Raising Bigfoot for more clearance??

[Brian B-P]

The previous owner/s already modified this rig by installing a 3" Dexter 5200# axle...

I didn't realize that the axle was already changed out to a higher capacity than stock. One consequence of that is that it has a larger tube size, so the curve of the spring seat (pad) must be larger - good catch, Steve.

Another consequence of the larger tube (and probably thicker seat), is that a spring-over conversion will add more height than it would with the smaller components... at least 5" sounds about right to me. Conversion to a straight axle would still provide a rise equal to the drop which is eliminated.

...It has been fitted with a shackle and a 4 leaf spring stack...

If the D52 axle (up to 5200 lb capacity) uses the same size springs as the D35 (up to 3500 lb capacity), then the stock is likely at least 4 leaves, since any less would not have sufficient capacity - these might be the stock springs.

Since every leaf spring setup (except slipper types) has shackles, I'm a little confused. Tom, do you mean longer shackles? That would be one way to gain a bit of height, may help explain why the big tires fit, and would be a good item to eliminate while the working on the axle. Long shackles are an ineffective and undesirable way to raise a suspension.

[Brian B-P]

I'm surprised the 15" tires fit inside the fender skirts at all. I wonder if the axle is narrower than original, or if negative offset rims were used as there isn't a whole lot of clearance even with the original 14" tires...

If the clearance problem is on the outside shoulders of the tires, then it would be helped by wheels that are centred further inboard than the hub faces - although it never seemed right to me, that seems to be called positive offset (I think the term refers to the mounting face relative to the wheel centre). Stock trailer wheels are commonly 1/2" or zero offset, but modern cars and trucks all have positive offset, and front-wheel-drive cars are routinely up to 50 mm (two inches) offset.

If too much offset (positive or negative) is used, the loads are not properly located relative to the bearings, and axle capacity is reduced.

So, I think Steve has a good point, although I think the terminology is reversed.

Tom, if you later decide that the springover was a good test of height but you want to go with a straight axle, I think you'll want to put some thought into the width (hub face to hub face) selection for the new axle beam.

[Tom Myers]

Thanx Steve, I will keep that in mind. As for now I will try the springover configuration and look into adding shock absorbers. My wife is but a wee person and hopefully the 1st step will not be too high for her. May have to build her a small platform. Or stretch her. Guess I better figure on a platform tho'.

[Steve C.]

If the clearance problem is on the outside shoulders of the tires, then it would be helped by wheels that are centred further inboard than the hub faces - although it never seemed right to me, that seems to be called positive offset (I think the term refers to the mounting face relative to the wheel centre). Stock trailer wheels are commonly 1/2" or zero offset, but modern cars and trucks all have positive offset, and front-wheel-drive cars are routinely up to 50 mm (two inches) offset.

If too much offset (positive or negative) is used, the loads are not properly located relative to the bearings, and axle capacity is reduced.

So, I think Steve has a good point, although I think the terminology is reversed

Brian,

You are correct, I wasn't thinking - I should have said positive offset. I will edit my original post to reflect the proper information.

Thanks,
Steve.

[Brian B-P]

Here's Tom's Bigfoot, in the original (spring-under) and new (spring-over) configurations:

Bigfoot.jpg Views: 34 Size: 59.1 KB ID: 8500" style="margin: 2px" />

The bottom edge of the body was just over the hub centre, now it's closer to the top of the wheel, visually suggesting about a 5" to 6" rise, which makes sense for a 3" axle, 0.6" pad thickness, and over an inch of spring pack.

The "original" picture is the same one from post #15 of this topic, shown again here for convenience.

[BobB]

I have been reading this thread with interest, as I bought a Bigfoot recently. It is a 2004 with a straight 3500# axle mounted above the springs. The story is the trailer was lowered about 2" by a previous owner. The question is how was that done? Did he just add the square piece as a spacer? Anyone familiar with the set-up as it came from the factory? Apparently the shocks were added at the same time. Thanks.

[Herb P]

I have been reading this thread with interest, as I bought a Bigfoot recently. It is a 2004 with a straight 3500# axle mounted above the springs. The story is the trailer was lowered about 2" by a previous owner. The question is how was that done? Did he just add the square piece as a spacer? Anyone familiar with the set-up as it came from the factory? Apparently the shocks were added at the same time. Thanks.

Yikes. That looks like a disaster waiting to happen. I would undo that fairly quickly.. That 2" square tube is probably the extra bit there. Looks like you have very little suspension travel left before the axle hits the frame...

