6x6 > 4x4?

[OverlandRockwell]

Toying with the idea of making a 6x6. If you guys could turn your 4x4 into a 6x6 would you?

Pros-
better breakover angle
better braking
more flotation

Cons-
MPG decrease
more parts to break

I must be missing something as far as cons because if 6x6 was so great than why would not every larger Unimog be 6x6?

All comments welcome!

 

[Dake21]

More tire to buy and the added weight will reduce power to weight ratio. Increased turning radius maybe?

 

[LR Max]

Depends. If you maintain your current overall vehicle length and (maximum) wheelbase, it could be better. Also you could put free wheeling hubs on the new axle so it would just be hanging out on the interstate.

Off road it would be better. More traction and a shorter...and longer wheelbase. However you are still driving a giant friggen pickup so an extra axle isn't going to help you get through the narrow trails.

Depends on what you want to do. Either way its gonna cost you $$$$. New, custom suspension on AT LEAST the new axle. Then either a new transfer case or something like it. Setting it all up. Then the axle, then matching wheels and tires. I'd think, just in parts, its at least a $3~4k endeavor. If you had a shop do it, then go ahead and round up to $10k and expect it to be wrong (just my experience with many shops that do custom work).

 

[Haf-E]

The Unimogs are designed for extreme articulation and maneuverability - this is lost with going to a 6x6 setup. The extra axle does increase load carrying capacity while reducing the weight carried by each tire - so it is great if you are talking about a loaded vehicle (such as a fully equipped camper) but if its an unloaded pick-up it is not worth it...

The Pinzgauers are offered in 4x4 and 6x6 and there are benefits to each. Both are extremely capable - the extra axle increases the cargo capacity by 50% and improves off-road manners. Since the 4x4 doesn't articulate much to start, the drawback of the 6x6 is mostly just the increased weight of the additional drivetrain - but, since it is the very rear of the vehicle, it helps out a lot since the 4x4 pinzgauers are nose heavy and can be tippy going down extreme hills.

 

[Ozrockrat]

Since I have a 6 wheel land cruiser I can probably add a few comments/thoughts. There are a few benefits to having the extra flotation and carrying capacity. My rig has gone from 1 tonne to 2.5 tonne safely and legally (and with good brakes). But mine is only 6 x 4. The rear rear axle is a tag axle that carries 40% of the load. And it is totally stable with minimal body roll even loaded.

6 x 6 does have more traction but at the expense of weight, tire wear and understeer. Also offroad it has disadvantages. It is very easy to unload an axle. If both the rear axles are drive axles it has the potential to load up the driveline. If the axles are not both driven it has a tendency to unload the drive and you can easily get stuck just rolling out a driveway (very embarrassing).

Personally I made the decision to go 6 x 4 for the extra load capacity and tray room (although the tray has been replaced by a camper body). The extra traction provided by the 6 x 6 was not enough to offset the added cost and complexity, reduced capacity (all those extra driveline bits are heavy) and general bad handling/steering characteristics.

Another disadvantage of either 6 x 4 or 6 x 6 is the added puncture rate for tires. My puncture rate for the rear rear tires was about 10 - 1 compared to the front rear or front axles. I very unscientifically blame that on the front rear tire kicking up nails, screws, rocks and other projectiles just ready for the rear rear tires to run over them. This included 3 punctures in a 30 mile stretch one dark and dismal night. (but at least I could hitch the rear rear axle up and continue on 4 wheels). Some of these could also be attributed to running the crappiest tires on the rear rear as they are basically just for keeping the the rims off the ground.

Tire wear on any 6 wheeler is increased. When cornering the wheels have to scrub. On mine due to the 60/40 split it is always the rear rear tires which get dragged sideways.

 

[OverlandRockwell]

Ozrockrat,

Did you notice a drop in mpg?

