In my first post, I made reference to sub-frame connectors and a brace for the rear of the front control arms. Here's one such brace: http://www.sfxperformance.com/parts/TABTUB032F.htm, although it's not the one I was thinking of - I know I've seen a brace that also combines with a subframe connector/cross brace, to thoroughly box the large transmission tunnel of these cars - the tunnel already being a strong point that becomes even more so when boxed and tied into the front and rear sub-frames, but I can't think of who made/makes it.

 

You must be really bored

 

Come to think of it, I do remember some set of braces that goes between the front crossmember, behind the control arms and it bolts to somewhere near the transmission tunnel...

Whatev... I just like ******* around.

 

ya i have seen these before, its like the stock brace that you would find on a convertable fc....although these look a lot better and are probably made with a better material.

 

try searching in icemark's posts, he had a writeup with part numbers of seam sealer he used. he had a vert daily driver and we all know how weak the frame torsion is on the vert models so he did his own R+D on stiffening the rigidity of the body and i have seen his car, there is almost no frame torsion when going into driveways on an angle lifting wheel+wheel.

 

Here's another thread link for an expanding foam which uses a higher grade foam product than the kind used by Mark.

https://www.rx7club.com/2nd-gen-archive-72/my-2nd-gen-foamseal-project-743378/

 

@rx7racerca: you mean the one from autoexe? I think corksport still sells those.

 

Dammit, you made me do it. You made me reply! LoL!

Bigger diameter wheels allow them to clear bigger brakes and also run flatter tires. The trade-off made having heavier wheels increasing inertia there for increasing unsprung weight is made to improve steering precision and feel. BMW world racing cars of the 70s/80s had up to 21 inch wheels 'cause it looked cool???

Nowadays drilled rotors mainly are used for the same reason as you wanting 15 inch wheels on Porsches (reducing unsprung weight). Along with improved initial bite they have plenty of downsides which should be carefully thought truogh for each different application.

Now I and I think anyone who has ever looked at FC's agree with the weakspots the Pro's pointed out. I could also add tens more maybe even a hundred more before coming to the point of strutbars being needed. This does not however make them useless, not noticable or styling. (Not that you claimed all those things) It's just not as important as the very few points mentioned by the pro's.

You will just go with whatever someone says instead of looking at the car your self, looking for improvement and testing them out? In the end of the day a strutbar is a great and icrediably cheap upgrade that won't hurt you car you could do for 10 bucks...

Riz.

 

You'd be hard-pressed to find factory, or even aftermarket "big brake" kits that need wheels larger than 18", and few that demand larger than 17" wheels - but the large wheels do hurt both acceleration and braking thanks to increased inertial momentum - think adding 4 heavier flywheels - racers certainly don't use big wheels, they typically look for as small a rim diameter as possible (though of course width is desired) - making 17s and 18s the big rims for road racers/endurance racers. For endurance, larger rims (17s and 18s) and tires provide advantage mainly in the form of more tire surface area, which is useful both for tire longevity, and more so for increased area to absorb and then re-radiate heat.

Moreover, the larger wheels actually demand larger brakes because of their negative impact on braking. Look at F1 - 13" rims. Champ car: 15", even heavy NASCAR stockers - 15" (although NASCAR specs are anachronistic generally, so hard to read a lot into that). Low profile tires do not requires large diameter rims, btw - I assume that's what you meant by "flatter tires".

I still stand by my point - reinforcing the already strong front and rear structures of an FC with strut bars is largely pointless, at least until the mid section chassis is reinforced. Otherwise, you aren't preventing chassis flex/deflection from suspension inputs, you're just directing more of that energy into the portion of the chassis that is already most prone to torsional flex - the cabin. PvillKnight's bar pic above looks to be a well done rear bar design - but worth noting is that it's in a stripped, caged chassis.

Can you show me any testing that shows strut bars improve the FC chassis, at least with spring rates and grip levels typical of street or autocross cars? I'd be interested to see if anyone has (although if the Efini IV bars were added for a primary reason other than style, I would think Mazda would have such data), but I'm very much in doubt such exists, having been a RX-7 owner and competitor for 12 years, and a fan longer, and I've yet to see anyone show benefits without adding the lower chassis brace and mid-section reinforcement first. Saying it "feels" better is, as was pointed out by another poster, often a case of placebo effect - having spent time and money, people want to be able to say it was worthwhile.

The FC is not a willowy economy car or sedan, or sport-y car derived from such - it was purpose designed to be a sports car with exceptional chassis rigidity - part of why Mazda's engineers blew through their weight goals for the car. One was achieved at the expense of the other.

 

That's what I think he's talking about too.



Corksport does indeed sell them, for a little over half a grand.

 

I know those facts and I'm very well aware of the effect of adding rotational weight.

