Coilover question

[The Dude]

I am trying to 3 link + panhard the front of my HJ61 and have a few questions. I have read Bellavista's suspension and coil over FAQ and I am gathering data to plug into his formulas to get spring rates and ride heights etc. My goal is to have a great on road driving truck, a good crawler and can haul all our gear that sits relatively low on a set of 37"-39.5".

The problem seems to be that everybody sets their rigs up for super soft suspension and goofy long travel.

I am wanting a dual (or triple ) purpose rig that can do the overland travel, play in the rocks and be a decent daily driver to tow the boat to the lake.

The big one, my truck weighs in at 7500lbs moderately loaded. Should I be looking at 3" CO vs the 2.5" CO? My understanding is the rates are the same but the cooling and fade are affected the bigger you go. Not sure if this applicable to a non race truck?

How much up travel vs down travel and length of coil over does a guy really need. I know this is asked all the time but I have never been satisfied with the answers I see. I am not a buggy, nor am I going to follow one around at the rubicon, but I would like to hold my own. Well as much as a full bodied rig can.

Right now I have a frame height of 21" with 7" of space between axle and frame and about 5" of space between pumpkin and engine. This would safely give me 4.5" of up travel (two on air and 2.5 on air bump stops) I think this is OK.

My other issue that has me concerned is I only have 22" of room at ride height for the coil over. That would limit me to a 10" travel CO. Am I going to be disappointed with 4" up and 6" down???

and a few pictures.

Got links?

Evo joints for the frame end... If the poly bushings don't work out I will replace them with more EVO joints.

3 link calc. These numbers are close but not exact yet. I may have to move the upper link to the other side because of room. Any pitfalls of having the upper link on the oposite side of the pumpkin/drive shaft?

 

[Mace]

So, why are you going to link your front end? Are the stock leaf springs not acceptable?

 

[The Dude]

I didn't want to go back to a spring under and I couldn't get low enough with a SOA and stiff enough to carry the weight. And too be honest, I have never felt the springs up front where all that great on the road.

Offroad, the SOA was fantastic and I have no issues with it.

And I just don't like the ride of a flat spring. I have brought the truck down 7" in the front and 9" in the back. I didn't see how I was going to do that and keep the springs up front.

And I guess to see if I can.

 

[The Dude]

am I crazy?

 

[Mace]

Just know you are going to spend a lot of time and money designing a front suspension to do what you want it to.

Most suspension designs on off road trucks are a compromise in one way or another. Actually, limiting the suspension travel to <10" would be the BEST way to get it into the range you want.


I am curious tho, 21" to the bottom of the frame on 40" tires and a FJ60. Can you even open the rear doors?

I think I am more than that with my 60 on 35's and about a 2.5" lift.. I'll check over lunch.


But, for a low suspension travel linked front end. Look into a radius arm suspension.

 

[The Dude]

The 40" tires might be a dream. I am prepared to get the sawz all out if it comes to that and move the rear tire back.

Here it is sitting at planned ride height and my 37" pushed in close. 5" of space in the wheel wells. There rear is sitting at 22" as I like a bit of rake in my trucks. The plan is to cut off the bottom of the rear rocker and trim the front lower corner. If I have to go up an inch or to, that's not a show stopper.

and how it sat with all the armor off of it before bringing it in the garage. 28" to the frame in the front and 29" in the rear. To tall...

 

[Mace]

Just measured mine 20". With ome 2.5" lift springs in the front and super cut fenders. I still rub with 35's.

Say the 40" tire is actually 5" taller than my 35's. That means the axle will be 2.5" taller than I am currently right? So that would put my frame at 22.5" with just the 40" tires. You want to lower the truck another inch and a half. Consider how much my fenders (and the rear doors for that matter) have been cut and that even with fairly liberally cut fenders and a 2.5" lift, I rub 35's. 37's would rub all over the place. And the 40" tire will rub like a bad dog, in the front when you turned...

 

[The Dude]

yup, that's correct.

Except I have two things going for me. (well, maybe) I have a 2" body lift (I know, but it works and looks good) and I am running a 6" wider then stock axles. So go up another 1" (lets say I need to go to 22" so that's 2") Would you still rub 37" tire with another 4" of room?

[STRIKE]Did you trim in the back as well? You're running a 4 link back there right?[/STRIKE]

never mind. I had a brain fart and was thinking of a different rig. I found Bob's build thread and I am searching through all the chatta.

 

[Mace]

4" additional room would clear 37's easily. As long as you limited Up travel considerably. Yes the test has been trimmed a lot. Even the doors got trimmed.

Rear suspension is a wishbone three link. It does not have mad flex. But it does what I want it to.

