Hey all! Ive dug through the massive thread on fixes for the FBs crappy rear geometry (https://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/)

However, Ive found it difficult to understand good chunks of it, due to the various image host armageddons that would help a visual learner like me.

So I'd like to ask, what suspension are you guys running in the back of your FB? and Id love to see pictures/diagrams of hoe you've done it. Im considering doing a panhard swap/3 link with the GC Panhard bar, but Im not exactly sure what that job would be like with how hard its been finding pics.

I guess what im saying is Id like to see images of the various options for the rear suspension im the FB, as a lot seem to have been lost to time.

 

https://www.rx7club.com/build-thread...-build-992966/

Starting on Post #13 and running to #18 details what I did on my race car. My solution is very invasive and is only going to be legal for certain classes in some of the sanctioning bodies that are out there. Had I to do it over, I would keep the three link and use a chassis mounted watts setup or some other multi-link device to locate the rear axle side to side. A panhard bar works and is cheaper than a watts but it is ultimately not as good.

 

Awesome build! Certainly a lot more invasive than what Id want to do though LOL.

I guess what Im looking for/dreaming of is a proper fix for the binding issues I've heard of. Its unlikely Ill encounter it since I dont plan on anything more intense than casual driving and AutoX, but Im a huge worrywart and if I totaled this csr Id be devestated.

Id love to retain the Watts link but also eliminate the binding. Not sure how I feel about the "PBJ" hack. Doesnt sound very safe to leave bushings loose. Ive also heard the roll center is stupid high, not sure how people go about fixing that too.

 

What Autox class are you running in? The new Extreme Classes - XA or XB - look fun for an RX7. I autox a Mustang in CAM-C which has a similar philosophy in terms of mods.

If you are running the OE suspension as is, you have fresh bushings everywhere (no polyurethane) and don't lower the car too much these cars work pretty well. Pro7 RX7s use all stock stuff and I have watched them go pretty fast.

The OE watts mount on the axle housing are known to break - seen this first hand on an ITA RX7. There used to be braces that could be added to strengthen the mount so some Googleing might be in order.

When my car was an IT car I used a device called a Tri-Link with a Panhard bar. The Tir-link attaches to the top of the diff and runs under the car and attaches in the tunnel beside the drive shaft. With one of these you can eliminate the OE upper links which fixes allot of the bind. The Tri-Link worked well in a lower powered car with smaller tires. In E Production with slick tires and 200+ RWHP the Tri-Link proved not to be very good at putting down power.

The next iteration for E Production was the modified 4-link with a panhard bar. One of my posts has pictures of this. Not very invasive if you have a cage or roll bar to attach to.

 

Wasn't it G Force or something that made those back in the day?
I think user 'Carl' and other posted some pics of that setup over the years. Instead of cutting up the car, there is a bracket that's installed under the trans tunnel and the 3rd link bar curves down from the top of the diff to that bracket.

It is pretty popular setup for ITA, Pro7 and IT7 iirc...

 

Yep - G Force by Jim Susko
http://foxed.ca/rx7manual/manuals/Se...A%20to%20Z.pdf

I actually met him briefly at Mid Ohio during the Runoffs. I was crewing for an E Production driver and we were paddocked with a three other EP FBs that were using variations of his stuff.

 

Does Mazdatrix's Watts Link Anti-Shear bracket work for this? Or is another kind of reinforcement needed?

 

Im not super familiar with where Id wanna fit in, I think the modified classes sound around what Im aiming for, mid level mods like engine parts and whatnot.

Id like to keep modifications uninvasive as Id feel bad tearing up my GSL-SE. So bushings and a Watts brace might be in order. Do you know what can be done to lower the roll center and stop binding? I probably wont ever be pushing it hard enough to bind, but Id feel terrible if I snapped into a tree and wrecked my car.

 

all of the local cars here are pretty basic, its not too low. rear suspension is usually mostly stock. even on 200tw tires, like in Lemons its ok.
we usually get understeer, you really need to wait to put power down coming out of a corner

 

Yeah something like that

 

I'll take your last comments first. I get the concern for your car, but I have been autoxing since July 1986 and have only seen three roll overs in that time. All of them were 3 series BMWs. You aren't driving a BMW and no amount of suspension bind will turn an RX7 into a top heavy tip-over prone 3 series BMW. Suspension bind in the rear could have the effect of making the car get loose. You might spin but you won't die and neither will your car. Also, SCCA autox events are supposed to be set up so that trees and light poles are not in the path of a spinning car. It is a safe sport.

There is no way to lower the rear roll center of an RX7 if the OE Watts link is used. The roll center is where ever the watts pivot is. I would study the link I posted up that takes you to the G Force PDF written by Jim Susko. He explains everything you need to know. His solution for the rear suspension does require some fabrication but it is reverseable and not invasive. It had to be because the classes it was designed for (CSP - autox and Improved Touring - road racing) do not allow holes in the floor. My car was built to a different set of SCCA specifications. The other option would be to look at Technotoytuning https://technotoytuning.com/mazda/fb. I am not crazy about there panhard bar solution but I have seen ones like them used over the years. They have other parts for the front and rear of your car that offer you a bolt in solution.

