Rating and selecting a vehicle: A guideline

[flyingwil]

Not only all the above are true, but the amount of aftermarket products aplicable to the vehicle is important as well. Sometimes it is best to be able to buy a well thought out and engineered upgrade part (suspension, skids, ect.) than fabricate your own and learn the hard way. I selected my rig based upon the upgradability and the stock performance. Since the stock performance of the vehicle is adequate to get to many i thought i couldn't, stock will do as I save up to upgrade certian aspects of the vehicle. Many rigs as mentioned above are highly capable right off the lot, as you fabricate and upgrade, the capabilities slow increase as well.

However, I disagree with Scotts pos't in regards to DVD players... in fact I have one on my list of wants, due to the inputs and posibilty of a self spotting system. This could also benefit the passengers, old or young, since most units can opperate independantly. For example, you could have an in dash unit displaying your rear view camera, and could be playing a children's DVD in the back with headsets (so you don't end up singing Barney songs all day) and you could still be listening to the radio. Infact, some DVD players have built in GPS, and vehicle monitoring systems, because of this I believe this technology is befitial and has a value to an expediton vehicle... But this is depending upon the set up of the system.

Wil

[Scott Brady]

However, I disagree with Scotts pos't in regards to DVD players... in fact I have one on my list of wants, due to the inputs and posibilty of a self spotting system. This could also benefit the passengers, old or young, since most units can opperate independantly. For example, you could have an in dash unit displaying your rear view camera, and could be playing a children's DVD in the back with headsets (so you don't end up singing Barney songs all day) and you could still be listening to the radio. Infact, some DVD players have built in GPS, and vehicle monitoring systems, because of this I believe this technology is befitial and has a value to an expediton vehicle... But this is depending upon the set up of the system.

Wil

Good point Wil. It was more of a general comment on luxury options and accessories. They take payload capacity from the vehicle, and add complexity (reduced reliability) which are both things of critical importance.

[flyingwil]

Good point Wil. It was more of a general comment on luxury options and accessories. They take payload capacity from the vehicle, and add complexity (reduced reliability) which are both things of critical importance.

While on thetopic of payload, if you were to have your frame strengthened what impacts does this have on the vehicle's payload? One, it is going to add weight to the vehicle, but because it is strengthened can the payload be increased? Also what about galvanized frames does this increase the payload?

I guess the root of the above questions is what determines the payload capacity of the vehicle? Is it the point where abrupt manuvers are no longer safe, or it where the frame fails, ect...?

[goodtimes]

The frame really isn't the limiting factor of your payload capacity. The frame is constructed to support the vehicle and load which is carried by the axles, and ultimately the wheel bearings. Of course, it isn't realistic to "upgrade" the wheel bearings without "upgrading" the axles.

There is alot more that goes into determining the payload and gross vehicle combined weight rating (maximum weight of vehicle, load in the vehicle, and total trailer weight all combined), but everything is engineered based on what the wheel bearings will put up with....they are basically "the bottom line".

[flyingwil]

The frame really isn't the limiting factor of your payload capacity. The frame is constructed to support the vehicle and load which is carried by the axles, and ultimately the wheel bearings. Of course, it isn't realistic to "upgrade" the wheel bearings without "upgrading" the axles.

There is alot more that goes into determining the payload and gross vehicle combined weight rating (maximum weight of vehicle, load in the vehicle, and total trailer weight all combined), but everything is engineered based on what the wheel bearings will put up with....they are basically "the bottom line".

.

Thanks GT!

[Jonathan Hanson]

Goodtimes, you're correct about payload and the vehicle frame . . .mostly. Historically, certain vehicles have suffered from serious frame issues even when not loaded to capacity. Mid-1980s General Motors trucks were notorious for frame cracks and broken motor mounts. The Arizona Game and Fish Department had something like 75 percent of their Chevrolet trucks certified as unsafe at one point. One truck was found with only a single mount holding the engine in. This was back in the days when Chevrolet told its customers "Oh, the frames are designed to flex."

So I consider proper frame design a bedrock foundation for an expedition vehicle. Toyota has been boxing the frames on Land Cruisers and trucks for decades, something American truck builders only recently adopted. (And even Toyota had some issues with the rear parts of frames on some Tacomas, I understand.) The Land Rover frame is a work of art in its intricately welded box section design (unfortunately of thin gauge steel and prone to rusting). Modern hydroforming techniques are making frames stiffer at no weight penalty.

Only a very few vehicles, such as the Unimog, are truly designed with frames that flex in a controlled manner.

[goodtimes]

Jonathon, you are correct. There are concerns with frames of certain vehicles, particularly for off hiway travel. 73 - 87 GM trucks and blazers (full size) tend to crack around the steering boxes when used heavily (big tires, etc). Most compact and mid size trucks seem to have rigidity issues right above the rear axle. This is where the MFR's tend to cut back on material...most go from a boxed design back to a C-channel, as they assume there wont' be a whole lot of stress on the frame in that last 2 or three feet. Of course, us OHV travellers then install tow hooks, etc., and once we use them, we end up bending the frame. Hard pulls from one side of the frame can also bend things....better to pull strait from a properly designed attachement point centered between the frame rails, IMO.

There really aren't too many non-custom solutions to fixing these areas. DeMello sells a frame stiffining kit (basically some 1/4" steel plate that gets welded to the outside of the frame, right above the rear axle) for the tacoma's...apparently this is a big enough issue to have some aftermarket support. Several companies sell a steering box brace for the GM vehicles...basically a stamped piece of steel that fits over the steering box mounting location and gets welded on. A reciever hitch will help stiffen up the back end of the frame on pretty much any vehicle, and provide a attachment point for pulling. But none of these items will actually increase your payload. That is still governed by the wheel bearings (and brake system, etc).

There are alot of reasons that a really rigid frame is a good thing, but it really doesn't affect your ability to carry a heavy load. My concern with poorly built frames would be with a heavy vehicle that gets used on very technical trails on a regular basis...you will lose the fit of the body panels, get waves in the sheet metal, latch and hinges will get loose, you develope squeaks, rattles, and thumps......and eventually you will start breaking things like motor mounts, suspension mounting points etc. For the type of trails that most of us spend time on, over working a frame probably isn't a huge concern. Now if you like playing on the extreme rock crawling trails, yea, frames do crack, link captures break off, etc. Which is one of the things that is spurring on the huge number of buggies that are being built. You are able to build a chassis that will hold up to the abuse of rock crawling, where you won't find a suitable frame to accomplish the same.