Modern Motorsports Adjustable LCAs

[RebekahsZ]

I am strongly considering buying a set of Modern Motorsports Adjustable LCAs. Ross replied to my email inquiry promptly (in less than one day); he has several sets in stock in the warehouse to be shipped, but he can't get to them to measure them for me because the warehouse is far away from from his office, maybe even a different country(?). Anyway, what I need from somebody who has already bought these, is an estimate of the range of adjustment. 2 specific questions:

 

1) what do you estimate the minimum and maximum possible lengths of these control arms, measuring center of outboard bushing to center of inboard bushing. I have attached a photo of my stock measurements.

 

2) how do you adjust these? Do you have to remove the spindle pin every time you want to adjust the length on these? How easy is it to adjust them once they are on the car?

 

This is a follow-up thread to one I started last week. The up-close photos exaggerate the angle of camber and the distant photo under-represents the amount of camber a bit. I included these to show that I'm not totally slamming the car like a low-rider-my LCAs are not even flat. My Wolf Creek axles have 3/4" to 1" remaining end-slack-it was easy to estimate-I just grabbed them and pulled back and forth; I don't think I'll have any problem bottoming them out if I shorten the LCA a bit. If I can pull the bottom of the tire in a bit, I may be able to kick the top back out a notch. I have looked at the TechnoToys LCAs and the old tubular Arizona Z LCAs (which are no longer in production-maybe?), and I don't think they have the range available to be shortened. I have a lead on a nice set of stock LCAs that I could shorten, but I'm afraid I'll over/under do it.

 

Thanks-Keith

Edited December 28, 2011 by RebekahsZ

[BrandenZ]

Hey Keith -- I can't answer your specific questions, but why rear LCAs instead of camber plates?

 

You've probably read this thread 10x over like I have, but it's been more or less my deciding factor in leaning towards the plates instead:

http://forums.hybridz.org/index.php/topic/54771-adjustable-control-arm-lca-lower-control-arm-faq/

 

Most specifically:

"adjusting the camber with the control arm in the rear is not a very convenient way to go. If one is using the on the car adjustable arms, the adjusters have to be turned out exactly the same amount front and rear in order to prevent a toe change. If one is not using an on the car adjustable arm, then the rod ends can be turned out x number of turns front and back, but in order to make an adjustment the spindle pin has to be removed to make the adjustment. In addition, some rear control arms have either the front or rear rod end on the car adjustable for toe, but not the other one. In that case the spindle pin would need to be pulled to make and adjustment AND the toe would need to be reset afterwards. Camber plates are a much better way of adjusting camber than adjustable rear control arms."

 

Again, it's probably information you're already aware of, so apologies for cluttering your thread if so, but wanted to make sure you didn't overlook it.

[johnc]

The stock Datsun rear LCA is very close to 14.5" center to center. IRRC, the range of adjustment on the MM rod ends is 3" although as you adjust them inward you'll have to cut off some of the threaded ends. These arms have the largest range of adjustment that I've seen, although I haven't worked with AZC's latest design.

[JMortensen]

http://www.modern-motorsports.com/catalog/mm_gallery.php?album=2005+Modern+Motorsports+Prototype+Control+Arms+Proven%2F&pic=IMG_3647.jpg

 

The way these adjust is by loosening the jam nuts and moving the rod end, then tightening the jam nuts again. What I don't know is if the rod end screws into the arm, or if it just slides in and is captured on each end by the jam nuts. I think it just slides, because if it screwed in you wouldn't need the jam nuts on both sides. This particular arm is on the car adjustable and you wouldn't have to remove the spindle pin to change the track, but you might have to cut the end off of the front rod end if it was too long and interfered with the control arm as John mentioned. Doesn't look like there is much room there.

 

The bad part about this arm IMO is that it has a LOT of threads in bending, and it uses rubber outer bushings. The threaded section is pretty huge IIRC, like 7/8" so that makes it stronger, but still not my favorite design.

 

Camber plate is a better way to do what you're trying to do IMO.

[johnc]

I don't think there's much bending load on the ends of the LCA. It takes mostly lateral (compression, tension) loads. There are some bending loads from acceleration and braking but most of those are probably tension compression also and the LCA tries to pivot forward and back. Vertical loads are taken by the strut and spring.

[Leon]

I don't think there's much bending load on the ends of the LCA. It takes mostly lateral (compression, tension) loads. There are some bending loads from acceleration and braking but most of those are probably tension compression also and the LCA tries to pivot forward and back. Vertical loads are taken by the strut and spring.