[Roger H]

I have been reading this thread with interest, as I bought a Bigfoot recently. It is a 2004 with a straight 3500# axle mounted above the springs. The story is the trailer was lowered about 2" by a previous owner. The question is how was that done? Did he just add the square piece as a spacer? Anyone familiar with the set-up as it came from the factory? Apparently the shocks were added at the same time. Thanks.

Bob,

I believe that removing the spacer is all that's required, but of course, the shocks will have to go as well. I suspect that the U bolts are longer than the stock ones, so you could either replace them or cut them off as required.

Roger

[Brian B-P]

I believe that removing the spacer is all that's required, but of course, the shocks will have to go as well. I suspect that the U bolts are longer than the stock ones, so you could either replace them or cut them off as required.

Yes, the bit of square tubing is a lowering block, it's a cheap and lousy way to emulate a real dropped-beam axle, and the biggest problem in this case is the lack of clearance to the frame, but...

Why would you you remove the shocks? I can't see the detail of the lower attachment point, but assuming they're attached to the tie plate they stay with the springs, and when the blocks are removed it makes no difference to them. If the lower attachment is some unsound design, that would be a different matter.

I would certainly get new U-bolts... even if the old ones could be made shorter, they're far to cheap to waste the time on them.

[Herb P]

Yes, the bit of square tubing is a lowering block, it's a cheap and lousy way to emulate a real dropped-beam axle, and the biggest problem in this case is the lack of clearance to the frame, but...

Why would you you remove the shocks? I can't see the detail of the lower attachment point, but assuming they're attached to the tie plate they stay with the springs, and when the blocks are removed it makes no difference to them. If the lower attachment is some unsound design, that would be a different matter.

I would certainly get new U-bolts... even if the old ones could be made shorter, they're far to cheap to waste the time on them.

Those lowering blocks look like they're done by the same people who think adding a 4 inch long chunk of tubing to their chevy suspension is a safe way to do a lift...

So the only reason I'd remove the shocks is if they were sized after the lowering block was put in there...

[Roger H]

So the only reason I'd remove the shocks is if they were sized after the lowering block was put in there...

They were added by the original owner of the trailer after the axle was lowered.

Roger

[BobB]

Roger and everybody else,

I'm not in a big hurry to undo the mod, as it works well. I just towed it 2000+ miles with no issues whatsoever. I'm just trying to understand where we started from! I gather the axle was underneath the spring to begin with. I guess the question is whether the spacer thing was added. Anybody got a Bigfoot like this one? Thanks.

[Brian B-P]

You might question any work done by the DPO (Dreaded Previous Owner), but other than that I see no issue with the shocks. Assuming that they are mounted to the tie plate, their size fits the spacing of tie plate to frame, which is dependent entirely on the springs, and has nothing to do with the axle position (as long as the spring mounting remains underlung). Remove the 2" blocks and the axle will be two inches lower, relative to the frame and body, but the tie plate will still be the same distance from the frame.

Think of the un-modifying as moving the axle down 2" closer to the springs, not raising the trailer and maybe this is easier to imagine.

I would pull the shock off one end mount, push it to the compressed end of its stroke to confirm that it has enough travel to allow the axle to move up a couple of inches, and pull or let it expand (its probably a gas-charged Monroe RV shock) to its full length and confirm that it allow the axle to droop to a normal position (probably less than 2" of extension from normal ride height).

[BobB]

Thanks for your input and straight answers. It is taking me a while to get up to speed on this axle thing and I eventually will "get it". I did call "Tink" (the DPO) and I'm not sure he remembers what he did. Apparently he does this kind of work all the time. Sounded like he moved the axle from under to over the springs, but now I'm not so sure! He wasn't able to recall the use of spacers. He did say the lowering was easily reversible. So much for talking to the guy who did it.

Yeah, the axle is a little close to the frame, but I'm not able to detect any evidence of contact. Stops? I don't see any, but really don't know what they look like. The springs have 5 leaves and seem pretty stiff. The lower ends of the shocks are welded to that plate underneath the springs, I think.

I certainly detect some feeling that the mod should be reversed ASAP. If I decide to do this, I would not do the work myself, but probably would take it to the place that installed the suspension helper air bags on my tug. They do lifts on a lot of pickup trucks. It would be nice if the job were as simple as pulling out the spacer blocks and installing new u-bolts. The spacer blocks look like they are welded to the spring perches, but the spring perches don't appear to be welded to the axle. I want to understand what needs to be done before I talk to the "sharpies" at Pickup Outfitters, a business that has all the earmarks of a "goldmine".