For the best street manners\steering the easiest front suspension would be a radius arm.

 

[The Dude]

ya, but then i'm like an 80 series.. booo. I'll see how the 3 link works out and then go from there. I also have another rig to use stuff on if need be.

Do my numbers look OK on the 3 link calculator?

 

[Tapage]

Do my numbers look OK on the 3 link calculator?

yeap . ..

I can take some measurements on Tencha so you get an idea of the room you need for 40" .. but I got some of fender trimming front and rear and move my rear back to gain space against the rear door.

At your coilover question ..

IMOP

at least 12" so it worth the investment .. ( or I should say expenses .. ) you can still have long links but much higher coil rate so it will give you better on road ride and control .. sway bar will also help along with the right valving.

Vendors usually build coilovers medium light .. you must specify something more like medium to heavy as your CO valving.

Another thing it's you will need ( or at least I will consider ) it's cut the upper fender to open space for CO in the engine bay at least ..

I did some homework for CO in Tencha ..

 

[4WheelUnderground]

Stiff springs from the OEM's are kind of a band aid so they don’t have to take extra time to dial in a shock and sway bar system. Coilovers have enough fore thought in their design to allow for valving amply enough to control soft springs. That’s what makes them so awesome. You can have what you're asking, its what I’ve strived for too. I know most people only play with the spring rate and don’t take the time to open the shock and play with it, which is the "MOST" important.

My own vehicle has what Bella Vista calls a 1.107 spring frequency, which he says is the middle of the road for off and on road performance. Its a crazy soft spring according to most people, but after shock tuning I was totally surprised at how controlled the vehicle is in all conditions. AND NO SWAY BAR. Its the beauty of Coilovers, they're totally adjustable at a moments notice. If you're going wheelin for the day but not hauling anything, you can roll the dual rate stops up and get easier flex. If you're loading the back for an expedition or just filling her full of soil from the home improvement store, you simply roll those stops down to the bottom spring and you've then change your spring rate at ride height. Coilovers can be very powerfull if you know how to use them. Most guys dont.

As for 3.0" vs. 2.5". Personally I don’t think you need either since you're not racing and chances are you won't be traveling through the whoop sections at even 50mph. A 2.0 with a res is more than capable of doing the job you would need and then some. If you're not desiring crazy wheel travel, go with a 12" stroke. Also note, that larger diameter shocks tend to be longer for a give stroke then the 2.0" do. Which could hinder packaging.

 

[4WheelUnderground]

ya, but then i'm like an 80 series.. booo. I'll see how the 3 link works out and then go from there. I also have another rig to use stuff on if need be.

Do my numbers look OK on the 3 link calculator?

Your numbers look very good, I personally would lower the anti dive some. I like no more then 50%.

 

[The Dude]

Thanks Tapage. I think I can go to a much longer link in the bottom if needed. The tcase cross member gets in the way right now but that can be fixed. I am also planning to go up into the inner wheel well to fit the 12" CO.

4WU, I tend to agree with the valving of the shocks and one of the reasons to look at CO at the same time. Thanks for the info.

 

[4WheelUnderground]

I just noticed one thing on your calc sheet that really needs changing. The separation between the links at the axle and frame are not enough to handle the torque loads. You have about 4"s of separation at the axle, I would recommend no less then 6"s but still try to keep the same anti dive numbers or less.

 

[The Dude]

Does it matter witch side the 3rd link is on in relationship to the drive shaft/offset pumpkin?

 

[4WheelUnderground]

I've had mine on both sides, I've never been able to tell a difference when driving. Just go with which ever has the most room. I tend to put them on the opposite side of the exhaust.

 

[Tapage]

Thanks Tapage. I think I can go to a much longer link in the bottom if needed. The tcase cross member gets in the way right now but that can be fixed. I am also planning to go up into the inner wheel well to fit the 12" CO.

4WU, I tend to agree with the valving of the shocks and one of the reasons to look at CO at the same time. Thanks for the info.

Just take some measurements in Tencha.. frame horns ( front ) sits 29" same at belly and 32" and the end ( rear ) without any load on her .. ( usually when I'm out for any trip she leave home pretty leveled )

 

[The Dude]

I might just be back at those numbers! The panhard has got me a bit stumped. I got the suspension out of the front and I don't have as much room as I thought. Same goes for trying to get 6" of separation and keeping the antidive.

This link stuff is fun

 

[Tapage]

If you are ready to .. remove spring packs while keeping the front axle in position and with some tape put the links lines there so you can see how they will be in the space you have .. believe you gonna make lower link brackets under the frame and upper link at frame height in the inner side of the frame .. there is not that much space there ..