Active rear toe LImiter idea

[prove_it]

I know the jays racing rear toe eliminator works very well, and welding up the front bushing to make it solid works well too, but I've been looking for a cheap and quick idea of a limiting brace that reduces the overall amount to active toe. Well I got to thinking about using a sway bar link connected from the arm to the frame somehow. I figure if a sway bar link can handle vehicle roll weight, then it should be strong enough. I think I finally found links that might work. Its a front sway bar link from a 02 nissan pathfinder. In the pics I mocked it up where the original rack tie rod would mount. As far as mounting to the frame there are two bolts for rear abs wires that could be used to mount a bracket. In a second idea I put the link on top and the link will reach perfectly to the rear sway bar mount hole. I mean it lines up perfect. You would have to remove the bolt and drill it out to mount the stud for the link. By the way that's a 25mm rear sway bar, and it seems to clear everything by at least 1/2"

I haven't done this yet, as I'm looking to start a discussion on whether this is a useful idea or won't do much. I'm only coming up with this idea as a cheaper solution to the jays racing kit and a easier way than to weld up the arm. The links can be had for under $50 at any local store too.

Pics:

 

[EMX5636]

I was going to do something like that before I did the split washer trick from a long time ago. That's why some people say it's better to block the rack off, and leave it in, rather than pulling it out. I think your idea will work, but probably won't be any easier than just welding the washers on.

 

[prove_it]

Split washer trick?

 

[89Patches]

Ya where you would weld the toe eliminator in, you take a big washer cut in half then then just weld to the trailing arm.

Like so!

 

[EMX5636]

Thanks for the pic Patches. It's really simple like that. Some people say it limits movement because the bushing wasn't designed to take twisting forces with the washer welded in (with suspension travel), but TONS of people have done it, and mine didn't feel to bind at all with the coilover disconnected and me moving the arm up and down in it's normal travel.

 

[fuel]

I would be concerned the sway bar links are not adjustable as you would want some kind of adjustment to get the alignment bang on.

 

[belize1334]

The alignment is accomplished by pulling the trailing arm forward / backward using an eccentric bolt. The tie rod accommodates this because it has a ball-joint on each end and is mounted perpendicular to the trailing arm. If you look in the FSM you'll see that there is no need to adjust the rear steering rack when aligning the vehicle so the same would be true if replacing the rack with a simple tie-rod assembly.

As far as fabbing a brace, I've thought about this a fair bit too. In my opinion the most elegant solution is a threaded pipe with brackets welded on that simulates the shape and location of the original rear steering rack. It sits on top of the rear subframe and attaches exactly the same was as the original rear rack. You choose the diameter and length of the pipe so that it accommodates OEM front tie rod ends.

 

[prove_it]

Thought about that too. Ideally it's the best idea in this form of active toe delete.

I feel that the washer method isn't very solid as there is a chunk of the bushing hanging out inside. Seems like to me that over time it will flex at the washer and possibly break. I know a lot of people are doing that, but to me it seems iffy. I'd honestly like to keep the oem "active toe" bushing for noise reduction, but the active toe must go.

Now with the straight bar, I think the cost will be much more. But it's worth looking at. It would allow for the tie rods to be adjusted like a the manual says.

I'm trying to find a "budget" idea that more members could utilize. Something that could be a long term fix. Something that doesn't involve taking the whole rear end out and taking it to a welder. Some people DD these cars and don't have the luxury of multiple cars, and deep pockets.

 

[EHmotorsports]

I like the Idea Prove it. I am just curious as to how much tow adjustment the link will make during the suspension travel. I am sure for a street car it may not be an issue as we already have something in the back adjusting. and possibly noting big as its close to the pivot point of the arm.

 

[prove_it]

Right, and that's why I wanted to use the original tie rod hole. I don't think there will be much toe change under compression. I wanna fab up a quick mount and take it up to the alignment rack and play with it and see the suspension arc to find out if there is much change. In my picks the car is lowered 1" in the rear already. I'm getting some ideas for a bracket that will bolt on to the two abs wire mounts. They use M8 bolts so I would think that would be enough torque on the bracket to keep it in place. I really like the bracket idea because then this becomes a full bolt on mod.

I put in rear mustache bar bushings a noted a big difference so locking down the active toe really got me interested in getting it done.

 

[EMX5636]

Quoting prove_it:
I feel that the washer method isn't very solid as there is a chunk of the bushing hanging out inside. Seems like to me that over time it will flex at the washer and possibly break. I know a lot of people are doing that, but to me it seems iffy.



I can see why you would think that, but the other end of the active toe metal end is bolted in place with the vertical bolt in the trailing arm. The bushing just allows deflection at the end of the trailing arm. As long as the bolt is retained, and the weld decent on the washer, it's a permanent fix, and you still have the rubber bushing into the cradle to quiet noise and road vibration.

 

[belize1334]

Clarification: There are two bushings at the front of the trailing arm. One of them is incorporated into the mounting point and the other is inside the arm itself. The latter is what people eliminate when trying to get rid of active toe. But, the trailing arm needs to articulate in order for the wheel to travel properly through it's range of motion. That's the problem with the washer method. It doesn't allow any twist, which puts all the flexion in the front bushing and if you have poly bushings you'll get bind. The only way to eliminate active toe without getting bind is to replace the inner bushing with a sperical bearing (twist but now lateral movement) as with the JayRacing kit OR to use a tie rod to eliminate side-to-side travel while keeping the bushing in place. This allows twist and up-down flexion but not side-side flexion.

