Front Ball Joint Discussion Thread and Potential Safety Concern

[Turn In Concepts]

Has anyone other than Bob and I given thought to the way the outer lower factory ball joint that is located in the bottom of the knuckle has the potential to be popped out of the socket since the force path has been changed with the relocated spring/damper?

In the factory Subaru configuration, under a heavy upward movement of the suspension (hitting a pot hole) the force is applied upward from the wheel through the hub and knuckle and into the spring/damper and then the chassis. The lower ball joint simply follows this motion and is under little stress. On the 818, the spring/damper is relocated from above the knuckle to the lower control arm. Now when a bump is hit the lower control arm is applying the force directly to the damper and into the chassis from the wheel and knuckle and relies on the connection of the ball joint to the knuckle to do so. There is now a separating force on that ball joint that is taking place and pulling in a direction that could separate the ball from the socket. In all other double wishbone designs the lower outer ball joint is reversed from the 818 configuration such that when the force is applied there is a closed end to the joint on which the ball can bottom out so as not to get pulled from the socket.

I worry that in a very hard bump the front suspension could pull apart.

This is all just theory as I have done no actual FEA or force path analysis to determine if it would hold together, but figured I would put it out there.

Tony


This picture is the 818. You can see the socket end of the ball joint in the knuckle.

http://i66.photobucket.com/albums/h276/svanlare/Suspension2014-08-14SVLDSC_1042_zps07503c33.jpg

Here's a NA/NB Miata which has a double wishbone setup. You can see the lower ball joint is oppositely arranged. The ball joint is behind the tie rod end, but in the same configuration.

http://www.miata.net/garage/images/thumbDSCF0027.gif

[Rasmus]

Has anyone other than Bob and I given thought to the way the outer lower factory ball joint that is located in the bottom of the knuckle has the potential to be popped out of the socket since the force path has been changed with the relocated spring/damper?
Yes. There are several old threads discussing this very topic.

[Frank818]

I worry that in a very hard bump the front suspension could pull apart.

I live in the place with probably the worst road conditions in a non-3rd World country, so I'll let you know how the suspension handles next summer after I start driving the car. :)

[Boog]

After the spring relocation isn't it the same separation force regardless of the orientation of the ball joint?

Is the concern that the ball joint shaft will leave its housing? or that the ball joint as a whole will detach from the knuckle?

[xxguitarist]

Boog, No, not in this case. Previously, the spring/damper acted on the top of the knuckle, so there was a direct force line from the hub, through the knuckle, into the shock. The ball joint just kept things aligned. The lower control arm was unsprung, just a geometry controlling feature.

Now, a force on the hub will go through the ball joint, pulling upwards on the lower arm, which then compresses the shock. The ball joint will see significant tension loading.

Note, I'm not making any claims either way for how much of a concern this is, or isn't.

Here's a crummy sketch of the mechanics in place.
Hub/knuckle is red, control arms green. Ball joint black.

http://i220.photobucket.com/albums/dd8/xxguitarist/Untitled_zps7bfb4a40.png

[billjr212]

i agree that the concern is valid and the design change is significant. however, the design of the 818 front suspension is similar to what has been used on the roadsters and I'm not aware of any failures of the nature that we are discussing here on that model.

[xxguitarist]

Bill,
Do you know what ball joint is used on the roadsters?

[billjr212]

Not sure. My roadster used the donor lower control arms from the Fox Body mustang. I *think* I swapped out the ball joints with OEM equivalent ones from NAPA, but since it was ~7 years ago that I built it, I can't say for certain.

[C.Plavan]

Remember this is a very light car also. Those ball joints are beefy

[Jaime]

That ball joint isn't just clamped in there, the bolt sits in a ridge in the ball joint body. It would take one heck of a lot of force to separate it.

Also, this issue is more important than being discussed here - the front end of the car literally hangs from that joint, even when you are not hitting a bump.

[Buzz Skyline]

Yes. There are several old threads discussing this very topic.

I've been hunting around for a while and haven't found one of the threads that covers it yet. Can you point us to one?

It shouldn't be that hard to determine how much force it would take to rip out the ball joint, I would think. Has anyone done a calculation?

[Rasmus]

Assuming two things:


The 818 weighs 818kg
The weight distribution is 40/60 (front/rear)


We can calculate that ~164kg of static weight rides on the ball joints.

My WRX Wagon, in SCCA STX trim, ran ~426 kg of static weight per front corner. Granted the weight wasn't suspended through the lower ball joints. But the braking forces and lateral turning forces still ran though those ball joints.

[Buzz Skyline]

Here's a NA/NB Miata which has a double wishbone setup. You can see the lower ball joint is oppositely arranged. The ball joint is behind the tie rod end, but in the same configuration.

http://www.miata.net/garage/images/thumbDSCF0027.gif

I can't really make out what's going on with the Miata ball joint. Do you think there's a way to modify the 818 design to take the load off the ball joint? Now that you've brought this up, it really concerns me.

