frame on a 1980 cj7

[gitz676]

I am quite pleased at the condition of my frame. I still might brace the end of the frame because it my be thin. Any thoughts?

 

[Petescj]

It's already boxed and that frame looks to be in great shape. I don't think you need to brace it.

 

[mriplaybass]

My thoughts would be first of all, how thin is thin? The pics look pretty good. Next, what will you be using the Jeep for? Extra bracing on a daily street driver won't hurt anything, but seems like over kill. Also, you don't want to brace the frame so much as to make it rigid. Frames are meant to flex some as the vehicle moves over uneven terrain. IMHO unless you are using this Jeep for moderate or above off roading, I would leave it as is unless there is damage that doesn't show in your pictures. A little bracing won't hurt, but I would concentrate more on applying some type of rust converter followed by a good frame paint.

 

[Lumpy Grits]

The frame is made to flex.
You take that away, and you'll start see'n cracks.
Leave it alone.......
LG

 

[Posi]

Frames were not made to flex, suspensions were made to flex.
The older c-channel frames would sometimes crack because of stiff suspensions (9/13 spring packs).

 

[Lumpy Grits]

Frames were not made to flex, suspensions were made to flex.
The older c-channel frames would sometimes crack because of stiff suspensions (9/13 spring packs).

Made to or not-They flex plenty off-road.
Come on out and play in our rocks-You'll see first hand. :driving:
LG

 

[Hedgehog]

Sorry but frames are made to flex. To a degree anyway. No flex = cracks. Most every thing is made to flex, boats, ships, airplanes space craft, trucks and cars .... Tanks, maybe not.

Your picture is of the rear portion of your frame, the part on the back of the frame IS a cross brace ... along with a pseudo bumper, but really a place to mount a bumper and possible part of a trailer hitch. I just replaced one that was removed on my '75. Where the frame was a sloppy SOB without the brace it became quite stiff with the brace in place. Then I added a big ol' bumper trailer hitch. The thing is super strong now. So, if you leave the stock brace in place then add a real, then in fact you WILL be stiffening up the frame in that area.

 

[Posi]

Made to or not-They flex plenty off-road.
Come on out and play in our rocks-You'll see first hand. :driving:
LG

Do the Ouray/Silverton CO rocks count?
I once took a rental yaris offroading in CA and AZ flexed it pretty good on some obstacle, oh wait, they don't have frames.


Kidding aside, I think if a boxed frame flexes where you can actual see it them I'm suggested something else is wrong. Thin frame, loose rivets on the cross members, suspension, etc.
I wheel fairly hard and have the cage welded in 6 location on the frame and never found a crack, and the top of my cage rubs trees often.

And thanks for the invite, I'll one day wheel my rig on the west coast, isn't as much pinstriping as the east coast.

Edit: spelling

 

[Lumpy Grits]

Good point about the cage as a reinforcement.
I noticed allot less body and frame flex after I installed my 6-point cage also. My front loop is tied into the frame via an OEM style frame to body mount.
The only frame issue I have had, was a crack in the front inside P/S near the front cross-member.
When you come out-We'll run the 'Hammers' in Luc. Vly. You'll see plenty of frame flex and a good bit of 'driver-pucker' too.
LG

 

[Posi]

Yeah, besides the 6 point tie in I also have the front 3/16” tube bumper welded to the frame horns, shock hoops, and 80 % of the frame is plated. It's a very ridged frame, I had my rig out wheeling 20-25 times this year without finding one crack.

Frames in general were built to “resist” flexing, opposed to made to flex.

 

[Lumpy Grits]

Frames in general were built to “resist” flexing, opposed to made to flex.

Watch a semi-tractor go in and out of a driveway when loaded. The tractor's frame flexes plenty between the front at rear axles.
Our Jeep CJ's do the same thing on the trail.
If you don't think so-Run a piece of scotch-tape from the frame to the body in a wheel well. Take it over a rutted road and you'll see.
LG

 

[Posi]

Have you ever looked at a semi-tractor's frame? Their frames are TALL and made that way to “resist” flexing not to allow them to flex. Tractors, pickup trucks, and Jeeps, all flex to a degree, but their frames were built to resist twisting.

The frame is made to flex.

frames are made to flex.

Your missing my point, frames are not made to flex, their made to resist flex.

 

[Torxhead]

The way I see it, yes, frames are made to flex. This will lead to fatigue and cracking eventually. I would go for keeping and eye on a CJ's frame from time to time. I have had my share of frame and body cracks and just figure its part of owning a CJ, and don't think much of the oem welds either.

 

[Lumpy Grits]

Well, as a former over the road truck driver, with 25+ years under my belt. I say your wrong about them not flexing.
We'll just agree, to dis-agree on this(even tho I'm 'rite').
LG

 

[Posi]

I wasn't wrong, you somehow miss it.

Tractors, pickup trucks, and Jeeps, all flex to a degree, but their frames were built to resist twisting.

One could ask the guys that build them. Throttle Down Kustoms builds some nice quality frames. If someone were to call their tech guys and ask them if their frames were made to flex their answer will be no.

 

[Hedgehog]

Posi - I disagree ... somewhat. Yes, frames are made to be as rigid as is possible. But engineers can't get around the fact that metal moves and flexes. Another example is a semi trailer or even a rail road car. Under a load these frames flex and move. I believe the key is for the frame to flex and return to it's original geometry consistently, even to the point where they flex consistently. You can't have your steering go wonky under a load and be perfect unloaded. All frame related systems have to react consistently.

Then again I remember my Dad saying that the original military Jeeps owed there performance to two things. 1 - They didn't have enough power to get stuck. 2 - Their frame was like a rugger band assisting the suspension by flexing on uneven ground.

Another side comment. In the '90s GP motorcycle frames got to be incredibly stiff. Then much to the designers surprise it was discovered that the super stiff frames were slower than previous more flexible versions. They then started adding in some frame flex. I'm not sure how the state of the art is today, but I do remember that. Then you could get into hard tail design where frame flex is important, it saves your back.

For those that believe flexing = cracking. Springs are made of steel, as are bridges. Generally speaking when properly built, with the proper steel, they don't crack.

 

[Posi]

“Somewhat” is better then not at all.

 

[Lumpy Grits]

I wasn't wrong, you somehow miss it.


One could ask the guys that build them. Throttle Down Kustoms builds some nice quality frames. If someone were to call their tech guys and ask them if their frames were made to flex their answer will be no.

Call Kenworth or Freightliner and ask them-I already know the answer.
Posi-Do the tape trick I spoke of, on your Jeep. You'll see.......
LG

 

[Posi]

Call Kenworth or Freightliner and ask them-I already know the answer.
Posi-Do the tape trick I spoke of, on your Jeep. You'll see.......
LG

, if you want to play you have to read all the posts. If you had, you would know using a tape on the frame wouldn't tell me anything I don't already know.


Ran a Freightliner for about 5 years, but never had it offroading. However, Throttle Down Kustoms builds Jeeps frames give them a call they will tell you they don't make frames to flex. I know their answer as well.

Yes, frames are made to be as rigid as is possible.

^^^ this is correct. Their made rigid as possible to resist flex. Flex is a byproduct (so to speak) of the frame and offroading. Or frames are simply “allowed” to flex.

 

[Kane]

Hedgehog, motorcycle frame still do incorporate flex for corner speed. Generally they flex side to side to help absorb small shock and bumps. It takes the stress off the tire carcass allowing traction to stay more constant.