Hummer h3 weight for spring rate

[atvspeed4]

So I am in the early stages of figuring out a possible coilover conversion for my h3 and was wondering if anyone had the approximate corner weight of their rig. Maybe Bebe might have hers from when she swapped to coilovers and had to figure out spring weight? I know it will vary with equipment installed but just trying to get an idea

 

[Hunner]

Are you taking each corner or curb weight?
A fully loaded and equipped H3 can hit 6001 lbs fairly quickly even with judicial packing. Which I believe is gross max.
Then as you probably know varying amounts of weight will affect the ride of whatever rate springs you decide are "average".

 

[atvspeed4]

Are you taking each corner or curb weight?
A fully loaded and equipped H3 can hit 6001 lbs fairly quickly even with judicial packing. Which I believe is gross max.
Then as you probably know varying amounts of weight will affect the ride of whatever rate springs you decide are "average".

Wow I forgot how heavy our rigs can get. To answer your question I am hoping from front driverside and passenger side corner. Thanks!

 

[4speedfunk]

I can't help you on the coil-over info, although I had the same question...What spring-rate should I get? I assume you're talking about an IFS, in which case you should probably ask Bebe. If you're talking about a SA, then ReconH3 would be the guy. You might also try some of the Colorado/Canyon guys on 355Nation.

I did traditional separate coil / shock arrangement on mine and I chose 2nd-gen Bronco (71-77?) +4" over stock springs. This was based purely on a guess at nose weight. I also think that +4" over JK springs would work well too, as its a similar size & weight. Its probably safe to say that whatever coil-overs the JK guys run...would be a good starting point. I have no real "numbers" on this...only hunches. Also I'm sure there is a difference between IFS spring weight and SA spring weight but, there again I don't know enough about it to add anything.

I would be a bit reluctant to simply pull the torsion bars off and bolt-on some coil-overs. The factory shock mounts are probably not suitable for supporting the weight of the truck, so I think welding-on beefier ones or hoops would be a good idea. Remember...a stock H3 supports its own nose off a cross-member five feet astern of the front axle. Because of this, the frame rails might not be as "beefy" as a normal truck that was designed to have coils, leafs, or struts. And even though the upper & lower A-arms are suspended off them...the frame rails don't carry any weight. That's accounted for back at the torsion crossmember. So when you convert to a type of spring that pushes directly upward near the front wheels...make sure you add some beef.

 

[atvspeed4]

Thanks

You are correct there is a totally different way to calculate spring rate of a coilover for ifs. Only piece to the equation I am missing is the corner weight of the h3.

 

[06 H3]

I thought bebe was in the 600s for spring rate?

JKs that come from offroad evolution are running dual rate coilovers and iirc they are in the 200-300s.

 

[06 H3]

CJ which crossmember holds all the weight for me? The crossmember with rancho emblem on it or the one the axle is bolted too?

If its the rancho one that scares me to be notching it for bolt clearance on the steering rack issue

 

[Former User]

So coilover's are for the IFS? I've had this idea rattling around in my brain for some time now. 4speed stated some good info however even if you wanted to retain the upper a-arm mount i don't think it's possible. It doesn't look like you could clear a coil over with the geometry of the factory upper a-arm. At least not that i can see. What are your thoughts? Custom upper and lower a-arms, custom upper a-arm mount/strut mount? Reinforce the frame under the firewall? Would love to get rid of the torsion bar set up but when ever i think that word custom & ifs suspension i think lots of money. Seems like it would be easier, more reliable, and most likely cheaper to link a d44 on coil overs, and set it up so it sits even with a sprung over rear. But then again i'd most likely take a "mid travel" ifs coilover setup over that just for the DD advantages. I once had a dream that ford raptor ifs stuff bolted right up and i was running king coilovers. It was awesome.

 

[Hunner]

Remember I revived this old thread from before.
http://www.hummer4x4offroad.com/for...-Outfit-Armor-Tools-and-Spare-parts-and-Weigh
I might have time tomorrow to get you the weight of the corners. I was over at the shop today but may go again in the morning. I can use some portable wheel scales and the alignment rack to place them. Not sure if I have time but if that will help in my street mode I will try.
That's how we set up the race cars.

 

[atvspeed4]

#1 that thread reminds me that I really want to learn to sail someday!

#2 6600lbs??!! Wow that's a well equipped rig haha

That would be great if you have a chance. If its too much work or not enough time, no worries I appreciate the offer.

 

[MTUH3]

This is one of the things I was going to pick the brain of the Icon guys this weekend. See what their thoughts are. Reinforcing the upper shock mount will be a must. I am also going to as about getting upper control arms with serviceable ball joiunts

 

[4speedfunk]

CJ which crossmember holds all the weight for me? The crossmember with rancho emblem on it or the one the axle is bolted too?

