1st Gen RX7 rear lower links

[joeracerx95]

I'm almost complete on the changes to my ITA Rx7 except for the rear lower links. Currently I still have the stock parts.

In theory they look like they would be very simple to make; steel tubing of the correct size and length, one left and one right rod end on each end. Install and adjust.

But theory and practice aren't always the same thing. What tubing will I need and where am I likely to find it? Can I use the stock parts and just cut off the ends?

Rod ends should be a straightforward purchase from Pegasus or Summit. I assume I'm going to need the "good" ones to tolerate the loads. I.E. expensive.

Any other tips? Or better yet, anybody got some for sale, cheap?

-chuck-

[ddewhurst]

Chuck, save yourself some time & money. Go to your local oval track parts house to get your R & L hand rod ends & to get your threaded lengths of tubing. There are both alum & steel lengths of threaded tubing complete in one inch incerements.

That's where I got my same stuff your looking for.

[joeracerx95]

Thanks David. Through the magic of Google I think I'm on the right track. Once I stumbled across the correct term for this, "Radius Rod", I found several sources.

Next question, steel or aluminum? It would be nice to go lightweight with aluminum, but is it strong enough? One of these links failing by having the rod end pull out would be pretty ugly. Anyone using aluminum?

-chuck-

[lateapex911]

Huh???????????/

Is any of what you guys are talking about legal?????

My opinion is that you may replace the bushing material in the existing suspension location device (the lower rod) but you may not throw it away and fabricate one of carbon or aluminum or change the length or shape or anything...

what the heck am I missing!?

[joeracerx95]

Perhaps I'm misinterpreting the GCR. I know that this is common practice in ITA on the West coast.

Doesn't this cover what we're discussing?

"Any anti-roll bar(s), traction bar(s), panhard rod or watts linkage may be added or substituted, provided its/their installation serves no other purpose. The mounts for these devices may be welded or bolted to the structure of the vehicle. No suspension control mount or component shall be located in the trunk or driver/passenger compartment unless installed by the manufacturer as original equipment. Traction bars used to control axle rotation shall be one piece solid bar or tube. Heim rod ends may be fitted."

[dickita15]

Jake, don't you know anything, those links are traction bars.

[lateapex911]

Uh, OK.

But, if the lower axle locating links were removed from the car, would the car suffer more from wheel hop (because of the lack of traction bars) or from complete undrivablity (because they hold the axle in place)??

I would be interested to see how the appeals court would rule on this, as the defense is that these are pure traction control devices and not suspension locating devices.

[joeracerx95]

I'm new to this class so I'm not trying to cause trouble, I just thought this was an accepted change on these cars.

Jake, I don't think the answer is black and white. The upper arms also hold the axle in place. Either the upper or lower bars missing would result in uncontrolled axle rotation, something a traction bar prevents. You need both the upper and lower arms to control axle rotation, doesn't that make them both traction bars?

But like a leaf spring which serves two functions, these rods also serve two functions. Fore-aft control as well as rotation. Without this interpretation, third link components that "replace" the upper links would be illegal, wouldn't they? Aren't a bunch of people running the G-Force and ISC third links in ITA?

-chuck-

[joeracerx95]

"Perhaps I'm misinterpreting the GCR. I know that this is common practice in ITA on the West coast."

BTW, when I said this I meant that replacing the lower arms was a common practice out here, not misinterpreting the GCR.

Wait a minute, now that I think about it......

-chuck-

[lateapex911]

I hear you Chuck, and it's an area that is rather debatable. The tri link adds a part, and the upper links remain in place. Now, effectively, their role is diminished, by the soft bushings.

Another method of solving the issue (Poor axle geometry when the car is lowered) would be to use offset bushings in the upper and lower links, but I assume when Susko (G Force) did the math, he decided he could get better latitude by using the "Add a traction bar" option in the rule book.

I know it's a fine line, but I fall on the side of the issue that thinks that the links are clearly suspension location devices, and that considering them traction control devices only (the rulebook doesn't list the allownace for traction control devices/suspension locating devices) is pushing things more than I'd feel comfortable with. I love a good rule loophole as much as anybody, (I've disovered and closed a few actually), but I've decided to stay out of the gray on this one. But others, as you've mentioned, have other opinions, and thats fine.

[ddewhurst]

Chuck, IMHJ you are reading the rule correctly. I had some, people looked at them & walked away after asking a question or two.

This has been discussed a couple times on this site & those that say it's gray or illegal usually walk away from the discussion without using common sense as to why the "upper link" is a traction bar & the "lower link" is not a traction bar. Some within this thread admit that the "lower link" is a traction bar yet they say it's a gray area. The friken rule don't say traction bar/Banjo location link, the rule says traction bar.............

The word "added" works for G-Force & the word "substituted" works for DD-Force.

Someone PLEASE explain why the "lower link" is not a traction bar.

IMHJ there is more within this rule that could be implemented very successfully. One may do about anything with the traction bars & their mounting as long as one has two or more bars. But that's for another arguement. Oh, I ment to say rule disagreement.

Chuck, I'll pay the protest fee & whatever when someone has the sack to protest your car.

***I've disovered and closed a few actually***

Threats Jake, when you going to CHANGE this rule.

[Greg Amy]

...those that say it&#39;s gray or illegal usually walk away from the discussion without using <strike>common</strike> Dewhurst sense...[/b]

Sorry, couldn&#39;t resist... ;)

Someone PLEASE explain why the "lower link" is not a traction bar.[/b]

Just as an apple is a fruit, but a fruit is not an apple.

