Another way to lower an M1101/M1102

[1stDeuce]

Greetings! I'm going to use these trailers as a base for brush fire units, and using a 12" riser for the hitch just isn't a great option.

Of course the first thing I did was to pull the runflat 37's and toss on some 285's. That brought the hitch down 2" or so, but it's still too high. In scoping out the axle mounting, I decided it wouldn't be that hard to do some cutting and push the axle up under the trailer a bit. As they are, the axle mounting pad is almost exactly 5" below the frame tube. If you put it all the way up against the bottom of the frame, you could drop the trailer 5". the downside to that is that you'd only be able to use the side bolts, which might be fine, but I didn't want to go that route.

Here's what I started with...


I ended up buying some 2-1/2" square 1/4" wall aluminum tube. I cut the pieces to ~14" long to put between the axle and frame so I could bolt the axle to the square tube, and then bolt the square tube to what was left of the inside plate after I cut ~2-1/2" off of it. I moved the outer plate holes up 2-1/2" and re-trimmed it, like I have scribed below:


On the inside, I had to drill out the rivets holding the brake line to the inner plate before I could cut it off. Actually had to drill out the forward one too, though I hadn't figured that out yet when I took this picture. It was easier to just grind the head off and punch it through. They're tough!!


I chopped the inner and outer plates 2-1/2" with my plasma cutter, and then made the notch for the axle to fit in. It turns out the side plate material is pretty soft. The 6061 T6 square tube that I bought was noticeably harder. I think you could pretty easily saw the same lines with a sawzall or jigsaw and a coarse metal blade.


Once I got this far, I put the square tube (With holes drilled for the axle bolts) between the two pieces and jacked the axle into place. Here it is with all the bolts loosely installed.


I jacked it up by the axle to seat it against the bottom of the trailer. Made measurements to ensure the axle was relatively square and shifted it around some before tightening all four bolts.

<Edit - 1/28/15> Here are some pictures of the finished product all bolted and riveted and done aside from paint. This is actually the second trailer that I did, and I moved the axle forward 1/2", which seems to work out well. (But I forgot to drill the holes in my square tube 1/2" forward, so it's not centered in the old bracket... Oops.)


Here's a side shot showing the shock travel left. This will be fine.


And finally, the tire is still pretty centered in the wheel well. Actually, it's just slightly forward of center, but on the first trailer I did, it seemed to end up just back from center. I'm moving them all at least 1/2" forward from now on! (This is only a 265 tire because that's what came on the rim.)



I did note that the first trailer, the shocks only have about 3" of total travel, even though they look like they would have much more... In stock configuration, they were fully extended with the tire off the ground, and though they look like they can compress about 4", the last inch of travel doesn't seem to be available. ??

Here's a final pic. The lunette is now right at 24" with the trailer empty and level. I can work with that!! The tires fit the wheel openings pretty well too! There's 7-1/2" between the top of the tire and the bottom side of the wheel well, so I'm pretty sure it would be OK lowered a full 5". I'll probably do the other two trailers like this though, since I have enough square tube for both. I think 24" hitch height will be OK for most pickups with a slight raised mount, or some lift on the truck.



Chris

 

[harleyhouse]

Nice results. Looks good too!

 

[dawico]

Nice work and write up.

 

[1stDeuce]

Thanks! I forgot to mention that I had noticed both hubs on this trailer run warm. There seemed to be a lot of drag on both that wasn't the brakes. Popped the caps to find that the bearings were cranked right tight. Probably torqued to around 50ftlb. I loosened both sides and then did my usual hand tighten, then back off until the cotter fits. One fit right at hand tight, so that's where I set it. The other got about half a flat backed off. Now they spin freely like they should! I bet they won't run warm anymore either.

I haven't checked the TM, but I can't believe the army is setting them up like this... no wonder they're 7000lb hubs on a trailer with a 3400lb or 4200lb GVW... they have to live with WAY too much pre-load!!

 

[1stDeuce]

Hmm. Here it is, right from the TM:

While turning the hub/drum slowly, tighten the spindle nut (3) to seat bearings.

Back off the spindle nut as required to align the cotter pin hole.

Install a cotter pin (2) and bend ends to secure the spindle nut (3).

I guess it's completely open to interpretation. It just says tighten... My brother would put about 100ftlbs on it, then back it off till the cotter just fit. Which is WRONG, but exactly what was done to my trailer.

I think it should have said "Hand Tighten to no more than 20 ftlb to seat the bearings" or something like that... Even the TM can use a little improvement it seems. As I said, good thing they're 7k hubs...

 

[cbear]

Thanks, you've confirmed an idea I've had in the back of my mind. Great work.

 

[rustystud]

The best way without knowing the Manufacturers specifications is to tighten to about 150 ft.Ibs. then back off 20 degrees. Then move the lock ring tighter until it fits. Some bearings take over 300 ft. Ibs. to set, so if you can use the TM's to set the preload properly.

 

[John Galt]

Well done. I like it much better than a tongue modification.

 

[Rockbottomfarm]

Well written and documented with photos. I hope to be this organized someday. The over tightening of axle nuts must be catching. I picked up some M101s recently and after pulling for a few miles I stopped to check the hubs. Both hubs were warm each time and a quick roadside adjustment was required.

 

[wvu dodge]

I like it. Thanks for taking pictures and documenting. I agree, this is much better than a 12" riser plate.

 

[Cleptomaniac]

Looks good!

 

[1stDeuce]

The best way without knowing the Manufacturers specifications is to tighten to about 150 ft.Ibs. then back off 20%. Then move the lock ring tighter until it fits. Some bearings take over 300 ft. Ibs. to set, so if you can use the TM's to set the preload properly.