Neither. Go five-feet rearward. Its the crossmember that the torsion bars plug into. This crossmember takes all of the "spring load" for supporting the front of the truck. If you crawl under a stock H3...you can see that the torsion bars plug-into hex-shaped receivers that are cast into the lower A-arms. This is where the corner weight (upward force pushing on the A-arms) essentially gets intercepted...converted to torsion...then sent rearward to the crossmember. The result is...the front frame rails don't actually support the weight of the truck. Theoretically, they simply provide a nice firm structure for the A-arms to pivot from, and of course to cradle the motor.

In reality...the H3's nose weight does rest somewhat on the bumpstops, so there is some "sharing" of the load especially during a bottom-out situation. But, those of us that have cranked the T-bars to where the stops are no longer touching...are riding solely on the torsion crossmember. So, its a complicated way of suspending a truck for sure.

When you get rid of the torsion bars and convert to coil-overs...you're essentially moving the "twisting spring load" from this crossmember, and applying a "direct upward linear load" to the frame rails. The weird thing is...your corner weight doesn't change. Each tire is still pressing down with the same amount. The A-arms would still work in the same fashion and still see the same basic load. The difference is...you're no longer using that interception point (the hex-shaped receivers) and sending the weight of the vehicle (along the torsion bars) rearward. Instead you are transferring the weight vertically, directly to the frame rails (along the shaft of the coil-over). All we're really talking about is: WHAT PART OF THE TRUCK IS RESPONSIBLE FOR SUPPORTING THE NOSE WEIGHT?

This same scenario would apply regardless of the spring type (coil-overs, coils, or leafs), and also applies to SA rigs. Leaf spring rigs have the advantage of spreading the total nose weight out over 4-points along the frame, however these can sometimes be out on the end of a lever. Coils and coil-overs will put the nose weight on 2-points so its critical that you get those points reinforced to take the load.

 

[06 H3]

why are you so smart? hahaha

or maybe I am just stupid...:giggle:

 

[atvspeed4]

I understand the concept of what you are saying about the torsion bar supporting the weight by the crossmember but if you ever have bottomed out (especially hard) on the bump stops you have exceeded the ability of the torsionbar to support the weight/ force of the vehicle and the frame rails/ bumpstop mount is now "supporting" the weight of the vehicle.

 

[bebe]

IIRC the front was roughly 1600lbs per corner and the rear 1300 lbs per corner.

My coils are 650/750 and I may go 750/850 at some point.

 

[atvspeed4]

IIRC the front was roughly 1600lbs per corner and the rear 1300 lbs per corner.

My coils are 650/750 and I may go 750/850 at some point.

Thanks!!

 

[bebe]

Now, most folks can calculate spring rates for SA all day long. But for IFS it's entirely different. When I was trying to research I found nothing - NADA. No one wanted to share their Calculations.

I called Mike Shaffer at Shaffer Offroad (he built many Baja racers , jeepspeed etc) and is a friend.

His advice - "Whatever you think it is....double it".

So we went with a JK spring rate. Thank god for Tommy at Poly, we had to triple it.

We went through 3 different rate and length combinations before we went for the big guns.

 

[4speedfunk]

I believe there are also factors for "leaning" your coil-overs. The rates are based on a truly linear (straight up & down) motion. If you mount the shocks with the tops shifted rearward or inboard (as is common)...it can change the performance and rate. Also in an IFS...the lower shock mount will travel in the arc of the A-arm's motion, so its angle can change over the range of travel.

This gives me a headache. I can see how calculating all this could get into "Stephen Hawking" land.

 

[atvspeed4]

Lol as I said I am in the early stages of calculating this. Truth of the matter is I have been told by some much more experienced then I am that the math only will give you a base line then reality sets in.

 

[bebe]

I brought in so many people - in the end - we had to experiment. So take it as I have laid it out - 650/750 to 750/850. There is not much room for shocks, so besides my build SamcoFab's Damien Michelin build is your only other option. Sam and I have discussed this at length.

 

[06 H3]

How does Sam pull 8in of travel in a stock setup? I remember seeing that on race dezert

 

[bebe]

How does Sam pull 8in of travel in a stock setup? I remember seeing that on race dezert

http://samcofabrication.com/projects/v/projects/michelinh3/

 

[bebe]

I believe there are also factors for "leaning" your coil-overs. The rates are based on a truly linear (straight up & down) motion. If you mount the shocks with the tops shifted rearward or inboard (as is common)...it can change the performance and rate. Also in an IFS...the lower shock mount will travel in the arc of the A-arm's motion, so its angle can change over the range of travel.

This gives me a headache. I can see how calculating all this could get into "Stephen Hawking" land.

You don't have to calculate anything, I've already laid it out. There is no room to get creative with shock mount's. Period.

 

[speedy]

How does Sam pull 8in of travel in a stock setup? I remember seeing that on race dezert

Got creative with a Sawzall:wink:.

 

[06 H3]

But stock bumps are still in place. I've seen those pics the droop stop is still there, the bumpstop may be trimmed but I don't think enough for 8in of total travel.