Arizona ZCar Rear Suspension - Design, Function, Flaw(?)

[NewZed]

What also adds to the problem is how the short nose uses the tubes for a front mount. The torque applied to the tubes from the diff movement will rotate the tubes. We pinned the tube with set screws and put flat 1/8" stock between the diff mount flanges to keep then from lifting. No more problems.

 

Joe

So the short nose diff mount system (actually two mounts), the front one, is an AZC product?  I've looked all over the AZC site and didn't find it.  I started another thread about it, since I've never seen it and there doesn't seem to be a simple mounting system out there.  Seems like the concept could be applied to the stock control arms, maybe with a bushing that allows rotation and a bar connecting the two, like you describe.

[RebekahsZ]

The most durable design is the factory design, all the adjustable designed are less stable, by the nature of their adjustability, so of course they should be inspected on some schedule. The ONLY reason I know of for all the billet pieces, whether AZC or any other, is bling. And it does look good, and is well made. The suspension doesn't move enough (with stiff springs) for most of this stuff (that we bench race about) to matter as much as we think (my opinion). Mock up the camber, toe and caster you want and drive it! Somebody does need to make rear LCAs that are shorter than stock (the rear LCAs from the defunct MM were the only ones I know of that are shorter than stock), then there will be no reason to buy the AZC rear LCAs. But until someone does, AZC is the only off-the-shelf LCA that can be used to narrow the track in back as a means to fit larger rear tires or reduce the negative camber induced by dropping the tail. I don't like the pendulum arrangement of the inner LCA mounts either. Once the car is mocked up and aligned, could they just be tig welded to the aluminum saddles that AZC provides?

[JMortensen]

Looks to me like you could use a shorter turnbuckle on the Silvermine setup too, if shorter was the goal. 

[Mike Mileski]

I used the AZ Z Car heim pivot idea when I designed my rear arms but did as someone suggested above and located them on the centerline of the original inner pivot points. As I've mentioned to Jon in the past, I am designing a new set with the floating arm towards the front of the car, vs. the rear, although I've had zero issues with the design as it currently exists.

 

Mike Mileski

Tucson, AZ

[clarkspeed]

I used a more simple and elegant design that I blatantly lifted from this website.  I slightly modified Tube80's design using a stock control arm from page 4 of this old rear control arm design post.  Used a 3/4x5/8 rod end for the forward one.  I recently sourced some oil impregnated bronze bearings for the inner pivots instead of polyurethane which falls apart if you get oil on it .  Works well and my rear RC is where I wanted it anyway.  Being able to adjust rear toe transformed my car, it went from a darty unstable handful at 120+mph to rock steady at 140 on the banks of Daytona with one hand out of the window waving to the crowd.

 

 

http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/page-4?hl=%20rear%20%20control

[ls240z]

So what everyone is saying is that the main 2 (AZC and T3) choices are not optimally designed? Are there any off-the-shelf options that are better than stock and those 2 aftermarket choices?

 

Keith, you say the stock LCA's are good, so are the AZC ones a suitable upgrade for a weekend track day cruiser?

Edited August 23, 2014 by ls240z

[1vicissitude]

The t3 arms do not relocate the inner pivots like AZC.

 

The inner are not Heim joints, just bushings through the stock location.

 

Do not think they apply to this discussion.

 

They do not offer the adjustability of the others though. So other than being stronger and having adjustable toe, I don't think they offer any optimization over stock.

Edited August 23, 2014 by 1vicissitude

[NewZed]

AZC and Silvermine are using the same basic design, that could allow the control arm structure to buckle and shorten under certain conditions of assembly and usage.  T3 is using a design similar the tube80z design, but without the independent toe adjustment, basically more adjustable than stock, bit not as adjustable as tube80z's.

 

Edit - actually, I think that the T3 design is essentially the same as tube80z's.  Maybe even more rigid.  Anyway, at least the pictures are all in one spot.

 

From previous posts in this thread, plus T3's site:

 

http://www.arizonazcar.com/lowarms.html

 

http://www.silverminemotors.com/datsun/datsun-260z/suspension/rear-lower-control-arm-cnc-for-240z-260z-280z

 

https://technotoytuning.com/nissan/280z/rear-lower-control-arms-datsun-240z-260z-280z

 

Post #76 here - http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/page-4?hl=%20rear%20%20control

 

 

Just to summarize, for clarity.

Edited August 24, 2014 by NewZed

[ls240z]

Thanks for the clarification, I had to spend quite a bit of time looking at each photo and design to realize what everyone was speculating on in this thread. I am very new to suspension tuning, so thanks again.

[G-E]

Ok just because this point has been brought up more than once (shortened control arms), and in lieu of the camber adjustable coilover adapters I'm producing [see here: http://forums.hybridz.org/topic/119399-240z-camber-adj-rear-coilover-adapters-bolt-on/ ]

 

Assuming one were to use my kit, which would be the best setup to use then?  Mike's or tube80z's seems to me the best style, since any toe adjustment with rodends will cause binding if the distance isn't accommodated with shims... What do you guys think?