[Buzz Skyline]

Here's a picture of the Miata knuckle design. It seems much better, with the ball joint in compression.

34689

http://rev9autosport.com/catalog/product/gallery/image/1915/id/324/

[Buzz Skyline]

Here's a picture of a separated ball joint in a Beetle, which has the same effective problem as the 818

34690

I got it from this page, which discusses mods to correct the design flaw for Beetles:
http://www.thesamba.com/vw/forum/viewtopic.php?t=491123

[wleehendrick]

Right, but that failure was experienced by overloading the Beetle suspension in a Dune buggy; certainly pushing the original design beyond it's intended use.

Yes, having the joint reversed would be ideal, but since the 818 is so much lighter on the front end than the WRX (and I'm not planning on jumping or rallying mine!) I'm not terribly concerned given the apparent lack of failures in the similar application in Roadsters.

[Buzz Skyline]

I found a paper that includes pull-out tests for six light truck ball joints.

http://www.hindawi.com/journals/tswj/2014/971679/

The failure force ranged between 43 and 45 kilonewtons, which is a range of 9666 pounds to 10116 pounds. With 350 pound/inch springs that means you'd have to compress the springs by 27 inches to generate enough force to pull the ball out of the housing.

That's a lot more travel than the 818 suspension has, so as long as you don't bottom out, the joint probably won't fail.

On the other hand, it would be nice to have a margin of safety. If you go with a factor of three, then compressing the springs by 9 inches reaches a conservative upper limit. That would still bottom out the the 818. But considering that bottoming out would put a lot more force on the joint than the spring does, I'd be a little worried that it wouldn't take too many potholes to bust a ball joint.

I assume the strength of the joints probably decreases with age and wear. So at the very least, I think I'll order a new set of quality joints before I hit the road.

I don't know the stiffness of the 818R springs. I'm sure they are a lot stiffer, which would put a lot more stress on the joints for a given compression, but hopefully they will spend most of their time on smooth tracks where they won't likely bottom out.

[Buzz Skyline]

Yes, having the joint reversed would be ideal, but since the 818 is so much lighter on the front end than the WRX (and I'm not planning on jumping or rallying mine!) I'm not terribly concerned given the apparent lack of failures in the similar application in Roadsters.

On the WRX, however, the joint is in compression, not tension. If it fails on a WRX, it just stops working as a bearing (i.e. it gets noisy and loose), which will hurt your handling. On the 818, failure means your frame will hit the ground and you might rip off a wheel.

[EODTech87]

I don't know the stiffness of the 818R springs. I'm sure they are a lot stiffer, which would put a lot more stress on the joints for a given compression, but hopefully they will spend most of their time on smooth tracks where they won't likely bottom out.

The Front Springs on the 818R are actually softer at 300lbs.

[Buzz Skyline]

OK, I feel better now. According to the Moog page, the most common configuration for load-carrying suspension ball joints is in tension, like on the 818, and the joints are designed to handle it.

http://www.moogchassistraining.com/sus_balljoints_t.php

I think I'll buy some new ones from Moog.

[wleehendrick]

On the 818, failure means your frame will hit the ground and you might rip off a wheel.

I realize that, I was referring to the fact that the FFR Roadster repurposes Mustang hardware similarly and doesn't have reported failures. The 818 takes even more weight off the front.


I think I'll buy some new ones from Moog.

Good to know; I already put new Moogs on!

[fact5racer]

I live in the place with probably the worst road conditions in a non-3rd World country, so I'll let you know how the suspension handles next summer after I start driving the car. :)

Sorry, but many and myself now consider the US as a third world country.

[Boog]

Boog, No, not in this case. Previously, the spring/damper acted on the top of the knuckle, so there was a direct force line from the hub, through the knuckle, into the shock. The ball joint just kept things aligned. The lower control arm was unsprung, just a geometry controlling feature.

Now, a force on the hub will go through the ball joint, pulling upwards on the lower arm, which then compresses the shock. The ball joint will see significant tension loading.

Note, I'm not making any claims either way for how much of a concern this is, or isn't.

Here's a crummy sketch of the mechanics in place.
Hub/knuckle is red, control arms green. Ball joint black.

http://i220.photobucket.com/albums/dd8/xxguitarist/Untitled_zps7bfb4a40.png

I think there is a misunderstanding here, probably because I needed an extra comma. The original complaint/concern was not that the ball joint was under tension but rather the orientation of the ball joint now that it is under tension. I think all double wishbone cars have a lower ball joint that operates under tension.
http://i.imgur.com/TcwHts5.png

I am curious if the concern, due to the inverted ball joint orientation when compared to most double wishbone setups, is about a separation of the ball joint shaft from its housing or about a separation of the housing from the knuckle.

