Rear Suspension Movement

[xnamerxx]

I was curious about something, so I took a video of the rear suspension during some "normal" driving just to see whats happening back there. Now the video proved what I was expecting but I'll get to that later.
The video proves that rear suspension bushings could be beneficial if you plan on racing, autox, road course or otherwise.

I know the zip ties look janky but they really don't do anything during normal driving.

http://www.youtube.com/watch?v=504PlSYzTVg&feature=youtu.be

[CTScott]

Cool video. There is definitely some wiggle due to the large, soft rubber bushings. Did you notice how much the spring perches flex as well?

[Yarflana]

Look exactly like I would expect. Thanks for making the video.

[CoryM]

It's not uncommon for torsion-beam bushings to rotate on different axes. Meaning if you put solid or stiff bushings in, the beam will bind. No idea if the Yaris is like this or not.
I would like to see that view, but heavy loaded in corner. I am curious where the torsion beam flexes and creates (I assume) toe out.

Neat vid, thanks for uploading.

[xnamerxx]

The video was taken in a heavily loaded right hand corner, the trailing links do move at slightly inverted paths so stiffer bushings might create bind.

You can stiffen the torsion beam AKA B-Spec Mazda 2 rear ARB, it will create some bind during compression/bump, but will also toe it out and possibly create good oversteer.

[CoryM]

The video was taken in a heavily loaded right hand corner

Yeah I figured that out after viewing it a second time ;)

Also figured the bushings and the angle of the bolts are what control the toe-out already built into the yaris. If you run a stiffer bushing you will see some bind, but maybe the toe-out will be more linear. In my stock yaris it feels like no toe, no toe, LOTS OF TOE! when doing steady state corners. I think the sudden toe change is also what makes the yaris sensitive to fast changes of load (fast slaloms). That being said, the bind might make the car completely uncontrollable in rear.

You might be able to just rotate the OE bushings to get the results you want. They are directional I would have to look at where the bushings are stiff and where they are open. I think someone should try stiff bushings if it hasn't been done yet.....

[xnamerxx]

My end goal is not to run stiffer bushings but I'm going to keep the cards close to my chest for right now.

[Viperoni]

With the angle that the Yaris's bushings are placed, I would NOT run anything that would cause bind, like a poly or delrin bushing.

The only replacement I see working properly is a spherical bearing in place of the rubber bushing.

Great vid OP!

[CrankyOldMan]

The only replacement I see working properly is a spherical bearing in place of the rubber bushing.

I'm curious about how you would propose to go about this. Calculating the loads to select an appropriate bearing would be beyond my skills as a Junior in engineering school, and the cost of said bearing that could resist road grit (and possibly salt) would be astronomical compared to a delrin/poly bushing. Not knocking/hating, just curious.

[Viperoni]

I'm curious about how you would propose to go about this. Calculating the loads to select an appropriate bearing would be beyond my skills as a Junior in engineering school, and the cost of said bearing that could resist road grit (and possibly salt) would be astronomical compared to a delrin/poly bushing. Not knocking/hating, just curious.

I've made some rod-end suspension links that have held up quite well in the past... I make sure I'm at least a few multiples of the maximum g-load that the car would ever really be able to produce (so in a Yaris/Echo, let's say 1.5g) multiplied by the car's weight.
So for a Yaris, figure 2400lbs x 1.5 = 3600lbs, and I'd shoot for at least 10k, ESPECIALLY in the rear axle situation where you'd only have the two bushings supporting all of the load.

Here's an example of some ball joint swivel bearings on McMasterCarr:
http://www.mcmaster.com/#rod-end-bearings/=lkzyc8


Even a small bearing with a 1/2" ID and 1" OD has a 19,875lb rating and costs $7.78.
I'd go bigger than this personally: there's a 1" ID and 1.75" OD bearing with a 82k lb rating that's $20.


On top of that, you'd want to get rod end boots or shields to keep the grit out... there's a few manufacturers for these.

[xnamerxx]

Rod Ends don't like side loads which this axle has quite a bit of, so it doesn't really solve any problems. A rod end would work if you have something that can control lateral movement but you don't need a rod end to do that in the first place.