[Brian B-P]

...Sounded like he moved the axle from under to over the springs, but now I'm not so sure! He wasn't able to recall the use of spacers. He did say the lowering was easily reversible. So much for talking to the guy who did it.

If the axle was moved from under the spring (over-sprung axle) to the current configuration (which indeed has the axle under over the springs, or a under-sprung axle) it would not be really readily reversible unless it used the bolt-on spring perch kit (which this one doesn't). Removing the blocks, on the other hand, is relatively easy.

Yeah, the axle is a little close to the frame, but I'm not able to detect any evidence of contact. Stops? I don't see any, but really don't know what they look like. The springs have 5 leaves and seem pretty stiff. The lower ends of the shocks are welded to that plate underneath the springs, I think.

Over-sprung axles usually don't have any bump stops (the axle just hits the frame in the extreme case). Under-sprung axles are supposed to have bump stops to keep the springs from being flexed too far, and the stop should be a chunk of rubber, but that's not the problem in this case - I don't see a bump stop and would not expect one (although if the axle is going to hit the frame routinely, some rubber would be good...)

5 leaves is pretty normal for a 3500 lb capacity axle; that's what my Boler has.

The shocks won't be welded to anything, but I'm guessing they are bolted to a bracket which is welded to the plate (which Dexter calls a tie plate, and some others call a spring plate).

If I decide to do this, I would not do the work myself, but probably would take it to the place that installed the suspension helper air bags on my tug. They do lifts on a lot of pickup trucks. It would be nice if the job were as simple as pulling out the spacer blocks and installing new u-bolts. The spacer blocks look like they are welded to the spring perches, but the spring perches don't appear to be welded to the axle. I want to understand what needs to be done before I talk to the "sharpies" at Pickup Outfitters, a business that has all the earmarks of a "goldmine".

I'm sure that a competent truck accessory business which does serious suspension work can do the job, but any trailer fabrication place would be an even better choice, and a spring-and-suspension business would be ideal. In this case, it really is home handyman stuff. Too bad the spacer welds need to be ground off, which adds some annoyance and few minutes to the job.

The welding of the stock perches to the axle is easy to miss, but they do need to be welded.

[Steve C.]

I have been reading this thread with interest, as I bought a Bigfoot recently. It is a 2004 with a straight 3500# axle mounted above the springs. The story is the trailer was lowered about 2" by a previous owner. The question is how was that done? Did he just add the square piece as a spacer? Anyone familiar with the set-up as it came from the factory? Apparently the shocks were added at the same time. Thanks.

Bob,

The square spacer has been added, the 2004 17' Bigfoots all came with straight underslung (springs under axle) 3500lb axles. I believe all previous versions used the 4" drop axle, but I'm not absolutely certain about the 2003 model year. I have never yet seen a 17' Bigfoot that came from the factory with an overslung axle, but many owners have installed the underslung to overslung conversion kit to lift their units.

I would suggest removing the spacer, as it doesn't appear to be very substantial. My concern would be that it would be difficult to torque the U bolts to the required tension without distorting the thin wall square tube spacer. This could lead to gradual loosening or failure of the bolts with unpleasant results. Don't try to save a few dollars and reuse the old bolts - go with new bolts of the required length. In the meantime, I would check the torque on the bolts to ensure they are tight enough - 50 ft lbs is about right. If this torque cannot be acheived, or the spacer begins to compress, it is definitely too weak and should be removed or replaced.

If you really like this ride height, assuming you still have at least 1 1/2" minimum bump clearance (Dexter's specification) between axle and frame at maximum expected load, a stronger spacer could be fabricated. I would suggest very heavy wall steel tubing at the very least, or better yet, a solid spacer (steel or aluminum) with the required locating pin and recess. I found that the maximum spacer thickness I could use with my trailer with my previous 3500lb straight axle was 1" - anything thicker compromised Dexter's recommendation. I went with an indexed 3/4" solid steel spacer - no problems in several years of use.

Removing the spacer should not alter the add on shock location, and assuming the shocks were installed properly, should not require removal or relocation of the shock absorbers. Brian has nicely outlined how to check to be sure.

I would be suprised if you find the spring perchs on the axle are actually not welded. It is difficult to tell from the picture, but these are usually welded on the outer edges of the perch. In any case, you should ensure that they ARE welded to the axle.

Sorry for the late reply, but I have been away - camping in my Bigfoot.

Steve.