[DMC7492]

Load-Carrying Type
Load carrying ball joints can be divided into two types. In the tension-loaded type, forces applied to the joint housing are pulling the stud against the housing. In the compression-loaded type, the same forces are pushing the stud into the housing. The tension-loaded is the more popular design.
The catalog will list vehicles that have four ball joints. If you are replacing the lower ball joints, it’s a good idea to check the uppers. NOTE: Never order a ball joint based on its size alone. Ball joints of the same size may have very different, application-specific engineering. Installing the wrong part could cause safety issues for which you could be liable.

These are from the MOOG pages,
The 818 is Load carrying in the tension loaded type, and so what if it is the more popular design, the main concern in the 818 is... Was this Subaru ball joint which is a following type initially from Subaru, engineered to be used in a tension load? I think NOT.

Can the engineers at FFR shed a light on this design decision? Thanks Don

[DMC7492]

http://thefactoryfiveforum.com/attachment.php?attachmentid=30555&d=1403731074

Here you can see how the stud will be pulling out of the ball joint housing when impacting the wheel!

[Mechie3]

The concern isn't the ball joint pulling out of the knuckle, but the ball joint itself ripping in two. It's because we're using "non-loaded" type ball joints in a "loaded type" application.

http://www.aa1car.com/library/ball_joints.htm

My gut feel is that with the same G loading we're going to see much less force. Would I do the same for a stock Subaru? No. For an 818? It's probably ok. Not that I want to find out the hard way.

http://www.tomorrowstechnician.com/wp-content/uploads/Articles/05_01_2007/50730cgif_00000000651.gif

[JAubin]

Aside from looking at the design critically, if anyone had a spare knuckle and ball joint they could pretty easily set up a test with some weights to get a rough idea of the failure point. Though I'd certainly be careful trying to do that as it's likely to involve a lot of exploding parts when it fails. If only I still worked somewhere that had an Instron, it would be pretty easy. Alternatively you could probably set up a welded in piece to limit the travel of the upper control arm so that it tops out as you're compressing the bump stop. If you limit the travel there it should prevent the displacement necessary to generate enough force to separate it would be my guess, but that's pure speculation...

[xxguitarist]

The major source of force that is being ignored here isn't the springs, or even the static weight of the car. It's a matter of shock loading, with firm dampers.
The dampers will respond to high speed step changes with many times the force from the springs.

An instron+ a couple simple fixtures would be the perfect solution to determining the moog ball joint separation force. I don't have access to one currently, though.

[Mechie3]

I only have a 250lb Chatillion here. Not exactly ball busting (lol) power.

[Buzz Skyline]

The concern isn't the ball joint pulling out of the knuckle, but the ball joint itself ripping in two. It's because we're using "non-loaded" type ball joints in a "loaded type" application.

The problem is when you try to source replacement ball joints, you'll always get the wrong type (compression) if you look for an OEM replacement for the WRX. What we need is a way to identify tension-type ball joints that will fit the Subaru control arms.

Anyone have an idea what those might be? I imagine someone at Moog might be able to help.

[tirod]

I think the concern it valid. And as with a lot of other hot rod parts, a kit to invert the joint would likely sell.

So, mocking up the parts to fit, can it be done? The adapters add another "interface" that has to carry the loads, and introduce the challenge of maintaining the same installed height.

The optimal solution has already been F5's path for other compromises - they now offer a complete spindle to correct the SAI and lack of a ball joint "interface" the Mustang strut spindle was missing. Expect the same solution, with the inverted joint to "correct" the load handling, and the addition of a top ball joint stud hole.

Donor parts are compromises for economical kit building, provide enough demand and you get the optimal part on the market to replace them. A true racing spindle for the 818 could be fabbed from aluminum plate with stud receptacles and would be lighter.

Here's a thread on some mouth watering fabricated spindles with some billet designs thrown in: http://www.locostusa.com/forums/viewtopic.php?f=5&t=12384

40 year old F1 tech now applied to street, track, and Pro Touring cars. "Detroit" just does them in cast iron because it's cheap mass production - note they do make forged aluminum control arms for trucks, SUV's and cars now . . .

[longislandwrx]

buy the highest quality, properly sized pinch bolts you can find.

[matteo92065]

I only have a 250lb Chatillion here. Not exactly ball busting (lol) power.

Our Tensile testing machine only goes up to 50N.... or 11lbs.
I'm no help testing this.
But I would like to redesign and build new front hub/spindle assembly that is specifically for the 818, aluminum, one piece, and addresses the ball joint design. Think really light, simple and strong. Who's with me?

[Buzz Skyline]

I just called Moog's technical support line. The tech acknowledged that non-load bearing ball joints should not be used in load bearing situations. Unfortunately, he had no way of identifying a replacement for me with the info he had available. He said he doesn't have the size specifications available to him. He suggested measuring the WRX ball joint and going through a variety of load bearing joints to find one that fits.

I have no idea how to do that short of getting a job at an autoparts store. Anyone have a buddy at a Napa warehouse who could spend a few lunch hours finding a bolt-retained, load bearing (in tension) ball joint for us?

