SRW Conversion Questions

boblynch

Adventurer
I'm considering a SRW conversion of a F550 or Dodge5500. I've read all the posts I could find on the subject (here and elsewhere).

I'd like to compile everyone’s feedback on the following issues. Please provide any and all pertinent details. Feel free to PM or email me if you prefer.

1. What wheel/tire combo to use for extended travel?
2. What spacers, lifts, or other mods are needed?
3. What rear lockers would work?
4. What would the effective payload be after the conversion?
5. Does the conversion void any or all of the warranties?
6. If the rig is kept under the GVWR and ratings of the wheel/tire combo are there any liability issues to be worried about?
7. Any other questions/issues to consider?

Thanks as always.
Bob
 
boblynch said:
I'm considering a SRW conversion of a F550 or Dodge5500. I've read all the posts I could find on the subject (here and elsewhere).

I'd like to compile everyone’s feedback on the following issues. Please provide any and all pertinent details. Feel free to PM or email me if you prefer.

1. What wheel/tire combo to use for extended travel?
2. What spacers, lifts, or other mods are needed?
3. What rear lockers would work?
4. What would the effective payload be after the conversion?
5. Does the conversion void any or all of the warranties?
6. If the rig is kept under the GVWR and ratings of the wheel/tire combo are there any liability issues to be worried about?
7. Any other questions/issues to consider?

Thanks as always.
Bob
I'd suggest either Michelin 335/80R20 XZL, 141K rating (5780 lb @ 68 mph) or Continental 335/80R20 MPT81, 147K rating (~6600 lb @ 68 mph). You'll need custom made "flippable" wheels. Since the wheels on the F550 are hub-centric rather than stud-centric with flat based mounting nuts, flipping the wheel shouldn't present mounting problems. Offset will need to be carefully calculated and the strongest possible centers will need to be used. Consider avoiding USA6X6.
I believe the only locker available for the Dana 135 on the F550 is a Detroit Locker, which I am very fond of.
Stay away from tires taller than this, reliability will suffer. You might get away with stock 4.88 gearing with the 335s.
Strongly consider a Dynatrac conversion for the front wheel bearings and spindle. The front Dana 60 will be stressed by the 170-180 lb tire/wheel (the Michelin weighs 121 lb; perhaps the wheel could weigh up to 80 lb) and the new "improved" "unit bearing" front axle setup has been criticised for reliability and field serviceability. Include wheel bearings and oil seals in your expedition parts kit. I do with my Unimog and I'm using stock tire/wheels (that weigh 340 lb). These parts, plus brake parts, shocks and some suspension parts take a beating with oversized tires.

Charlie
 
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boblynch

Adventurer
Thanks Charlie. The tire size you've suggested is the one used on the TurtleV F550. Where can I go to get educated on the subject of gearing vs. tire selection?
 

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It's very simple. Multiply the ratio of old tire diameter/new tire diameter times axle ratio to get new effective gear ratio. Or multiply tire rev/mile (513 in the case of 335s) times axle ratio (4.875 for F550 diesel) times highest trans ratio (0.72 in the case of F550 6spd ZF) to get rpm @ 60 mph.
Etc.

Charlie
 

boblynch

Adventurer
So it seems there are wheel/tire options (albeit expensive) that will allow for setups at or near the DRW factory GVWR. Also sounds like lockers are available if the LSD is not enough.

Now the big ones... liability and warranties? Thoughts?
 

boblynch

Adventurer
I contacted the folks at Earthroamer regarding the SRW conversion. They stated that "all Ford warranties are in full effect when you take delivery of your new EarthRoamer". They went on to say that Ford is aware of and approved the things they've done and they have had no issues. They stated that the XV-LT with fuel and water tanks topped of weighs about 16000 lbs. With a GVWR of 17950 lbs that leaves room for passengers, food, gear, etc. With the 22.5 wheels and tires they claim to be well below GVWR.

Not sure if this type of support would apply to others that did a one-off SRW conversion of an F550. However, given the longstanding Ford support for the Turtle Expedition, and their recent move to offer units for sale, it may be okay after all.
 

milo12

Adventurer
I've been doing some research into the 5500 since I plan to build a camper on one. As you've seen tires are around to keep the useful load high. I plan to keep the GVW to around 12,000 lbs max. I feel this is important to keep the offroad ability as capable as possible. In my calcs I have less than 7000 lbs on the rear axle. This makes tire selection much easier. Also with only 7000lbs on an axle designed for 13500 lbs bearing load is a non issue.

