2G 2g SPC Upper A-Arm replacements discontinued

[jtmcinder]

Yeah, well, the decrease in compliance you'd get from switching the OE bushings for poly makes it better to go with those over ripped OE, anyway. Oh, well.

 

[Scott McIntyre]

Regarding my bushings pictured above, I simply greased them up and threw them back in. There's no slop in them currently.

But as Charles said, it's only a matter of time before the metal wears away at the rubber. So my greasing them was just a short term measure. I'd rather have spherical bearings in there anyway.

 

[greengoblin]

Depending on your reading of the Street Mod rules, there may be a very useful change to make when you redo the anchor bolts. The math says that extending the length of the anchors, such that the eye is moved downwards, will not only get you a bit more camber, but will also steepen the bump-camber curve so that you gain more negative for the outside front as the car rolls in a corner, while also taking out more negative from the inside front, so it's a win-win.

That's sound like a really good idea.
However wouldn't that also increase the amount that the ball joints are extended beyond their full range of motion already? That might end up being a bad idea for those using the SPC arms.

 

[greengoblin]

The rubber being ripped in the anchor bolts bushings would also allow the arm to move forward and backward too. Not just allowing the arm to swing in it's normal up and down arch.

 

[jtmcinder]

That's sound like a really good idea.
However wouldn't that also increase the amount that the ball joints are extended beyond their full range of motion already? That might end up being a bad idea for those using the SPC arms.

Wow. I never thought about the ball joints. But as long as you run a decent amount of static camber, moving the inboard pick-up on the upper arms downwards would actually bring the ball-joints back towards centered, this is a win/win on that, too.

The only downside I see so far is that the shock towers are a known weak-point on the chassis, especially after rust sets in. Extending the eye-bolts downward would increase the torque at the place where the eye-bolts connect to the chassis. Maybe some strengthening is called for. But the math says this would up the bump-camber curve quite a bit. The more non-parallel a non-parallel suspension system is, the more steep the bump-camber curve can be.

- Jt

 

[greengoblin]

Scott,

How much static camber are you running? Curious since you are already seeing wear on the ball joints from them being extended beyond their full range of motion.

Thanks,

Kevin

 

[PieEyedPiper]

I cannot describe my fury at this moment. I just spent an hour detailing my afternoon replacing my eyebolt bushings. Even the pictures are gone.

All I will reconstruct is my inquiry to Jt, how much longer would newly designed eyebolts be? Spacers could even be used for adjustability, no? Do you know of an equation that describes the camber curve? I'm not trying to talk out of my ass or anything but there must exist a mathematical or graphical representation that uses variables such as pickup location/arm length.
These could be very easy to produce with access to a cnc. Threading them would likely be the hardest part.
It took me a second to visualize what you said, but I agree, lengthening of the eyebolts should improve the posture of the balljoint.

[space reserved for amusing photograph of applying a little too much bfi]


Also, I highly recommend this: https://addons.mozilla.org/en-US/firefox/addon/lazarus-form-recovery/
This is the last time I will learn that particular lesson.

Well the photos went to the bottom, but you can plainly see some vice destruction. It was the last bushing, it just didn't want to go in straight. After being a little forceful it appeared to be going in straight, finally. About half way done I start having to really crank on the vice and I noticed I was actually shaving one of the surfaces with every millimeter further the bushing went into the eyebolt. Not cool, but way too late for regrets. "Onward! Mush!"

The best I got out of it was 3mm shy of centered before "BAM!!" the vice self-destructed. That will have to do, I suppose. Upon re-installation there was no qualm. The difference was just too miniscule to matter.

Also, somewhat directed to the goblin, those bushings would have to be really shredded up to be gaining any forward/backward movement. I discounted it due to what I've seen on my own car but thanks for spelling it out as in Scott's case he might be looking at "bad things happening" since his destruction was far worse than my own...which was little to none. More on that once I get aligned and some driving impressions.

 

[jtmcinder]

1/2 to 3/4 inch should do it.

I will search again for my model of the 2G suspension. I haven't seen it for years, but I have a pile of zip disks to check. I had most of the standard parts memorized, but this is something new. Plus, I did some things in the 1970s that weren't so great for the memory.