Here's the load bearing joint for a VW Beetle (1974), but it's a press in type, and I have no idea what size it is.

http://www.fme-cat.com/overlays/part-detail.aspx?brand=MC&PartNumber=K9014&pt=Ball%20Joint%20&lu=1974%20VOLKSWAGEN%20BEETLE&vin=

Here's the non-load bearing joint used on the same car.

http://www.fme-cat.com/overlays/part-detail.aspx?brand=MC&PartNumber=K9014&pt=Ball%20Joint%20&lu=1974%20VOLKSWAGEN%20BEETLE&vin=

[Buzz Skyline]

But I would like to redesign and build new front hub/spindle assembly that is specifically for the 818, aluminum, one piece, and addresses the ball joint design. Think really light, simple and strong. Who's with me?

I'd support that. If it's too costly or time consuming, I still at least want to find a better ball joint.

[Frank818]

if anyone had a spare knuckle and ball joint they could pretty easily set up a test with some weights to get a rough idea of the failure point.

I have 4 spare knuckles but 0 balls. I mean 0 ball joints!


A true racing spindle for the 818 could be fabbed from aluminum plate with stud receptacles and would be lighter.

Craig are you in? :)


But I would like to redesign and build new front hub/spindle assembly that is specifically for the 818, aluminum, one piece, and addresses the ball joint design. Think really light, simple and strong. Who's with me?

Maybe Craig, he can do anything cuz he's the best bracket guy on the market. That's a big bracket but hey, we must always have challenges, right. :)

[Turn In Concepts]

I found a paper that includes pull-out tests for six light truck ball joints.

http://www.hindawi.com/journals/tswj/2014/971679/

The failure force ranged between 43 and 45 kilonewtons, which is a range of 9666 pounds to 10116 pounds. With 350 pound/inch springs that means you'd have to compress the springs by 27 inches to generate enough force to pull the ball out of the housing.

That's a lot more travel than the 818 suspension has, so as long as you don't bottom out, the joint probably won't fail.

On the other hand, it would be nice to have a margin of safety. If you go with a factor of three, then compressing the springs by 9 inches reaches a conservative upper limit. That would still bottom out the the 818. But considering that bottoming out would put a lot more force on the joint than the spring does, I'd be a little worried that it wouldn't take too many potholes to bust a ball joint.

I assume the strength of the joints probably decreases with age and wear. So at the very least, I think I'll order a new set of quality joints before I hit the road.

I don't know the stiffness of the 818R springs. I'm sure they are a lot stiffer, which would put a lot more stress on the joints for a given compression, but hopefully they will spend most of their time on smooth tracks where they won't likely bottom out.


That is certainly a lot of force, but keep in mind that as soon as the damper contacts the bump stop and compresses it fully the suspension goes solid and all forces is transmitted to the suspension components and frame.

Let me also be clear that I was bringing this up as a matter of discussion. I am personally considering building an 818 and would in no way would this topic persuade me to not build one.

There are higher strength ball joints that are on the market than the factory Subaru units. Moog is one manufacturer that comes to mind.

Here's something else to consider. This is a company, Mooresport, in Canada who we work with frequently. They make high end rally cars and a lot of very nice parts. They fabricate aluminum knuckles in house that can be used with a stud coming out of the lower part of the knuckle with a spherical bearing for the outer ball joint connection. These have been proven in rally to hold up without issue. Only downside is cost as a pair of these is about $5000.

http://www.mooresport.com/images/grandes/67-2011-11-04-upright-1.jpg

Tony

[Buzz Skyline]

I couldn't swing $5000, but I'm definitely interested in a solution.

It seems to me that it wouldn't be that hard to make a bracket that takes the load off the ball joint and puts it back on the knuckle. Here's where I could see it attaching.

34740

[Turn In Concepts]

The problem with that bracket is it would have to hinge between the shock mount and the ball joint pinch bolt.

[Buzz Skyline]

I would ditch the attachment to the LCA and put a perch high enough that it wouldn't contact the control arm. Hopefully, we could do it without modifying the suspension geometry much.

It could be of the same gauge steel as the FFR knuckle bracket. It could attach to the ball joint bolt to make a truss instead of a cantilever.

[FFRSpec72]

Bill,
Do you know what ball joint is used on the roadsters?

Uppers are from 79-82 Chrysler (Moog 772)
Lowers are from 87-93 Mustang (Moog 8259)

[Jaime]

It doesn't matter if it's cantilevered. The only thing holding the hub from floating off the LCA is the ball joint. If you connect the LCA to the hub, that connection will have to have a ball joint, since the hub moves in so many axes relative to the LCA. If effect, all you would be doing is making an alternative ball joint mount - not that it would be a bad idea, just an not a different idea. You would still need to switch to a load bearing ball joint.

[Buzz Skyline]

If you look at post #5 by xxguitarist in this thread, you can see how the ball joint in the WRX is designed to be used. The bracket I'm proposing would restore things to the way the WRX ball joint is supposed to be used.

As things currently stand, the entire weight of the car in front hangs off the ball joint. With the added bracket, the ball joint only locates the LCA, while the weight of the car goes through the hubs, as is true of the WRX.