As for rod ends that can survive salt and such, look at what the dirt track racers run, its usually a good idea as to what works.

[Viperoni]

True - something like this joint would be ideal: http://www.rustysoffroad.com/builder-parts/threaded-forged-ends-inserts/rustys-builder-flex-joint.html

The funny part is that particular joint isn't too far off from being the right size either!

[Jason@SportsCar]

Video from my car: http://www.youtube.com/watch?v=Lf67POsSSi4&feature=youtu.be

This is from back in 2010. First clip is with nearly stock suspension (and car), Tein springs with stock shocks, bushings and no rear bar.

Second part is with AST shocks (with droop limiters) and 600lb Eibachs in the rear. Still no rear bar and stock bushings. Not much movement with this setup.

[Viperoni]

Can't see too much movement because of the low resolution vid Jason.... can't really tell how much movement there is or isn't.

[xnamerxx]

Thank Jason, your video has shown me everything I needed to see.

[NJ Drive]

Thanks to both of you for showing those vids. I really would like to run without the sway bar because I'm running 225s/205s F/R anyway. I just don't see the significance in running one using higher-than-stock spring rates on a torsion beam especially with a staggered tire setup.

[xnamerxx]

It depends on what's important to you. After some very long conversations with my chassis engineer friend who's helping me setup the car the consensus was to keep the swaybar and the 20lb weight penalty that goes with it.

As the swaybar is designed stock it does more than just stiffen the torsion beam it also helps reduce flex between the links.

The main reason it was decided to keep the swaybar was that I could accomplish better bump compliance while still getting roll stiffness I require. He was also pretty sure that I might be about at the limit of roll stiffness I need for the Dunlops, but not at the limit for the Toyos.

[Viperoni]

I find with my current soft rear springs, I unload the front inner tire coming out of a corner. Doesn't matter what kind of tires either (R888's, RS3's, R1R's, even snows lol)

[racerb]

Is there anyone making a replacement bushing for the trailing beam on these cars? I ran a Nissan several years ago with a simular rear set-up and the Nismo replacement bushings for that car made a world of difference.

[NJ Drive]

Is there anyone making a replacement bushing for the trailing beam on these cars? I ran a Nissan several years ago with a simular rear set-up and the Nismo replacement bushings for that car made a world of difference.

I have the Delrin sitting here just for that reason, but I'm uncertain if it will provide more gains over headaches in terms of bind. Perhaps something of a softer durometer to merely fill in the voids is the approach I may take.

[xnamerxx]

From what I've seen the suspension moves in a sideways arc so you'd need a ball and cup to accommodate the movement. Look at the mustang rear control arm bushings to understand what I mean. Going to a solid 1 piece would be a really bad idea.

[CTScott]

Is there anyone making a replacement bushing for the trailing beam on these cars? I ran a Nissan several years ago with a simular rear set-up and the Nismo replacement bushings for that car made a world of difference.

There is a TRD set:

48726-NP900 Rear suspension arm seat inner
48726-NP910 Rear suspension arm seat outer

Each side requires an inner and an outer. They are one of the standard upgrades for the Netz Cup Vitz race cars.

http://www.trdparts.jp/english/parts_bush-vitz90.html

49934

49935

[CTScott]

Actually a third part is needed: 48752-NP900 (one for each side {part 4 below}).

49936

[racerb]

There is a TRD set:

48726-NP900 Rear suspension arm seat inner
48726-NP910 Rear suspension arm seat outer

Each side requires an inner and an outer. They are one of the standard upgrades for the Netz Cup Vitz race cars.

http://www.trdparts.jp/english/parts_bush-vitz90.html

49934

49935

Those would probebly work best since in all likelyhood they are only about an 80 durometer bushing material. A urethane based mount would have enough give to not create so much bind. Or am I seeing them wrong and they are a delrin type material?

[NJ Drive]

From what I've seen the suspension moves in a sideways arc so you'd need a ball and cup to accommodate the movement. Look at the mustang rear control arm bushings to understand what I mean. Going to a solid 1 piece would be a really bad idea.

Exactly my thoughts as well.

