Tuesday, January 3, 2017

M101A1 Axle Swap

The M101A1 is a great choice for a full size camping and bug-out trailer.  I've had several smaller trailers, around M416/Canadian M101 size, and find myself both running out of room and never taking them on anything more that fire-trails.

The 3/4 ton M101A1 has been in service with the military for decades, and you can be sure they are built as the best compromise between weight and ruggedness.  For example, I find the thickness of the metal making up the bed to be very thin and easily bent and dented.  But the reality is that it's strong enough to haul over 2,000 lbs and cosmetic blemishes won't end an overland adventure.  The frame and axle, on the other hand, are built very strong (and heavy).


Here's my M101 with no modifications.  I purchased it from GovLiquidation for $500, and it appeared to have just gone through a military rebuild.  The paint was fresh, tires were new, and axle hubs looked like they had just been serviced.  I towed it back from the Sierra Army Depot in Herlong, CA to the Bay Area, a five hour drive, with no issues.

My first modification is to convert the wheels from the military Budd type, to a standard lug pattern so I can use a "normal" spare tire if I ever get a flat.  A few people have tried converting the hubs with no luck, and consensus seems to be to simply swap in a new axle.  Technically, a 3,500lb axle should be sufficient and I could get hubs to match my Jeep Wranglers 5x5 lug pattern.  However, the military used something closer to a 6,000 lb axle and I have to believe there was a good reason. I'm sure a 3,500 lb axle would be fine if the trailer never left the asphalt, but I'd like to know I could run this down washboard roads with nasty pot-holes for days on end.  Here's a great video from the Adrenalin Campers folks for inspiration:


One wrinkle is that 6K axles can't accommodate the 5x5 hubs to match my Jeep.  It's possible I could find an adapter, but that would push the wheel centerline far outside the trailer hub face and put extra stress on the smaller outside wheel bearing, as well as introduce another possible failure mode with the aluminum adapter.  In the end, I decided to go with a 6x5.5 hub that matches many Toyotas and Chevys.  In a pinch, I'll just go make some new friends :)

For the first phase of my build, I'm using idler hubs and will lose the parking-brake feature.  I'll run this for a year, and if I can't live without the brakes, I'll add them back in.

Here's the axle build tag.  Hopefully this helps someone else with their measurements:


Note that the 6K axle has been derated to 4,879 lbs (lower right corner).  This happens when the spring perches are too far in-board from the hubs.  I'm assuming Dexter's computers calculated this new value.  For this trailer, 4,879 lbs is still far over the GVWR and I have the benefit of the bigger bearings.  But I'm left to wonder, are the 3,500 lb axles derated to under the GVWR... does anyone know?

For tires and wheels, I scored a set of three well worn 33x10.50 BFG tires mounted to 15" steel wheels with a 15mm offset, all for $60.  Thank you Craigslist!

The axle swap is very straight forward.


I've heard problems with spinning off the u-bolt nuts over the years of built up paint, so I wire wheeled them first.  The air-impact wrench made short work of removing the nuts, but only one of the bolts broke free from the lower casting enough to move.  The rest were frozen/rusted to the casting.  I used liquid wrench and a heavy hammer to try to free them up, but after several days of soaking I broke down and simply cut the u-bolts off.


Next wrinkle was to free up the Budd wheel lug nuts.  Turns out the nut size is 1 1/2 inches and I didn't have a socket.  Both Orchard Supply and Home Depot didn't stock sockets that large, but Lowes had one for $7.  One important note is that the lug nuts on the right hand side are left-hand threads, meaning you turn them *clockwise* to loosen them.  The ends of the lug nuts are labelled with a "L" or "R" to help identify this.  With the impact wrench and the proper socket, they spun right off.

Next up was to put the trailer on jack-stands, remove the wheels and tires, unbolt the parking levers and cable stays, and drop the axle.


Ten minutes later the axle was liberated, and a fresh new one bolted in its place.


I used a new u-bolt and plate, tightened the u-bolts in a cross-pattern to 60 lbs, and put on the new wheels/tires.


I'm very happy with how this turned out.  Here's the trailer cost so far:
  • $500 M101A1 trailer
  • $265 Custom Dexter axle (see axle tag above for details)
  • $42 UPS ground shipping for axle
  • $60 (3) 33x10.5r15 BFG tires and steel wheels
  • $15 3" x 7" x 1/2" u-bolt kit with plates and nuts
The axle swap only cost $382 and I now have a spare, a lug-pattern that's readily available, and hubs with bearings I can service with standard parts. 