It doesn't matter if it's cantilevered. The only thing holding the hub from floating off the LCA is the ball joint. If you connect the LCA to the hub, that connection will have to have a ball joint, since the hub moves in so many axes relative to the LCA. If effect, all you would be doing is making an alternative ball joint mount - not that it would be a bad idea, just an not a different idea. You would still need to switch to a load bearing ball joint.

[Buzz Skyline]

This is what I'm proposing, based on xxguitarist's sketch.

34743

[Junty]

Very interesting thread, I wish I had the conclusive answer - FFR might help? When I first ordered my kit and started with the registration process in NZ, scratch build kit car... I submitted an application to Low Volume Vehicle compliance NZ. They initially raised these same concerns - relating to the push or pull tension on the lower ball joint. This was very quickly concluded by FFR - who have provided LVVCA NZ with detailed drawings and Subaru information relating to the ball-joint. Although I don't have these, I understand that it relates to Subaru building all WRX and STI's same as rally cars with a ball joint design for both push and pull tension. In short although the appearance of the joint is that it is now upside down, it can still hold almost as much force in either direction...
Low Volume Vehicle compliance engineers in NZ are convinced, from the number of images for WRX cars fully airborne with all brakes, wheel and suspension weight pulling on this joint - also under heavy braking with sway bars pulling on one side to push on the inside - I too am convinced that these joints will more than sufficiently do their job for all 818's - just as FFR designed it. :)

[STiPWRD]

I couldn't swing $5000, but I'm definitely interested in a solution.

It seems to me that it wouldn't be that hard to make a bracket that takes the load off the ball joint and puts it back on the knuckle. Here's where I could see it attaching.

34740
Are you proposing at attach the spindle to the lower shock mount with an L-bracket? Because this would greatly reduce the rotational degrees of freedom of the ball joint and mess up the suspension travel. Even if the L-bracket attachment was able to pivot at the lower shock mount, the ball joint would still be over constrained.

Edit: Just saw your latest sketch, your going to de-couple the lower shock mount from the LCA. That might work.

[Buzz Skyline]

Thanks, Junty. I'd love to see the specs for the Subaru ball joints.

I'd still pay for a different knuckle or a bracket that would restore the ball joint to a non load bearing configuration. Even if these things are tough, it would be nice if failure could be a safer mode than would occur if joint in its current configuration gave way.

(I'm hoping to give the car to my daughter someday to race autocross, so I want to do everything I can to avoid "fail dangerous" designs.)

[Buzz Skyline]

Edit: Just saw your latest sketch, your going to de-couple the lower shock mount from the LCA. That might work.

Yes, that's what I have in mind. The main issue would be how high the perch would have to be to make sure the end of the shock never contacts the LCA.

Of course, I can't actually make anything because I don't have any shop equipment to speak of. But I would buy them if one of our enterprising vendors would make them.

[Jaime]

This is what I'm proposing, based on xxguitarist's sketch.

34743
Why would your new brackets not need ball joints themselves? You can't simply bolt something to both the LCA and hub because they rotate in two different planes relative to each other.

In a MacPherson design, the body rides on the hub on a load-bearing ball joint at the top of the strut and is located at the bottom with a non load-bearing ball joint. In a wishbone design, the LCA hangs from the lower load-bearing ball joint and the top of the hub is located by a no load bearing ball joint. In both cases, the tie rod connects to the hub with a ball joint. Everything that connects to the hub needs to connect via a ball joint and exactly one of those ball joint needs to bear the load.

[Buzz Skyline]

Why would your new brackets not need ball joints themselves? You can't simply bolt something to both the LCA and hub because they rotate in two different planes relative to each other.

The ball joint is still there in the same location, but the shock is now attached to the hub, as is true of McPherson struts. It's not a great sketch, so it may be hard to tell that I've deleted the bracket that connects the shock to the LCA. This might be a bit clearer
34744

The first sketch is effectively the WRX set up. The second is the 818, and the third is what you would have with the bracket I'm proposing. In both the first and third sketch, the ball joint only fixes the relative position of the LCA and the hub (and carries very little force). In the second case (i.e. the 818) the ball joint feels the weight of the whole car pulling on it.

[Jaime]

But, what about the ball joint that attaches the shock to the hub? What about the side-load that is created on the lower ball joint that should be about 60 or 70 percent of the magnitude of the vertical load?

[Buzz Skyline]

The ball joint at the end of the shock is designed to handle the forces that we're talking about. Changing from a LCA mounted bracket to a hub mounted bracket won't change the forces on the shock's ball joint.

The ball joint in the control arm (probably) isn't designed to handle high pull-out loads because it would never have seen them in a WRX.

The side loads on the ball joint in the LCA are going to be comparable to the side loads it would have experienced in a WRX, so I'm not worried about that.