 

[greengoblin]

With the scp eyebolts you could add a spacer that is around .489 That is what one of mine miced out when I checked it for fun. you could grind the mounting point tops down a bit and gain even more.I'd guess close to .75

Now the question is just how big would you really want the spacers and will it cause you to tear the mounts out?

Kevin

 

[PieEyedPiper]

Now the question is just how big would you really want the spacers and will it cause you to tear the mounts out?

Kevin

That's what I was worried about, too, when thinking of this last night. You, however, of all people, might know what the mounting looks like on the inside - I figure that taper on the eyebolts is fairly deliberate.

But we do have .5" to .75" of head-room as far as the threads are concerned.

 

[jtmcinder]

Well, the lower lateral arm is much much closer to the center of the wheel, so a majority of the force goes through it. And, yet, we all know from the rust adventures that the upper tower is a serious weak point. If this isn't a daily driver, I'd go for it and keep a close eye on the tubes in the towers that hold the eye-bolts. If it's a daily driver or you race at 120, instead of autocross speeds, maybe not.

If you suddenly stop posting, then we'll assume that you tried it and it wasn't safe.

 

[greengoblin]

I welded a washer around the top posts on each side of mine to brace it some.

Here is what the strut tower looks like deconstructed. You can see the anchor mounting post there. Not the best design.
http://www.dsmtuners.com/forums/152098615-post31.html

 

[PieEyedPiper]

I welded a washer around the top posts on each side of mine to brace it some.

Here is what the strut tower looks like deconstructed. You can see the anchor mounting post there. Not the best design.
http://www.dsmtuners.com/forums/152098615-post31.html

The support, or lack thereof, is astounding to me. I'm not a metal engineer or a suspension genius but common sense tells me I should have saved $1.00 in supplies at some other location.

How much more torque is being introduced into the system if the eyebolt is extended half an inch, as far as destruction/detachment of the tubes is concerned?

Is there a nominal load/torque that we already know as an upper limit?

 

[jtmcinder]

How much more torque is being introduced into the system if the eyebolt is extended half an inch, as far as destruction/detachment of the tubes is concerned?

Com'on, man. You can do this on a napkin. Have some self-confidence. It's just lever-arm math. Take the new distance from the center of the eye to the center of the tube and the old distance, divide, and that's the multiplier for the new level of torque. Based on my memory for these things (warning: see previous posts about the 1970s), you're probably going to increase the torque on the tube by less than 20%.

 

[PieEyedPiper]

Com'on, man. You can do this on a napkin. Have some self-confidence. It's just lever-arm math. Take the new distance from the center of the eye to the center of the tube and the old distance, divide, and that's the multiplier for the new level of torque. Based on my memory for these things (warning: see previous posts about the 1970s), you're probably going to increase the torque on the tube by less than 20%.

You should see what I do to coasters when I'm in front of a pint. Somehow the physics begins to pour like the golden goodness that is a good IPA.

But I'm just gonna run out in my skinnies, toting tools and such at 6AM to go take measurements? I'm sure I already abuse my interpretation of "reasonable expectation of privacy" as far as the neighbours are concerned.

I wanted to inspire discussion. Something for those following along at home to do.

However, the variables are not all known. Do you, Jt know the exact length of that tube? Now that I've had some coffee, and it's no longer 6AM, I've done a little bit of napkin math and have concluded that the tubes are 2.25" or 57.5mm. I had crude means but I'm feeling self-confident.

(A)Tube length = 5.75cm

(B)Dist. from center of eyebolt to bottom of tube = 4.20cm

Dist. from center eyebolt to center of tube = ((1/2)(A))+(B)
= ((1/2)(5.75))+(4.20)
= 7.08cm
(C) = 7.08cm

