Tailgate difficult to open after changing wheels

[Gusman]

Hi, I recently changed out the stock wheels on my Bronco Wildtrak for Method MR305 NV 17's with a +25mm offset. Using the stock tires too. Now when I open and close the tailgate, it seems to take more effort. Especially closing it. Seemed before I could push the tailgate a bit and it would close on its own. I think I've saved around 5 lbs going to the Methods from stock wheels. So it doesn't make sense that losing the weight on the tailgate would make it harder to close? Didn't jump it or do any thing crazy (yet). I've had my Bronco for about 2 months now. Any help or insight is greatly appreciated. Thanks.

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[TRACKTOY]

Hi
stock difference offset = +35 stock versus +25 did you adjust your bump stops on your tailgate for the difference?
tracktoy

 

[tock13]

the strut on the tailgate is pretty beefy and takes some force to push open. Maybe the inertia of the heavier stock wheel swung the gate easier, now you have to provide the extra force with the lighter wheel. I don’t know, just seems like a physics thing to my brain.

 

[Lifeliberty]

My thought was that the tailgate is set to sag a certain amount from factory based on weight of stock tire. The sag lines up the latches. Different weight on tailgate throws that sag off so latches are lined up differently.

But I see people adding weight to their tailgate without mentioning this, so I dont know. You can try removing tire and see if it affects anything

 

[thesocalexplorer]

My thought was that the tailgate is set to sag a certain amount from factory based on weight of stock tire. The sag lines up the latches. Different weight on tailgate throws that sag off so latches are lined up differently.

But I see people adding weight to their tailgate without mentioning this, so I dont know. You can try removing tire and see if it affects anything

The tailgate definitely has some sag accounted for in its design. I was rotating my tires the other day, and had the spare off of the tailgate. When trying to close the tailgate, the latches wouldn't line up until I pushed down on it a bit.

 

[Gusman]

Thanks very much to everyone that responded. @TRACKTOY, I checked and the bump stops are right up against the tire with the Methods on. No gaps. Seems as though the difference in offset is small enough to not affect the position of the bump stops against the tire. @tock13 makes a good point about the heavier stock wheel providing the extra inertia to aid in closing the tailgate. I didn't do well in physics so thanks for the help on that, lol! Kinda bummed that in trying to shed unsprung weight the tailgate is harder to close now. @Lifeliberty and @thesocalexplorer, it also makes sense that the tailgate hinges and locking mechanism was designed for the stock wheel/tire weight. I guess the takeaway here is I gotta hit the gym so I can close the tailgate easier!

 

[Area51BS]

I’m going with inertia as said above. Bump stop move with the entire gate assembly, so they absolutely do not change open and closing of gate.

 

[5GENIDN]

All of the comments make sense.

I just find it interesting because I did a spare delete and my tailgate closes just fine... with no adjustment.

It does sound like an alignment/momentum/inertia issue. And I taught a class in physics at the university. I love physics. If the only change is the weight????? But you are saying only about 5 lbs? That really should not be causing this. Has there been a significant temperature change (expansion/contraction)? I am reaching with this one.... Very odd....

 

[SierraBronco]

Thanks very much to everyone that responded. @TRACKTOY, I checked and the bump stops are right up against the tire with the Methods on. No gaps. Seems as though the difference in offset is small enough to not affect the position of the bump stops against the tire. @tock13 makes a good point about the heavier stock wheel providing the extra inertia to aid in closing the tailgate. I didn't do well in physics so thanks for the help on that, lol! Kinda bummed that in trying to shed unsprung weight the tailgate is harder to close now. @Lifeliberty and @thesocalexplorer, it also makes sense that the tailgate hinges and locking mechanism was designed for the stock wheel/tire weight. I guess the takeaway here is I gotta hit the gym so I can close the tailgate easier!

The answer to anything in life is almost always the gym

 

[Brian_B]

I just find it interesting because I did a spare delete and my tailgate closes just fine... with no adjustment.

Well, having just done the alignment on my tailgate -

The tailgate definitely will sag with weight, but a “proper” alignment is done so it’s on the high side of latching with no tire, and on the low side with the tire.

If you change the weight without adjusting the latch it’s entirely possible one or the other of those points could get off

 

[5GENIDN]

Well, having just done the alignment on my tailgate -

The tailgate definitely will sag with weight, but a “proper” alignment is done so it’s on the high side of latching with no tire, and on the low side with the tire.

If you change the weight without adjusting the latch it’s entirely possible one or the other of those points could get off

I would assume the "sag" in this case is a function of the attachments not being torqued to specification. IF everything was to specification the design should not allow for "sag". My anecdotal example of removing the vast majority of weight from my tail gate is an example of how it should work to design specification, I removed 95% of the weight and alignment remained unchanged. A 5 lb weight difference suggests that something is out of spec allowing the change in fitment. The easiest answer usually the correct one. Something changed away from spec. Is it possible that the hinges moved? even an imperceptible movement of a hinge could cause this misalignment.

