OK, here's a "winter" question:
Let's assume you have a beach with hard to medium soft sand, and a big wheeled trolley (Cat Trax etc). Does your trolley roll best with the tyres (tires) inflated hard or soft? Hard is good for a hard surfaces, but does 'soft' roll better on soft sand by spreading the load?

Come on, at least it's a bit better than 'test'!

My experience - low pressure is harder to roll. I have a slow leak in one tire that I have to keep an eye on because on all surfaces, that side is harder to roll when it gets low.

From the physics side - more surface area of contact between a surface and a tire (spreading the load, as you say) creates more friction. This is good for cars, as more friction means better traction - wider is better. But increased force is needed to roll a wider tire that "holds the road" better.

But doesn't a hard tyre cut through soft sand, ending up quite deep, whereas a softer tyre will spread the weight across the surface? We need an engineer to conduct some tests to determine which approach reduces effort, taking into account the rolling resistance due to the surface area, and the effort for a hard tyre to push through soft sand...

If your rolling on a hard surface, asphault, concrete, grass, or packed sand, high pressure will be easier to move. If you have to get through deep soft sand, low pressure will spread the load to keep the wheels on top of the sand instead of digging in, and as a result, be easier to roll.

My experience with big tyre Cat Trax is that to keep them rolling smoothly on any surface you need to keep them inflated hard. The big balloon shape does the trick in the sand. Inflating the tyres below recommended pressure means you'll be nicely warmed-up from pulling or pushing your cat like an ox.

I think you guys are confusing off-roading vehicular drive systems with an idling wheel dolly. When driving wheels (i.e. from a drive train) over inconsistent and soft ground, it will keep them from digging in and getting stuck if the tire is deflated quite a bit - more contact area spreads out the loads and keeps it from burrowing under power. However, for an idler wheel like on a cat dolly, my experience is that more pressure is always better as you loose a LOT of energy when the tire is squishing in (ever notice how hot a tire gets when run with low pressure - that's the result of a loss of energy...i.e. extra energy required to get it to roll).

You don't need traction, you need easy rolling. Harder tires = less rolling resistance. The reason you use those big inflated tires in the first place is to keep from sinking into the sand.

Of course, this is coming from a guy that doesn't have a set of beach wheels. I launch from my trailer every time, so take-it or leave-it <img src="http://www.catsailor.com/forums/images/graemlins/smirk.gif" alt="" />

I just load the boat on then play around till it is easy to push and pull. You should be able to move it with one hand if balanced right and right pressure, even with heavier boat (Old H-17 was around 375).

Just my 2 cents,

Doug

Inflation has been a problem I have had with every brand of beach wheels I have ever owned.., they all leaked air and the more the leaked, the harder they were to roll on ANY surface.
My Cat Trax leaked badly. Finally, our supplier advised I should try tubes, which I also discovered we sell on our website www.OnLineMarineStore.com
Ooops! So I tried them. I keep them pretty full and they roll like a dream. Don't know of the Euro Tires can use the same tubes or not, but they are also leakers.
And, now we find that Cateez can't get wheels at all anymore and are on backorder indefinitely. <img src="http://www.catsailor.com/forums/images/graemlins/crazy.gif" alt="" />
Rick

I have a set of cattrax that I bought new 6 years ago. I just had to add air for the first time to one of the tires this past summer.

Tire pressure is still important for Beach Wheels on differing surfaces. Same as for use on a 4x4 in sand or on the road.

On the extreme end of hard tires... the plastic Tiger Trax.

These are horrible in soft sand and rough surfaces, but great for hard sand and surfaces.

So... softer is still better in soft sand, but even the Cat Trax rubber wheel, when pumped up, is softer than the Tiger Trax wheel.

Rick:

Going to add a handle when I move to Jacksonville for the Rudder Club ramp for CatTrax. I can't find the tubes on your site. How about a link.

Doug

G'day Simon, I've got two sets one big wheel and one small wide tyre type the other guys have put you right on rolling resistance and pressure, the big wheel version floats higher in the water making it a bit harder to get your rollers from under your rudders at launch.
regards

Alright Rick, you need to pay for an ad on the websight or else.....

I have always kept mine fairly firm, when they get low they do create extra drag.