Another benefit of an axle swap is to drop the trailer weight down.  These trailers weigh 1340 lbs with the canvas top, bows, original axle, tires, and wheels.   Here's a break-down of what I removed:
  • 112 lbs each for 9.00x16 military tire and Budd split ring wheel
  • 208 lbs for the axle with drum brakes
The new axle and tire weights:
  • 69.6 lbs for each 33x10.50 BFG tire (well worn) and steel 15" rims
  • 65.8 lbs for the axle WITHOUT drum brakes
Running the math, I saved 42.4 lbs on each side by swapping the tires and wheels, and another 142.2 lbs by going to the Dexter axle.  Total weight savings was 227 lbs.

What's next?  I'm going to cut off the lower u-bolt castings from the old axle and bolt it on the new axle.  This will let me use the stock shocks and bump stops.

I hope this helped answer a few of the questions I was left wondering after reading hours of posts on M101 axle swaps.  If you have any questions please post in the comments section below.

Monday, September 26, 2011

Lucas Valley Road to Tomales, Point Reyes, and Mt. Tamalpais

This weekend seven of us rallied for a ride along the Marin coastline and nearby hills. Rain had threatened to cancel our ride at the last minute, but we took the plunge and hoped Weather.com's "30% chance of precipitation" would convert into a few light mistings at worst. Our gamble paid off and the reward was much lighter traffic than usual for this time of year and area.

One of our many group stops for the day to get our bearings and pick the route forward.

I'm a little torn on the *best* way to run these rides. The romantic part of me favors the trip over the destination and letting adventure win over perfect planning and a Garmin to guide your every turn. But, I want to value everyones time and possible frustrations over a few wrong turns or delays. So far we've been pretty lucky and the unintentional pivots have turned out well.
Our morning ride consisted of heading west on Lucas Valley Road, through Nicasio, then Samuel P. Taylor Park, up Highway 1, and then a big arc consisting of Tomales/Petaluma Road, Chilleno Valley Road, and then Petaluma/Point Reyes Road we land in Point Reyes Station for lunch.

Some locals pointed us to the Pine Cone Cafe where we enjoyed a good old-fashioned American lunch. If you're trying to lower your cholesterol level or counting calories this is not the place for you. But if you want some great comfort food while sitting on outside benches soaking in the sun then you can't beat this place.

After lunch we continued south on Highway 1 to the Bolinas Lagoon where we jumped on the Bolinas Fairfax Road towards Mount Tamalpais. The first few miles we had to punch through the marine layer which was rolling in. Once out of the fog we found ourselves in a surreal environment: Ridgecrest road runs literally along the ridge gaining altitude quickly over a series of whoop-de-dos while the view off to the right has a sea of white clouds swirling along under a clear blue sky. My only regret for the day was not taking a picture.
Our group ride ended at the road up to the top of Mount Tamalpais. From here we all rolled down into Mill Valley and went our respective ways. The ride turned out great and I look forward to the next one in this area.

Monday, August 1, 2011

Mt. Hamilton to Mines Rd, Livermore, and back through Sunol

Two words: The smells. This is one of the descriptions Gary's wife, Andrea, used to depict the ride and she meant it in the best of ways. We passed through miles of golden yellow fields of grassland, forests of bay trees and oaks, and miles of curvy roads and straight-aways with virtually no traffic. And the weather was a nearly perfect: 70 degrees with blue skys. What's amazing is that all this is right next to San Jose, a city of a million or more people in a metropolitan area of another 5 million. In fact the last leg of the journey for me was surreal; Miles of open rolling hills which dropped me in the course of five minutes into the middle of suburbia.


We started in Alum Rock in San Jose at Starbucks, but the venue quickly changed as we realized it's a Sunday, we weren't in a rush and there was a cafe across the street serving pancakes. After a quick and light breakfast we headed up the hill to Lick Observatory at the top of Mount Hamilton. From there we headed down to Mines Road and out to Livermore for lunch. After Livermore Gary and Andrea headed north to their home, and I went down through Sunol to Calaveras Road, and then another loop up Felter onto Sierra and down into San Jose.


The crew: Gary, Andrea, and myself at the top of Mount Hamilton looking back down onto San Jose.


At Lick Observatory the bikes shelter in the shade from the rising temperatures. We met some really nice Ducati riders on a 1100 Hypermotard and a 900 Monster - some very beautiful bikes. They ended up following us down the hill to The Junction Bar and Grill.

An oasis in the middle of nowhere. Seriously. The Junction Bar and Grill was packed with bikes and their riders lounging in the shade. There was also an interesting family that was camping out literally in the middle of the cafe entrance driveway watching the bikes come in. We had to veer almost off the driveway to avoid the ones seated in the middle of the road. I guess this is what you do on a Sunday in these parts.