I normally agree, but in this case, the TM needs a little clarification. If you tighten the bearings to 100ftlbs and then only back off until the cotter fits, or just install the cotter, you're running the bearings with a LOT of preload. Probably in the realm of as much overall load as they were ever intended to see. That's a great way to lose the entire hub and tire assembly while you're tooling down the road. Trailer bearings should always be run with very little to no preload, and that bit of info is missing from the TM completely.

 

[rustystud]

I normally agree, but in this case, the TM needs a little clarification. If you tighten the bearings to 100ftlbs and then only back off until the cotter fits, or just install the cotter, you're running the bearings with a LOT of preload. Probably in the realm of as much overall load as they were ever intended to see. That's a great way to lose the entire hub and tire assembly while you're tooling down the road. Trailer bearings should always be run with very little to no preload, and that bit of info is missing from the TM completely.

That's why I said to back off 20 degrees. This will usually give a zero clearance. What I personally do is back off until there is no pressure on the nut, and then slowly turn in "just snug" by hand. Of course I have been doing this for over 37 years, so it's hard to tell someone what it should "feel" like.

 

[gimpyrobb]

That's why I said to back off 20%. This will usually give a zero preload. What I personally do is back off until there is no pressure on the nut, and then slowly turn in "just snug" by hand. Of course I have been doing this for over 37 years, so it's hard to tell someone what it should "feel" like.

I was told the hub should be able to "feel it click" but not see motion(pushing it back and forth), if that helps.

 

[rustystud]

I was told the hub should be able to "feel it click" but not see motion(pushing it back and forth), if that helps.

I know of one mechanic who used to take a 5ft long pinch bar and try and rock the tire after installation, by placing the bar under the tire (which was about 2 inches from the ground) and pulling up on the bar. If any movement was felt he would retighten the hub nut. Lot of work this way though.

 

[gimpyrobb]

I just do it by hand. I was told a long time ago, loose bearings hardly ever go bad - too tight will ruin them quick.

 

[1stDeuce]

That's why I said to back off 20 degrees. This will usually give a zero clearance. What I personally do is back off until there is no pressure on the nut, and then slowly turn in "just snug" by hand. Of course I have been doing this for over 37 years, so it's hard to tell someone what it should "feel" like.

Easy there. Check your post. You said back off 20%. That's a lot different than 20 degrees. (20% means if you tightened it to 100 ftlbs, you loosened it to 80ftlbs, which is still wrong...)

While 20 degrees might be ok, it also might not... What we're all after is no preload, and that's where the TM fails completely.

We're all on the same page here. My point was that they're all coming out of service WAY too tight, and I think we all know that's a recipe for failure. If any of these "military trained" mechanics come out of the service and set the bearings this tight on a 3500lb axle, they'll get some pretty swift feedback from customers who are loosing tires/wheels on the first trip after service.

IMO the only reason there aren't a lot of failures on these trailers is that they have HUGE bearings for the loading that see relatively low speeds thanks to 37" tires. Everyone who bought one of these trailers and reads this needs to CHECK YOUR BEARINGS!!!
C

 

[rustystud]

Easy there. Check your post. You said back off 20%. That's a lot different than 20 degrees. (20% means if you tightened it to 100 ftlbs, you loosened it to 80ftlbs, which is still wrong...)

While 20 degrees might be ok, it also might not... What we're all after is no preload, and that's where the TM fails completely.

We're all on the same page here. My point was that they're all coming out of service WAY too tight, and I think we all know that's a recipe for failure. If any of these "military trained" mechanics come out of the service and set the bearings this tight on a 3500lb axle, they'll get some pretty swift feedback from customers who are loosing tires/wheels on the first trip after service.

IMO the only reason there aren't a lot of failures on these trailers is that they have HUGE bearings for the loading that see relatively low speeds thanks to 37" tires. Everyone who bought one of these trailers and reads this needs to CHECK YOUR BEARINGS!!!
C

I think your assuming I'm mad or angry. I'm not. I was just saying it is hard to describe a "feels like" to someone else. After doing this job for so many years you need to "show" someone what you mean. This is one of the problems in a technical forum like here. Pictures help, (but if I knew how) video would be best. It is also hard to tell if someone is angry or just using sarcasm or just slightly witty.
As far as your post goes usually zero preload is best. German manufacturers tend to have positive load on there bearings though. "MAN" manufacture likes to have there wheel bearings set up with almost 20ft of pressure or more. One bus had the wheel bearings torqued to 300 ft Ibs , then backed off 2 studs leaving a lot of preload ! So the TM or manufacture's manual is the best way to go.

 

[74M35A2]

I just do it by hand. I was told a long time ago, loose bearings hardly ever go bad - too tight will ruin them quick.

We just had a presentation on this from Timken. They mentioned there should be approx 0.003" of movement in the hub when pushed in/out at final adjustment. They said as the bearing heats, this play becomes almost zero. If one starts with zero play, this then becomes tighter and can tear up the bearing.

 

[1stDeuce]

Well, working on lowering the 2nd trailer. I am moving the axle forward 1/2" too, to help with shock length, but it turns out this trailer has shocks that compress completely, so it probably wouldn't have been a problem anyway. Perhaps I'll swap shocks between the two. (Both are 2009 trailers, but made under different contracts, and perhaps by different mfg's too. ??)

I also debated lowering it more than 2-1/2". I could "rip" the square tube down to 1-1/2x 2-1/2 and still have plenty of room to get the bolts in. But I didn't. I'm probably going to run 265's on this trailer instead of 285's so that'll bring it down another 1/2".

Perhaps I'll lower the 3rd trailer 3-1/2" and see what I think. The shock length will be fine if they compress completely... Not sure why both shocks on the first trailer stop with 1" to go...
Oh, and this one has really tight bearings too.
Chris