How to correct uneven "Bump Clearance" ?

[TundraTower]

I have a slight sag on the passenger side of our travel trailer. After extensive measurements, I find the bump clearance is actually less on the right side. Bump clearance is the space between the top of the tire and whatever stationary part of the trailer it will hit above it.

Unloaded, unhooked, and as level a spot as I can find, I measure:
LF 2.9"
LR 2.7"
RF 2.6"
RR 2.5"

Dexter and E-trailer recommend a minimum of 3". This is a Lippert suspension system, double 3,500# axles, but could not find their minimum.

I am actually starting to see signs of scuffing where that RR tire is periodically brushing against the bottom of the trailer. Ironically this condition existed to some extent even before we had the rear axle/springs replaced 1 year ago (we bent it somewhere on a 3,500 mile trip).

The right side is the kitchen and the left side has an extra large slide. I attempted a crude method of weighing side to side using a tongue scale and although far from absolute, the relative difference was only 100 lbs or so heavier on the right side.

Spring hangers look OK and measuring centerline of the bolts to trailer frame shows no appreciable difference. Measuring leaf spring to frame shows the same differences as the bump clearances.

I found a dealer nearby willing to help, and they contacted Forest River and Lippert and took dozens of pictures and additional measurements at their request. That was just before the holidays and we are still waiting for their reply/recommendation.

Since we are out of warranty, I am a bit concerned they will come back and say this is essentially normal.

If there is no silver bullet finding from the OEM's, I am seriously considering building shims to mount between the spring pack and the spring perch on top of the axle to level the rig. At a minimum this could involve 1/4" flat stock on the RF and 1/2" flat stock on the RR. It would not be hard to customize the shims on 3 wheels and get it exactly level.

I've done this on Tahoe's several times after lifting the front a bit with the torsion bars. Not terribly complicated.

1. Suspension work is almost always done symmetrically. Anyone see a problem in having 2 different size shims on 2 wheels and none on the other two ??

2. I have considered changing springs. They offer a 2000 lb spring that has the same centerline spacing as my 1750 springs, but they are only 3 leafs instead of my current 4 leafs and the bump clearance spec would be 1/2" LESS than a new 1750 spring, so they would still require shimming. Just wondering if there is an appreciable difference in QUALITY of springs? Mine are marked made in China - would it be worth the trouble to consider replacing all 4 springs with a better quality, and what would that be??

Would welcome any other any other suggestions you might have.

[justafordguy]

Sounds like that was a great upgrade, hopefully you have many more trouble free mile.

[CavemanCharlie]

TundraTower wrote:
I try to close the loop on these postings but got so involved in this that I forgot this one.

I convinced an RV dealer to submit measurements and pictures to the OEM hoping for at least some sound technical guidance, but after 6 weeks got tired of waiting. Finally found a (non-RV) trailer shop about 50 miles away that agreed to look at it.

This guy crawled out from under the trailer shaking his head - said the suspension was just loaded to the max and starting to sag. Was well aware of the under-axle condition of many new travel trailers and had replaced several suspension systems.

We cut a deal to replace my two 3,500 lb Lipperts with two 5,400 lb Dexters. Same size wheels but 6 lug instead of 5 lug so new wheels all around. Tires go up a size from 205 to 225/75-R15 but I was due for new tires anyway --- found 10 ply Maxxis. The shop always uses manual adjust axles, and since I have had problems with over-adjustment on my auto-adjust Lipperts I agreed to go manual on the new ones. Re-used the spring hangers and equalizer.

This guy's normal deal is to take all your hardware in on trade for the new stuff so price was not as bad as I was expecting. He also swapped my emergency stash of spare bearings/brake parts for a similar set of parts for the new axles.

I'm still burnishing-in the new brakes, but they are MASSIVE! Went from 10"x1.5 brakes to 12"x2".

The modification raised the trailer about 3". I was concerned it was going to look like BigFoot but if you had never seen the trailer before I don't think you would notice the extra height. Still playing with the WDH adjustments.

Really looking forward to not worrying about this. Some of the best money DW has let me spend !!

Thanks for letting us know you found a solution. I'm glad you got the problem fixed to your satisfaction.

On my 1993 TT the springs have flattened and the tires drag on rare occasion. I only go about 1000 to 1500 miles a year so I let them drag.

[TundraTower]

I try to close the loop on these postings but got so involved in this that I forgot this one.

I convinced an RV dealer to submit measurements and pictures to the OEM hoping for at least some sound technical guidance, but after 6 weeks got tired of waiting. Finally found a (non-RV) trailer shop about 50 miles away that agreed to look at it.

This guy crawled out from under the trailer shaking his head - said the suspension was just loaded to the max and starting to sag. Was well aware of the under-axle condition of many new travel trailers and had replaced several suspension systems.

We cut a deal to replace my two 3,500 lb Lipperts with two 5,400 lb Dexters. Same size wheels but 6 lug instead of 5 lug so new wheels all around. Tires go up a size from 205 to 225/75-R15 but I was due for new tires anyway --- found 10 ply Maxxis. The shop always uses manual adjust axles, and since I have had problems with over-adjustment on my auto-adjust Lipperts I agreed to go manual on the new ones. Re-used the spring hangers and equalizer.