[NJ Drive]

There is a TRD set:

48726-NP900 Rear suspension arm seat inner
48726-NP910 Rear suspension arm seat outer

Each side requires an inner and an outer. They are one of the standard upgrades for the Netz Cup Vitz race cars.

http://www.trdparts.jp/english/parts_bush-vitz90.html

49934

49935

You are my hero Scott. LOL, that's all I want. Now who can import these the fastest? :clap:

Actually a third part is needed: 48654-NP900 (one for each side {part 4 below}).




Looking over the part#s though, part #4 looks to be a front control arm bushing.

[CTScott]

Those would probebly work best since in all likelyhood they are only about an 80 durometer bushing material. A urethane based mount would have enough give to not create so much bind. Or am I seeing them wrong and they are a delrin type material?

Toyota lists them as "Resin", but I would suspect they are either Nylon or Delrin.

[Yarflana]

Perhaps I totally missed it, but what is the OP trying to correct, or improve? I completely saw the video and didn't notice any problem, but I am not well versed in suspension so I likely am missing the obvious to you track/racing guys.

[NJ Drive]

Just an FYI, JapanParts estimates $250 shipped to NJ for those white torsion beam bushings. Steep price to pay over an afternoon and some 3M window weld.

[xnamerxx]

Perhaps I totally missed it, but what is the OP trying to correct, or improve? I completely saw the video and didn't notice any problem, but I am not well versed in suspension so I likely am missing the obvious to you track/racing guys.

I was looking for lateral movement and found it.

So your asking why is that bad???

Well lateral movement is bad because you decrease the tractive capacity of the tires when there is deflection. What that means is during turn in when the rear suspension deflects the total amount of traction the tires can hold is reduced, when the suspension settles in mid turn you get more total traction, and then a decrease in traction during corner exit. So during transitional elements, think moose test or NATO test or Slalom, deflection in the rear suspension is really bad as it makes the rear want to walk away and makes the car unstable.

[Viperoni]

Just an FYI, JapanParts estimates $250 shipped to NJ for those white torsion beam bushings. Steep price to pay over an afternoon and some 3M window weld.

Window welding the stock bushing would likely introduce bind... That JapanParts bushing is built such that it won't bind.

[xnamerxx]

Just an FYI, JapanParts estimates $250 shipped to NJ for those white torsion beam bushings. Steep price to pay over an afternoon and some 3M window weld.

Here is a link to some real poly mix just as an FYI.

Poly Mix (http://www.mcmaster.com/#catalog/119/3623/=lmkg1b)

[NJ Drive]

I'm no stranger to Forsch casting urethane. Thank you though. Window weld isn't anywhere remotely close to even a 50A, as it has the consistency of silicone when it's hard. There'd be no risk of binding but in hindsight probably not worth the effort. Guess I just need to plunker down the dough for something TRD already engineered correctly.

[CTScott]

You are my hero Scott. LOL, that's all I want. Now who can import these the fastest? :clap:




Looking over the part#s though, part #4 looks to be a front control arm bushing.

That's right - The correct part number for the rubber piece for the center of the resin pieces is: 48752-NP900 (Rear suspension support stopper)

[DeathBeard]

I installed the trd rear swaybar on my car on saturday and took it off on Sunday, made my car feel weird and didn't like the added oversteer made it feel sketchy on the freeway

[NJ Drive]

That's right - The correct part number for the rubber piece for the center of the resin pieces is: 48752-NP900 (Rear suspension support stopper)

Scott, out of the parts listed, only the two white resin rings are applicable to the torsion beam bushing. 48752-NP900 pertains to a replacement bushing that resides on the shock shaft, just above the dust boot.

[CTScott]

Scott, out of the parts listed, only the two white resin rings are applicable to the torsion beam bushing. 48752-NP900 pertains to a replacement bushing that resides on the shock shaft, just above the dust boot.

OK - I see that now too. I am coming up blank then on the actual rubber piece that goes inside of the two plastic cups. Unless there actually isn't one, and in the installed picture that I posted above, the black piece in the middle of the white is just simply the metal bushing from the middle of the OEM rubber piece.

