Suspension GURUS???

[gsracer]

i was thinking about reinforcing the rear of my car. I got an extra subframe and im redoing it out of the car with a lot of spl goodies, but anyway this is my idea.

Im gonna do some work inside my trunk. Im gonna weld a piece of roll bar piping in between the two rear shock towers with plates mounting it to the shock towers and then from there weld to more from the plates to the trunk floor. I think it would stiffen up the rear of the car incredibly. I attached a picture drawing of the general idea.

Now what do you guys think is this gonna make a real big difference other than looking cool or is it not gonna be worth it. And question two, i do a lot of drag racing, auto cross, and im trying to do some drift now also, will this mod be illegal with any of the santioning bodies.

Critisim will be appreciated.

for some reason this is not letting me upload attachments but you get the genreal idea.


itll be like a bar between the two shock towers and from eac mounting point a bar coming to the floor like an X

[FRpilot]

pictures would help. cuz i have no clue what you're talking about? but if you're going to weld a bar between both rear strut tower, i think a rear stb will accomplish the same thing. as for making the xbar, go w/ a custom rollcage setup.

[dori2 s13coupe]

www.cpracing.ca

http://www.cpracing.ca/productimages/s13rear.jpg

[gsracer]

very similar to that excep welded to the shock towers and coming farther back and welded to the trubk flor in an X pattern from the shock towes.

[sykikchimp]

The rear upper shock mounts flexing inward do not affect the alignment of the suspension like the front Strut towers do. Tieing the floor into the equation is really the only good way to brace the rear of a 240. It will make a big difference to do what your saying. However, since the Upper shock mounts don't actually see any load that would cause a suspension change, there isn't a reason to specifically tie them together. I think a good roll bar that tied into the floor would do more, and be safer.

this is what I think I'm going to do:

[that180guy]

welded suspension parts, or welding the strut towers together....umm...isnt illegal in scca, but itll run you in a higher class...i fergot which one. dont hav my book with me cuz im at school. check the scca hand book

[gsracer]

the bar two tie in the two strut tower bars was just an alterantive to a strut bar, the real reasion i wanted to do this was for the X bar that would attach to it, i figured that would help out alot not only that but im sure it would look bad ass when you open the trunk. since i weld it my self and i have acces to chrome moly piping for free, it seemed like a cheap effective upgrade.

im utting to gether a new reinforced subframe, with spl aluminum bushings, and all the spl bars, except for the lower a arm(to expensive). I was also thinking about fabing up a bolt in cross bat tht would look some thing like this I-------------I to go in between the rear chassis rails around the area of the bottom rear seat with a built in driveshaft loop for a one piece drive shaft. And im also gonna FAB up my own nismo power brace. what you guys think.

[gsracer]

also i dont know if i mentioned this or not but this is for an s14 not an s13 .

[sykikchimp]

those all sound like excellent ideas man. Most will bump you into classes with very highly modified cars.

I'm moving to motorsports to possibly get you more input.

[gsracer]

thansk dude

[DS 240R]

I think you'd be tieing to a stronger part of the unibody if you went forward instead of back into the trunk. I'd do the X forward to where the B piller meets the bottom "frame rail". Additionally, you could omit the bar between the towers to save some weight and just have the X, like in the attachment.

The rear trunk is just kinda overhang and the floor doesn't provide a lot of structural support... unless you go through the floor to the rear subframe... now that would be interesting...

[DS 240R]

I think a good roll bar that tied into the floor would do more, and be safer.

But how strong is the floor? And, if you tie to the top of the strut towers, you can put your rear cage X in the plane from the towers to the floor instead of to the roof which would probably lower the center of gravity some.

[DS 240R]

since i weld it my self and i have acces to chrome moly piping for free, it seemed like a cheap effective upgrade.

Sweet. Free tube + welding skills = lots of chassis reinforcement :)

I was also thinking about fabing up a bolt in cross bat tht would look some thing like this I-------------I to go in between the rear chassis rails around the area of the bottom rear seat with a built in driveshaft loop for a one piece drive shaft.

Making your own NPB is an excellent idea, as is the driveshaft loop, but I think this area of the car is pretty stiff because the rear seat hump above provides a lot of struture.