I've checked wheel offset and to get the front and rear able to use the same "flipped" wheel the wheel offset has to be increased about .6 inches. This pulls the front in and moves the rear out. The truck still ends up around 82 inches wide to the outside of the tires. I was concerned about that width so I did some research and found some interesting results. A stock Tundra is 80 inches wide and would be wider with large tires. The most amazing fact is a stock 2008 Jeep JK is 82 inches wide.:Wow1:

The front axle on the 5500 is a Magna Steyr 275 MM. I can not find any lockers. I have not been able to find a locker for the rear either. As Charlie said a Detroit may exist but no one seems to know anything.

As far as warranty goes that is very dealer dependent. Some don't care what you do, others are just looking for a reason to void the warranty. I don't really care since I will be doing many other things that will void the warranty anyway. I don't see liability being a problem as long as you stay within the allowed tire weights. Of course if you blow a tire and take out a school bus all bets are off.

One issue you didn't mention is a commercial truck issue. On the Dodge and Ford forums there are many posts about getting fined for not going through the scales or having the commercial paperwork. The law says we shouldn't have to worry about it if the truck is not for commercial use. The problem in CA at least is the CHP seems to be out to mess with F450 owners. One key is to do everything you can to tone down the commercial truck look. make it look like an RV.
 

boblynch

Adventurer
Milo, have you determined what wheel/tire combo you'll use? Have you purchased the 5500? Would be curious to find out details regarding your spec decisions (axle ratio, wheelbase, options, etc.). If I run across any locker info I'll send you a PM.

As far as CA registration, you may want to check out this Fuso thread if you haven't already.
http://expeditionportal.com/forum/showthread.php?t=10160
 

boblynch

Adventurer
Thanks for the update. So far this is what I'm hearing...

Lockers - It sounds like LSD only for new F550 or 5500. Lockers available for older trucks.

Wheels/Tires - Tires for 16-18 wheels commonly available in the 3800-4000 lb/tire range. Other less common options for 19.5-20-22.5 wheels allow payload of 6000-7000 lbs/tire. Custom wheels and backspacing probably required.

Warranties - might be okay (dealer dependent bs on a case-by-case)

Liability - carry good insurance and don't wreck
 

boblynch

Adventurer
Help - What wheels for max payload?

I've received a bunch of good feedback on tires. Now the question is wheels...

Most aftermarket wheel suppliers don't list the load specs. Also, the truck companies offer a number of different OEM wheel types and sizes, but don't detail the payload differences. For example, the 2008 F350 SRW may be ordered with 17s, 18s, or 20s. How do you determine the actual load specs for each?

If I decide to go with an aftermarket wheel, what brands and models should I be considering? My preference is for maximum payload (would prefer black to chrome).

Bob
 

toyfunraider

Observer
Great question Bob. Can we include the 19.5 " wheel set up as well. How about putting the two treads together.

I think Alcoa is the highest rated wheel that I have found @ 3750 lbs for a 16" and is is a feather weight @ 19 lbs.
 

boblynch

Adventurer
toyfunraider said:
Great question Bob. Can we include the 19.5 " wheel set up as well. How about putting the two treads together.

I think Alcoa is the highest rated wheel that I have found @ 3750 lbs for a 16" and is is a feather weight @ 19 lbs.
Sure - the more wheel size and payload info we collect the better.
 

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milo12

Adventurer
Here's my $.02

If you are sticking with high pressure 19.5 inch tires, go with the Alcoas. You can't air down anyway so the rim is safe.

If you are going with 20 inch wheels so you can use Michelin, Continental or Toyo tires, go with steel wheels. At the low pressures used off road you want a tough rim to resist damage. Stazworks and Stockton wheel will make custom steel rims for you. With steel strength will not be a problem, but they are heavy.
 

boblynch

Adventurer
David thanks for the specs. The Ford OEM 18x8 wheels are rated at 3525lbs. Wonder if anyone sells aftermarket 18s that are exceed this load? Sounds like I should contact Stockton.

Milo did you ever decide on a wheel/tire setup for your 5500 build?
 
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