PvillKnight7

iTrader: (16)

I was going to suggest this. 1'x2' 0.065" mild steel plate and about 4' of 1"x1" 0.062" wall square tube. Weld the speaker tower seams. Bend and weld a 1'x1' square to each tower then cut, notch, and weld the square tube to each plate. Paint it some pretty color like hot pink and your done. Easy weekend project. If you really want to get fancy figure out some way to make grommets to go around the carpet where the bar goes through to the towers.

Pele

iTrader: (28)

Oh ****! That is the good stuff.

I thought it'd be a replica where I'd have to cur **** up and hack at it and make it look like complete ***.

Ordered.

PvillKnight7

iTrader: (16)

That's not even pink!

Yence

it touches the speakercovers slightly, but they didn't need trimming or anything.

Hypertek

iTrader: (3)

haha nice vid thanks for posting. sadly cusco probably wont sell much of those strut bars here in the US , people tend to run towards the cheaper route *no offense before someone tries to murder me lol

Molotovman

iTrader: (49)

Get the one that supports between the struts. Unless the TC sportline has an inside bracket too. If you're just bolting it to the strut tower metal with no inside reinforcement it's full of bullshitfail. Whats your goal here, to have a sportscar right? You don't need to be hauling **** around in a sportscar, thats why you Honda Assport GET.
YOU BRACE THE STRUT ASSEMBLIES AGAINST EACHOTHER TO PREVENT THE CHASSIS FROM FLEXING. IF YOU BRACE IT TO THE SPEAKER TOWER IT WILL STILL BULLSHITFLEX.

satch

iTrader: (1)

None of them do such, even TC Sportsline.

afpreppie04

iTrader: (5)

The TC Sportline has inner braces. There is a sort of L shaped part that mounts on the strut nuts and that part then passes through the speaker tower and bolts to the part you see in the car.

The one linked in that ebay auction is a TC Sportline one. You can see the part that goes inside the tower and mounts to the strut mount, its semi-circular and L-shaped.


The two bolts are what passes through the speaker tower and hold the two parts together.

Pele

iTrader: (28)

The one on eBay looks kinda generic... But same basic structure:

iamxeddiex

iTrader: (1)

Yeah, I have a lot of time for product research. I have one of the worst broken ankles in history, thanks to bmx. I wish I could drive my Wankle.

scathcart

Doubtful. What part of the chassis wears? You expecting spot welds to break? Iron to change its physical properties because its been around for a while? Metals tends to maintain their fatigue properties until the point of failure... Torsional rigidity doesn't decrease with age...

Pele

iTrader: (28)

^

Revised safety standards? Structural engineering R&D? Rust?

scathcart

Safety standards have nothing to do with chassis "strength". Think crumple zones. Compare the torsional rigidity values of the FC to pretty much any brand new car meeting 5 star safety ratings and you'll see they have nothing to do with each other.

Engineering... stucture always comes from triangulation. Find a way to out-engineer the triangle and you're a millionaire. Building a chassis is always just a matter of compromises between weight, cost, and physical dimensions. The entire RX-7 platform was built around the "no compromises" ideology... I don't think the same can be said about nissan using a powerplant shared amongst 15 different vehicles.

Rust is an unfair variable; a 10 year old car can easily have more rust that a 20 year old car, or vice versa.

mikeric

iTrader: (20)

Or for $500, you can get a real chassis brace.

Mine is on order

http://www.ioportracing.com/Merchant...ory_Code=AP591

jjwalker

I personally would like the mazdatrix bar with the firewall supports, but alas, I cannot afford one.

Pele

iTrader: (28)

Got a custom welded one in one of my first gens and a bolt in one going into another first gen... The bolt in one is a full cage that goes up front and follows the A pillars to the dash. It also has dual door bars.

That's front bar. Rears just hit the strut towers.

Crumple zones, being designed to crumple as their name implies, are very flexible... Older cars might actually be stiffer. Also, the location of various bracing and cross members will affect chassis rigidity.


I can't out engineer the triangle... However are you stating that the FC and S15 look exactly the same? Because they are different shaped cars, the triangles that lie benieth the body panels are different and therefore have different properties.

Additionally, metallurgy may have changed. It's reasonable to think that someone may have come up with a different alloy or the market for a certain alloy may have changed within the 10 year production difference of the two cars in question...


And rust is indeed a fair variable. We're talking strut bars here... This is an accessory which spans across many models and years of cars. The discussion is as applicable to the FC RX-7 as it is to the 1970's Datsun 240z... This can not only get bigger than a single model, but also more specific as in the difference between my car and another S4 GXL.

A strut bar can be installed on my Rust Free daily or on the rust bucket that has huge holes in the floor that I'm going to dump after I strip it for parts.

It will have a different effect so long as the cars are not identical.


The point is that there are theoretical possibilities that will make the chassis rigidity different between the given examples of the cars.

Unless you have torsional rigidity figures from two examples in question, I'll accept that both cars are different.