[gsracer]

I think you'd be tieing to a stronger part of the unibody if you went forward instead of back into the trunk. I'd do the X forward to where the B piller meets the bottom "frame rail". Additionally, you could omit the bar between the towers to save some weight and just have the X, like in the attachment.

The rear trunk is just kinda overhang and the floor doesn't provide a lot of structural support... unless you go through the floor to the rear subframe... now that would be interesting...


i dont think it is really feasible to do the X forward because of the design of the s14. I would have to look to be certian. what i was thinking is the space between the rear uppper frame rail and the trunk floor is onlu like about 3/4 inch (like the area were thhe rear bumper bolts are) i would cut that out mount it directly to there. Im gonna order the hoop premade from chassis enginering for the roll bar. I just need to find pictures of s14's with them to know what to do from there back and were to mount it not the hoop just the bars that go to the back.

[DS 240R]

i dont think it is really feasible to do the X forward because of the design of the s14.

Ah, yeah, you'd be going over the gas tank there the hump might be too big. I thought this was on an S13.

Well it all sounds interesting- I can't wait for pics!

[sykikchimp]

I think you'd be tieing to a stronger part of the unibody if you went forward instead of back into the trunk. I'd do the X forward to where the B piller meets the bottom "frame rail". Additionally, you could omit the bar between the towers to save some weight and just have the X, like in the attachment.

The rear trunk is just kinda overhang and the floor doesn't provide a lot of structural support... unless you go through the floor to the rear subframe... now that would be interesting...


Dude.. your giving me all kinds of ideas.

I suggest the floor of the hatch b/c that is typically where I've seen them attached, and When I've been under the back of the car it appeared the frame rails were attached directly to that floor. Is that incorrect?

[DS 240R]

I suggest the floor of the hatch b/c that is typically where I've seen them attached, and When I've been under the back of the car it appeared the frame rails were attached directly to that floor. Is that incorrect?

I dunno, I haven't been under that part of the car yet except to notice that the diff housing is missing. If you go to the floor that's right above the frame rails, then that makes sense, but I still am not too sure about extending the cage back that far.

I mean, besides surrounding and protecting the gas tank, what structure do you need to secure back there? Isn't it just overhang? I'm kinda thinking that anything past the rear strut towers is just increasing weight and polar moment. But honestly we haven't even finished stripping the car yet, so I haven't examined it that closely. Still trying to clean out the animal hair or whatever it is: http://www.zilvia.net/f/showpost.php?p=448298&postcount=1767

[MovinUp-1]

Your bracing idea is good, but illegal in SCCA for all but prepared and mod classes (not street mod). You can only have one upper and one lower lateral chassis brace at the front and rear. These braces may only attach at two points and therefore not have any triangulation. You can install a roll cage with up to 6 points of attachment in stock through street mod.

I didn't write the rules, I just try to live at the edge of them.

[TBreu007]

A rear strut bar won't do much in the 240 because there isn't a whole lot of lateral flex on the top of the rear struts. Pretty much all the struts do on the rear is go up and down...the front is another story. If anything, run a piece of 1.75" tubing down the floor in the inside of the car along the rocker and weld it to the body and floor anywhere you can....this works wonders for taking out chassis flex.

Why don't you just put in a roll cage? Your car will be 1000x's stiffer than any amount of misc. bracing you can do, and with just a racing seat, 5 or 6 point belts, a kill switch and fire bottle or fire system you can race wheel to wheel in Improved Touring "S". If it's you only car, I've seen lots of daily drivers raced. In fact, after racing in the Homestead 12 hours a couple weeks ago, I saw a guy in a Miata driving his race car home! With a little thought on design of your door bars, it's not that much harder to get in and out of either. In most classes, metal to metal contact is rare unless you're really pushing.

If you're going to replace most of your suspension bushings with sphericals, I would recommend doing all of them, or your rear end will be more likely to bind causing unpredictable handling. I got all of them done by Tim at West Tek in Kansas. I sent him all my suspension and they came back all sphericaled (if that's a word). It was $1200 for the front and rear, but he may work something out with you if you just want the LCA done.
E-mail me if you want me to look up his number.
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