[CTScott]

Here's a translation from a Japanese blog:

"TRD rear suspension arm sheet Inner / Outer (:48726-NP900 Number) is (:48726-NP910 Part).


I mounted onto the rear arm bush, as sandwiched between inner and outer cover made ​​of this Duracon.
Rear left and right movement is restricted by it, there is no blurring.
It is the cancellation of the rear toe control.


When it comes to the effect, I did not see it not good impression of the effect of the strengthening of the front bush is too strong, he felt a sense of rigidity of the rear is better than before, as if conscious.
Quick minute there is less sense of play out but I like to skate faster.
Once you get used because you know the feeling of good start, but are easy to the control.
To track run is much better - I'm afraid."

[NJ Drive]

OK - I see that now too. I am coming up blank then on the actual rubber piece that goes inside of the two plastic cups. Unless there actually isn't one, and in the installed picture that I posted above, the black piece in the middle of the white is just simply the metal bushing from the middle of the OEM rubber piece.

They're precisely just that- to be mounted on either side of the stock bushing to quell side-to-side(lateral) movements of the torsion beam while leaving articulation of the beam as intended. Someone correct me if I'm wrong but that is how I see it.

You have to love Japanese to English translations too. :biggrin:

[xnamerxx]

I'm not seeing how they would work correctly. The outside of the bushing is solid so how would it articulate in a twist motion, think one wheel bump, and not bind? If it were the other way round I could see this bushing working correctly but you wouldn't get any help with the lateral movement issue.

Toyotas engineers aren't stupid so I have to imagine it works as intended, or its a bandaid issue to something they couldn't fix correctly given the rules allowed.

[xnamerxx]

So out of curiosity sake, I asked a chassis engineer co-worker of mine the question on what will these bushings do?

His response...
Since the axle is setup like this |/-\| the bushings will limit articulation movement and introduce bind, but that's not necessarily a bad thing. Under bump conditions since the axles are no longer able to pivot freely they deflect the trailing links on bump and cause a toe-out condition on both tires, and modeling how much bind is introduced you can use is as roll resistance rather than using springs or an ARB. In his opinion its a cheap way of solving a problem but not the correct way to solve the problem.

[NJ Drive]

I'm not seeing how they would work correctly. The outside of the bushing is solid so how would it articulate in a twist motion, think one wheel bump, and not bind? If it were the other way round I could see this bushing working correctly but you wouldn't get any help with the lateral movement issue.

Toyotas engineers aren't stupid so I have to imagine it works as intended, or its a bandaid issue to something they couldn't fix correctly given the rules allowed.

In reality, the rear shock absorber lower bushing and even the front lower control arm bushing on the Yaris is also 'binding' but not enough that worry about it usually. Hell, there's some B Stock S2000s that rely on this very thing to help lower the ride height(think preloading the car, then torquing down the bolts through the control arm bushings).

Having the void area that is present in the stock torsion beam bushing has to result in some kind of weird lateral 'mush' when the suspension is worked hard. and I gather this is just a band-aid fix like you said without resorting to a steel bearing, which wouldn't work anyway.

I do understand what you're saying now about the beam not necessarily rotating about axis of the torsion beam bushing on the Yaris.

[xnamerxx]

The rear shock absorber is also being used as a lateral location device. There will always be some sort of bind on the axle but as long as your aware of how much bind is introduced it might not be a problem.
These are production cars not race cars so some issues just have to be worked around.

[Autocross72]

Couldn't you just fabricate a track bar for the rear axle? That would eliminate almost all the side to side movement, but not vertical, or even the torsional movement along the axle. It would only take some basic welding skills, some rod ends and some steel tubing (I would use DOM tubing). I have no idea which rang classes that would be legal in, however.

[Autocross72]

That should read, "I have no idea which racing classes that would be legal in, however."

[DJYojimbo]

deathbeard did u sell the rear sway bar?

[malibuguy]

Couldn't you just fabricate a track bar for the rear axle? That would eliminate almost all the side to side movement, but not vertical, or even the torsional movement along the axle. It would only take some basic welding skills, some rod ends and some steel tubing (I would use DOM tubing). I have no idea which rang classes that would be legal in, however.

