Radius Arm setup for mild Utah Wheeler...

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dieslcruisrhead

Registered User
Location
Park City & Heber City Utah
I know I'm over thinking this but thought I would post up anyway... I have the idea to maybe do a solid front axle (already:) ) on my new to me pickup. I would be down with it except I don't want 4" of lift (I want 2-3" if that) and my experience with leafs is they wheel awesome but rattle around like crazy on rough roads unless really beefed up... Maybe I'm wrong about this, I dunno...

So anyway, cross posted from Pirate:


This is on a new to me '89 Toyota pickup I acquired.. The idea for this truck is a light wheeler but mostly a daily drive and desert runner... I'm thinking of SFA swap already (imagine that)... I have some time in a mid 90's 80 series land cruiser. Stock setup on these is radius arms, traction/panhard bar, coil springs, drag link parallel with the panhard, and shocks are the spring limiters. With a set of 35's they haul ass and take bumps great, and seem to do everything well including wheeling... So I am thinking of mimicing this with this new truck.

Anywhoo, was curious on your thoughts about building a traditional coil spring (ie not coilovers) vehicle for the ultimate daily driver. And not a 3 or 4 link, as its a daily driver and light wheeler I do not need killer articulation and want to run a traditional steering setup... The 80 series Land Curiser have their draglink and the panhard very close to parallel as already mentioned, so there is little bump steer from this type of setup. I was also planning to mimic the same radius arm style setup, which is two bushings on the underside of the axle, no "Y" in the radius arm... I will use nice fat bushings for ease of binding... Tire size will probably be about 32" or 33" not a whole lot bigger... In theory I would be able to go 75-80 on decent dirt roads, but be able to stop, put in 4 low, and be able to wheel the max ability/difficulty that 32-33" tires can provide... Not too tall, about 3" of lift I figure...

The goal is to get the truck nice and low and handling really well, but still ahve the advantages of SFA/live axle. Curious on your comments on this...
 
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No problem with it, it'll work great. You'll get more articulation easier if you make longer radius arms, or extend stock 80 ones. (the longer they are, the less bushing deflection there will be for a given amount of flex) The tradeoff to that is you may have a configuration that has a lower-hanging radius arm.
 
I think the biggest factor with a low-height conversion is going to be the tight constraints to mount coils, control arms and a track-bar without picking up too much height or losing too much ground clearance. Doable but tight.
 
It only took me two years to get to it but here we go..


To the top for this old thread.. Again this is on a '91 pickup I am super psyched with how it turned out. I wasn't able to get it as low as I thought I would be able to (as of right now). I can easily control height of the coils with the adjustable height buckets. I set it at approximate height of about 4" of lift and with my frame that does not have accommodations/design for a live axle, unlike a 40 or 60, I was able to max out at 5" of uptravel before metal/metal contact. I cannot say for sure but I anticipate about the same with a 40/60 that it will take some lift but not tons...

Specs:

GM 1 ton tie rod ends and linkage from Luke at 4x4Labs. Luke bent the arms in a spring under type method but because the TREs come in from the top (and are huge) they are still pretty tall.

I used ballistic fabrication parts (coil buckets, etc) that I basically trimmed up to make work. I fabbed the brackets for the radius arms out of 3" strap. I intended to use .120 wall (1/8") DOM for the panhard and the drag link (because I didn't know how long I would need so I didn't get one of these from Luke) and bought GM TRE adapters from Ballistic and 3/4" heims with the matching rod ends for these as well. After I did this I found out 1/8th wall is too skimpy, it would work for the drag link but is probably too thin for the panhard even though I set it up so I would probably have no bending issues. Instead I went to Summit Machine (which is **awesome** and all sorts of neat stuff) and they sold me some 1/4" wall for about $11 a foot (I only needed 3'). I will use the .120 wall for the drag link now but have already ordered the right one that is about 1/4 wall from Luke though its also overkill and probably unneeded...

In all I'm pretty psyched with especially how it's turned out.. I have never had a 80 series and messed with its front axle, just wheeled with them and particularly in the rear was always impressed with the flex so I didn't realize how little they flex up front and why some folks have done 3 links & such... Because... They flex like shit with the bushings and that is OK particularly with a locker. I think it will work really well for the intended use of the truck but it took so long to set it up even with the radius arms (way longer than I had anticipated getting all the angles right) that if I were to do it again I would just link it 3 or 4 link it and call it quits.. So in that regard Kurt and others were right The cost difference and honestly the time difference would be so minimal that 3 or 4 link would probably be superior.