 

That's exactly what I was going to say, so I'll just second that statement. Acceleration will add bending loads but those threads are pretty beefy, and I wouldn't worry about it unless you were running a ton of power (even then you're probably ok). Braking loads should be much less significant since the front end takes up most of that.

 

It's not a bad arm design, and although the rubber bushings do introduce some (possibly unwanted) ride compliance, I wouldn't consider that a deal-breaker.

Edited December 28, 2011 by Leon

[RebekahsZ]

Thank you all so very much for your advice. I'm going to follow this thread hoping someone can put a tape measure to their LCAs. Johnc, 14.5" is what I got on my stock LCAs, too. JMortensen, I hope you are right about the arm NOT being threaded, because if it is, the spindle will have to come out to adjust. Brandon, I already have camber plates-I'm working around a bunch of conflicting issues to get my tires to clear my unrolled fenders. I would roll my fenders, but they have been cut and spliced together and I don't think they would roll correctly. I wish I had a ratsun so I wouldn't worry so much about my paint job, but I have really nice paint and I truly regret not fixing my fenders before having it painted. If I didn't have stock fenders, I wouldn't have this issue at all. Over the years, my goals for this car have changed. First it was to look good, then it was to handle as an L24 autocross car; now it is to drag and autocross with an LS2. Compromise is the enemy of excellence, but I have to make a lot of compromises. I'm going to order a set of the MM LCAs and I'll give a report back in a couple of months. If anybody has a used set, I'm in the market; I'll put a parts wanted thread in and see if anybody bites before ordering new. The LCAs and an R200 LSD are competing for the same pot of money.

[Leon]

Thank you all so very much for your advice. I'm going to follow this thread hoping someone can put a tape measure to their LCAs. Johnc, 14.5" is what I got on my stock LCAs, too. JMortensen, I hope you are right about the arm NOT being threaded, because if it is, the spindle will have to come out to adjust. Brandon, I already have camber plates-I'm working around a bunch of conflicting issues to get my tires to clear my unrolled fenders. I would roll my fenders, but they have been cut and spliced together and I don't think they would roll correctly. I wish I had a ratsun so I wouldn't worry so much about my paint job, but I have really nice paint and I truly regret not fixing my fenders before having it painted. If I didn't have stock fenders, I wouldn't have this issue at all. Over the years, my goals for this car have changed. First it was to look good, then it was to handle as an L24 autocross car; now it is to drag and autocross with an LS2. Compromise is the enemy of excellence, but I have to make a lot of compromises. I'm going to order a set of the MM LCAs and I'll give a report back in a couple of months. If anybody has a used set, I'm in the market; I'll put a parts wanted thread in and see if anybody bites before ordering new. The LCAs and an R200 LSD are competing for the same pot of money.

 

I'm 99.9% sure that the arm is not threaded, since it's slotted and as Jon points out, there are jamb nuts on both ends.

[johnc]

Its not threaded.

[johnc]

For drag racing a little compliance could be the difference between a hard launch and breaking loose.

[RebekahsZ]

Great. Thanks Leon, that is reassuring-I have ordered a spindle pin puller, but I don't want to use it very often. JMortensen, I'm not worried about the fact that the outer bushings are rubber instead of poly. Honestly, there is not that much rubber in the outer bushings to start with if you figure there is the metal casing and a metal tube that the spindle pin goes thru. That leaves very little room for either rubber or poly-I can't imagine there is much deflection either way. Thread for a used set posted. LSD I was chasing sold to someone else. If nobody bites on used add, I'll order a new set at week's end. Decision made, thanks everybody, I'll post my results. Ordering a camber gauge too, so I can speak intelligently and compare apples to apples. I have a toe gauge, but I will only use it for mock-ups and will still have an alignment shop double check my track measurements and my final toe using bearing plates, etc.

Edited December 28, 2011 by RebekahsZ

[RebekahsZ]

So, johnc, are you in favor of a little compliance, or against it? I'm just going to the track to have fun, I'm not trying to win a national championship-I got a non-automotive day job. I'm finding there are three basic categories of forum members: 1) tire-kicking, bench-racing, critics and hackjobs who need to wear a belt more often; 2) guys who are building sweet driving machines while balancing priorities of family and a steady job; and 3) the pros. I'm in category #2. I really appreciate the advice I've gotten on this thread-it seems to be all from categories #2 and #3, and none from category #1 for a change. Thanks, guys.