 

If TTT's are really just rodend converted factory style arms, no huge bonus points there right?

[NewZed]

Added an edit to clarify my earlier clarification/summary (#28).  Still seems like there's another design iteration that could give people everything they want.  Interesting subject.

[logr]

All of these designs incorporate a rod end as the outer pivot but when braking or accelerating aren't the rod ends working on a side force instead of the way they were made to work. In case that isn't clear, the bolt through all of the mentioned designs is horizontal(spindle pin) so the acceleration and braking forces act against the side of the rod end. If the bolt was vertical wouldn't the rod end work the way it was designed to?

 

By changing to an A-arm design aren't most if not all braking and acceleration forces acting on the one fixed rod end, instead of 2?

 

What is the reason for changing the floating arm to the front from the rear?

 

I believe the TTT designs main function is to give adjust ability which it does.

 

The AZC/Silvermine design would be illegal for SSM as it changes the pivot point however it would be legal for XP.

 

edit: I see you guys have discussed the rod ends working direction in an 08 thread with no firm answer.

 

http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/page-8?hl=%20rear%20%20control

Edited August 24, 2014 by logr

[rsicard]

I agree with NewZed. Allowing the control arm structure to buckle and shorten under certain conditions of assembly and usage is not a good design.  As for the other design, I contend that it is better to sacrifice a little articulation than a lot of strength.  If I am to change the rear LCA's, it will be the TTT/MM type design.

[G-E]

So without being design specific, what features are most important, assuming it's strong enough, and all bearings are oriented in their strong axis?

 

I played around with several designs for a rollcenter adjuster, but aside from making it compatible with stock arms, it doesn't really allow you to fix the major faults of these other arm designs. So if I do progress with it, it will likely be a design around a new arm as well....

[logr]

Helping the roll center  would be nice.

[logr]

I have an idea. What about using an adjustable length ball joint on the spindle? I think there is a way to make the arm adjustable in and out as well as adjusting toe separately. Mounting a tapered hole for the bj on the spindle is easy enough and the bj is made for the application. I drew up a quick diagram but I can't upload a pdf to photobucket and the jpeg doens't show all of the pic but here is what I have. What do you guys think?

 

The upper left is the ball joint and there would be rod ends at the ends of the other arrows. The bj would hold the main loads and the rod ends would all be working the proper direction. Roll center could be changed on the bj. Toe and in and out of the spindle is adjustable on the car also.

 

Edited August 24, 2014 by logr

[G-E]

I agree, there should be balljoints at the hub and sphericals involved on the inner pivot...

 

Just curious, why did you choose the toe adjustment on the leading edge?

[JMortensen]

Monoballs can take a pretty decent axial load with no problems, witness just about every camber plate you can buy and all the aftermarket arms running 5/8 rod ends with no trouble. I did bump up the size to 3/4 rod ends on my arms just for a little insurance, but apparently quite a few people are running around with A-arm toe link setups with 5/8" rod ends.

 

The benefit to running an A-arm with toe link is that it doesn't side load the strut. Read in RCVD and it says that the problem with the stock H arm design is that it does. If the joints are strong enough, then the fact that you're putting more load into a single joint simply doesn't matter. The reason for the toe link in front is that the rear (fixed) pivot will be directly under the strut, so there won't be side loading on the strut from being loaded by the front pivot which is not directly under the strut. 

 

Agree with G-E, if you're going to change it, CHANGE IT. Do a different axle and hub, integrate better brakes, might as well do SLA suspension while you're at it. Why start modding the strut to take a ball joint? If you're going to that trouble, throw the whole strut in the garbage and start with something better.

[G-E]

Agree with G-E, if you're going to change it, CHANGE IT. Do a different axle and hub, integrate better brakes, might as well do SLA suspension while you're at it. Why start modding the strut to take a ball joint? If you're going to that trouble, throw the whole strut in the garbage and start with something better.

 

I like to design parts in a way that everything is cumulative, like a clean upgrade path one by one, or all at once, sometimes that means a little compromise...

 

That said, I'm looking at finally cracking this nut that people have been hammering on for decades, and I think to do that, convention has to go out the window, it has to be a fresh approach.

[logr]

I'm not looking to reinvent the wheel. I am building for a class and to keep the car drivable on the street, which is pretty much mutually exclusive if I am real serious. I'm not.

 

The ball joint could be on either end of the spindle so I think I will try to make something along these lines. I can't change the inner pivot point for SSM and I have cv's as well as 12.25" rotors, Superlights, and Bilsteins that I like. My diff is also what I need for ABS, so...

 

My rear toe is excessive (.25" not sure why) and since I need to fix that, I'm just hoping to make a better mousetrap along the way.

 

 

RCVD?

Edited August 25, 2014 by logr