[DMC7492]

Okay Buzz your on to something here. I just. Looked over the knuckle and the only time it would be close to the lower control arm is when the front end was off the ground.
The issue is the lower mount of the shock/spring will now make the swing of about 2.5" radius as the wheels are turned and the shock will have to pivot within itself.
The other issue is the springs will both windup or unwind as the suspension compresses and relaxes and also when turning the steering, Toyota had this issue in the early Camrys as both springs were wound the same direction, when loaded it would steering would naturally pull in one direction... More deciphering but the new bracket along with some slight machining to the knuckle would end up being about a new bracket from upper ball joint mount to the lower spring mount. 14 inches by three inches wide and some properly sized spacers to as sandwich everything.
Once again will the shock/spring be able to handle the pivoting action, it does have a spherical mount on both ends to help with the misalignment.
Food for thought?

[Buzz Skyline]

Good points. You're ahead of me now. I haven't had a chance to go out to look at my 818 after realizing there was a potential problem with the ball joint. It's certainly not a simple to solve as I had thought. Hmmm.

[tirod]

Being I am a parts counterman, no, we can't spend days sorting thru all the boxes measuring them to discover what spec's are out there. First, the books don't say. Second, we usually stock less than 5% of what is out there. Auto Parts stores only stock what sells - not what might speculatively work for a one off kit builder in that region.

The MOOG rep does that - when you are talking 250,000 unit's. Not only will they send you a list of what joints might work, they send drawings, too. And if you like, they help design one for your car. It's what they do. You were politely rebuffed as there is simply no money in it for them. C'mon, "I haven't got the specs" is like a Colt rep saying "I can't tell you how long the barrel is on the M16." In the case of the MOOG rep, tho, he's got thousands to choose from, and they generally replicate what other engineers specify.

Use the HSLD Subaru joint and call it good until it does blow up, but use it in a way that promotes taking the load - oriented the way it's supposed to be used. I suspect that fabricating a new spindle would offer other more tangible benefits, like having steering arms set up to reduce bump steer, optimize the Ackerman, tilt the joint to center it's working envelope, incorporate a bracket for larger calipers, get the SAI to work with the scrub radius of wider tires, etc.

There IS a lot of stuff going on up there, if and when someone starts pulling out ball joints then the market will respond with a newer spindle design because demand will increase. That underwrites the expense of development and a small shop will take the plunge. At which point the escalation in 818 racing will have started and the donor runners will be left behind as money starts sorting out who takes first.

Be careful what you ask for.

[Buzz Skyline]

After a little more thought, the bracket I proposed is a TERRIBLE idea. It would couple the shocks into the steering and probably make the car un-drivable. Assuming you could even get it to go where you wanted, a bump mid-corner would rip the steering wheel out of your hands. Ah well. I think we need a redesigned (and expensive) knuckle.

[Buzz Skyline]

Use the HSLD Subaru joint and call it good until it does blow up, but use it in a way that promotes taking the load - oriented the way it's supposed to be used.

It's not possible to use the joint the way it's supposed to be used. It's not supposed to carry any significant load at all. It's not even a good idea to exposed a compressive load bearing joint to tension, or the reverse.

So 818s are going to be running around on critical, but fragile, suspension pieces that will leave your frame on the ground or rip off a wheel if one fails. I can't imagine what that would be like if it happened after hitting a pothole at 65 mph.

What's more, I had hoped to share this car with my son and daughters. While I might consider calling it good until it blows up, I'm sure not going to send my kids off in it.

So, I will continue hunting for a solution I can trust.

[Blitzkrieg]

push-rod suspension.

[Bob_n_Cincy]

push-rod suspension.
Or maybe something like this.
34759

[STiPWRD]

So 818s are going to be running around on critical, but fragile, suspension pieces that will leave your frame on the ground or rip off a wheel if one fails.
That's a bit of a stretch. These cars have been raced with no ball joint issues and I'd have to imagine FFR did some bit of homework before choosing this design. I'm not saying these things can't fail but I just won't believe it til I see it on this car and this particular ball joint.

[FFRSpec72]

What's more, I had hoped to share this car with my son and daughters. While I might consider calling it good until it blows up, I'm sure not going to send my kids off in it.

The sky is falling... I have been racing the challenge car since 2005, no issues, challenge car uses same setup as 818, my daughter races the challenge car also, she will race the 818 and I have no problem in letting her do so

[Buzz Skyline]

The sky is falling... I have been racing the challenge car since 2005, no issues, challenge car uses same setup as 818, my daughter races the challenge car also, she will race the 818 and I have no problem in letting her do so

The challenge car re-purposes a non load bearing joint as a load bearing joint? There's nothing fundamentally wrong with the configuration in the 818. But the joints have different designs and different specs based on their applications.

[Buzz Skyline]

This looks like a load bearing ball joint to me (I got it from this thread http://thefactoryfiveforum.com/showthread.php?7413-Can-I-shim-upper-control-arm)
34760
Do you know the part number for the roadster's lower ball joint?

