Malcolm's 1984 Patrol - Poelies Vehn

[Peter Connan]

Malcolm why did you use the smaller wheels on the Faces trip? I would have thought that's exactly where the 33's would have come into their own, and probably even saved you some juice?

By the way, how did the 4.2 go on the dunes? Does it have enough power?

[mvcoller]

I was worried that the bigger and wider wheels would hamper the Hulk's climbing ability up the steep dunes.

Some people also say that wide tyres build to wide a sand wave in front of the tyres, requiring more power to drive on soft sand. After this trip, I cannot say the narrower ones were better.

[Peter Connan]

Malcolm this has been discussed on this forum before.

Personally I have very little experience on open dunes, but a fair amount of experience driving 2x4's on soft sand (river beds and kalahari dunes) and my experience indicates to me that flotation is king in sand. The bigger the wheel, the more it rides on top of the sand and therefore the lower tha wall is that you have to push around.

An increase in diameter is more beneficial than an increase in width, but there is a limit in diametral increase that can be accomodated, and an increase in flotation is still beneficial in my experience.

I beleive that there is about a 45-50% increase in contact area between 31 x 9.5 x 15 and 33 x 12.5 x 15 at 1 Bar on my Patrol.

[Mrowka]

Malcolm this has been discussed on this forum before.

Personally I have very little experience on open dunes, but a fair amount of experience driving 2x4's on soft sand (river beds and kalahari dunes) and my experience indicates to me that flotation is king in sand. The bigger the wheel, the more it rides on top of the sand and therefore the lower tha wall is that you have to push around.

An increase in diameter is more beneficial than an increase in width, but there is a limit in diametral increase that can be accomodated, and an increase in flotation is still beneficial in my experience.

I beleive that there is about a 45-50% increase in contact area between 31 x 9.5 x 15 and 33 x 12.5 x 15 at 1 Bar on my Patrol.

Getting ever further off-topic: how do you rate skinny tires vs. fat tires when you are not in sand?

[Peter Connan]

Kevin it can get very complicated, this discussion.
In my opnion, fat "tekkies" give superior traction in most conditions, with the following exceptions:
1) When a tar road is exceptionally wet, your chances of aquaplaning are increased.
2) In a relatively thin layer of mud with a solid base, where narrower tires will bit through the mud and find traction on the solid ground beneath.
Other disadvantages are:
1) Increased fual consumption on the road.
2) More risk of punctures under some conditions.

They give superior traction on tar, and on something as heavy as the Patrol this is particularly evident on whet roads. They will also be better in clay deep, where flatation is king and if you don't have enough you are entirely buggered.
They also give better traction on rocks.

Of course a lot depends on the tread pattern, and the above is based entirely on the BFG A/T which is the most popular off-road tire here, and the tire I and most of my 4x4 buddies use.

[Mrowka]

I ask because I've heard the arguments for and against fat tires, but I wonder why do tractors have relatively skinny tires?

[Peter Connan]

Kevin the driving wheels on tractors are pretty fat (certainly wider than anything I have ever seen on a Patrol), it's only the front wheels that are skinny, and that is only on 2wd tractors.
These wheels are used unly for steering, and it works better if they "dig in" a little bit. They are also generally fairly lightly loaded.
By the way here in SA the 2wd tractor is an endangered beast now. In the last 10 years, 4wd tractors have really proliferated.

[Mrowka]

Would you say that tractor tires are fat or skinny relative to the weight of the tractor?