This is characteristic of the whole day. I spent five minutes walking around in the middle of the road taking pictures from various angles and there were no cars to be seen. What's amazing is that I was on a hill overlooking all of San Jose and from this spot it was only five minutes until I was back into stop lights, tract homes, and malls.

Wednesday, July 27, 2011

Upcoming ride: Mount Hamilton and Miners Road, Sunday July 31

Here is the proposed route for this coming weekend:


View Larger Map

We will meet at the Starbucks at 3107 Alum Rock, San Jose, at 9am and KSU is 9:30 sharp. There will be three 40 minute segments before brunch in Livermore and then a 1 hour ride through Sunol to get back to Milpitas. Some SF riders may want to head back from Livermore which would make this a quick and easy Sunday morning ride.

Monday, July 18, 2011

Retracing a pedal bike trip to SLO

Last weekend I tagged along with some friends who were riding from SF down to San Luis Obispo to retrace a bicycle ride they had taken years earlier. I was short on time so I only joined the group for the Highway 1 trip south and then I cut inland over Nacimiento-Fergusson and made my way back up to the Bay Area.

We warmed up by taking Old Santa Cruz Highway from Los Gatos over the Soquel, and then slabbed Highway 1 down through Carmel. Although the weather forecast had called for clouds and 62 degrees, the day turned out great with a lot of sun and higher temps.

We stopped for lunch in Big Sur and our stomachs did the talking which ended up with an order for $17 nachos along with an entree for each of us. $17 nachos?! The waitress said, "Enough to serve 4". Ok, let's give it a try. Sure enough we were paying tourist prices and should have asked for the "locals" menu.


Highway 1 south from Carmel was fantastic as normal. Traffic wasn't too bad and the views were incredible. A few times I saw the other riders coming into corners too hot as I'm sure they were distracted by the scenery.

Just past Limekiln I separated from the group to take Nacimiento-Fergussen road over to Fort Hunter Ligget and the highways that would take me north again. I had never taken this road past the summit and didn't know what to expect, nor if the guards at the base entrance would let me pass through.

The road was 15 minutes of curviness up with great views, and another 20 min down the other side and into the base. This is the southern most area of the Los Padres National Forest that burned extensively a few years back. Here you can see my Dakar in front of a Redwood tree that is recovering from the fire. Note the new sprouts covering the entire tree making it look like a bush or shrub.

Coming onto the base I wasn't greeted by armed guards, but instead a small sign saying "don't use cell phones except for emergencies" and an empty guard station. So much for base security.

The roads on the base are great; empty valleys and smooth sweeping curves with an occasional shoot house or abandoned tank to remind you of the lands purpose.


I took a detour to visit Mission San Antonio de Padua which is located on the base. The only person there was an old guy relaxing on a bench in a cause way. Upon approaching we exchanged greetings and he told me the place was closed for the day. I said I'd hoped to see the inside courtyard and he ended up giving me a full tour of the place. Cool.


Here's my bike in front of the Mission.

The inside of the church. This is the site of the first marriage ever in California!


Once back on the road I was running out of daylight so I headed north on 101 instead of doing my original route which included Highway 25. Several lessons were learned during my 2 hours coming up the Salinas Valley in the afternoon. First, it gets windy and I was heading straight into it. Maybe a heavy touring bike with good fairings might have made the trip better but my mini-fairing on the F650 Dakar did little to protect me. At times the cross winds were so strong I felt the bike trying to come out from under me sideways and my HJC CL-16 helmet was letting a lot of wind noise in. Not a very fun way to end what was otherwise an awesome day ride.

The other silver lining was the Dakar's gas mileage. My fill-up in Big Sur was enough to last me the next 200 miles home and I snuck into my garage with the fuel gauge on "reserve".

Sunday, April 17, 2011

Save the Hammers and Johnson Valley

The Marines want to expand the Twenty Nine Palms Training base. They have several options including going east, but their preferred option is to go west. This will close 188,000 acres of BLM OHV area! You may not have visited Johnson Valley, but I can tell you it is a great place with something for everyone. There are dry lake beds, dunes, and mild to extreme rock canyons known as the Hammers. Most of the area is accessible to 2wd vehicles.

Please take some time to send in a comment

The Draft Environmental Impact Statement is available online

You can get more information by checking out the Johnson Valley Page on Pirate 4x4

Thanks for your time and support!

Monday, April 4, 2011

One good turn deserves another

The day at Hollister was a lot of fun, but not without a few suprises. Spencer broke a shock mount so Matt fired up the Lincoln to weld it back up.

At the same time Matt was welding, a Toyota decides to help Mike's 90 Series out of the frame-twister.