 

[Brian_B]

A 5 lb weight difference suggests that something is out of spec allowing the change in fitment.

Not necessarily. If it was on the edge of in spec (and here, "in spec" I am assuming just means you can close properly the latch going smoothly into the striker plate and not hitting on the tailgate itself, not necessarily just the visual alignment of the body panels) - then it may not take much of a change to drive it to where it hits. Those are two distinct and different things here - the alignment of the strike plate/latch, and the visual fitment/alignment of the body panels - you can have one aligned without the other. I'm just talking about striker plate / latch here.

The tailgate moves up when you pull the spare off - even with a re-enforced carrier. Just the physics of it. Mine is a bit less than 3mm of vertical movement on the drivers side with/without the spare on, even with the TOR reenforced carrier. It doesn't look out of alignment visually, it's not a lot of change, but it's still there.

You removed 95% of the weight - yeah, it's supposed to still close properly. It should close properly anywhere from 0-100% of the weight. That's the alignment procedure - align it high at 0%, and it should still closes low at 100% weight. If you don't notice a change in alignment visually, that's good. But I would bet if you went out with an accurate enough tape measure you'd see it's got some movement in it still.

If something were "out of spec" - it would be that you couldn't complete the alignment procedure properly - either the latch mechanism has insufficient play to allow for the tailgate movement (which isn't likely, since most people are making it work just fine) - or you've overloaded the tailgate, the tailgate is tweaked/bent, or the hinges are damaged or out of alignment.

 

[5GENIDN]

Not necessarily. If it was on the edge of in spec (and here, "in spec" I am assuming just means you can close properly the latch going smoothly into the striker plate and not hitting on the tailgate itself, not necessarily just the visual alignment of the body panels) - then it may not take much of a change to drive it to where it hits. Those are two distinct and different things here - the alignment of the strike plate/latch, and the visual fitment/alignment of the body panels - you can have one aligned without the other. I'm just talking about striker plate / latch here.

The tailgate moves up when you pull the spare off - even with a re-enforced carrier. Just the physics of it. Mine is a bit less than 3mm of vertical movement on the drivers side with/without the spare on, even with the TOR reenforced carrier. It doesn't look out of alignment visually, it's not a lot of change, but it's still there.

You removed 95% of the weight - yeah, it's supposed to still close properly. It should close properly anywhere from 0-100% of the weight. That's the alignment procedure - align it high at 0%, and it should still closes low at 100% weight. If you don't notice a change in alignment visually, that's good. But I would bet if you went out with an accurate enough tape measure you'd see it's got some movement in it still.

If something were "out of spec" - it would be that you couldn't complete the alignment procedure properly - either the latch mechanism has insufficient play to allow for the tailgate movement (which isn't likely, since most people are making it work just fine) - or you've overloaded the tailgate, the tailgate is tweaked/bent, or the hinges are damaged or out of alignment.

Actually the "spec" I am referring to is the design "spec" which is a measurement of the mechanical deflection within tolerance that allows the tailgate to function properly. It takes into account the quarter panel rigidity as well as that of the tub and all the supporting structure. Also any deflection of the hinges and the tailgate structure itself. Because many of these parts are aluminum they will have more deflection than if they had used a more rigid (less elastic) material. That is typically accounted for in the structural design and the calculations are using a given weight on a specific lever arm.....

I do know how to design mechanical objects. I have taught physics and mechanical design. It appears you know what you are talking about as well. Please do give me a little credit here.

If there is a misalignment, which we have in this case, something has moved. Period. the options for that are deflection or mechanical alignment changes. Which is more probable? My bet is that something changed with the mechanical alignment. I was and continue to discount deflection due to what I feel is an insignificant change based on the relatively minor torsion changes applied.

 

[Brian_B]

If there is a misalignment, which we have in this case, something has moved.

I'm not intended to insult your intelligence here. Just I think here we have a differing perspective.

I wouldn't say "something has moved" necessarily, but I do agree that something has changed. In this case, I think it's just the weight, which is a factor in all of this. More, or less, weight = more, or less, deflection.

 

[5GENIDN]

I'm not intended to insult your intelligence here. Just I think here we have a differing perspective.

I wouldn't say "something has moved" necessarily, but I do agree that something has changed. In this case, I think it's just the weight, which is a factor in all of this. More, or less, weight = more, or less, deflection.

Let me clarify movement..... The tail gate is not in the exact same positional arc that is was previously.... Therefore it does not align properly when closed. Deflection IS movement.

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