Regarding range of motion - Regardless of whether the tie rod attaches directly to the subframe or the chassis or a rack-replacement I don't see how the tie-rod method could have any negative effect of suspension travel. The changes in geometry in the front are minimal even at full droop / full compression. The tie rod basically won't move at all but it will pivot at the outer ball-joint, thereby allowing the trailing arm to twist, which is the point.

 

[prove_it]

Good info. This is why I posted the idea. I'm not an engineer so getting posts like that really help. What I would like to figure out is an estimated amount of force applied across the tie rod. I'm thinking it will handle the stress just fine, but wanna make sure the idea is fully sound before attempting.

 

[belize1334]

Well, if the max lateral acceleration is 1 G, then the side-load on the whole wheel assembly is gonna be about 1200 lbs with all the weight on the outside wheel. Most of that is going to go onto the control arms, which are located almost, but not exactly, inboard of the contact patch. Let's say that they are an inch behind the contact patch, which is an overestimate. The trailing arm is about 2 feet long so at most the tie rod would see 60lbs during heavy cornering. Not much, but plenty to deflect the bushing (if you push on it with your hand you'll see it doesn't take much). But, much more importantly, the bushing also sees lateral forces during vehicle acceleration. Launch will be the biggest effect. Let's say you're traction limited again, with a heavy launch where all the weight is on the back wheels (an extreme example). That means each wheel is generating 1500lbs of thrust. The control arms don't allow the wheel to move left right but it can pivot as the front bushing is deflected. The ball joints for the rear control arm are roughly even with the inside edge of the tires, so 5 inches inboard of the contact patch center. The torque about this point created by the thrust is 7500lb-inch. This has to be countered by the front attachment of the trailing arm, which as we estimated is 24 inches long, so the lateral force on the front bushing is maybe 300lbs. That means that if a big heavy guy could hang from the bracket without stressing it then you're good to go. For safety, make it twice that strong and it'll never break.

Another way to look at it is to reverse engineer based on the design of the original steering rack, which was built to handle this exact stress. Clearly ball joints aren't the week point, it'll be the mounting bracket or the spot that the ball joints attach to. The original rack had tabs that were bolted to the subframe with m10(?) bolts? So if you use a bracket it should be of the same strength or higher. If you're drilling a hole to attach a ball joint then make sure that the material is at least as thick as where the ball-joint attaches to the trailing arm.

 

[prove_it]

/ubbthreads/images/graemlins/applause.gif Well done. So yea I suppose tie rods should take the beating. Seeing how they support side to side sway of a 4000lb truck.

 

[SSGdave]

Quoting prove_it:
Right, and that's why I wanted to use the original tie rod hole. I don't think there will be much toe change under compression. I wanna fab up a quick mount and take it up to the alignment rack and play with it and see the suspension arc to find out if there is much change. In my picks the car is lowered 1" in the rear already. I'm getting some ideas for a bracket that will bolt on to the two abs wire mounts. They use M8 bolts so I would think that would be enough torque on the bracket to keep it in place. I really like the bracket idea because then this becomes a full bolt on mod.




I Like your Thinking, you have my attention sir.

 

[vr4play]

Quoting belize1334:
The alignment is accomplished by pulling the trailing arm forward / backward using an eccentric bolt. The tie rod accommodates this because it has a ball-joint on each end and is mounted perpendicular to the trailing arm. If you look in the FSM you'll see that there is no need to adjust the rear steering rack when aligning the vehicle so the same would be true if replacing the rack with a simple tie-rod assembly.



This is wrong. If you read how to do the rear alignment on one of these vehicles you will see that you must disconnect the rear tie rod from the trailing arm, adjust the rear toe, and then adjust the tie rod to fit back into the hole without changing the rear toe. You would need to be able to adjust your link if you want this to work without putting unwanted forces on parts back there. All you would need to do is cut the link and use a LH and a RH die to thread the link and put a piece of hex stock that has been internally threaded in place with some lock nuts. Problem solved. That is how we make adjustable links for race cars to eliminate sway bar pre-load.

 

[marvinmadman]

^ correct

 

[prove_it]

Quoting vr4play:
Quoting belize1334:
The alignment is accomplished by pulling the trailing arm forward / backward using an eccentric bolt. The tie rod accommodates this because it has a ball-joint on each end and is mounted perpendicular to the trailing arm. If you look in the FSM you'll see that there is no need to adjust the rear steering rack when aligning the vehicle so the same would be true if replacing the rack with a simple tie-rod assembly.



This is wrong. If you read how to do the rear alignment on one of these vehicles you will see that you must disconnect the rear tie rod from the trailing arm, adjust the rear toe, and then adjust the tie rod to fit back into the hole without changing the rear toe. You would need to be able to adjust your link if you want this to work without putting unwanted forces on parts back there. All you would need to do is cut the link and use a LH and a RH die to thread the link and put a piece of hex stock that has been internally threaded in place with some lock nuts. Problem solved. That is how we make adjustable links for race cars to eliminate sway bar pre-load.




You can still set the toe with the link being solid. I do see your point about pre-loading the link. You did mention the word racecar too. I think locking in the rear active toe will make a bigger difference than having one side more loaded than the other. You could if you wanted to thread them, but I don't think that it is necessary for a dd car. It could help the joints last longer, perhaps.

 

[belize1334]

Although having them threaded and read to go would allow for inconsistencies in individual vehicle geometry. How about a "kit" that involves two front outer tie-rod ends and a threaded rod to go between them. They'd both be right hand thread so adjustment would be limited to increments of a single turn, but that's still 1/16" precision or so...