Raising Bigfoot for more clearance?? - Fiberglass RV


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Old 06-12-2007, 05:36 PM   #1
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Hello, I'm a fairly new member of this forum. I have recently purchased a 1994 17.5CB Bigfoot travel trailer. This trailer will be towed over the road mostly. Also on gravel roads and some unmaintained roads. I would like some add'l. ground clearance. We are planning an extended Alaska trip next year. Is it feasible to rotate the drop axle 180 degrees to attain more ground and trailer body clearance? Thanx in advance for any help this forum may extend!
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Old 06-12-2007, 06:14 PM   #2
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It's possible, but I don't think it's a very good plan. I can't remember what the drop in that Bigfoot is, but it's likely the same as my Boler, which has a 4" drop. Flipping the whole thing over (even if the springs stayed on the same side of the axle tube, e.g. still below the tube), would take the tube from 4" under the hub to 4" above it, a huge 8" rise. There are couple more issues:
  • the spring perches would rotate as well, so you would either need to do a spring mount conversion, or get another roughly 4" of height change due to having the springs on the other side of the tube
  • if the axle has a deliberate bend to it (normally bent up in the middle, so that is goes straight under load), then the bend will be the wrong way up.
The best way I know of to gain a few inches with a drop-beam leaf-spring axle is to replace the beam with a straight one. You can reuse all of the hub and brake components, and the springs, if you want. This has been done before by others members:
  • Dan Quinn (Amerigo)
  • Rob S. (Boler 1700)
see the topic NEW AXLE for some discussion.
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Old 06-12-2007, 07:05 PM   #3
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Tom,

No, you should not rotate the axle 180, trailer axles are cambered (bent upwards in the center) to become more straight under load and keep the tires reasonably perpendicular to the road. Rotating the axle will cause the axle to sag and the tires to lean in too much at the top. I assume you still have a 4" drop axle under your '94, reversing this, besides being potentially dangerous, would probably raise the trailer 9 to 10" and put severe loads on the springs.

What you can do is relocate the spring perches from the bottom of the axle to the top. This will raise the trailer close to 5", and even allow the fitting of larger and taller 15" wheels and tires for more clearance. Dexter manufactures a conversion kit for this, part #K71-384-00, or you can buy spring perches from a trailer shop and have them welded on the top of the axle. The only major disadvantage to this is that the drop axle tube will hang down well below the wheel centerline.

A replacement straight axle mounted underslung would give a 4" rise with 4" more clearance under the axle, but if you really want the trailer sky-high you could go for a straight axle with the springs on top (overslung).

Relocating the perches from the bottom to the top of the axle has been described as "flipping the axle", an unfortunate term that often leads people to mistakenly believe they can just remount the axle upside down.

Off the topic, I am a bit curious why you refer to your '94 as a 17.5CB, as the 17.5 foot was not manufactured until 2005. The earlier 1500 series trailers were deemed 17 footers, even though the actual length was closer to 16' 7"

Have fun with your Bigfoot!

Steve.
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Old 06-12-2007, 07:18 PM   #4
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Hi Steve;

Glad you chimed in on the subject.

As you went through the steps of replacing your Bigfoot's axle, we, Bigfoot owners, are listening!

Yves.
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Old 06-13-2007, 06:42 AM   #5
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Trailer: 29 ft Arctic Fox and 17 ft Bigfoot
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Quote:
Hi Steve;

Glad you chimed in on the subject.

As you went through the steps of replacing your Bigfoot's axle, we, Bigfoot owners, are listening!

Yves.
Thanx for the pertinet info on raising my Bigfoot. Perhaps I will opt for an axle replacement for safety sake. By the way, this unit already has 15" wheels and 225x15" tires on it. The tires, IMHO, are dangerously close to the skirts. Steve, I listed my Bigfoot as a 17.5 as this is what is on the registration. The lady that I purchased it from listed it as a 17.5CB. You may be correct as stated. If so, I stand corrected.
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Old 06-13-2007, 11:17 AM   #6
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About the model designation:
Is it possible that this trailer is a 1995 15B17.5CB, and it is the year, not length, which is incorrect? Tom, if you post a photo I'm sure the Bigfoot owners will be able to tell which one you have.
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Old 06-13-2007, 04:10 PM   #7
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One thing to remember if anyone does relocate the springs from under to over on an axle is to install a bumper or stop so that the springs can only flex as much as they did before being moved, otherwise they may flex beyond their design and break (been there, done that). Dexter has a note to this effect in their under/over-slung kit.

