car were on the ground entirely. I have yet to see coupe or fastback do that.

The 4 point should be more than enough to provide lateral rigidity. In fact, a 2 point would get it done, but I'd be worried if the car ever turned over. The 4 point is more of a safety issue than a performance issue to me.

If the vert intends to be your track car, then I would think you would be better off with a cage rather than a 6 point bar. But because of the added weight of the structural reinforcements, the vert doesn't lend itself to being the best track car of all the trim levels.

I have a feeling you will be sorry if you jettison the heater core, though. I don't know how often you drive your vert during the colder months, but I know I would get ran out of my car from frostbite if I didn't have the heater. Instead, I get ran out of the car from being too hot!

Post by **Mr. Foully** » Tue Dec 28, 2004 9:47 am

My car has been on a slow conversion to be less an less drivable, but more fun to drive.

Three years ago when I first started hanging on 240 forums, some young buck conceptualized a 'vert with the top completely removed and the windshield cut down. It may take years to get there, and at that point it would strictly be a "funride", but that is eventually where I hope to be. By the by, I wish I could take credit for that radical theme but I can't, some "out of the box", non-convertible inked it first.

Since I don't use my car for daily transport, I can get progressively wilder, but it has to remain streetable, even if only in concept.

And why does my car seem to flex so much? I have a hard time believing that a coupe or HB flexes so much when jacked that the doors won't stay closed or open.

Mr. F

Post by **AZhitman** » Tue Dec 28, 2004 1:16 pm

Mr. Foully wrote:Young Mr. Hitman, that is surprising to me. My car feels like a hinge, pivoting around my ***, yet most every review I read of the 240 touts it's structural integrity.

I have a conventional (cheap) FSTB. I am considering upgrading or fab'ng my own fender ties. After doing some research, I was going to put up a post about all available aftermarket chassis braces.

Hmmmm.

Well, being far from young, I realized long ago that cheap FSTB's are not worth the shipping cost to get them to your door.

The triangulated bar I bought is quite beefy, cost less than $100, and eliminates a lot of the "cowl shake" which is the majority of the flex in the 'vert.

There are some other braces available (see our sponsor, SPL Parts), but the 'vert already has most of those installed by ASC.

If you've already replaced all suspension bushings, springs and struts, it's not a bad idea to look into a RSTB. Of course, then you're interfering with the continued operation of the top, but....

Post by **Hijacker** » Thu Dec 30, 2004 12:13 pm

Mr. Foully wrote:And why does my car seem to flex so much? I have a hard time believing that a coupe or HB flexes so much when jacked that the doors won't stay closed or open.

Mr. F

This is a typical problem with most long bodied 2 doors. The car has just enough flex that once you open the door, it can interfere with closing the door (doesn't necessarily mean you can't close the door, it's just a bit tougher than usual). A car with good longitudinal rigidity will eliminate this problem. Shorter cars are best because they have less leverage on the chassis itself.

but I digress...

most cars have a micro amount of flex, but it's just enough flex. The vert in my experience (and i've worked on about 5 verts now) has enough bracing to eliminate that flex. The torsional rigidity of the car is another matter all together.

Post by **topdown240** » Sat Jan 01, 2005 7:57 am

I personally don't like the idea of a cage, even though it would be the best way to stiffen the chassis. I've been thinking about fabricating an X brace under the car to tie the frame rails together. I've seen pics of miatas with a stamped piece that bolts to the frame rails with lots of triangulation. It seams like the frame rails are the lowest part on miatas though. Clearing our exhaust might pose a problem.

Anybody got ideas on materials and connecting points?

Also saw a brace on ebay recently that connected the front cross member to the trans mount to the passanger side fraim rail. Did anybody else see this?

Post by **Hijacker** » Tue Jan 04, 2005 5:47 am

Mazda did two things with it's Power Plant Frame (PPF). It stiffens the chassis longitudanily, and it keeps the transmission and the differential even with each other under acceleration and decelaretion.

Ladder bars, and floor bars would be best for stiffening up to the S13 chassis.

Post by **IveBeenBad** » Tue Jan 04, 2005 2:43 pm

my fastback never exhibited the door closing problem with the nose jacked up, and it was that way for a long time...

Post by **AZhitman** » Wed Jan 05, 2005 5:31 am

Mandatory FIRST modification on a 'vert should be the triangulated FSTB.

Post by **Eikon** » Wed Jan 05, 2005 12:24 pm

Any links to purchase that FSTB? I have a standard one (not triangle), but it doesn't fit due to my stock RB20 blow-off valve.

Here is a link to a car on ebay right now with a roll cage. I think it ruins a 'vert, but that's just my opinion.

LOOOOOOK..... Modified Silvia 'vert with roll cage on ebay. http://cgi.ebay.com/ebaymotors...=6396

Post by **topdown240** » Mon Jan 10, 2005 9:11 am

[QUOTE=tenkawa_akito]Mazda did two things with it's Power Plant Frame (PPF). It stiffens the chassis longitudanily, and it keeps the transmission and the differential even with each other under acceleration and decelaretion.

The piece I was refering to wasn't the PPF, but a flat stamped piece that bolted horizontally to the undersides of the frame rails. It would serve the same purpose as a set of triangulated ladder bars.

I wish I remember where I saw that pic.

Post by **AZhitman** » Mon Jan 10, 2005 12:20 pm

Can't find the auction right now, but it's from CP Racing.

Post by **Mr. Foully** » Mon Jan 10, 2005 9:35 pm

Do we know if that Roll Bar is an off-the-shelf piece or custom made? It looks asymetrical and, well, crooked, but I like the idea. Sadly, it doesn't seem to tie to the firewall, only the floor pans in the foot area.

I agree that it spoils some of the 'vert lines but there's no way around that.

Back to this Roll Cage deal........

Back to this Roll Cage deal........

Re: (AZhitman)

Re: Back to this Roll Cage deal........ (Mr. Foully)

Re: (Mr. Foully)

Re: Back to this Roll Cage deal........ (Mr. Foully)

Re: Back to this Roll Cage deal........ (tenkawa_akito)

Re: (AZhitman)

Re: (tenkawa_akito)

Re: (Eikon)

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