New dist. from center of eyebolt to center of tube = (C)+(1.27)
= (7.08)+(.5)
= 8.35
(D) = 8.35cm

~~~~

Torque = Force x Dist.
Force = Arbitrary quantity such as 1000N
(D1) = 7.08cm
(D2) = 8.35cm
T = (F) x (D1)
= (1000)x(7.08)
= 70.8Nm

T= (F) x (D2)
= (1000)x(8.35)
= 83.5Nm

(T1) = 70.8Nm
(T2) = 83.5Nm

%increase in torque = ((T2)/(T1))-(1)x(100)
= ((83.5)/(70.8))(-1)x(100)
=17.9

There is a 17.9% increase in torque applied to the eyebolt mounting tubes when extending the eyebolts downwards 0.5".

If this is at all correct then it looks like the increase in torque is less than 20%. What do you think, Goblin? Can the factory welds take an additional 18%? Were the welds on the tubes exhibiting stress when you dismantled your towers?

I've also concluded that stock eyebolts should work fine as replacements or substitues for the SPC supplied eyebolts. They are slightly wider but should pose no issues. Not sure yet if the bushing dia. matches.

 

[Gonzo]

This is being anal, but you forgot to take into account the angle at which the force is applied.

Regarding the strength of the upper a-arm mounts, does anyone remember the Neuspeed upper strut bar? It was unique in that it mounted to the rear a-arm eyebolts. I always thought this made more sense than a strut tower mounted bar on a non-McStrut suspension like ours.

 

[PieEyedPiper]

This is being anal, but you forgot to take into account the angle at which the force is applied.

Regarding the strength of the upper a-arm mounts, does anyone remember the Neuspeed upper strut bar? It was unique in that it mounted to the rear a-arm eyebolts. I always thought this made more sense than a strut tower mounted bar on a non-McStrut suspension like ours.

I'm pretty sure the simplistic formula I used assumes 90*. That is the critical angle anyways, anything more or less should decrease the torque seen at the mounts. At least that's how things are going inside my head today. Tomorrow could be very different.

I actually just had an error (that your keen eyes missed!) in my previous post come to me while standing at the urinal. Damn near forgot to finish up and zip it up before I tried bolting for my laptop. I'm sure there are further edits to come.

EDIT: Such as this one, can we assume that critical angle is not going to be 90* since the angle at which the most stress is applied would, instead, be a minimal angle created when hitting your bumpstops. Surely those forces are more severe than normal condition cornering forces.

EDIT II: Another moment of insight. sin(90)=1

 

[greengoblin]

You should see what I do to coasters when I'm in front of a pint. Somehow the physics begins to pour like the golden goodness that is a good IPA.

But I'm just gonna run out in my skinnies, toting tools and such at 6AM to go take measurements? I'm sure I already abuse my interpretation of "reasonable expectation of privacy" as far as the neighbors are concerned.

I wanted to inspire discussion. Something for those following along at home to do.

However, the variables are not all known. Do you, Jt know the exact length of that tube? Now that I've had some coffee, and it's no longer 6AM, I've done a little bit of napkin math and have concluded that the tubes are 2.25" or 57.5mm. I had crude means but I'm feeling self-confident.

(A)Tube length = 5.75cm

(B)Dist. from center of eyebolt to bottom of tube = 4.20cm

Dist. from center eyebolt to center of tube = ((1/2)(A))+(B)
= ((1/2)(5.75))+(4.20)
= 7.08cm
(C) = 7.08cm

New dist. from center of eyebolt to center of tube = (C)+(1.27)
= (7.08)+(.5)
= 8.35
(D) = 8.35cm

~~~~

Torque = Force x Dist.
Force = Arbitrary quantity such as 1000N
(D1) = 7.08cm
(D2) = 8.35cm
T = (F) x (D1)
= (1000)x(7.08)
= 70.8Nm

T= (F) x (D2)
= (1000)x(8.35)
= 83.5Nm

(T1) = 70.8Nm
(T2) = 83.5Nm

%increase in torque = ((T2)/(T1))-(1)x(100)
= ((83.5)/(70.8))(-1)x(100)
=17.9

There is a 17.9% increase in torque applied to the eyebolt mounting tubes when extending the eyebolts downwards 0.5".

If this is at all correct then it looks like the increase in torque is less than 20%. What do you think, Goblin? Can the factory welds take an additional 18%? Were the welds on the tubes exhibiting stress when you dismantled your towers?

I've also concluded that stock eyebolts should work fine as replacements or substitues for the SPC supplied eyebolts. They are slightly wider but should pose no issues. Not sure yet if the bushing dia. matches.

Maybe it would be fine with the load. I'm far from an engineer so maybe not. IDK. Rust is going to be a BIG enemy here since there is no good way to see if it is in there.

If you want exact tube lengths I can get you those since I have a few spare strut towers laying around.