BTW, one result of doing a "spring-over" is to raise the underside of the trailer which will lessen or remove the air dam effect between the truck and trailer and result in less wind resistance when towing, despite the higher profile on top. Of course, the center of gravity of the trailer is also raised, so caution must be used.
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Old 06-13-2007, 04:29 PM   #8
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Quote:
One thing to remember if anyone does relocate the springs from under to over on an axle is to install a bumper or stop so that the springs can only flex as much as they did before being moved, otherwise they may flex beyond their design and break (been there, done that). Dexter has a note to this effect in their under/over-slung kit.

BTW, one result of doing a "spring-over" is to raise the underside of the trailer which will lessen or remove the air dam effect between the truck and trailer and result in less wind resistance when towing, despite the higher profile on top. Of course, the center of gravity of the trailer is also raised, so caution must be used.
...and you will have to buy longer jack stands and/or scissor jacks... You will probably also have to buy a different hitch insert as well...

My 1700 has had a spring-over and I actually like it so far ... Though, as noted in another thread, it needs shocks now.
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Old 06-13-2007, 05:04 PM   #9
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It seems that the "air dam" improvement assumes the trailer, before modification, has less ground clearance than the tow vehicle. While that may well be the case for many, my stock B1700RGH sits at least as high as the van towing it... and it towers way above the van roof. Every bit I might raise that trailer means a bit taller wall being pulled through the air - not something I expect to be a net improvement. It may well be a different matter for Tom, who is likely towing with a truck - right, Tom?

I think the aerodynamic effects of trailer height are dependent on the specific trailer/tug combination.
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Old 06-13-2007, 05:29 PM   #10
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[quote]
It seems that the "air dam" improvement assumes the trailer, before modification, has less ground clearance than the tow vehicle. While that may well be the case for many, my stock B1700RGH sits at least as high as the van towing it... and it towers way above the van roof. Every bit I might raise that trailer means a bit taller wall being pulled through the air - not something I expect to be a net improvement. It may well be a .

I am towing the 17CB Bigfoot with an '01 F-250, 7.3L, 4x4 diesel P/U. This truck has a cab high topper on the bed. BTW, I/we also own a 29' Arctic Fox travel trailer that we have towed all over the U.S. The fuel mileage at best has been 10.5-11.0 mpg. I do not think that my 17' Bigfoot is really going to affect my fuel mileage as the Arctic Fox has. It may bring the mpg down to 12-15 mpg. But, that is that! Now, I e-mailed Bigfoot Industries for info on what they call flipping the drop axle. According to them, this is a viable option, said it is common. I am now somewhat cautious given this forums experience with these trailers. I do have the skills, tools and ability to rotate the axle. But again, I am now somewhat cautious. This will require some study. I will weigh the safety and ground clearance gain from flipping as opposed to a springover modification. If I do the springover I would fabricate shock mounts and install a good set. Again gentlemen, please chime in on this latest info that I have rec'd. from Bigfoot Ind.
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Old 06-13-2007, 05:36 PM   #11
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As for posting a pic of my '94 Bigfoot. I am much more adept with a welder and cutting torch than this blasted 'puter. My skills are with steel, fiberglass and a set of wrenches. So, if someone could post a pic for me I would e-mail it to them. Thanx greatly for all input thus far.
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Old 06-14-2007, 11:57 AM   #12
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Quote:
...So, if someone could post a pic for me I would e-mail it to them.
Sure. Tom, I have sent you message (you'll see it in your control panel) with my e-mail address; send a photo there and I'll post it.
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Old 06-14-2007, 12:06 PM   #13
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I would be surprised if Bigfoot Industries really meant rotating the drop axle beam when they say "flipping the drop axle" - my guess is that they mean springover conversion - but I suppose anything is possible. I have not been able to get any technical information from them in e-mail queries - although offers of plant tours and marketing material are no problem - so I suppose I'm biased.