That lower link performs all the actions of a traction bar, but a traction bar does not perform all the actions of that lower link. To justify the modification you are picking a single function of that link and giving it the specific definition you choose to ("cherry-picking") which is the essence of the "prohibited function" clause of the IT rules...

[lateapex911]

Threats Jake, when you going to CHANGE this rule. [/b]

I&#39;m not going to sponsor any rewrite, David, because as has been explained here, by both Greg and I, the component is not just a traction bar. The rule is fine as written.

Don&#39;t assume those who have looked at your car, have decided that your interpretation is the fianl word, by their "walking away". For example, would I protest you on the items ? No, not worth the effort, honestly. But that shouldn&#39;t be taken as me judging them legal, because IMHJ, they are not.

[ddewhurst]

***The word "added" works for G-Force & the word "substituted" works for DD-Force.***

***without using common Dewhurst sense...***

I like that ^ Greg, it&#39;s kind of like using a "substituted" lower link by DD-Force.

Now on to the fruit of the subject.

***That lower link performs all the actions of a traction bar, but a traction bar does not perform all the actions of that lower link. To justify the modification you are picking a single function of that link and giving it the specific definition you choose to ("cherry-picking") which is the essence of the "prohibited function" clause of the IT rules...***

Greg, it would be my humble judgement that the "upper link" & the "lower link" do the exact same function. (Other than that the uppper links shape & mounting points screw up the rear 4 link geomerty.) If one disconnects either pair of links both traction & location will be eliminated from the OEM function.

Greg, when you explain what is different between the lower link & the upper link & their capability that each functions as a traction bar & that each functions as a location link I&#39;ll buy your thoughts. IMHJ both fruit do the same functions. If you don&#39;t buy these thoughts ^ how about YOU talk to Jake G. about taking either pair of links off his 1st gen RX-7 & we&#39;ll see the results in a hurry. Also disconnect the Tri-link when the upper links are disconnected. NO location/NO traction & a bunch of busted parts.

If G-Force may say that the "upper link" is a traction bar, DD-Force says that the "lower" link is a traction bar.

***because as has been explained here, by both Greg and I,***

Jake, I almost forgot about you ^. You could have said by all of us, Greg, Jim & I. When one looks at the information by Jim, he calls the upper & lower links trailing arms. Well my friend, the rule says NOTHING about addition or subistution of trailing arms. Oh, I forgot the master of G-Force can call stuff anything he pleases. He also told me that I had the ONE 1st gen in the entire world that had the odd ball strut mounting holes different than every other 1st gen with respect to his G-Force strut spacers fitting. BS............ Hey, I don&#39;t dislike Jim, I don&#39;t like people who pass gas.

All said with a

[Greg Amy]

To be honest here, David, I am not intimately familiar with the design of the rear suspension on the RX-7. However, inferring from what is being written in this topic, the link(s) in question performs a function other than that of a true traction bar. If that is correct - that link(s) you&#39;re talking about have a function of *anything* other than what a pure traction bar does - then its replacement is performing a prohibited function, and is expressly prohibited by the rules. - GA

[Joe-Racer]

The rules aside, I&#39;m not sure why you&#39;d want solid lower links WHEN a 3 link is used. The upper link is bushingless (sp) and must remain per the rules. Yes, it rattles like crazy - but its a soothing rattle

I just wonder if the combination of a tri and sold lower would bind in compression and induce snap oversteer. Just speculating so let the flames begin :P

[dickita15]

Okay really I am not being a jerk here or at least not trying to be one. I understand the argument that the lower links can be swapped out, but if that is the case why do you have to retain the upper links. Can’t you remove them by the same argument.

[Joe-Racer]

No the links must remain in place. The ends can be hollowed out, but anyone in IT7 will get protested if they arent running them.

The tri-link is open b/c its considered a sway. At least thats my interpretation.

[dickita15]

Actually I think they are calling it a traction bar rather than a sway bar.

I guess I am not sure why if the lower meets the definition why the restraint on the upper link.

In the SE IT7 is the lower link replacement accepted practice? Just curious. I can see some advantage is squaring the rear end placement in the car, are there any other advantage available with adjustment of the length.

[kbailey]

Okay- here is my $.02. What I was told by several people as I was building my car is also what makes sense to me:

The upper and lower links are locating arms, not traction bars.

The popular setup I have seen is:
Add a tri-link to the top of the axle. This is an added traction bar, there is no question it is legal.
Replace the bushings on the stock upper locating arms with soft foam. This effectively renders them non-functional, and it is clearly legal.
Replace the bushings in the lower arms with spherical bearings. I personally think the interpretation of the old GCR wording "any bushing material" meaning spherical bearings was legal was crap. Now the wording has been changed in the GCR and it is officially legal now without argument. The Mazdamotorsports part listing for the bearings is below.

Nowhere do I see allowances to replace ther locating arms or the ends. Just my opinion.......but it seems to be the common interpretation of the folks I race with.

0000-04-7422 C BRG KIT,LOW TRAIL. ARM 1 ALL RX-7 1979-85 $263.40

Kit includes four (4) spherical bearings to replace stock rubber bushings in lower trailing links. Requires pressing rubber bushings out of stock links. Uses stock bolts. Legal for SCCA &#39;IT&#39; classes. Recommended to use with old, soft, upper bushings to prevent binding. Kit also available via special order that includes modified lower trailing links, fitted with sperical bearings (0000-04-7423).