Custom A Arm Question

[Jetboy]

First: Hello from a newb. Been a Land Cruiser guy for a while. Just bought a '15 TEP to replace my 3rd gen 4runner.

I already have an FJ40 on 39's with lockers, winch, 1300 rti, etc. No need for a "hardcore" build on my daily driver. But I see a lot of issues with the front body mount and tire fitment. The 5th gen is 1000lbs heavier than my 3rd gen and obviously with the same tires, a lot less capable offroad due to the weight alone. So I've been thinking about a solution that doesn't require a huge lift for some reasonably equivalent size/weight tires. I'd like to keep the driving dynamics as close to stock as possible.

This is probably just day dreaming at this point as I'm at least a year or two from getting the itch to start cutting on my new 4runner. For now it's just going to be sliders and a hidden winch.

That said, this is the idea: custom front a-arms that relocate the front wheels forward approximately 2". Combined with a 2" lift, this should provide room for ~35" tires, maybe 37's with some trimming. Of course you'd need to cut up the front bumper and what I'd do is remove the fender flare, and make a custom one that is the same profile but 3-4" longer to make a factor look wheel well that's just longer. Same for the rear, possibly moving the rear axle aft 2" as well, but maybe just opening up the rear wheel well on both sides.

The biggest issue I see is moving the front diff forward 2". I think there is room with a bit of modification to the front cross member. Since it's fixed relative to the transfer case output, a milled spacer should work just fine for the driveline extension. And of course I'd want to move the steering rack forward as well.

This would allow us to keep the KDSS - which I would not want to remove, keep the ride height reasonable, and fit some bigger tires to help offset the big weight gain. I think it could all be done for around the same cost as some of the higher end lift kits.

Thoughts?

 

[1engineer]

Sounds feasible bit I am missing the correlation between heavier and big tires to offset this obese condition.

 

[Jetboy]

The offset is about the ground pressure. In my experience ground pressure is the single best predictor of overall offroad performance. And there's no reason to put a big lift on if you don't need it for larger tires or more travel. It makes most things worse, not better offroad and on road. For my use, I'd much rather have no lift, 2" forward movement and 34's than a 3" lift and 33's. The axle cv angles should be less stressed, the clearance greater, and all around performance should be better in most situations.

Here's a very quick and dirty photoshop of what it would look like with 3" fender well widening 2" forward and aft axle movement and 37's and 3" lift.

Also thanks for the pic to whoever's white T4R I used. It was the first one Google came up with that was the right profile to make photoshop easy.

For comparison to stock form:

 

[1engineer]

Understood. Contact patch calculations? You might need to factor in the cost of regearing to 4.56.
With that said it would be a very cool mod. I take it this is not your first rodeo lol. Good luck and this mod might just edge out all those "build" threads people recently started to show off their floor mats and window tint! Make sure to post up when you start getting ideas together. There are some seriously talented guys here.

 

[Jetboy]

I'm mostly just spitballing right now. I'd like to have it paid off before I start cutting out cross members. . The main reason I started thinking about this was that I see a lot of the lifts replacing the upper a-arms. And the tire fitment is limited by the body mount more so than lift height, so I thought this might be a different solution that could also be cost competitive. If you're doing the uppers, why not just do the lowers too and solve the body mount issue? The rear is pretty easy.

Or it could be a mild solution, where you'd just go with a 1" forward relocation, no lift or maybe 1", clearance should be good for 34" tires and those would fit in the rear with minimal lift. I think in this scenario no relocation of the front diff would be necessary and I think it could look pretty nice as well. This could probably be done for the maybe $1500? Not sure what custom a-arms would cost. IFS is something I've never re-engineered before. My last IFS truck I just cut it out and replaced with a solid axle. I can fab my own a-arms, but it'd be nice to have the volume like a manufacturer would do to get them cast aluminum and spend the time to do a full cad drawing set to workout any geometry quirks so it's a fully engineered plug and play setup. I'm just not sure I'd have the time to spend on it and hate to admit it, but I'd probably just throw a set together and see how it drives. Could make a huge mess out of the handling, by going this route though.

 

[BlackWorksInc]

Keep in mind that you're going to change the suspension geometry as well as the steering geometry as you will have to locate the lower ball joint forward to make this work, thus creating a lot of positive camber. This in turn will pull the tie rods forward and stress them more (the J120 & J150 platforms have a circular hole that the arms go through which is part of the structural part of the frame so you can't just push the rack further forward.) Honestly to move the ball joint forward 2" is going to be a lot of work and engineering to make sure everything fits/works correctly, even before you start adding in a lift kit and non-factory tires. That's if you can even use the factory spindles in that application, then you need to think about the leverage forces of the steering rack on the new geometry and if that will cause excessive stress on the power steering rack, ect. You're probably looking more realistically as more like .5~1" to maintain an acceptable amount of flex/stress on the steering and suspension components, otherwise you're pretty much redesigning the front suspension.

 

[gm350reratliff]

While I'm sure it could be done, I'm thinking it would be a huge undertaking. You would need both upper and lower control arms in order to somewhat maintain alignment. The tie rod ends may be another can of worms though due to the forward angle the control arms would cause. You would have to also relocate the steering rack in order to get around that. That would be a huge mod to the frame which may not be worth it at that point.

I'm guessing it would be easier to completely cut and move the offending body mount and sheet metal.

 

[Jetboy]

I'm not sure I follow on the camber problem. If both upper and lower a-arms are replaced moving the ball joints forward by say 2", how does that add to the camber? Do they need to be relocated laterally also?

I think the steering is a tricky issue. I have no problem modifying frames or structural cross members on my own junk - I've actually cut the cross member out and modified it in my land cruiser for the steering shaft, but I don't think most weekend mechanics want to take a plasma cutter to the frame of a $40K suv... yet. So - that leaves the option of either custom spindle or a bolt on steering arm bracket to re-locate. Then you'd have to sort out the ackerman angles. Life is a whole lot easier with racks that live behind the axle.

 

[marshal]

i did quite a bit of figuring with a similar thought process. it would be financially cheaper to do a SAS on it than to go through the efforts of shifting the entire front suspension and driveline forward.

 

[Jeremy556]

I'm not sure I follow on the camber problem

Think he meant to say caster.

If you want to fit 34s, you can do so by cutting the body mount and using commonly available aftermarket UCAs.

 

[bimrunner]

I think a small lift, a arms and 34s will get you there. You can prob do it at a 2" lift and some serious trimming. It will give you room for up travel and look right and get you some clearance.

 

[Jetboy]

So I took a pretty good look underneath and 2" shouldn't be a problem. More than enough room for steering rack to move. The Diff shouldn't need to move for 2" of forward relocation, but I think I could squeeze it with maybe just some brackets and a machined spacer for the drive shaft. The only other issue is that the steering may interfere with the stock placement of the shock shaft. So a new set tabs on the lower a-arm to relocate may be necessary. I think I'd probably just use a set of factor lower a-arms and modify them with an offset. They are well built and well engineered, no reason to reinvent the wheel.

This should be a lot more functional than the current crop of basic lift kits. I think I may need to make this happen this summer when I get some time.