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83 RX7 Stage Rally Car Suspension

Posted by zack13277 
Pete
Pete Remner
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Re: 83 RX7 Stage Rally Car Suspension
March 18, 2015 06:01AM
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mekilljoydammit
Pete, just throwing this out there because you've actually screwed with this, but what do you think about swapping ball joints in the 1st gen control arms to take 2nd gen spindles/struts/etc? I *think* I may have had a cleverish rack and pinion idea that as far as I can tell nobody has done before and should be fast as hell. To wit, the MGB steering rack has the inner pivots the same distance apart as the control arm pivots on the 1st gen 7, the ratio is fast as hell, and if you flip a front steer rack upside-down, it magically becomes a rear steer rack.

I know the 2nd gen subframe swap isn't that bad (I got partway through one) but just got to looking for a better mousetrap, in an "overthinking things" sorta way. Not for rally, just nasty street stuff.

Where you gonna put the input shaft? So you get a right hand drive MGB back and throw it backwards under the engine. The input shaft necessarily has to be more inboard than the inner tie rod pivot at maximum lock. Maximum lock puts the left inner tie rod under the middle of the engine.

Ain't gonna work. There was a company that made a setup that used a Rabbit rack, and to get around that problem they made the left tie rod about 8 inches long and the right tie rod about two feet long. They went out of business before they sold very many kits, I guess they had some problems delivering parts or something. (I have one of their strut braces. People used to joke "Oh, they actually shipped one!" Now nobody jokes because nobody recognizes the name anymore)



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mekilljoydammit
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Re: 83 RX7 Stage Rally Car Suspension
March 18, 2015 07:03AM
Problem with mocking this up on a shell with no engine I guess. I actually have a CP strut brace too, and am aware of what they did; I always thought their issue was just rack choice.
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Re: 83 RX7 Stage Rally Car Suspension
March 18, 2015 09:36AM
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zack13277
I do have a83 gsl with limited slip, but I think I'll see how that works out for now and then if I hate it I'll look into other stuff.

Thanks

-Zack

Zack the beauty of making your own mounts and these whacked LOOOOOOOOOOOOOOOOOONG upper and lower links is: you have the axle you have and cool it'll do for now---you put the tabs for the links HERE (or where ever) then you go play with that axle...when the weakness of the Mazdog tubes and shafts finally is an issue---then zip zip whip out a few bolts, trolly jack out the RX& axle and squeak squeak roll in the Toiletta 8" thing---with tab welded HERE so you just lift it up and slide in 5-6 bolts, hook up brakes and BRAAAAAAMP!bap bap bap off you go with a basically unbreakable axle..



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zack13277
Zack Rondeau
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Re: 83 RX7 Stage Rally Car Suspension
March 18, 2015 02:38PM
Hay gravity fed, do you have any pictures or write up or advice of the rear end swap?



-Zack
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Gravity Fed
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Re: 83 RX7 Stage Rally Car Suspension
March 20, 2015 08:30PM
i suppose i can answer that here. Ill get better pictures later.

Essentially the stock mazda axle pigeon holes you into the 4x110. that is doubly true the 83 and earlier axle as there is no alternatives, unlike the later ones. Also the rear geometry of the Mazda axle leaves you wanting.

The toyota axle requires some machining, however, I was able to get this done locally with an axle shop. Gave then brake rotor i wanted to match and voila! 100 bucks later, done.

Aside from that its just some cutting and welding. It is more money than using the oem stuff? Of course. Is it far far superior. of course!

if you want to cheap out and compromise some, an 84-85 GSLSE axle would compliment the FC front axle from the 4 lug FC models. Then you can retain the bottom link, remove the top and add your own links of comparable length. Then figure out the watts link deal. That, while not that great, it hell of a lot better than what you have otherwise.

the best is the toyota 8" however.



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zack13277
Zack Rondeau
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Re: 83 RX7 Stage Rally Car Suspension
March 20, 2015 08:36PM
Ok, this I'd starting to make more sense. Yeah if you had pictures that would be awesome. Thanks a lot guys.

-Zack



-Zack
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Eric Ewert
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Re: 83 RX7 Stage Rally Car Suspension
March 20, 2015 11:27PM
I just 4 linked my volvo and have a fair amount of pics regarding how I did it if your interested. However...

I actually thought about using a ford escort 4 link kit which you can buy... so I did. I did so because I figured if I didn't like the sizing of the links no biggie; it would just give me an excuse to build a short wheelbase rwd car in the future... like an rx7. Also it gave me a great template to use to build my own wide box 4 links in order to accommodate bigger bushings. Well they were a little small for my liking after seeing them mocked up in my car so I build my own.

But honestly for a really light 2200lb or less rx7 they would be just fine. So if you don't want to go through the effort of building your own setup you can buy a complete ready to weld in kit. It will cost around 450-550$ by the time it's in your hands. But it simplifies things a bit in terms of getting this stuff in your car. Not everyone is in to building every last thing and that is ok. Also the kits are a fairly nice quality and the company I bought them from was great to deal with and happy to send it overseas (motorsportstools.co.uk) Not trying to plug or promote; they were just a good bunch to me.