This guy's normal deal is to take all your hardware in on trade for the new stuff so price was not as bad as I was expecting. He also swapped my emergency stash of spare bearings/brake parts for a similar set of parts for the new axles.

I'm still burnishing-in the new brakes, but they are MASSIVE! Went from 10"x1.5 brakes to 12"x2".

The modification raised the trailer about 3". I was concerned it was going to look like BigFoot but if you had never seen the trailer before I don't think you would notice the extra height. Still playing with the WDH adjustments.

Really looking forward to not worrying about this. Some of the best money DW has let me spend !!

[spike99]

Many trailer makers design their suspension system on "minimum" specs and nothing more. And, this is after 13% tongue weight is subtracted from Trailer's GVWR number. This allows cost savings - which means more profits in their pockets.

If planning to keep Trailer a few more years, I would simply take trailer's GVWR weight number and divide by 2. Then, round up to obtain Axle & leaf spring pack size. For example.... If trailer has 7,855 GVWR, then /2 = 3,927.5 lbs. I would then replace its existing axles with 2 x 4,200 lbs and 4,000 lbs springs. If 4,200 isn't available, then go with +1 size of of 4,500 lbs (axles and springs). Especially if one packs heavy.

Note: Doing +1 size upgrades doesn't mean one can exceed 7,855 GVWR number. +1 allows for extra buffer of rough roads and/or extra support from trailer's heavy side - from a pull in slide.

If wondering, I always +1 size all my trailers (utility, RV, boat) and it works great. Yes, I do the work myself. And where possible, I also upgrade their tires (rubber) as well. Money well spent - especially if keeping trailer for many years.

Note: When ordering new Leaf Spring packs, remember to order Leaf Spring packs with needed arc shape as well. If proper arch shape isn't available, then re-design using Leaf Spring Packs "on top" of axle tubes (instead of default under axle tubes). This works for me.

[hohenwald48]

It seems that now days most trailers come under axled, under sprung and under tired.

[WayneAt63044]

I had a broken spring on my trailer with 3,500 lbs. axles and replaced all with OEM spec 1,750 springs. They looked too flat and almost a reverse curve to them. Subsequently replaced them with 2,400 lbs springs (PR4 with 4 leaves) and it raised the the frame 2" and the springs have the appropriate looking curve while loaded. The weight on my axles at the scale loaded for RVing with full fresh water tank & empty holding tanks was 5,700 vs 7,800 GVWR.

I believe the original and first replacement springs didn't meet the 1,750 spec because at that weight they should not be flat. Perhaps the 2,400 lbs springs don't meet specs either but they do the job for my 7,800 GVWR trailer. I would suggest you change the springs and then shim IF required.

[rbpru]

I guess I do not understand what your end objective is. If the most you are off is 1/2 inch when the TT is empty and level. I suspect you will find much greater variations each time you load up for a trip.

If you want more wheel clearance, I suppose stiffer springs or an axel flip already mentioned would do that. I suspect there are a number of TT wheels that scuff the wells when turning, especially with the flexible axels mounts in use these days.

Of course none of this will change the axel load rating.

[skinnyme]

Try tires with a lower profile / smaller diameter. Maybe a LT tire.
This would give you the little bit of clearance you need.
This would not be a big concern to me. Enjoy the trailer, Have fun.

[Huntindog]

I would not worry about such slight differences in measurements. Those measurements are constantly changing due to the equalizer. Towing it around the block will likely result in different measurements. I would be concerned about the rubbing.
Complete axle assemblies can be had pretty reasonable. It appears that you are well capable of doing this job yourself. That is what I would do if I was going to keep it awhile.
You can sell the old stuff on CL to defray the cost.

[Boband4]

Could you flip the axle mounts to the underside of the springs? It would raise the trailer box and gain you some clearance.

[ScottG]

I would not worry about .3" or .5".
These things just aren't built to that tight of tolerances. Heck, in this regard I'm sure it wasn't built to any tolerance at all!
Tow with it and if you have a problem, do something (lower equalizer, etc) to get more clearance.
But I really dont think you have a problem there.

[westend]

Bigger spring replacement is probably the least expensive and effective solution. If you plan to keep the trailer forever, new axles with bigger springs might be the most technically best solution.

[gmw_photos]

TundraTower wrote:
...snip....

This is a very inexpensive trailer, although exceptionally nice and relatively trouble-free and a unit we both truly enjoy.

We've pulled it 14000 miles over 3 summers .....snip...

I say throw some new tires on it, and go pull it for another 3 summers and another 14,000 miles. Enjoy it.

And don't let the naysayers of the forum steal your joy ! 🙂

[hohenwald48]

Yeah, I'd just replace the springs with some that are a little heavier. Won't get you any additional weight carrying ability but should raise the trailer frame a little higher over the axles due to less spring compression. You don't want to get too high on the springs though or the trailer will ride like it has no springs.

I recently changed out my 2200 pound springs with 2600 (I think) pound springs and all seems good. Springs are pretty cheap ($100 or so) and easy to swap. I think I got mine at etrailer.com