Frame Problems (Magazine Editorial)

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Kumu

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December 2011 InBox - Letters To The Editor
Raptor Frame Problems, Where Are the Commanders, And More!
By Rick Péwé
4Wheel & Off-Road, December, 2011



Raptor Frame Problems?
When you told me how much you enjoyed your raptor I just had to buy one to drive while I rebuild my Jeeps, but I left the country before even getting 1,000 miles on it. When I got back recently I saw something on a Raptor forum and wondered if you were aware of it. It basically says that Raptor frames have been bending under hard use as evidenced on a recent Raptor run. Is this true? Considering I may be a victim of all the frame bending hype I’m wondering what your opinion is.

Maybe I’m thinking too hard. I crawled underneath and looked at the size of the holes on the inside of the framerails above the rear bumpstops. They’re oddly oversized. Take a look at how close the bumpstop is to the axle. The 12 inches of “usable” (as advertised) rear travel is hard to buy unless they’re talking droop at a 70 percent plus/minus ratio being where the travel is. There is very little uptravel before contact, which should normally be fine barring the gaping holes in the framerails directly above the impact zone. Even including bumpstop compression, there doesn’t seem to be much uptravel available before the frame feels the impact. It seems to be hard, if not impossible, to run average dirt roads without the axle slamming into the bumpstops (they’re only 3 inches away).

Over time I think this will take its toll due to metal fatigue. Because of the size of the holes inside the framerails this area of the frame is inherently weak, and unfortunately it’s in crucial impact areas. In the end I think it’s likely this will affect most people who run their trucks hard.

It actually scares me now to use the truck the way I think I should be able to. I don’t mean to say that I want to run it like I see it run in the commercials. Honestly, I’d only like to be able to use it running dirt roads and sand pits as hard as I run my Jeep and like I have run all my trucks, but my confidence is gone. I’m afraid to bend my frame now. I think that anyone with mechanical ability never would have put a hole of that size in that spot considering the clearances. I think it was an oversight, that it never occurred to Ford that it could be an issue or they wouldn’t have weakened the frame in that spot by what is likely over 50 percent due to the holes.

I’m buying a reinforcing kit, as it’s actually easier and quicker then fabbing my own, and I’m sure it will address the issue. Screw the warranty—I just don’t want a bent frame. Once it’s bent I will always be unhappy and never get over it, even if it’s perfectly straightened. I’m weird like that.
Scott the Jersey Devil
Pine Barrens, NJ

You are thinking way too hard. Like the engineers at Ford I am well aware of the hole, why the bumpstop is there, and the whole engineering scenario. I also know I have thrashed the Raptor far harder than most owners have with zero issues. Remember that the 12 inches of travel accounts for lots of downtravel. Yes, it has more droop than compression, and it is supposed to.

Remember that while running a trail at speed, if the suspension is already bottomed out on the stop and hits another bump, something has to give, and ideally it isn’t your back. Certain bumps on a road will compress a suspension, and then another bump may put it over the edge. The choice an engineer has is to make a weak link or a fuse somewhere, and bending an area near the frame seems better than an axletube, which could cause other handling problems.

Frames have been bent, fixed, straightened, and built forever. It’s a myth that once they’re bent they won’t ever be the same. The allegation that the bent-frames issue is a design flaw doesn’t hold water. I don’t think it is a problem and neither does Ford. The soft suspension of the Raptor is designed to have only 3-4 inches of uptravel, and the bumpstop continues compressing as part of the suspension design. Yes, weld a piece of steel on the frame so that is will never bend, but do remember that everything will yield at a certain point, and if the frame doesn’t yield when this type of force is applied, something else will have to give. Hopefully it won’t be your vertebrae.
 

KaiserM715

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Péwé speaks the truth. He is a smart dude and has been around the off-road scene for decades. Not to mention, his response falls right in line with Jamal's (SVT engineer).
You are thinking way too hard. Like the engineers at Ford I am well aware of the hole, why the bumpstop is there, and the whole engineering scenario. I also know I have thrashed the Raptor far harder than most owners have with zero issues. Remember that the 12 inches of travel accounts for lots of downtravel. Yes, it has more droop than compression, and it is supposed to.

Remember that while running a trail at speed, if the suspension is already bottomed out on the stop and hits another bump, something has to give, and ideally it isn’t your back. Certain bumps on a road will compress a suspension, and then another bump may put it over the edge. The choice an engineer has is to make a weak link or a fuse somewhere, and bending an area near the frame seems better than an axletube, which could cause other handling problems.

Frames have been bent, fixed, straightened, and built forever. It’s a myth that once they’re bent they won’t ever be the same. The allegation that the bent-frames issue is a design flaw doesn’t hold water. I don’t think it is a problem and neither does Ford. The soft suspension of the Raptor is designed to have only 3-4 inches of uptravel, and the bumpstop continues compressing as part of the suspension design. Yes, weld a piece of steel on the frame so that is will never bend, but do remember that everything will yield at a certain point, and if the frame doesn’t yield when this type of force is applied, something else will have to give. Hopefully it won’t be your vertebrae.
 

jondle

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So the question is, and I'm sure this has already been asked and overly debated...Does a bump stop kit, such as RPG's stage 2, provide benefit without upgrading the rest of the rear end? What is the second weak spot in the rear end?

Maybe benefit is the wrong word. Obviously it is best to upgrade your weakest spot, making something else your weakest spot. What I mean is, is the situation where you break your second weakest spot going to leave you stranded vs. the driving home with a bent frame?
 

Boss327

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I don't think you create a weak link since your using air bumps to control the impact instead of using a fixed rubber piece.
 

RPG

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So the question is, and I'm sure this has already been asked and overly debated...Does a bump stop kit, such as RPG's stage 2, provide benefit without upgrading the rest of the rear end? What is the second weak spot in the rear end?

Maybe benefit is the wrong word. Obviously it is best to upgrade your weakest spot, making something else your weakest spot. What I mean is, is the situation where you break your second weakest spot going to leave you stranded vs. the driving home with a bent frame?

One of the major issues with the rear is the amount of flex. The purpose of a kit like our Stage 2 is to not only fix the direct weak link issue, but stiffen the whole rear frame section to allow the suspension to work without having to deal with excessive flex (think how race cars are designed). The Bumps are designed to handle the large amount of compression energy during the bump travel cycle. It's also important to remember the further out you have the bumps, the less duck walking you get of the rear axle. When you reduce duck walk, you settle the rear-end down and allow it to stay in control. The bump should always be the last line of deffense. You want the shock doing the work and the bump to be set up to handle the excess the shock could not. Basically, with a system like ours, it greatly strengthens the whole rear section. The frame gets considerably stronger closer to the cab, and a Stage 2 allows for the narrower rear section to be firm and less jittery.

Also, the section that was the weak link, the whole is now a non-issue. The energy is being absorbed over a much greater area and not consentrated on a small impact portion of the stock frame. It's important to keep in mind the frame is only as thick as about 20 $1.00 bills stacked together

Watch this and you can see how the frame doesn't move in the rear, and how hard the impacts have to be to fully compress the bump.
RPG Testing - YouTube

Hope this helps.
 
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surfer

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How much more stable does the rear end become with the RPG stage 3 rear kit. Is there a big difference in the highway manners/ride between the heavy duty and the normal national springs?
 
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