I've seen dozens of Bigfoot units in this size range on the road, and I've never seen one that looked high enough to have an axle rotation.
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Old 06-14-2007, 12:16 PM   #14
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I have made a decision to do a spring over modification on my Bigfoot. I did some measuring and put a lot of thought into the outcome of rotating the drop axle, flipping as suggested by Bigfoot, or a spring under modification. I am of the belief that the spring under is the safest and most expedious method. I will order the Dexter kit this afternoon. Brian, I will take pics soon and e-mail them to you. To all I thank you for your valued suggestions and input.
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Old 06-14-2007, 07:23 PM   #15
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Here's Tom's Bigfoot:

Click image for larger version

Name:	Bigfoot.jpg
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ID:	8288


To me, it looks like the official factory photo of a 1500-series trailer which starts off the FiberglassRV Bigfoot Album, as well as the 1989 and 1997 examples which follow (makes sense, for 1994). As of 2004 when I first downloaded specs from them, Bigfoot was listing the small 1500 as a 15B17CB or 15B17G, 16'-7" long. Since then, they have switched to the 2500 series, and the corresponding model is designated 17.5, and is specified to be 17'-5" long.

In a previous post, I babbled something about 1995, because I was a decade out in my thinking
... the change from 1500 series to 2500 series did not occur until 2005, as Steve said, so I assume Tom's trailer is a "17 foot", 15B17CB. I sometimes feel a decade behind in other ways...

So I guess we didn't really need the the photo.
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Old 06-14-2007, 11:28 PM   #16
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A friend replaced his whole axle assembly with the 15" wheel and axle when Bigfoot changed to 15 " wheels. He did this not to gain clearance but because he had a history of bearing problems on the heaviest side of the trailer. He had the Center Bath arrangement.The trailer exceeded the rating per wheel on the heavy sde. The new axle-wheel -tire combo is higher rated than the 14" assembly.He verified the uneven side to side weight by weighing each side of the trailer.
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Old 06-15-2007, 12:21 PM   #17
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Brian, indeed you are correct about air dam and relative vehicle heights; in the case where the trailer is already higher than the truck on the bottom, raising the trailer will likely have no air dam effect and there would be more wind resistance at the top of the trailer.

Tom, the concern about actually rotating the axle is that the axle beam normally has an arch for weight-bearing purposes and rotating it may affect its load capabilities. Also, the axle orientation will likely affect the alignment of the wheels/tires.

I would be more likely to consult with the makers of the axle than the makers of the box that sits on the axle in regard to application modifications...
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Old 06-15-2007, 08:54 PM   #18
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Trailer: 2000 Bigfoot 17 ft (15B17CB)
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When I purchased my new to me 17' Bigfoot a number of years ago, one of the first modifications I did was to raise the trailer. I bent the tongue jack in the first 5 minutes of ownership just going over a driveway crossing, and soon discovered it was very difficult to dump the tanks unless the sani-dump was at or below ground level (which around here many are not, being slightly raised with a curb surround).

At that time, I viewed several Bigfoot units with different axle configurations to see what to do. My original 14" tires and factory aluminum rims were in fine condition, so I did not want to discard them. The original 4" drop axle with the spring over conversion kit raised the trailer a little to much (around 5") for my taste. It just didn't look quite right to me with 14" tires - just a personal opinion. I do think, however, 15" tires would suit this option well.

I ended up ordering an identically dimensioned underslung 3500lb straight axle tube to which I installed my existing brakes and drums. I made custom 3/4" spacers which I inserted between the springs and axle to reduce the 4" lift to 3 1/4" to give me the look I wanted. If I remember correctly, the fabricated axle, U bolts, new bearings and seals cost around $200 and pretty much solved my clearance problems.

Last year, I finally got around to actually weighing the loaded trailer and discovered that I was at the limit of my tire capacity of 3500lbs when hooked up to my tug with the WD bars engaged. I was also somewhat over the GVW , even though visually there was no trace of any strain or overload. Since the tires were approaching 7 years old and would have to be replaced anyway I decided it was time for another upgrade.