[Buzz Skyline]

The lower ball joint that comes with the Roadsters is this

http://www.summitracing.com/parts/mev-mk772?seid=srese1&gclid=Cj0KEQjw_IKiBRD7rPqut_OZ4qgBEiQASm4GArrruaiT jt5IzOwTq69_BRVFkENX4KH7jTwxBxB_FFwaAnQZ8P8HAQ

It is a load bearing type. I'm not surprised that they don't fail catastrophically. They are designed to be used that way. The 818's are not.

Edit: The roadsters lower ball joint may be this one, also a load bearing design
http://www.oreillyauto.com/site/c/detail/MOO0/K8259.oap?year=1992&make=Ford&model=Mustang&vi=1134043&ck=Search_C0317_1134043_-1&pt=C0317&ppt=C0106

[Blitzkrieg]

Or maybe something like this.
34759
That would fix the problem also. I don't think it would be to hard to build a push-rod suspension for the 818.

[Buzz Skyline]

That would fix the problem also. I don't think it would be to hard to build a push-rod suspension for the 818.

It sure would. But I don't think I can manage it in my home shop. It would probably cost as much as the whole kit to have someone else do it.

[Frank818]

I don't understand why we compare with racing different cars. How many potholes have you guys hit on a race track?

[Blitzkrieg]

It sure would. But I don't think I can manage it in my home shop. It would probably cost as much as the whole kit to have someone else do it.
The big cost would be the pivot arm but if you did a group buy you would have someone like Boyd make some up. Basicly they are a box of steel with a bearing and you could use off the self adjustable rods.

[matteo92065]

We (my boss and I) are seriously thinking about building front knuckles made for the 818. Not just different Subaru knuckles. And not because we thought the ball joint was a problem, but because, have you lifted one of those things'?! :eek:

To fix concerns about the lower ball joint we could maybe flip the A-arms, to put the ball joint into compression.

I would like to start with a knuckle from a car that has aluminum knuckles, with the 5x100 bolt pattern, to use bearings and hub. After a quick search, the 03 350z looks close enough to start with.

Any other thoughts on this?
34761

[Buzz Skyline]

We (my boss and I) are seriously thinking about building front knuckles made for the 818. Not just different Subaru knuckles. And not because we thought the ball joint was a problem, but because, have you lifted one of those things'?!

That would make me very happy! But when you design them, please make sure that they use load bearing ball joints, not the donor car's joints.

[D Clary]

The Red FFR car is going 150+ mph and pulling over 1g. They have been beating the crap out of the blue car for a year. I would hope if it was a problem they would let us know. If you call Moog and expect them to tell you that can use their parts for anything other than their application they will lawyer up and say no. But this is a kit car and everyone has the right to re-engineer or change the design. That been said if you redesign to much the car will never be completed some of the compromise has to be lived with.

[johngeorge]

How heavy is a stock subaru? 3100lb? so if we remove 1000lb from the car doesnt that mean all parts designed for the stock subaru overbuilt for the 818? And thats not even taking in account the engine is no longer on the front axles.

[Buzz Skyline]

How heavy is a stock subaru? 3100lb? so if we remove 1000lb from the car doesnt that mean all parts designed for the stock subaru overbuilt for the 818? And thats not even taking in account the engine is no longer on the front axles.

But the ball joints in question hold almost zero load when used on the WRX. Now they have to hold up 450 pounds while you're standing still, and lots more force when you hit a bump.

Unlike many quality load-bearing ball joints, they have no lube nipples or wear indicators. Even in their designed use on a WRX they eventually wear out. I would guess 80k miles is a reasonable lifetime of a ball joint on a WRX. But they WILL fail at some point, especially with so much more load on them. How long will it take on the 818? I don't know, but I'd bet much less than the lifetime on a WRX. How much less is anyone's guess. Will you be able to tell they're done in before the ball pulls out and you skitter across the track or the highway? Who knows? Why take the risk if you can find a fail-safe alternative?

The bottom line is you're risking your investment (and yourself) on waaaaay under-engineered components. It's like holding up the car with the steering ball joints! That would be nuts. And this is pretty close.

There are lots of things that can be improved on the 818. This is the most important one I can see because so much is at stake in the event of a failure.

Edit: To put numbers on it, when a WRX is sitting still the LCA ball joint holds up the weight of the LCA. Let's overestimate it at 10 pounds. When the 818 is sitting still, the LCA ball joint is holding up a quarter of the weight of the whole car, or about 500 pounds.

When you go over a bump, the ball joint on a WRX has to handle the acceleration of the LCA. When the 818 goes over the same bump, it has to handle the acceleration of a quarter of the weight of the car.

In other words, the 818 ball joint will routinely handle 50 times the loads it sees on a WRX. Even if you believe the components are over designed, are they really over designed by a factor of 50?!?!