 

[Davev1954]

Axles are added to increase carry capacity. If you need more capacity than 2 axles can carry - then more axles make sense. Otherwise I reserve the right to make fun of your custom rig 

 

[Ozrockrat]

12 mpg full or empty at 35 or 70. Didn't change much and was not noticeable. But it if the F series gas engine. I am hoping for the 18 to 20 with the 1HZ and a turbo. (A bit less than the troopy gets)

 

[sargeek]

6x6 or 4x6 will also give you less traction in specific conditions, than a 4x4. In snow/ice and other low traction situations, you have way less traction. You can see this in OTR buses/truck who un-weight tag axles in the winter to get the extra weight on the drive axle. I have also had to chain up a military deuce and a half to make it up a snow packed hill with the front drive engaged (all tires were spinning) that normal cars were driving up without a problem. Unless you need a low ground pressure vehicle, the extra axle is not worth it.

 

[free radical]

Toying with the idea of making a 6x6. If you guys could turn your 4x4 into a 6x6 would you?

Pros-
better breakover angle
better braking
more flotation

Cons-
MPG decrease
more parts to break

I must be missing something as far as cons because if 6x6 was so great than why would not every larger Unimog be 6x6?

All comments welcome!

Why not go all out and get yourself 8x8 like this Czech Tatra :Wow1:
http://youtu.be/eo0yXW66jmM

 

[comptiger5000]

6x6 or 4x6 will also give you less traction in specific conditions, than a 4x4. In snow/ice and other low traction situations, you have way less traction. You can see this in OTR buses/truck who un-weight tag axles in the winter to get the extra weight on the drive axle. I have also had to chain up a military deuce and a half to make it up a snow packed hill with the front drive engaged (all tires were spinning) that normal cars were driving up without a problem. Unless you need a low ground pressure vehicle, the extra axle is not worth it.

That's only an issue with an un-driven tag (like a 6x4 with only 1 rear axle driven). A 6x6 with all axles driven doesn't have the same issue, as there's no un-driven axle to take weight off a driven axle. In the same way, a 6x4 with 2 driven rear axles and an un-driven front is as good as or better than a 4x2 with an un-driven front and single driven rear axle.

 

[sargeek]

On the rear of a multi-axle vehicle you are spreading the weight over two axles instead of single axles - lets pretend that the rear axles carry 1,000 lbs. in with 4 tires on the ground, you are getting 250# of weight on each contact patch, event if all four tires are live, the weight does not change. With only a single rear axle you are getting 500# of weight on each tire or contact patch. You do have a better chance of getting traction if all the tires are being driven, over a non-driven axle. Another example of this is in snow country all you can see a lot of pick-up truck with dual real wheels, take the inside dual off during the winter to increase traction. It is all about flotation and ground pressure. The second rear axle increases flotation, and decreases ground pressure which in specific conditions decreases traction. If you can get away with a 4x4, then I would not add the additional axle.

 

[Charles R]

Remember that adding an axle may also require higher registration fees. The mini truck crowd found that out during that fad. A three axle vehicle is considered a heavy truck, no matter how light it was, and carried the same fee structures as big rigs. Granted, this was how the police attacked them here in California... But it's still worth verifying before you build.

 

[IdaSHO]

6x6 or 4x6 will also give you less traction in specific conditions, than a 4x4. In snow/ice and other low traction situations, you have way less traction.

All true


And the exact reason I run a SINGLE rear wheel (not dually) rear on my pickup.

Winter traction is FAR better with all the weight on 4 wheels instead of 6.

 

[1stDeuce]

On the flip side, one slight benefit of having 2 rear axles on a walking beam vs. one single axle is that for a given bump height, the truck will only displace 1/2 the height when you have two axles going over it, whereas with one axle, it will displace the whole height. (Obviously this is for low speed bumps, or trucks with spring packs that are WAY too stiff to yield.)

Getting power to the rear-est axle is not always the easiest thing, either... Pretty difficult to do "custom" units that reliably get the job done...

While it looks cool, unless the rear of your rig is REALLY heavy, two axles are probably not a significant improvement in soft terrain because the front is still on a single axle, and it's likely just as heavy. (Front axle of my truck with the camper in back is almost as heavy as the rear axle...)
Chris