mustanghammer

iTrader: (3)

Here are the spring mounts I made recently. They replace the "cones" that locate the 5" stock springs. These will weld into the car in about the same location.

Hyper4mance2k

iTrader: (40)

I hate how terribly the 5" springs locate on the stock mounts on the rear end.

mustanghammer

iTrader: (3)

Yeah, that was one of the reasons I went to coil over springs. You can help the stock springs stay in place by welding a little piece of strap next to spot where the pig tail on the spring rests. I'll see if I can get a picture in a few days.

peejay

That's because stock aren't 5" springs, they're 4". Or 4 1/2", or some weird goofball size.

A lot of why I like to eliminate the upper links is that it allows different springs to be used without having to be exactly the right diameter.

Hyper4mance2k

iTrader: (40)

I'm running respeeds springs and adjusters. They're fine on the chassis, but on the axle they fit terribly. Close enough to work, but enough to be loud and annoying moving around when pulling in and out of my driveway. Click, bong, click, bong!

Kentetsu

What rear shocks are you using? The reason I ask is, when I tried to go really low with the Illuminas, I reached a point where the shock was bottomed out. This left slack in the springs, and they knocked around quite a bit. That's why I switched to the shorter Bilsteins that I run now...

peejay

That's weird, because the stock shocks basically won't bottom out. First the axle will hit the bumpstops, remove those and then it will hit the Watts, remove that and then the axle will finally come into contact with the body rails, but the shocks will still have an inch or two of travel to go.

mustanghammer

iTrader: (3)

Whether or not the shocks bottom out depends on the shocks. My PRO shocks came very close to running out of travel long before axle was close to the frame. I know for a fact that you can bottom out illuminas on the front I would imagine you can on the rear too. When you do that it breaks the adjusters.

Rogue_Wulff

I'm trying to catch up on all this stuff mentioned here. Kinda forgot this forum even existed after I built the new PC back in late '08, so I've got a lot reading to do yet....

Not 100% positive, but I do believe I've talked briefly with Scott P., and wanted to ask a lot more questions at the time.....

I will ask one question now though. Does the S3 rear suspension work better than the S1/S2? I know Mazda relocated the front lower link mounts, but did it really help? I'm getting ready to start focusing on my carb converted GSL-SE for CSP or SSM.

mustanghammer

iTrader: (3)

The lowered mounting point would be a negative in clases that do not allow the relocation of the mount on the rear axle. Such as Improved Touring in club racing or CSP in autocrossing. I do think there are loop-holes in the rules that allow a person to add "traction bars" that skate around some of the rules, however. On the previous page in this thread you can see how I addresed this on the rear end housing I am building for my car.

In short it is a bad deal because as you lower an RX7 the lower control arm goes out of geometry. Because the 84-85 have reposistioned mounts this problem is worse. Ideally you want the lower control arm mount on the rear axle to be slightly lower than the mount on chassis when the car is at a specific ride height.

Now, that said, when you are dealing with a lower HP engine - like in an IT RX7 - this doesn't seem to cause allot of issues as long as you have a tri-link installed. Because there are no bind issues once a tri-link is installed getting an IT car off of a corner is not an issue.

Rogue_Wulff

That makes sense.
Thus far, my 83 (pictured over there <---) has everything stock under the rear, aside from GC 200#/in springs with the natural ~1" or so lowering designed into them, and the front is GC coilover with 350#/in springs. Heck, I've done nothing else to the suspension, and it still seems to work decent.
KYB GR-2's and factory swaybars, combined with the GC springs, and a front strut bar, keep it hooked up ok *most* of the time. Sometimes the rear will suddenly let go, without any warning. This is what I want to prevent with my SE chassis.

If I read the rulebook right, the tri-link and panhard bar are both CSP legal, but the lower links are off-limits. Sounds like the 84/85 chassis shouldn't be quite as low as the 79-83 before the rear links can become an issue, especially when the HP is bumped up a bit.
I want to build this 84 to do solo, track days, and still be road-freindly, so sperical bearings are likely out.

MountainScreamer

What do you guys think of this setup for an equal length 4link? It would require moving the upper arms inwards, but would this have any negative effect?

http://i251.photobucket.com/albums/g...6/PA010647.jpg

Not the best shot but you get the idea of where the upper arms are
http://i251.photobucket.com/albums/g...6/CIMG7136.jpg


Pictures from a nice corolla build: http://forums.club4ag.com/zerothread?id=29053&page=1

j9fd3s

iTrader: (3)

my friends hatchi is like that. they just added those "boxes" and used 4 lower links. i notice the 79 factory prepped daytona SA actually has the same thing done to it.

http://speedhunters.com/archive/2009...sa22c-rx7.aspx

and in case anyone is wondering the car actually has TWO different places they could relocate the arms, currently as of summer 2010, its like the hatchi, in the middle, there is another spot more outboard that isn't being used

MountainScreamer

So what is the advantage of putting the arms more outboard?
And with this could you do use spherical bearings in the top links as well?

j9fd3s

iTrader: (3)

i'm not sure why they have two spots for upper arms, especially since it looks like the cars racing career was done after practice at daytona.

it might be possible they used the car for development before that.

the second question is a yes, you can as the links are all the same length

gawdodirt

Has anyone considered using a "Satchell link?" There are reasons on the plus side. No one has mentioned it so far, or have they?

