Blazer 4x4 flexing

[shocker]

I am building a 72 blazer on 37 inch tires. From past experience i find the doors dont close properly after a good day in the mud and trails. How do i stop this from happening? Do i stiffen the frame or body?

[Bentblazer]

Top on or off makes a big difference, also are the torsion boxes/rocker boxes good and solid?

[shocker]

torsoin boxes and rockers are perfect, want to prevent damage to the body with the top off.

[Turkey nest]

I would love to here more opinions on this subject.
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[SeventyOne]

Boxed frame rails and a full cage would be the way to minimize the flex.

But let's be honest here - it's a convertible, and you're likely never going to eliminate it.

[mustardjimmy71]

Are you running a body lift?
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[shocker]

3 inch body lift. Does the body flex and bend in the floor when the doors dont close properly? Has anyone else had this happen?

[29od1]

The body is flexing in the door opening area because there is very little stiffness to resist it. You only have the floor and the rocker/torsion boxes to stop the flexing. And they're not really that effective since they are pretty close to the neutral axis of the cross section. That's why in the 2nd gen Blazers 1976+, they incorporated the upper part of the cab because it stiffens up the door opening cross section. Since the upper part of the cab is quite a ways from the NA of the cross section, it is very effective in reacting the bending moment across the door opening.

One way to stiffen the tub is to tie in a full cage from behind the door opening to in front of the door opening into the floor and firewall. I've also seen some take out the torsion boxes and build in truss type stiffening members in their place that are more effective than just the sheetmetal boxes. As mentioned, boxing the frame will also stiffen things up.

[Burt4x4]

My door open when flexing sometimes. Also If I try to open my door when flexed, my door is usualy jammed shut...my body flexes all over the place but it's still in one piece

[FoxHound]

I haven't been on any tough trails in my k/5 yet but i can tell you from experience that the body will flex considerably with the top off, even on paved roads. It's way harder to get the top on than it is to get off because of this. So i'd imagine with the top off the flex will be even worse on a trail.

[mustardjimmy71]

I know its often nescesary for tire clearance, but I dont like body lifts on suv's. When flexing it multiplys the stress on the body. The side twisted to the right is 3" further from the axis, as is the left. If you are doing this to a 40 year old suv with no roof and want no body damage i think your going to need to remove the doors, or the body.
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[Burt4x4]

Originally Posted by mustardjimmy71

I know its often nescesary for tire clearance, but I dont like body lifts on suv's. When flexing it multiplys the stress on the body. The side twisted to the right is 3" further from the axis, as is the left. If you are doing this to a 40 year old suv with no roof and want no body damage i think your going to need to remove the doors, or the body.
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Ya and if yer stressin the body that much yer wheeling terrain that will most likely cause body damage anyway LOL

[shocker]

thanx for all the replies, i dont intend to beat this blazer to death but want to keep it looking good. i figure the 8 inch lift will allow the leaf springs to flex more, box the frame and stiffen the torque boxes and we will be good to go.

[SeventyOne]

Did you say 8" leafs and flex in the same sentence?

[Luba]

So did you box your frame?

[shocker]

ive been so busy i have not worked on the frame yet. Suspension, motor, tranny and transfer case are ready for install. I plan on building a ladder type crossmember system when i box the frame.

[truckster]

Originally Posted by 29od1

That's why in the 2nd gen Blazers 1976+, they incorporated the upper part of the cab because it stiffens up the door opening cross section.

Actually, it was because the federal government introduced proposed rollover-protection standards that couldn't be met without a stiffened roof. That's why American convertibles completely disappeared for a few years and T-tops became the rage. The proposed standards never went into effect, though.

Still, you are correct that the added metal increases the stiffness in that part of the cab. But what fun is a Blazer if you can't see the sky above you? (Unless that sky is full of cold, white flakes, of course).

[Firebirdjones]

I like the box frame idea.

If you could do sections of it so as to minimize difficulty in working on anything inside the frame (aka: fuel lines, clips, brackets)

Then I wonder if boxing the frame would still be somewhat beneficial? Hmmm.

[29od1]

Originally Posted by truckster

Actually, it was because the federal government introduced proposed rollover-protection standards that couldn't be met without a stiffened roof. That's why American convertibles completely disappeared for a few years and T-tops became the rage. The proposed standards never went into effect, though.

Thanks for the info, I didn't know that!

[Luba]

Originally Posted by Firebirdjones

I like the box frame idea.

If you could do sections of it so as to minimize difficulty in working on anything inside the frame (aka: fuel lines, clips, brackets)

Then I wonder if boxing the frame would still be somewhat beneficial? Hmmm.

I would just move the lines and do it all. I would think that you would just move the stress points to the unboxed sections......but idk?

[Firebirdjones]

Originally Posted by Luba

I would just move the lines and do it all. I would think that you would just move the stress points to the unboxed sections......but idk?

I was wondering if it would move the stress points too, or maybe be at least somewhat beneficial?

Don't want to move the lines, that just opens up a can of worms for me, more work than I care to tackle. I don't want to box the frame that bad

[910hugger]

a body lift of any size will increase body flex. Depending on the condition of body mounts, type of spacers, condition of body bushings and the strength of the bolts will all effect the total flex. I have seen some poor lifts that have actually bent the body bolts.

Are you running a rollbar that is tied to the frame ?

[Ole Beater]

I plan on welding any frame overlaps, boxing what i can and then putting some tubing on a diagonal across whatever corners in the frame that i can get to. I also plan on getting rid of the torsion boxes. In my opinion all the rust in those areas come from a combination of trapped dirt and metal fatigue from body stresses. You have the bed sides wanting to flex inward and outwards, and the firewall wanting to fold backwards and forwards. I think tubing, sqare or round, would be a hell of a lot better design than going back to factory style torsion boxes. Especially if the truck will be seeing any off road use.

[BobbyK]

My 71 has stock suspension with solid torsion boxes.

In this shot you don't see too much body flex.
Bottom corners of the door is out a little but I opened + then closed the driver's door to get out the truck to take this shot.

Solid (rust free) torsion box's are a key in my opinion.









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