[JMortensen]

I don't think there's much bending load on the ends of the LCA. It takes mostly lateral (compression, tension) loads. There are some bending loads from acceleration and braking but most of those are probably tension compression also and the LCA tries to pivot forward and back. Vertical loads are taken by the strut and spring.

STB puts bending loads into the rod ends. Apparently a big front bar was enough to snap Pete's front control arms, and 7/8" rear bars aren't that uncommon on Zs. Brings to mind the failures that Dave Kipperman had on his chromoly AZC arms. Different arms, I know, but they still broke at the arm where the nut was welded on. IIRC, he fixed one side and then the other side broke. Shouldn't have happened were there no load there.

Edited December 28, 2011 by JMortensen

[Leon]

STB puts bending loads into the rod ends. Apparently a big front bar was enough to snap Pete's front control arms, and 7/8" rear bars aren't that uncommon on Zs. Brings to mind the failures that Dave Kipperman had on his chromoly AZC arms. Different arms, I know, but they still broke at the arm where the nut was welded on. IIRC, he fixed one side and then the other side broke. Shouldn't have happened were there no load there.

 

I think Jon means ARB?

 

This is true, but considering that rear bars are smaller than fronts and the rear LCA has 2 rod ends (as opposed to 1 on the front LCA), I think it's OK.

[johnc]

STB puts bending loads into the rod ends. Apparently a big front bar was enough to snap Pete's front control arms, and 7/8" rear bars aren't that uncommon on Zs. Brings to mind the failures that Dave Kipperman had on his chromoly AZC arms. Different arms, I know, but they still broke at the arm where the nut was welded on. IIRC, he fixed one side and then the other side broke. Shouldn't have happened were there no load there.

 

Never said there was no bending load. Just not much compared to all the other loads going into the arm. Also, those 7/8" bars have longer arms then the rear mounted 3/4" bars. Pretty much the same load at the LCA for either bar. The 7/8" bar with 14" arms generates about 150.5 lbs per 5 degree of twist and the 3/4" bar with 12" arms generates about 150 lbs per 5 degrees of twist.

 

And I've repaired four of those old style AZC arms. They would have failed in that exact spot even if there was zero bending load on the arm. Poor design, material selection, prep, and welding. Three of the four arms I worked on were ERW tubing.

[JMortensen]

I think Jon means ARB?

Yes. Brain fart.

 

This is true, but considering that rear bars are smaller than fronts and the rear LCA has 2 rod ends (as opposed to 1 on the front LCA), I think it's OK.

The point here was not that the rod end failed, because they didn't. The point was that the arm itself failed and that is an indicator that there vertical loads imparted onto the control arm. Now you could say that MM's design looks much more stout and is better built than AZC's, and I can't really disagree with that. It's still 3" or so of threads in bending, which is the part that I have trouble with.

 

Poor design, material selection, prep, and welding. Three of the four arms I worked on were ERW tubing.

ERW cromoly tubing? They make such a thing?

[deja]

Do any of you have any experience with Techno Toys version of these? Techno Toys

[luseboy]

This is a pretty interesting thread. Usually most people are interested in adding negative camber. It seems to me that camber plates would solve this problem much better than adjustable lca's. I personally plan to run the techno toy LCA's front and rear to induce negative camber (around -2 degrees), but I will be using ZG flares, so that's a little different. You say you're already using camber plates, well make sure you have them set as inward as realistic first, then tell us what difference it makes. Better to try and make what you have work than throwing parts at it. You could also probably get away with a slightly thinner tire, looks like the next size down would be just fine. But either way, camber plates are going to do the trick here, because that will acctually pull the top of the strut tube, and the top of the wheel inward instead of pulling the bottom inward. Also, what offset are your wheels? That could very well be the problem, and if you're running spacers, take 'em out!!

[74_5.0L_Z]

It sounds like she is trying to fit the largest tire under the rear of her car without getting carried away with negative camber. Too much negative camber hurts forward traction. I went through the same issues trying to fit 275/35-15 Hoosiers under my SubtleZ rear fenders.

 

In the end, I had to use 15x10 wheels with a 5.5 inch backspace, shorten my control arms to 14.25 inches, and max out my camber plates (toward positive camber).

 

One issue that you have to watch when trying to shorten your lower control arms is bottoming of the CV axles.

[johnc]

 

ERW cromoly tubing? They make such a thing?

 

Not that I'm aware of. But there was a nice protruding seam inside the tube(s) when I did the repairs.