GD

MountainScreamer

So with the satchell link would you locate the bars from the axle outboard to some point on the chassis in the middle? Sorry if thats not clear. So for instance parallel bars on top and then two bars coming from the outside of the axle to a center point on the chassis, yeah?

What are the advantages?

Hyper4mance2k

iTrader: (40)

Satchel link has a big potential for bind, 3 links do not. Plus I can't imagine there being enough room for a proper setup.

gawdodirt

Actuallly, it would bind less as the links now work around the center of the chassis when it rolls. It lowers the roll center and eliminates the panhard rod. Remember that the axle rolls when in a turn and unless you have spherical bearings everywhere, any bushing will bind. You are putting each link in a minor torsional and urethane or rubber will resist.

As far as implementing this in a car, some of the drastic pics I've seen here of the three link appear to be major surgery too. Most of these ideas and modifications are in a different realm than just going to urethane bushings. I would leave the upper link locations and do this on only the lower links and THAT will give way more options to do it correctly and more efficiently.

Many race teams used this system with success, as well as 4 - links. Terry Satchell has a huge resume for chassis and supension innovations. This should be examined as viable.

GD

gawdodirt

These pics should add some clarity. I can't see how it is more complicated than installing a three link with a panhard rod. Make that rod adjustable , and add complexity. I'm basically a fabricator so either is no biggie, but this would intrude into the passenger compartment less.

Back to the binding issue, these pics let you see how long the lower links can be, so if each wheel moved only a few inches, as is normal, bind wouldn't be an issue.


Merry Christmas!
GD

peejay

It's important to differentiate between bushing bind and geometrical bind.

Unless everything is perfect, a Satchell will suffer from geometrical bind. An easy way to see geometrical bind is to disconnect one end of one link and articulate the axle around. On the 1st-gen's stock rear setup, if you do this, you'll see the link's preferred distance "shrink" and "grow" an inch. THAT is the kind of bind that is a problem. It can only be solved by using soft, oddly-shaped bushings (Fox-body Mustangs did this) or throwing the whole mess away and going with something better engineered.

gawdodirt

Why wouldn't every mount point be perfect? Within the range of suspension movement, this style of suspension will not have any geometric issues. I have laid this out in SusProg3D and it's about as simple as it gets. When I was in GM in Chassis development , the only time soft bushings were used was in Cadillacs and Buicks. Odd bushings , or even bushings with voids are to handle NVH issues and not usually "geometric bind." In these days of CAD and FEA, it just doesn't happen to mass produced products.

GD

peejay

But we're not discussing that, we're discussing one-off stuff.

FWIW - The stock 1st-gen rearend is an upside-down Satchell. You can, indeed, drive around with no Watts and not really notice, as the angling of the upper pivots is plenty to hold the axle under the car under normal street conditions. The bushing compliance would prevent it from being useful beyond those limits, and spherical joints would just highlight the horrible geometrical issues, if the mounts didn't rip out of the body first.

Roundabout way to get back to the beginning... the Watts is there to augment the roll center built in to the stock 4-link. Changing the ride height or link locations destroys everything. Of course, what did Mazda do? Started making the car heavier and heavier (changing the ride height) and then they lowered the lower pivot's body mounts to increase roll understeer, most likely in an attempt to help curb the snap-oversteer that the porky newer cars were developing. A '79-80 at stock ride height is an absolute joy to drive.

I would imagine that having the links equal in length (side-view) would go very far to eliminate any bind, as would being parallel. Limiting suspension travel would be nice, too. Even with 200lb springs, I was witnessing regular ~3-4" suspension motion in the rearend just driving down the highway.

mustanghammer

iTrader: (3)

My concerrn with this suspension would be exhaust clearance and the need to make room for the two upper links. Which was my concern with the Lotus Link suspension that I considered.

I have to think about this design some more but it may not be any worse than the Lotus Link and that suspension doesn't have bind issues. Interesting to think about.....Thank you for posting this.

As a fox Mustang owner I can tell your the Ford messed around with bushings in the rear of these car for more than just NVH issues. They messed around with them from 79-2004 changing durometer ratings and shape to get that crappy suspension design to work. The aftermarket also struggles with this issue on aftermarket parts for these cars.

Speaking of bind or a lack of it - here is my 3 Link Equped Mustang back in 2001 at McConnel AFB. Note that the rear end is contacting the ground and putting the power down despite the body roll. That corner was fun!

mustanghammer

iTrader: (3)

As I mentioned in an earlier post, I own a Fox Mustang (85 GT - 4 Eye) street car. While researching the aftermarket for this car I came across and interesting idea for poly bushings. 3 Piece Poly bushings that consists of a hard center bushing surrounded by two softer bushings (one one each side). The theory is that the softer bushings allow the control arm to twist as the suspension moves while the hard center bushing resists compression and helps the car maintain traction.

The hard center bushing is actual round on this design

http://www.hotpart.com/shop/index.ph...ct_images&p=43