Sway bars for 1st Gen Rx-7?

So I've been trying to decide on some stuff for my Rx-7 before the autocross season starts (in 4 weeks!). It's an 83 GSL (12A with Nikki carburetor, 4-wheel-discs, LSD) that's pretty much all stock. It runs well and did pretty good last year with just a set of 195 Falken Azenis Rt-615's on 14" factory alloy wheels. Pictures from the events show LOTS of body lean so I want to get some beefier sway bars for it. The shocks are OEM but are only 2 years old so I'm skipping those until a complete suspension rebuild.

The problem is there are a lot of choices! Ground Control, Suspension Techniques, Tri-Point, and Racing Beat all have sets plus Mazdaspeed shows some in stock. I'm leaning towards the RB setup. Any thoughts?

Also, class-legal means nothing to me as I run with the Porsche Club, so my class is "non-Porsche".

Okey doke. First thing, body roll on a 1st gen means nothin' and you can't really get rid of it. Push that whole thing out of your mind.

Rear roll steer and roll stiffness are quite another kettle of fish, though. These cars tend toward snap oversteer when pushed hard, not good. So far, the only setup which shows any real promise is: 1) really big front sway bar, like 1 1/8" 2) get as much caster and camber as you can in the front. If you run SCCA Street Prepared rules, the CSP rules allow for camber plates but you cannot cut the upper strut mounts. So that limits the total amount of caster/camber you can get, but that's life. At this point we are done with the front unless you want to run a coilover conversion and adjustable struts which I highly recommend.

In the rear, the stock bushings bind like crazy and the stock sway bar contributes to oversteer. Step 1: Lose the rear sway bar. The easiest way to do this is to remove just 1 of the end links. That way you can still use it if you want. Step 2: you gotta get rid of some of the stock rear bushing bind some kind of way. Do NOT use urethane bushings! Bad news, BTDT. The best method is either a 3 link (which helps with the rear roll steer) or making new control arms for the 4 link with rod ends (which does not help with the rear roll steer), both are big $$$. Next best, soften the stock rear bushings. You do this by removing the rear control arms and use a sharp 3/16" drill bit to drill holes through the rubber part of the bushings. This takes patience and sharp bits! Now, when you reassemble the rear suspension, use grease inside the bushing sleeves, install the bolts but use nylon lock nuts. Tighten them down until the bolt can't wiggle but the bushing rotates freely in the bracket. This mod makes the most AMAZING difference in a 1st gen's handling. It's not as good as a 3 link but it's light years ahead of the stock setup. Here's a writeup which shows details of this mod: http://www.pbandjracing.com/rear_suspension.html

Again, this doesn't fix the stock rear roll steer but man does it help with the bind.

Hmmm, I'll have to try that for the rear!

So I think I'm going to do the RB 1 1/8" front bar for now and try disconnecting the rear if I need a little more. My whole suspension needs to be redone soon but I don't want to get into it for too much money. Right now I'm thinking new Tokico HP struts, RB drop springs, and new Mazda Rubber bushings. I think trying the G-Force "Tri-Point" thing for the rear sounds like it might do some good. It'll be summer at the earliest for this stuff though, I have to paint the thing first!

I've repeatedly heard of taking off the rear sway bar. Bit counter intuitive but I'll give it a try.

Billy at Re Speed make an tubular front control arm that I have heard good reviews on when run with the stock rear bar. Awesome customer service and he also has a R&P kit that gets rid of the "wonder steer."

http://mrcmfg.com/catalog/product_info.php?cPath=112_41_92&products_id=264

I would disconnect the rear sway bar and see how you like it. Easy and free. My front and rear sway bars are still stock for now and I kind of like that way. See readers ride pic.

http://grassrootsmotorsports.com/reader-rides/476/

I have no direct experience with the tubular lower control arms, those were not legal for CSP when I built my car. In the front I used urethane bushings since you don't have the 'twist' problem like the rear does.

