Speaking of frame flex.. to box or not

[tag187]

As some of you know I am starting a full rebuild and upgrade to my 1988 F250, well I have been tossing the idea of boxing the frame around and still am not sure about it. The frame is in very good condition but I was thinking of boxing it for the added strength. The downside I see to this would be less flex under hard offroad conditions. What do you guys think?

 

[chasespeed]

If everything is in good shape, I would leave well enough alone. I see no adverse affects to boxing, and plating in area like spring perches, etc... but, otherwise....

Chase

 

[motomech]

Let it flex, it was designed to.

 

[CapelConcepts]

I would say it's a good idea to box the frame. The vehicles I've see and done have all benefited from a more rigid platform. The increased ride quality in vehicles with more ridgity (through frame boxing or solid mounted roll cages) is pretty incredible. I have to say that this is assuming you've done other mods to the truck like some quality springs and shocks. That's what I would do if it were mine

 

[Rot Box]

If you do box it go the entire length (which would be very time consuming) or you really won't gain much. What do you plan on doing with the truck? If it's a mild wheeler/expedition vehicle I'd leave well enough alone. Boxed frames are better over all but time is money and it could be better invested else where imo.

 

[ntsqd]

If you do box it, use metal of the same thickness or as reasonably close as you can get. Thicker is a can of worms from a stress riser point of view. Thinner might work, but would need more analysis than most (including me) would want to put into the project.
Think through how you're going to handle the cross-members as they more than likely intrude into the opening of the 'C' and are riveted in place. Though preferred, full length isn't necessary but from the first suspension mounting point to the last suspension mounting point is necessary. Usually that doesn't buy you a lot, may as well do the full length.
Ideally the boxing plates are flanged so that you are not welding across two edges that meet at a 90*, but rather at a lap. That isn't so easy when the rail isn't straight.

 

[tag187]

Well I think I may go ahead and box. The truck will be used for new trail expeditions (blazing new paths in remote areas of the US) to allow for less foot imprint on the heavily used ones. Not FWD rec. ares think more along the lines of places where paved roads don't exist but people still travel. Well any way enough of my boring rambles, the truck is getting a full frame off anyway so I figure hell y not. This will be a future upgrade as we are focused in other areas right now but I will post pics when I get to it.

 

[DiploStrat]

A Cure for Which ...

there is no disease?

Turn the question around. What is the truck incapable of doing now and how will it do it better after you increase the weight and increase the number of stress points on the frame?

Frame twist (and even body twist) is not a problem for most vehicles. It is a HUGE issue if you have a large volume camper and the twist damages either the camper or the cabinets, etc. in the interior. (Oh yeah - don't make your roof rack stiffer than your truck.)

Think carefully about what you are trying to fix.

Best wishes!

 

[dzzz]

I've thought about diagonal cross members between the rails. If the subchassis on the camper is raised for a moving suspension (like a pivot), there is room to weld on top. For campers, it seems to me that the worst twisting is the rails moving separately.

As far as rails, it's interesting to me that the F150 has a box frame, and the F550 has a C frame.

 

[RocKrawler]

As far as rails, it's interesting to me that the F150 has a box frame, and the F550 has a C frame.

To me that says if you are going to be carrying a lot of weight its better to allow twist than to be rigid & snap it. If industry engineers decided that lighter trucks could live without the flex & stresses but heavier ones cant, but instead engineered flex INTO the chassis, I'd leave it.
There are exceptions - several vehicles are known for specific weak links. In older Chevy's its the steering box area. In Jeep CJ's its the spring hangers areas and frame at the clutch pivot bracket. Find your vehicles weak spot and address that area, but dont waste time or money that could be better used for more worthwhile projects & upgrades.
If you're that concerned, buy & keep a Ready Welder on the vehicle for field repairs. Often I find my recovery & repair equipment keeps my vehicle from having the problem in the first place, but puts the curse on others I'm with because it usually gets pulled out for the unprepared vehicle thats tagging along!

 

[JIMBO]

:sombrero: If you don't have suspension capable of EXCESSIVE FLEX (mod?)

Then whats the use of boxing the frame, with all probably sub-par cross member conns (per ntsqd), you're going to end up with a mis-aligned CRAB !!!

:Wow1::smiley_drive::safari-rig::safari-rig: JIMBO

 

[RocKrawler]

you're going to end up with a mis-aligned CRAB !!!

Crabs? might want to have that checked by a doctor... :Wow1:

 

[dzzz]

To me that says if you are going to be carrying a lot of weight its better to allow twist than to be rigid & snap it. If industry engineers decided that lighter trucks could live without the flex & stresses but heavier ones cant, but instead engineered flex INTO the chassis, I'd leave it.
There are exceptions - several vehicles are known for specific weak links. In older Chevy's its the steering box area. In Jeep CJ's its the spring hangers areas and frame at the clutch pivot bracket. Find your vehicles weak spot and address that area, but dont waste time or money that could be better used for more worthwhile projects & upgrades.
If you're that concerned, buy & keep a Ready Welder on the vehicle for field repairs. Often I find my recovery & repair equipment keeps my vehicle from having the problem in the first place, but puts the curse on others I'm with because it usually gets pulled out for the unprepared vehicle thats tagging along!

There's a chinese tig type machine that gets good reviews. It's small enough to bring, but I don't know how big the gas bottle needs to be.

Ford pickups are not designed to flex. This is a big deal with ford. The flexiest is Toyota. It's not too hard with the Tundra to get the box to hit the cab.

 

[tag187]

There's a chinese tig type machine that gets good reviews. It's small enough to bring, but I don't know how big the gas bottle needs to be.

Ford pickups are not designed to flex. This is a big deal with ford. The flexiest is Toyota. It's not too hard with the Tundra to get the box to hit the cab.

thanks guys, I get more answers to questions on here than anywhere else on the net and what I find most important is that each one provides a different point of view and makes me look at the situation in a new light. Good info I appreciate it.