The shock towers were the first thing I did and made a noticeable difference. Albert kun's car is setup with only towers and works well from what I heard. After poking around at way too much f cup stuff I've noticed that a good amount of very competitive cars actually skip on the custom 4 link. But they all have extended towers. Based on this it is in my opinion the more important of the two parts.

That being said I am talking stock volvo 240 and toyota starlet rear suspension links. Maybe the rx7 links really suck and you would want to consider the 4 link further. I don't know enough to make a quality comment.

John supplied the rear coilovers for tower/turreted setup and I am very happy with them. Took a bit to get them (like anything custom made) but he supplied dimensions while they were being done up so I could build the towers before getting the shocks. Happy to report that all of that was bang on.

Among many other things he supplied me he supplied the axle link tabs to weld to the axle so you don't have to build your own. Makes it simple. After the measurements its a fairly quick final fitting of them (sanding) to the axle then weld them in place. Saves a good amount of time and they are cheap.

Poke though this. Good amount of photos

http://www.doublegmotorsport.com/rsprep/prepindex.html

And if you have any doubt as to how well this stuff can work...


I am 95% sure this car is setup with just towers and beefed up stock links. Its getting chucked around a fair bit but keep in mind the speed he's going. With less (stock) travel there is no doubt he and the the car would not be coping even remotely as well.
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john vanlandingham
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Re: 83 RX7 Stage Rally Car Suspension
March 21, 2015 11:13AM
Eric in F-cup I think they MUST RETAIN + or - a lttle the stock link pick up position UNLESS the car was Homologated at some point wif something different like Escort was in old Group 4...

And 1st Gen RX7 is the first car that I even paid any attention to this whole link thing because I got to see Rod Millen dance that car so well---and then when I looked at a stocker I saw an upper link maybe 5-6" long..
Model that out and see...



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Edited 1 time(s). Last edit at 03/21/2015 11:19AM by john vanlandingham.
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mekilljoydammit
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Re: 83 RX7 Stage Rally Car Suspension
March 21, 2015 01:06PM
Hey Zack, when you come down for the subframe tomorrow, I'll show you some of the roadrace solutions to the same rear end issues they're talking about (I wouldn't copy it for rally, I'd do 4-links, but it's easy to point out what's what with physical bits) and crap like that. If you can weld and fab at all, getting the rear axle housing swapped from Mazda to Toyota really shouldn't be that hard, aside from nuts and bolts crap like finding a place to change the bolt pattern if you don't have a machine shop.

I have precisely fuckall actual experience running 1st gens (or anything else) on gravel, but a bit of experience with running them in roadrace stuff. I know that's different, but some of the weaknesses and crap to fix are going to be common to both.
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zack13277
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Re: 83 RX7 Stage Rally Car Suspension
March 21, 2015 04:42PM
Ok cool, I really just want a better picture of the rear and how I should make it.



-Zack
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zack13277
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Re: 83 RX7 Stage Rally Car Suspension
March 22, 2015 09:56PM
Hay John Vanlandingham, are the rear shocks for the rx7 coilovers so that I wouldn't use rear springs, or are they more like actual shocks, also how long from when I order the front and rear coilovers does it take to get them? I talked with mekilljoy today and the rear end and 4 link mod doesn't seem to hard, so I might swap in a Toyota rear axle too. Thanks again Dan.

-Zack



-Zack



Edited 1 time(s). Last edit at 03/22/2015 10:23PM by zack13277.
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Re: 83 RX7 Stage Rally Car Suspension
March 23, 2015 04:41AM
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I'm pretty sure I can make a roll cage, but I don't know about cutting and welding in a totally different rear end.
This sentence scares the fucking hell out of me. If you question your abilities to just cut and weld some brackets on a rear axle then you have no business trying to build a roll cage.
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zack13277
Zack Rondeau
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Re: 83 RX7 Stage Rally Car Suspension
March 23, 2015 05:11AM
With a roll cage I have seen what other people have done, but before yesterday I didn't have any idea of how to correctly modify the rear 4 link.



-Zack
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john vanlandingham
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Re: 83 RX7 Stage Rally Car Suspension
March 23, 2015 09:09AM
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zack13277
With a roll cage I have seen what other people have done, but before yesterday I didn't have any idea of how to correctly modify the rear 4 link.

Dave read it as "I can do things my life depends on potentially, but I can't zap on some brackets"..

Which sounds scary...



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mekilljoydammit
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Re: 83 RX7 Stage Rally Car Suspension
March 23, 2015 09:36AM
Devils advocate: there's lots of examples of well setup cages out there whereas reading about the 4 link setup without seeing stuff sounds like more work than it probably is, especially before seeing the relatively minimal mods needed.

Non-devils-advocate: I don't know what fab ability / experience you have handy. If you have any doubts about your ability to do a safe, logbookable cage, find a builder to do it. You guys were asking intelligent questions when you were out but don't chance the cage.
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