A watts link would be better however welding to the beam (which is suppost to twist) may cause a weak spot and snap...would have to find a diffferent way to attach to the beam...possibly a bracket bolted to the spring seat?

[Viperoni]

A watts link on our rear suspensions would be interesting... you could have the bars connect to a bracket off the lower shock bolt, and by keeping them very long, keep the "arc" motion down to a minimum...

[xnamerxx]

A watts link is right on the money.

I do have a basic design on the Watts link ready to go once I get clarification from the SCCA on what exactly defines a solid axle. The one thing that is a potential downside is that the parts will weigh 20-30 lbs which might be detrimental to the potential gains. There is no need to weld a beam you only need a solid mount at the lower shock point.

I also have a plan for a track bar that is extremely simply to mount and install that would be legal in almost any sanctioned race body.

The rear has 2 semi heavy duty tow mounts that have 2 holes already drilled in them that could provide an easy spot to mount a trac bar, the only thing that would be required is a slight reroute on the tailpipe.

I do have another idea for a Anti-roll bar but that's going to be secret since it can create a potential failure in the axle over a long period of time.

[CrankyOldMan]

The only class in the 2013 Solo rule book to call out a Watt's link by name is Prepared, in section 17.7:
Any anti-roll bar, camber compensating device, panhard rod, watts linkage, and/or other suspension stabilizer is permitted. Attachment points of such components are unrestricted. Components may pass through body panels, chassis panels, and frame members.

Streed Modified is more lenient in general, section 16.1.E, but the deal breaker is the "original attachment points" bit:
Suspension components are unrestricted as long as they use the original attachment points. For the purposes of this rule, “suspension” is defined as any item that is designed to move when a wheel is deflected vertically. This includes shocks/struts, control arms, steering knuckles, uprights, etc., but not tie rods, steering racks, and subframes. In addition, shock absorber/strut upper mounts are to be considered suspension components.

[malibuguy]

Sounds like a done deal

[xnamerxx]

The only class in the 2013 Solo rule book to call out a Watt's link by name is Prepared, in section 17.7:


G. Solid axle suspension allowances:
1. Addition or replacement of suspension stabilizers (linkage connecting
the axle housing or DeDion to the chassis, which controls
lateral suspension location) is permitted.86 — 2013 SCCA® National Solo® Rules
14. Street Touring®
2. Traction bars or torque arms may be added or replaced.
3. A Panhard rod may be added or replaced.
4. The upper arm(s) may be removed, replaced, or modified and the
upper pickup points on the rear axle housing may be relocated.
5. The lower arms may not be altered, except as permitted under
Section 14.8.B, or relocated. Methods of attachment and attachment
points are unrestricted but may serve no other purpose (e.g.,
chassis stiffening). This does not authorize removal of a weldedon
part of a subframe to accommodate the installation.

Watts link/panhard/dedion etc are just arbitrary names, adding a watts link is allowed otherwise the mustangs wouldn't be doing it in STX and ESP.

[Viperoni]

A watts link is right on the money.

I do have a basic design on the Watts link ready to go once I get clarification from the SCCA on what exactly defines a solid axle. The one thing that is a potential downside is that the parts will weigh 20-30 lbs which might be detrimental to the potential gains. There is no need to weld a beam you only need a solid mount at the lower shock point.

I also have a plan for a track bar that is extremely simply to mount and install that would be legal in almost any sanctioned race body.

The rear has 2 semi heavy duty tow mounts that have 2 holes already drilled in them that could provide an easy spot to mount a trac bar, the only thing that would be required is a slight reroute on the tailpipe.

I do have another idea for a Anti-roll bar but that's going to be secret since it can create a potential failure in the axle over a long period of time.

Something like this is what I was thinking too for a watts link:
http://www.richardaucock.com/astra-suspension-by-automotive-engineer/

[xnamerxx]

^ And there you have the parts I'm going to be using.

Some models of the Chevy Cruze a watts link with a sum total of parts that would cost less then $200 to procure, and require only minor modification to the support beam and stabalizer arms to make them work in the way I'm trying to make them work.