The stock steering box can be finagled to tighten it up. Most people only adjust the small screw on top of the Pitman shaft, the big nut on top of the box (where the steering shaft comes in) should be adjusted too. It's possible to get it down to around 1/2" of slop, it just takes time and cusswords. In some ways the 'parallelogram' linkage is superior to a R&P.

The Tri Point setup is pretty cool, you just have to be able to properly weld the thing together.

The Tokico HP's are okay for street use, but I would go with the Illumina adjustables. Yeah they are more expensive but it's worth every dime. BTDT. On springs, Ground Control recommended 350 inch pound front and 175 inch pound rear. Since I got mine pretty floppy in the rear, I ran 200 inch pound springs. That setup worked very well in AX situations running Kumho Victoracers on 13x7 wheels.

IMHO, the biggest bang for the buck is more gear in the rear. The stock 3:9-1 just don't get it. A rather simple upgrade: some 1.8 Miatas have 4:3-1 open diffs which can be had pretty cheap. The cool thing: the carrier bolts directly into a RX7 axle housing. Even better: the ring gear bolts directly to a GSL (not GSL-SE) limited slip. So you can get a Miata 3rd member from fleaBay, install your limited slip in that housing and stuff it into your axle. Instant cheap gearing change. If you can find it, a B2600 4x4 pickup front diff is 4:44-1 and the R&P will bolt right into a RX7 diff. However, you now have to set up the R&P pinion depth etc which takes it out of the 'weekend warrior' upgrade unless you have access to the tools and stuff.

Opps I said control arm. I meant tubular front sway bar.

IIRC in I blew up the ring gear in the rear end on my first car and bolted the ring gear and pinion from a GSL on to my carrier. I couldn't tell the difference between the 4.1 and 3.9 but I have heard a 4.4 is a good upgrade for NA cars.

I'll get to the steering box one day. Right now mine's actually pretty tight and steers nice. It's amazing how nice well taken care of FB's steer. John's 82 was a JY reject and it steers like a UPS truck with a doughnut spare on one of the fronts!

Coil-overs are too much coin for me and the adjustables just don't seem worth it for me. I'm not fast enough to get any use of the few tenths quicker they are and I don't know enough to be able to adjust them right. Maybe a few years down the road, but right now they'd probably hurt my times.

The rear diff thing sounds neat. I though the GSL was already a 4.44 though? My LSD needs a rebuild so the Miata gearset while I'm in there sounds really good.

Right now the stock exhaust is being taken off (yes, the STOCK exhaust, it still unbolts!) and the RB header and custom setup is getting all welded in. Should make some power and lose some weight from that reactor/manifold thing.

I spent last year focusing on the nut behind the wheel and only upgraded to Azenis half way through. I plan on continuing that work this year but with a little more handling and a little more power.

Nope, all GSL's were 3:9-1. Got a spare in my shop. The GSL-SE was 4:10-1.

That header and exhaust will add a LOT of punch. It's possible to pick up some more HP by advancing the ignition timing but be CAREFUL! 12A apex seals do NOT like preignition and with rotaries you really can't hear it happening. Best way to set it is at 3000 RPM, with both the vacuum and mechanical advance fully in it should be around 24 degrees. Less is OK but no higher!

If you are going to rebuild the limited slip, get ready for some sticker shock. Those plates are OUTRAGEOUS. Most times, rather than replace all of the discs, you can get a couple of oversize plates and new Belleville washers and put one oversize plate on each end to tighten up the pack.

There are some adjustable lower control arms (that's what i thought Greg was talking about) that make it easy to add camber. Only problem is, you are still limited in caster adjustment which an RX7 desperately needs to properly load the front tires. Before I'd put money into adjustable control arms I'd do camber plates, more bang for the buck.

The Ground Control coilover sleeves are nice stuff and go on the original strut housings, I was very pleased with them. Having said that, those of us on a budget can get the fleaBay coilovers with the 'questionable' springs for cheap and work with that. I got a set of the Miata sleeves and stuff, it was something like $65 and the springs were in the, IIRC, 450 pound range. The rear springs from GC are pretty reasonable.