The stock eye bolts are much shorter than the SCP units so I doubt they would work as well. I have several set so I can get you exact lengths on those too.

Also the ID on the OEM eyelet is larger than the SCP unit.

I do have a pretty good idea on how to space the eyelet down and add strength. However I'm in bodywork mode for now so it will be a bit before I have time to mess with suspension again.

What would be really nice is moving the mounting for the shock up higher so there would not be clearance issues and you could lower the car more and gain both camber and camber curve. That would be much harder but more fun.

I tried to get Andrew to come in to this disscusion but he is in Japan and is blocked from the site. Boo.

Kevin

 

[ACM]

I can answer this easily.

Running race tyres, the stock eyebolts will crack loose every year of autocrossing with monotonous regularity. If they don't crack then you aren't trying !

The inner fenders of my car look like the heliarc equivalent of a spiders web. These days we're welding the welds !

No calculations required...

 

[PieEyedPiper]

Maybe it would be fine with the load. I'm far from an engineer so maybe not. IDK. Rust is going to be a BIG enemy here since there is no good way to see if it is in there.

If you want exact tube lengths I can get you those since I have a few spare strut towers laying around.

The stock eye bolts are much shorter than the SCP units so I doubt they would work as well. I have several set so I can get you exact lengths on those too.

Also the ID on the OEM eyelet is larger than the SCP unit.

I do have a pretty good idea on how to space the eyelet down and add strength. However I'm in bodywork mode for now so it will be a bit before I have time to mess with suspension again.

What would be really nice is moving the mounting for the shock up higher so there would not be clearance issues and you could lower the car more and gain both camber and camber curve. That would be much harder but more fun.

I tried to get Andrew to come in to this disscusion but he is in Japan and is blocked from the site. Boo.

Kevin

Exact sizes would be best, just for peace of mind. But I don't think we're going to stray too far from the 20% mark.

I swear my eyebolts (both OEM and SPC) were as same as the eye could tell when put side by side (in length). But you guys have already been down that road with me.. haha! I should just stop "recalling".

I can answer this easily.

Running race tyres, the stock eyebolts will crack loose every year of autocrossing with monotonous regularity. If they don't crack then you aren't trying!

The inner fenders of my car look like the heliarc equivalent of a spiders web. These days we're welding the welds !

No calculations required...

Well, there's certainly a lot less numbers in your method.. until you start counting missing money. But I bet you're the type who can weld his shit on the side of the road.

Kevin, does Andrew have further suspension mods planned? I wonder how long his eyebolts are..

 

[jtmcinder]

I can answer this easily.

Running race tyres, the stock eyebolts will crack loose every year of autocrossing with monotonous regularity. If they don't crack then you aren't trying !

The inner fenders of my car look like the heliarc equivalent of a spiders web. These days we're welding the welds !

No calculations required...

Not sure what your point is. If you're saying "don't do it!" because it will break the car, then that doesn't make much sense because you're also saying that the car going to break without the change. If you're saying that trying to get an idea of how much faster the car will break isn't useful, then I simply must beg to differ. If the math says that the car is going to break twice as quickly, then, yeah, this might not be worth it. But if the math says the car will break 10% sooner, it could easily be worth it to some people. Not having to run as much static front camber would be a huge plus in both launching and braking.

 

[greengoblin]

I will not comment on what has, is or is being done to anothers car. Sorry about that. Maybe when Drew comes back stateside he'll comment.

Kevin

 

[PieEyedPiper]

No worries there. Wasn't meaning to pry, just conversate. We'll have to get him in here though when he comes back.

 

[knochgoon24]

Couldn't you cut the welds out from around the old tube, and weld reinforcement plates in around the holes? Then you'd have something a little thicker so you can get a meatier weld?

Might not be worth it to the occasional track goer.

 

[PieEyedPiper]

Couldn't you cut the welds out from around the old tube, and weld reinforcement plates in around the holes? Then you'd have something a little thicker so you can get a meatier weld?

Might not be worth it to the occasional track goer.

That's the thing. It'd be a huge undertaking. At least for myself or the occasional track goer. But, really, I think we were thinking along similar lines.

Charles, if you were rewelding so often, was it just simpler and faster to maintain the car that way? Basically what I'm interested to know is if you did or why you did not enlist an enhanced support for the tubes?