I'm not sure about American forms of motorsports, however I have been following F1 for all my life. You name one F1 car designer of lets say the last 30 years who says 13 inch wheels are their prefered size... The 13 inch maximum diameter rim rule has been there for many decades and probably will never change. It creates problems all teams have learned to work with over the last few douzens of years, greatly improving tire development. There have been other solutions like dual brakedisc per wheel and such to cope with the limited space. Ever noticed how high a F1 tires sidewall is? Imagine how heavy those tires are for them to be so sturdy.

In my country profile (profiel) means the thread which is only a few mm deep. So sorry yes I meant low profile tires. Low profile tires in combination with small diameter rims obviusly results in smaller overall diameter. This is (not always) wanted.

I'll just leave these pictures of classic race cars with big wheels (up to 21 inches) from way before it was fashionable to have big wheels... Rice?



















I'm not cheering for huge heavy wheels, by no means. I would never run bigger than 18 on my FC, probably keep with 17 inches, but I just don't like the fact how black/white you are. You think the people who developed the cars above were stupid, didn't know their profession? No, there is different products needed for different cars in different situation, not every car is the same, and even if they are, not very car is used the same way in teh same setting

No I can not. However I will try to get those figures some how when I continue development on my car. You might be surprised to know that I largly agree with you, however like I said: I hate the black/whiteness of you oppinion. My expierence has shown (even without hard date, but still) that connecting the struts together makes the suspension work more constant and (probably effective) on multiple cars. I can not say what this will do stresslevels in certain other sections of the car, but it doesn't seem to hurt balance or lap times, if so we would have removed it. The change in feel gives me more confidence in the linearity of the suspension which to me is worth the few bucks and couple of minutes is costs to make/install. It doesn't have to be pretty to work.

Alot of weight also comes from the design. But still you are correct, and still it could be alot stiffer and many areas (though mainly mid section) and would be more stiff if it were made today.

About those AutoExe parts. If you look under your car, and you can imagine a bit and got basic understanding of the forces put of the car you can make those parts yourself for less. The perfect fit is convient though if you have the cash for AutoExe.

Riz.

 

People got different ideas on what setup is right, and what setup works for them..

Nothing wrong with visual cosmetics being reason to do some mods, its good to make your car look good and not some POS looking fast car.

 

Just received my $66 with shipping 3 piece eBay strut brace as seen on page 2, it's the same as the $170 one!!! The allen bolts they give you for the speaker mounts are a little too short, thus Ace hardware for me in the morning then I'll post the pictures. Another great eBay buy!!!!

 

I had to paint the ugly color of orange.

 

Looks very very nice!

 

No doubt! It looks like a strong design and crazy easy to install. Anyone know if the front bar by the same people fits the turbo models with the top mount?

http://cgi.ebay.com/ebaymotors/86-87...item5886274e53

 

The rear one in the pic above is either a TC Sportsline or knock off of one.


Post #8: https://www.rx7club.com/showthread.p...urbo+strut+bar

[QUOTE=SpeedOfLife;9847190]No doubt! It looks like a strong design and crazy easy to install. Anyone know if the front bar by the same people fits the turbo models with the top mount?

 

The one in post 8 where you linked is definitely labeled TCSportline. The fitment looks really good. I might have to sell a pinky so I can pick those both up...

 

The one you asked about is a knock off of the one I linked but they are one in the same design, I just didn't have a pic of the knock off so I provided you with a pic of the "non-knock off." I'm sure the knock off is probably cheaper in case you want to go with the knock off.

 

In their separate listings they include in the description:
"BRAND NEW ALUMINUM STRUT TOWER BAR BY TC SPORTLINE. THE BAR IS BUILD FOR EACH SPECIFIC VEHICLE FEATURING MULTI-CHAMBER CONSTRUCTION WITH NON PIVOTAL ENDS FOR STRENGTH AND STABILITY. THIS STRUT TOWER BAR WILL IMPROVE YOUR VEHICLE'S HANDLING, CORNERING ABILITY, AND STEERING RESPONSE."

I know the images don't show the label though, which is strange. Personally I wouldn't mind if they aren't TCS because they look solid to me, but it would be kinda stupid for them to say that's what they are if they're not.

Front:
http://cgi.ebay.com/ebaymotors/FRONT...item27afa4f992

Rear:
http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

 

it's the ebay knock off one that's identical to the TC Sportline! It's only $66 with shipping!

 

This looks like a great deal, I'm going to buy the pair.

 

http://www.srbpower.com/cusco/strut-bar?Make=MAZDA
Rear OS Bar and 3-Point Lower Bars

http://www.tanabe-usa.com/underbrace.asp

http://www.fujitaengineeringusa.com/fc3s3.html
Last item on that page

http://www.imageinmotion.com/cuscopillarsidebars.php

The old H-M0201 bar from Mazdatrix, discontinued now for the Front Strut Towers, bolts to the towers, the firewall and serves as an engine torque brace.

Those are the only things I've heard of that will stiffen the chassis short of the cage.