Originally Posted by
pyze-guy
Sand=snow is silly. There is no road beneath the sand so of course a skinny tire will harder to steer, and have poor traction. The tire has nothing solid underneath to provide stability. And skis, snowmobiles et.al have a huge contact patch that prevents the user from sinking into the snow, as does a fat bike at 8 psi. I have yet to see anyone ride in snow that is 15 inches high either, your post holing analogy seems pretty silly too.
I didn't say that sand and snow are equivalent but they share similar characteristics. Anytime you "punch" through either, the power requirements to keep moving forward are greatly increased. Vehicles with internal combustion engines usually have enough spare power to keep moving but bicycles have a very limited power plant (i.e. the rider) which limits them.
Bicycles also have the added problem of needing to steer
and balance. When the front wheel digs into the material, it usually throws the bike off the line it is taking which requires correction to keep it moving in a (reasonably) straight line. This requires even more power and both sand and snow work against those corrections if you "punch" through them. Snow does have one property that sand doesn't (usually) have. Snow compacts and builds mounds when driven on by vehicles. A narrow tire is more difficult to keep on top of the mounds so it slides off to the side and brings up that steering issue again. Wider tires will do the same but to a less extent.
Sand is not infinitely deep either. I've ridden on sand that covers solid rock and on snow that is deep enough that you could never punch through it to pavement. In neither case would I want to ride a narrow tire because I would have to move more of both materials to keep moving forward.
Your point about the huge contact patch is exactly the point I was making. Snowmobiles, skies, snowshoes, fat bikes, etc. all have large contact patches to keep them from falling through the snow and make them ride on top of the snow. Dune buggies also have wider tires to stay on top of the sand. The whole point is to stay on top of the snow (or sand) rather than dig down into it. Even nature has numerous examples of animals that travel across the snow rather than trying to plow through it.
Originally Posted by
pyze-guy
Skinny tires cut through the snow so the tire is in contact with road. Same reason mud tires for mtb are skinnier. To get through the soft stuff and to get some purchase at the bottom. I never understood the rational of using wide tires that allow the rider to 'float' over the snow. Floating IMO is a nice way of saying the tires slip all over the place and provide no traction or stability. I ride 23's at 115psi in the winter. Tires are on the road, not slipping, provide great traction as they are gripping the road, not loose, soft shifting snow. I have studded mtb tires for another bike and hate them for anything other than a thin layer of snow that might be hiding ice. As soon as the snow if more than 1 inch the bike gets all squirrelly, the treads fill with snow, and the studs cant even come in contact with any ice. I've used wide2.25 tires at26 psi, same issue. The bike shifts and slides.
I understand the idea that thin tires are supposed to cut through the snow to make contact with the road. I just question the idea. Once you cut through the snow, you have to constantly push that snow out of the way which requires much more effort. Again, go back to the post holing vs snow shoes. Which is easier? The rational for "floating" a wide tire over snow is the same as why you use skis or snowshoes or a snowmobile to travel across snow. It's not that the tires "slip all of the place"...skinny tires do that...it's that a wider contact patch offers more traction and control. To use your idea, you should run skinny tires off-road because they would punch through the terrain and offer better traction and control. They don't for rather obvious reasons.
Mud tires for mountain bikes, by the way, come in all kinds of widths. Again, you don't necessarily want to use a narrow tire to get through the "soft stuff" because then you have to constantly push the soft stuff out of the way. That requires more power. If anything, a narrow mud tire would be used to keep from clogging the fork or chain stay, not for added traction.
I don't know what you are doing wrong with the mountain bike but I've found the opposite to be true. Anytime the snow gets over a dusting, the mountain bike goes where my road bikes can't. Because of the larger contact patch, there is a larger margin of error if the tires do happen to slip.