Here is the link to the SCCA rules: https://cdn.connectsites.net/user_fi...pdf?1679601089
Its a free download. I would check out APPENDIX B - SUPPLEMENTARY CATEGORIES Classic American Muscle / Xtreme Street Category starting on page 260. Your car would fit in XB. The cars in this rule set have to be street cars with an interior, carpeting, external lights, etc. Tires have to have a 200TW. Body work, engine, drive line and suspension mods are wide open - do as little or as much as you want. Aero is also allowed now. Last Sunday I watched a bunch of cars in in XB - first gen MR2's, MR2 Spiders and Miatas of all build levels. An RX7 like yours would fit right in.

 

You should PM Carl , he races his FB and knows his stuff.

 

Awesome stuff Mustang, thanks a bunch! Ill have to dig through when I get some free time

 

I would start with good tires and fresh shocks, pads, and bushings. Then go to an event and have fun. Tell us all about it, good and bad, and then we will bury you with more advice.

Should get a good baseline feel for the car at the limit before you start spending time and money on mod's that may not be that important to you. Then do your upgrades, but not all at once, so you can determine what is working or tune accordingly. I will second on T3's stuff. Ground Control also good. Most of it bolt in.

I have read a lot here over the years about the rear end binding issue. I agree that is sort of a thing, but not that big of a thing. At least in track cars. Auto-x driving might be more sensitive to it. But if you haven't drastically lowered your car, it should not be that big a deal...something you can manage with driving technique. Assuming good tires, shocks and bushings, of course.

 

Lots of great advice here. I like Kurt's the best for your situation. In my mind, unless your car is a serious race car (autocross, road racing, rally, whatever) any of the serious changes, especially when spherical bearings are involved, will result in a car that is not fun to drive on the street. The tri-link/panhard system that I have installed, works great with the race car seriously lowered and stiffly sprung (way more than you would want for enjoyable street driving). It is incredibly noisy and bumpy driving around the pits though as the links/bearings clank. Not noticeable at WOT on the track, but drives me instantly crazy anywhere else. Sounds like the rearend is about to fallout.

If someone were to manage to get their RX7 to snap oversteer due to rearend binding while driving in public on the street, it is my opinion that they probably shouldn't have a driver's license :-) I don't think you need to worry about the rearend bind at the moment. Follow Kurt's advice (and everybody else's if you decide to go serious racing)

Carl

 

In that case, anyone got recommendations for bushings? I dont remember who makes some. I think Ive heard that the Energy bushing are too hard, but maybe I am misremembering.

Would some fresh KYB shocks work well too? Or are there better options.

 

Hopefully someone who has auto-x's their street FB will jump in here. As someone who has never owned a street legal RX7 I'm probably not the best to give specifics. I do have a street legal 99 NB Miata HPDE car that I can draw comparisons however. I definitely have gone too far with upgrades on that car where it's not pleasant to drive on the street (but is the best handling car I have owned).

I would go new OEM rubber on all things suspension. I would get mid range adjustable shocks that you can stiffen for an event. Would make sure the sway bar(s) have adjustment to tighten up as well. Maybe street-able hawk pads. Then probably a set of 200TW tires. If you only have time/money for one thing I would pick the tires.

Anyone else?

PS nice seeing Carl at the track last weekend. I won't mention what he was driving tho.

 

What Kurt and Carl said. Tires and seat time are what you should be after

 

Any good ideas where to source bushings? All I can seem to find are the Energy bushings, but Im not sure if I want hard plastic urethane bushings.

 

Oem bushings also exist. You can use a mix of both but from what i understand is poly bushings in the rear cause binding.

 

My favorite supplier:
https://mazdatrix.com/vehicle-year/1...cat=suspension

 

Which parts am I looking for for the rear on Mazdatrix? I see a kit for the rear for poly bushings, but the oem/rubber ones all seem to be sold individually and im not sure which ones id need to make a full set.

 

You might want to call them to double check. They also have the complete arms listed with new bushings already installed which aren't super expensive all things considered.

 

You would be looking for oem link upper and lower. I would suggest you copy and paste the manufacturer sku which is the oem part number and buy the links from a mazda dealer website. They are atleast $45 to $60 cheaper each link. For rear shocks I've used KYB AGX adjustable shocks that are for a fox body mustang. They worked really well and you can soften or stiffen them up. Ground control offers 200 lbs springs for the rear with dead coils u can cut off to lower the rear how ever you want. I have my rear suspension setup like this. The only difference is that I got lucky and found some adjustable tokico illuminas rear shocks. So I am running those right now. My front suspension has pretty much all the parts t3 offers besides the brake kit. I'm running a 7k spring rate, my car handles pretty good. I use it on that local tracks in Southern California. I seen a guy tracking locally and he was running the t3 rear panhard bar and when he hit a corner hard at Buttonwillow his rear end started shaking/ vibrating crazy causing him to lose control. He put the stock watts linkage and didn't have that problem anymore. That showed me that the t3 panhard bar is no good.

 

Buying OEM parts from Ray Crowe at Nucar is cheaper than most dealer websites charging you retail.