This said it is still a nice, durable match to my Old Man Emu rear springs from Cruiser Outfitters and I still think it is a good front suspension and again will match the setup well. I like how durable it appears to be and how it will handle on the road just like a OEM 80 series... And with a locker it will wheel well. I am planning on using the original length shocks that comes with OME in the rear (8") and 10" shocks in the front because the mounts are outboarded from their location in the rear so it will need a little more travel. I will probably set it to 4 or 4.5 inches of uptravel (I'm not sure if this will be too much with the coils) and about 6" of droop or so... Which I know the radius arms will have trouble reaching I believe...

Placement of the panhard was the most difficult aspect of it all besides the time consuming aspects but this is also because I set all of this up from scratch. I think a "kit" would still do pretty well and relocating the axle is very easy -- basically as difficult as moving the upper links at the end of the radius arms. So that is nice...

Here are photos...
 

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That looks great Andre, nice work! I really like how you used the 80 Series radius arms, I think you'll be very pleased with the ride on-road and control off-road that radius arms will give you. I also think you will be pleased at how well this setup will flex offroad, without the locker engaged. Between the coils in the front & OME leafs in the rear, I think it will work well.

Have you decided what coils to use? It will be interesting to see how you plan that out considering the reduced weight of a Toyota mini-truck vs. a 80.
 
The buckets are designed for 5" coil aka TJ which is great because the data and options are really wide as far as spring rates, lengths, etc. The 80 series Land Cruiser springs just happen to work. But when I started mocking everything up (and this was a doozie too) the Ballistic fab buckets stick the springs out to far. It took me a while to figure this out with lots and lots of measuring. They are basically designed for a wider Dana alxe of some sort. So I had to inboard them after some messing around, about a 1/2".

Before I figured this out I was really thankful that when looking at a set of stock 80 series springs they taper inwards to the bottom so, I kept thinking how awesome that was and how it would allow me to trim up the lower coil buckets for this. At one point I had the buckets right up to the steering arms at full inward clock so I was squeezing for every bit of room on the axle and trimming the buckets more and more from their original 5" diamter. But, at the end of the day the springs were too close to the tires so on flex they might rub and inboarding the adjustable height upper coil buckets was a saving grace.

So in short.. I now have room to run regular TJ springs again. Even with the metal removed from the lower coil buckets (see pics) it will take a 5" TJ spring just fine. So, it's designed so if these 80 series springs don't work I can switch them out very easily/quickly. But for now I'm going to try the 80 series springs. I'm also basically going to load the shit out of the front between all the extra metal, the heavier diesel engine (Mercedes OM617 turbo diesel out of a '82 300D) and the doubler, and with my M12000 winch (yes a M12000 on a mini truck) which is basicaly otherwise taking up room in my shop and I need a winch, and an ARB bull bar that hopefully the M12000 will easily adapt to and allow room for. And then, hopefully it will behave OK...

If not I'll start working towards TJ springs. I think the TJs are basically pretty similar to the mini truck up front as far as weight and general design/body. Kurt didn't see this but I really think it is the case particularly when they were heavy with the inline 6 cyls.

So we'll see..

Greg I think I'll end up agreeing about your comments there and I'm pretty psyched all in all, regardless. I really think it will work well and I'm psyched...

My #1 question right now is about how the coil springs behave and how much uptravel I'll need. The last thing I'd want is to slip off something and hit a bump stop with a hard bang. So I'm curious about 3" versus 4 to 4.5" of uptravel.. And if I'll max out 6" of droop with the radius arms. 6" of droop is actually a pretty good amount...
 
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the biggest reason why I don't like radius arm suspension is because you have no control over how much it brake-dives... (i.e. how much the front of your rig dives down when you slam the brakes) and that is why its un-useful on rear suspensions because you can't control the squat.. (i.e. how much your rear end sinks when ya hit the skinny pedal)
 
Chocflip201 said:
the biggest reason why I don't like radius arm suspension is because you have no control over how much it brake-dives... (i.e. how much the front of your rig dives down when you slam the brakes) and that is why its un-useful on rear suspensions because you can't control the squat.. (i.e. how much your rear end sinks when ya hit the skinny pedal)
Click to expand...

It's true you have no adjustment for the anti-dive, but it works out well since you end up with very little brake dive most of the time.
 
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