Must have been the SE I was confusing. Is there anyway to use a Miata LSD or even better the Torsen? My LSD is hurting bad, even some Royal Purple didn't help much. I kinda figured it would be cheap to repair as a clutch type though.

The exhaust is an RB street-port header with a custom made collector that's a true 2.5" (we hacked off the original collector and started with just the 2 pipes). It's going through a complete 2.5" mandrel-bent setup to a Dynomax race bullet (which acts like a resonator) to the rear axle (up and over) and into a Summit fully-welded race muffler (straight-through) and a nice SS dual tip (from PFYC). It's probably going to be LOUD but I'm OK with that Wrapping the header's primaries with DEI wrap also.

Who makes caster/camber plates besides GC? Their's look nice but man it's pricey. I'll do the plates when I do the whole suspension.

The 1.8 Miata shares the same spline diameter as the 2nd gen RX7 meaning the spider gears are too big for the 1st gen RX7 axle. AFAIK there were no 1st gen axles that shared the larger spline. You could probably have some custom axles made but that's big bux.

Is your LSD chattering? If so, try the Redline gear oil and mix about 5% of their limited slip additive into it. That helped mine a lot. If you add the thicker plates, the lockup will be more aggressive and if it's too aggressive it can cause the car to understeer on acceleration.

I had the GC camber plates, sorry no matter whose you use they just ain't cheap. If you know someone with access to a CNC machine, they could probably make you some. I saw some made of 1/4" steel which, while heavy and not pretty, were effective.

You mentioned drop springs; those won't work with the coilover conversion. So, if you plan to do that later save your bux and instead cut the stock springs. It's going to be a bit trial and error, but IIRC when I did this (before I did the coilover thing) I cut one full coil off of each spring, all the way around. YMMV! This will lower the car and make the springs stiffer. The only problem with this: the stock front springs are a large diameter and this keeps you from getting full travel with camber plates.

For the camber plates... Once again check out Billy's site. They run about 100 less than ground control.

http://mrcmfg.com/catalog/product_info.php?cPath=112_41_92&products_id=38

I have his full coilover setup front and he is now making rear "coilovers". They are not true coilovers but act height and coner weight adjusters. ISC used to make them which is who I bought them from. They stopped so Billy started making new ones. Call him with any questions again his customer service is second to none.

Jensenman,

Thanks for all of your help first of all! So what I need for the diff is any NA Miata rear? And none came with an LSD at all? Bummer. Mine doesn't chatter but the gear set itself is worn and it will smoke the inside tire on a sharp corner. If I'm just drag launching it sticks well enough to lay down two strips but it's not strong enough for autocrossing right now. Think I can just add a plate and tighten it when I swap gears? I already have fresh RP Gear Oil in it with additive. It helped but there's only so much you can do with a 232xxx mile rear...

I just can't justify coil-overs from anybody. I'm not fast enough and I don't have the adjustment/tuning knowledge. By drop springs I meant Racing Beat's sport springs. They are about a 3/4" drop with a stiffer rate and are pretty affordable. I know my originals are getting worn. I'm thinking RB Springs, Tokico HP's, Mazda rubber bushings, RB 1 1/8" front sway, mod the rear bushings, disconnect rear sway (maybe), and the tri-link (maybe). I'm going to start with just the front sway and see what happens.

Those RE-Speed C/C plates look AWESOME! I'll get those!

I have had the RB Springs on my car. They are a good option. Personally if I were to do it again I would probably put the RB's on the front and these on the rear. I believe I have 175 or 200 on the rear. It rides a little rougher obviously but I can adjust the height very easily and tune how happy the tail is. If you do this don't forget to cut the bump stops.

http://mrcmfg.com/catalog/product_info.php?products_id=367

One thing that bugged me with the RB (and many FB rear springs) is that the drivers side would sit lower than the passengers side. I actually have a set of RB front springs that I may never get around to using.

About the rear spring height difference: a cheap easy fix is to stack up a pair of the rubber end cups on the left side, this levels the car out. The rear coilover (welll, not really a coilover) kit wasn't IT or SP legal until recently. That would have been nice to have. The GC rear springs came over-length with 4 'dead' coils on one end, the idea was you trimmed the 'dead' coils so you could adjust the ride height yet not affect the spring rate.

