Different axle track widths - is it necessarily bad?

[TheOtherLeft]

Is having different track widths always a bad thing?

I'm referring to the new Troopies with the rear trackwidth about 4" shorter then the front. I know it's for economics why they still use the old axles and some people even use wheel spacers to compensate for it.

With a different track width the rear tyres will be creating a new path which may be a problem, esp. in sand.

Could it cause steering problems as well?

[Shadow]

I dont understand the economics bit.

i really dont understand at all why toyota did it. but i dont think its so they can use old stock of axles.

[chimpboy]

I can't think of many cars that have identical track widths front and rear.

Admittedly four inches is more than most, but then relative to tyre/vehicle size I can't see why it would matter more than it does for, say, any stock commodore that has over an inch more rear track than front.

[rockcrawler31]

But chimp, we're not talking commonwhores here. I agree, after recently taking a new cruiser for a drive it's only detraction in my mind is that it handles like a bag of shite in mud because the back end seems to jump from rut to rut that the front end makes.

[rockcrawler31]

Not to mention that the rear wheels have to compact/dig through virgin ground instead of using the compacted sand or using the tracks cleared of mud by the front wheels

[marin]

Not to mention that the rear wheels have to compact/dig through virgin ground instead of using the compacted sand or using the tracks cleared of mud by the front wheels

Which in many cases can also be a good thing, due to the front wheels not having chopped up the line that the rear wheels are taking, hence there is still some traction on that virgin ground. Not always the case, but sometimes.

marin

[Gwagensteve]

Nissan have done the same for years too - the DX Cab chassis patrols are (effectively) MQ width in the rear and GQ/GU in the front.

Some other reasons:

Roll stiffness - Nissan/Toyota will be doing this to raise roll stiffness in the rear for load carrying. The further from the tyre the spring mounts get the lower the roll stiffness.

Axle housing strength - The closer to the wheels the spring plates are, the less leverage on the housing- note this is always done on load carrying models.

Steve.

[Shadow]

Nissan have done the same for years too - the DX Cab chassis patrols are (effectively) MQ width in the rear and GQ/GU in the front.

Some other reasons:

Roll stiffness - Nissan/Toyota will be doing this to raise roll stiffness in the rear for load carrying. The further from the tyre the spring mounts get the lower the roll stiffness.

Axle housing strength - The closer to the wheels the spring plates are, the less leverage on the housing- note this is always done on load carrying models.

Steve.

this i can see some validity in, but i dont see why during design they could not move the chassis and suspension to suit the track of the front.

[Gwagensteve]

True - Although the obvious way of doing this would be to use outboarded rear springs alongside the chassis as used by the Americans, but that tends to be with SPOA and very very long, flat sptings, something the Japanese don't seem too keen on in their heavy duty vehicles.

Steve.

[Guy]

Ackerman angle ?

[Gwagensteve]

Depends on how you measure it - I've seen ackerman referred to as a line between the tie rod, king pin and opposite rear wheel, but also the centre of the rear axle too (ie half of track width) so track width would have no bearing if set up that way.

However, manufacturers can be pretty relaxed about ackerman - sierras don't have different arms between long and SWB and I bet LWB and SWB nissans, and 90, 110 and 130 Landies don't either.

Steve.

[brad-chevlux]

I dont understand the economics bit.

i really dont understand at all why toyota did it. but i dont think its so they can use old stock of axles.

the economics would be more towards not needing to retool to make new diffs.

[Shadow]

I dont understand the economics bit.

i really dont understand at all why toyota did it. but i dont think its so they can use old stock of axles.

the economics would be more towards not needing to retool to make new diffs.

which is 100% insignificat when your designing a totally new car.

[brad-chevlux]

I dont understand the economics bit.

i really dont understand at all why toyota did it. but i dont think its so they can use old stock of axles.

the economics would be more towards not needing to retool to make new diffs.

which is 100% insignificat when your designing a totally new car.

HOW?

might be a new car, but if they use an old design diff they save money by not having to retool to make a new design diff.
it also means the stock piles of spare parts they have for that, do not become obsolete.

[Gwagensteve]

I'm not buying it.

It might be more to do with a narrower axle being cheaper to make (lower material costs, lower transport costs, lighter tube can be used for the reasons I stated above) etc - but manfacturers don't have a "stockpile" of parts - no manufacturer "stockpiles" anything anymore - not more than about 1 day's production.

If a manufacturer can engineer a cheaper way of doing something, they'll do it every time. They don't keep using the same part for fun or so you can grab one from a 25 year old car in a wreckers.

Steve.

[joeblow]

designing a new diff also means new sub-components also, hanbrake cable etc. also those 'little' bits add up to a lot of extra costs.

[-Scott-]

A totally new vehicle is rare, even for Toyota. Every new model has a development budget, and they have to make decisions on where they spend it. Just because there's a cheaper way to make something doesn't mean they have the budget to design, test, prototype, tool etc for the "new" product.

It is possible that Toyota simply chose to not spend that money - yet.

[Gwagensteve]

I don't believe we'll see matching trackwidth front to rear with rear leaves with these cars before they switch to all coil... or all independent... or something.

Just my guess.

Steve.