[myjones]

Or maybe something like this.
34759

Funny choice for a substitute;
That set-up uses an upper ball joint that is in compression from the impact loading of hitting a pothole so It's the 818 problem turned upside down.
I replaced my 33 uppers with an early mustang joint that was designed for compression loads like the 33 generates. No advice for the 818 sorry.
DB

[MrDude_1]

We (my boss and I) are seriously thinking about building front knuckles made for the 818. Not just different Subaru knuckles. And not because we thought the ball joint was a problem, but because, have you lifted one of those things'?! :eek:

To fix concerns about the lower ball joint we could maybe flip the A-arms, to put the ball joint into compression.

I would like to start with a knuckle from a car that has aluminum knuckles, with the 5x100 bolt pattern, to use bearings and hub. After a quick search, the 03 350z looks close enough to start with.

Any other thoughts on this?
34761

Yes I have been looking into it myself. The aftermarket and WRC subaru uprights are not what I am looking for. The odds of me getting to use the Ti-3d printer at work are near nill... so no point designing them here... I keep eying all the aftermarket lotus stuff... but no measurements yet. If the locations are close for that spindle you posted, that could be a better starting point. Whats the distance between the upper and lower?

[C.Plavan]

Yawn..... Yep, put me to sleeeeeeeepppp.

[HCP 65 COUPE]

Dont compare the WRX ball joint to the fox or sn-95 ie roadster lower ball joint the WRX ball joint was not designed to be in tension the
mustang one was, the Fox and sn-95 mustangs have a tension ball joint from the factory the front springs sit in a pocket in the a arms the
struts just locate the top of the knuckle and contain the shock.

I have had 2 of the mustang ball joints fail 1 time in a fox and 1 time in a sn-95 while in motion after hard pot hole hits
and both times the suspension colapsed on its self.
I was lucky both times cause the car was moving slow in a parking lot but if it had been on the high way or on a race track the car would have
ran over its own wheel causing a major disaster. I would suggest to all 818 builders to replace every ball joint with a better or tension designed
ball joint and dont risk your life or your investment over a 15-30$ part its just not worth it ,plus alot of the donor cars have been in an accident
the wrx ball joints may have taken a hard hit and been damaged. DONT RISK IT yours and others lives are at stake.

[HCP 65 COUPE]

Why cant you use the FFR spindle the only compromise I can think of is the need for STI wheels aren't they 5x114
I don't think the .0118 difference in bolt circle would be to much of an issue. I'm not sure about the suspension pickup points but they may be better.

[Buzz Skyline]

How about replacing the ball joint with this
34776

The high strength one from McMaster-Carr with 1/2" hole and 1/2"-20 threads is rated for 16,000 pounds.

http://www.mcmaster.com/#end-links/=u74bj8

Edit: Forget it. It couldn't take the lateral loads. It's gotta be a ball joint.

[CHOTIS BILL]

I am not sure I fully understand the issue because I am not familiar with these parts but from the pictures it looks like the same setup as used on the roadster and type 65 coupe and I have never heard of a problem on those.

Bill Lomenick

[RM1SepEx]

I think that you are over analyzing the situation, this steel part is not loaded all that highly in either application, the increase continual loading should only result in wearing out a bit more rapidly... IMO: no big deal how many of us drive our kit cars as much as Ralph Button drives his Cobra? Replace them more often and be done with it

[DMC7492]

This would be a nice set up.
34789

[RM1SepEx]

In ALL engineering decisions there are compromises, FFR did the best they could within the scope of the design goals. It is a safe design with some reasonable compromises... A totally custom setup would dramatically increase the cost of the kit for marginal improvement. The resultant design is far better that the original Subaru design. Check out cars with toitally custom suspensions, finished kit cost would double or triple... :(

[Scargo]

I started a thread about a different front upright (or a spindle) (http://thefactoryfiveforum.com/showthread.php?12802-Lighter-race-oriented-Suspension-Parts-Primarily-Uprights). Now, with this discussion, what we discussed there seems relevant. Could we possibly go there to discuss options at least for racing?
I show some options I found at post #68 (http://thefactoryfiveforum.com/showthread.php?12802-Lighter-race-oriented-Suspension-Parts-Primarily-Uprights&p=138704&viewfull=1#post138704) and after as well as the link to the discussion about spindles for locost kits (http://www.locostusa.com/forums/viewtopic.php?t=1292).
I am interested in something new or adapting existing spindles, which also means a different LCA. I want to do inboard shocks. I want 5x114 wheel stud pattern, too. That's what I have for the rear (STi).

I didn't finish my engineering degree but I know about arguing. To me it is evident that there is a potential problem with the current design. I dropped a ball-joint at 100+ and it was not a pretty sight. To speculate that the ball-joint design is OK "'cause nobody's seen a failure" is just untenable. Driving over the curbs in the bus-stop at Watkins Glen is pretty jarring. What if you hit something more substantial? Cars do go off into unexpected places and hit humongous pot-holes; they don't always stay on a smooth track or street. And what happens when they are worn and forgotten about?

A simple solution might be for FFR to offer a "Hot-rod" based front suspension.
However it can be accomplished, I'm in when it comes to wanting something better, lighter and racier.