1.6 NA Miatas were available with a viscous limited slip and IIRC 4:11 ratio R&P but the innards are not FB friendly plus it's sorta weak. The later 1.8 R&P can be used on a FB diff but the splines in the later Miata spider gears are bigger, meaning custom axles. Assuming the stock plates are all within factory tolerances, you can add one 'thick' plate to each end of the clutch pack and this will make it more aggressive. The more 'thick' plates you add, the more aggressive the lockup. Mazdatrix has a listing for all the different innards along with a good interchange page on their Web site: http://mazdatrix.com/g5.htm

Just a note on Jensenmans excellent post, the latest method to reduce your rear bind is to remove/undo the rear sway bar and use poly bushing on the lower control arm but foam bushings on the upper bars.

I am doing the custom coil over set up and four link plus panhard

I remember hearing about the soft upper bushings, IIRC it is a 3 piece that has a hard disk in the middle and then a soft piece on either side of that. I think G Force (same people with the Tri Link) have those bushings.

I would not buy tokico HP struts. I had a set on a nissan sentra and they wernt even really any better than the stock ones, and with lowering springs it was really bouncy (the only reason i used them is i got all 4 struts and springs for $100). I would suggest taking the money you were going to spend on struts and springs and just using it to get some better struts and get springs later.

For shocks find some Koni reds (ebay), they are old stock, only one way adjustable (out of the car) and only fronts can be located, but they are far superior to Tokicos

I forgot one thing about the later 1.8 Miata NA rears: they had two different ratios in the 1.8 cars. There were both 4:10 and 4:30 gearsets available. Also Kia Sportage 4x4's used the same type gearsets in the front and those were available in 4:625 and 4:778 ratios. IMHO I wouldn't bother with the 4:10's, there just wouldn't be enough extra mechanical advantage for the amount of aggravation involved. For instance, the Jensenator is getting 4:86-1's.

Count the number of ring gear teeth then divide by the number of pinion teeth to get your ratio.

Jensenman wrote: The 1.8 Miata shares the same spline diameter as the 2nd gen RX7 meaning the spider gears are too big for the 1st gen RX7 axle. AFAIK there were no 1st gen axles that shared the larger spline.

ALL 7" Mazda rearends (RX-7 non turbo/Miata/trucks) made 1984-up were the same spline, except for the S2000 which had the even bigger spline size used on the 7.5" truck diffs.

This means that diffs will not interchange between '79-83 and '84-85 RX-7s BUT they will interchange between '84-85 RX-7 and 1.8 Miatas and non turbo FCs and trucks.

This is all info available on the Solomiata website.

I would go to the G-Force Engineering guy and buy his book on the 1st-gen. And then buy stuff from him :)

Yep, you are right. The 84-85 used the big spline and the pre-84 used the small spline. That means the 1.8 Miata Torsen can be used in the 84-85 rear axle. But, the 1.6 Miata diff and parts therof won't work.

So what I want is an 84-85 rear axle and a 1.8 Miata Torsen...

Yep, there ya go. Make sure you check the axle splines. I think the GSL calipers will bolt to a GSL-SE housing, but I am not sure. The GSL has the 4x110 mm bolt circle and uses bolts, the GSL-SE the 4x114.3 bolt circle with studs.

Hey, an easy changeover to studs for a GSL car: EMPI makes screw in wheel studs for aircooled VWs that works perfectly. Put 'em in with Loctite Red.

I'm sticking with the 4x110, thank you. I like my wheels and there's nothing wrong with wheel bolts. I'll just shop for an 84-85 GSL rear axle as they tend to go for pennies compared to GSL-SE stuff. Same rear discs that I have now. Actually come to think of it, I should be able to find a peg-leg 84-85 S or GS axle for stupid cheap (since I'm swapping in the gearset/LSD anyways) and bolt my discs on it. I even already converted to an 84/85 flange and driveline when I busted mine.