This year, I ordered a slightly narrower 3" diameter underslung 5200lb axle with six bolt hubs and 12" brakes, to which I installed HiSpec 15" aluminum trailer wheels with ST 225/15 load range D tires. I purchased new springs which were listed at 2050 lb capacity each and installed them with Dexter's HD greasable shackle kit along with all new bronze bushings replacing the prematurely worn out original plastic bushings. I also installed Dexter's shock absorber kit at the same time to finish up the suspension.

So far I am very happy with the new set-up. It looks good to me with the larger tires compensating for the loss of the 3/4" lowering blocks, and overall height only a around an 1 1/4" taller due to the combination of taller tires and the slight lowering effect of the thicker axle. Most importantly, even though the "official" GVW is unchanged, I have peace of mind knowing the effective load capacity of this axle configuration now comfortably exceeds the actual load.

Please note that I am not a mechanical engineer and cannot certify that my modifications are safe or correct. Anyone who choses to try this combination does so at their own risk.



Steve.
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Old 06-16-2007, 05:56 PM   #19
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Trailer: 29 ft Arctic Fox and 17 ft Bigfoot
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The previous owner/s already modified this rig by installing a 3" Dexter 5200# axle with 6 bolt drums. The rims are 15" aluminum with ST 225-75R-15 load range "D" on them. It has been fitted with a shackle and a 4 leaf spring stack. This was all done by a previous owner. BTW, the fender skirts are dangerously close to the wheels now. A good bump and I'm sure they might touch or worse as is. I have purchased a Dexter K71-383-00 spring over kit. Yes, it will give me 5" of add'l. trailer height. But, that is what I am looking for. I hunt some areas that the roads are rough. I mean rough! The add'l. height will be a plus. My plan is to weld the spring perches on for additional strength. I am less concerned about air dam effect as I am about hitting the bottom of this rig with a rock, tree stump or anything else that might cause damage to the underside. This Bigfoot is going to get a lot of back country use. I have an adjustable tow hitch that will allow trailer to be towed level. If the swing down stabilizers are not adequate, I will grind 'em off and weld on the scissor type. My tow vehicle is not really a mileage miser anyway. But, it will tow this Bigfoot very well.
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Old 06-17-2007, 11:24 AM   #20
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Trailer: 2000 Bigfoot 17 ft (15B17CB)
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Quote:
The previous owner/s already modified this rig by installing a 3" Dexter 5200# axle with 6 bolt drums. The rims are 15" aluminum with ST 225-75R-15 load range "D" on them. It has been fitted with a shackle and a 4 leaf spring stack. This was all done by a previous owner. BTW, the fender skirts are dangerously close to the wheels now. A good bump and I'm sure they might touch or worse as is. I have purchased a Dexter K71-383-00 spring over kit. Yes, it will give me 5" of add'l. trailer height.


Tom,

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

Dexter's conversion kit K71-383-00 works for 2 3/8" diameter axles which I believe were factory installed on all earlier (pre 2005) 17' Bigfoots. I think you will need PN# K71-385-00 for your replacement 3" axle. Since you have access to a welder, it may be cheaper to just buy 3" spring seats and weld them on, as the kit is made to bolt on with a recommendation to tack weld to prevent movement. Of course, beefing up the kit installation with full welds is a good plan.

As Pete has said earlier, Dexter recommends the installation of bump stops to limit the suspension travel to what it was before the installation of the conversion kit. I think this will be especially important for rough road travel. Also, if you do not already have it, you may want to consider Dexter's heavy duty greasable shackle kit PN#K71-358-00. The standard shackles are flimsy and the thin plastic bushings don't last very long at the best of times. If you go this route, don't forget to order two extra bronze bushings for the frame mounts, as they are strangely not supplied in the kit.

Another option that you might want to consider is the addition of shock absorbers. Both Dexter and Monroe make kits or you could fabricate your own mounts and just buy the required length shocks.

Good luck with your project,

Steve.
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