Tofuman FC3S

iTrader: (1)

I don't know if you are stupid, or just have no feel for your car...? Hmmm...

rx7racerca

iTrader: (1)

Strut bars are largely a cosmetic affectation on FC's - the chassis, unlike most cars from the eighties or even newer, has quite excellent torsional rigidity in both the fore and aft sections. As a consequence, the greatest flex in these cars is in the mid-section of the body, mainly due to the large door openings that cut into the roof, more so on sunroof equipped cars. I've actually seen a FC that creased the sail panel near the roofline with chassis flex coming from a launch at the strip, on street tires (but putting down 500whp). Not unlike the flex you can see in some older uncaged body-on frame muscle cars drag racing, although not nearly as bad. As someone mentioned earlier, unlike most manufacturers, Mazda took a pretty much no-compromise approach with the 7 - and chassis rigidity was one the engineers top goals.

The flex and creaking people notice coming from the hatch area is mainly from distortion of the top of the sail-panel/roof area. Although that in turn makes the whole hatch squeak against its rubber seals as its attachment points move relative to the stiffer rear suspension/hatch area.

The real way to deal with chassis flex on an FC is to cage it. Making the stiff parts (marginally) stiffer while leaving the relatively flexible cabin section unreinforced just channels more torsional energy into the weakest part of the chassis.

Sub-frame connectors and a lower control-arm brace help with the mid-section chassis flex, but aren't easy, and don't add visual appeal, and of course, caging a street car may make it stiffer, but less safe (if you don't wear a helmet all the time!), and make it uninsurable.

FWIW, I run 350lb/in front springs, 275lb/in rears, so quite a bit stiffer than typical lowering spring kits sold for street use, and I don't notice a lot of chassis flex or hatch creaking (really, not any) despite autocrossing and tracking the car regularly in addition to street driving on the frost-heaved concrete of local expressways.

RotaryEvolution

iTrader: (30)

buy a 6 point cage and you'll notice a real difference you bunch of d-bags. the torsion is in the unibody and as i said, strut bars do make a difference but not a huge one. try filling the frame rails with seam sealer or bolt in the cage and you will see what i mean...

the other guys are right, this section has turned into a shithole.

PvillKnight7

iTrader: (16)

Something like this is what I described in my earlier post.


Like others have pointed out, any differences you feel in "torsional rigidity" after installing this will be from the placebo effect of accomplishing something on your own. On some engineering paper sure...but in reality you will have less time, less money, and a heavier car. What you really need is seat time to improve your driving. Invest in tires?

Tofuman FC3S

iTrader: (1)

OK, I'm giving up on all the ignorance in this thread...

I wonder why Mazda themselves installed strutbars on their Infiny's...? Probably because after they tried so hard removing excess weight they decided the FC needed some weight put back in the from of a "strut weight bar"... Plus it also looks good! Yeah, that's very much something Mazda would do.

Riz.

rx7racerca

iTrader: (1)

Mazda putting in strut bars is not a compelling argument one way or the other, since like any manufacturer, they will supply what customers expect. 19 or 20" rims on a Porsche (as with any car, I merely use Porsche as an example of a true performance-centric manufacturer that nevertheless succumbs to fashion dictates of customers) contribute only extra weight and inertial momentum. Cross-drilled brakes are a performance anachronism (still offered on Porsches, Vettes, and other high performance cars) whose value faded away in the 60's and 70's, when better pad materials removed the outgassing issue that could prevent good pad contact with rotors under repeated hard braking, while the cross-drilled rotors actually contribute to stress risers and rotor cracking under hard use. But again, many customers expect to have that visual bling, so manufacturers supply it.

You'll note I didn't say the strut bars have no effect, I merely pointed out their effect is minimal and mostly cosmetic, given that that fore and aft sections of these cars are well-designed and quite rigid, while the cabin portion is where most chassis flex is found. And it is a general truism that strengthening strong points while ignoring weak points will not produce much, if any overall improvement - it tends merely to amplify the weaknesses.

http://grassrootsmotorsports.com/articles/lucky-7/ - this article discusses prepping FC's for autocross and roadracing. It addresses the few weak points of the car, such as factory adjustable dampers - not that there are many still running these - insufficient camber adjustment in the front, and rear DTSS. The midsection chassis weakness is specifically mentioned. Nowhere are strut bars suggested as being useful. The article was written with input from successful RX-7 tuners and racers like Sylvain Tremblay of SpeedSource Racing - as opposed to the "ignorance of this thread", as you so kindly put it.

MaczPayne

iTrader: (5)

+1

rx7racerca

iTrader: (1)

Although the issue has probably been beat to death now, I do want to clarify that FC's are by no means two sturdy boxes joined by a flimsy cabin section - contemporary reviews and technical analyses consistently comment on how solid and exceptionally rigid the FC RX-7's chassis is. The cabin is just the relatively weak part, and even that really only shows in competition use, or when really big power has to be put down.

Pele

iTrader: (28)

Okay.. so how can one sitffen up the cabin without adding a cage?

I've heard of adding that expanding foam to the frame rails and empty sections around teh door jambs... Is this a good idea?