One of the design challenges for snow/sand bikes is the rim width / tire clearance. The concept behind a fat tire on snow/sand is that the wider the rim the more float is will provide. Float is increased by being able to increase the footprint of the tire. The challenge is that these wider rims/tires have an effect on the drive-train and chain alignment.
The flavor of the day seems to be 100 mm wide rims. A 100 mm rim will easily support a 4 inch tire. That same 4 inch tire on a narrower rim creates a potentially wider tire as the tire overlaps the rim. This does not really translate into a wider footprint because the tire does not create more contact area relative to the narrower rim.
100 mm seems to be about the widest rim options that will still fit on snow/sand bike frames. Frames have to be made specifically for handling these wider tires as the current mountain bike models cannot accommodate these fat tires because the forks and rear triangles on the frames are too narrow.
Snow bikes have been built specifically to handle wider rims and tires without worrying about tire rub on the frame. In most cases, frame builders stuck with the regular width rear hub of 135mm. The problem with this width is that the rear wheel cannot fit on there symmetrically or centered because of the chain-line. Even with a wider bottom bracket the chain rubs against the tire in the higher gears....what to do what to do?? There are two options to this fix...a wider rear hub (170mm) or an offset wheel where the wheel is not symmetrical.
THe problem with a wider 170mm hub is that there are few people who make one and therefore they are expensive. The upside is that the wheel can be built and installed without having to include spacers for offsetting the wheel.
The upside to the 135mm offset option is that the rear hubs are readily available and cheaper - the downside: you have an offset wheel...
At this point it starts to become personal preference - snow bikes were originally built with tons of modifications and that 'standardization' in the industry is continuing to sort itself out. It is almost like when full suspension bikes first came out and there were lots of designs and it took several years before things started to normalize and frames started to use similar designs. That is still happening at a fast rate in the snow bike industry where companies are starting to get closer to standards which is great for the consumers because it is less work in regards to modifications and not having to go dig for hard-to-come-by parts.
The wider wheels definitely create for some interesting challenges as it impacts the drive-train. It has been fun to learn about all this and I still feel it is the proverbial tip of the learning iceberg for me - there is a ton to think about when buying a snow bike as whatever choice a person makes in the snow bike world, it will impact the downstream future buying decisions based on availability of parts and upgrades.
The flavor of the day seems to be 100 mm wide rims. A 100 mm rim will easily support a 4 inch tire. That same 4 inch tire on a narrower rim creates a potentially wider tire as the tire overlaps the rim. This does not really translate into a wider footprint because the tire does not create more contact area relative to the narrower rim.
100 mm seems to be about the widest rim options that will still fit on snow/sand bike frames. Frames have to be made specifically for handling these wider tires as the current mountain bike models cannot accommodate these fat tires because the forks and rear triangles on the frames are too narrow.
Snow bikes have been built specifically to handle wider rims and tires without worrying about tire rub on the frame. In most cases, frame builders stuck with the regular width rear hub of 135mm. The problem with this width is that the rear wheel cannot fit on there symmetrically or centered because of the chain-line. Even with a wider bottom bracket the chain rubs against the tire in the higher gears....what to do what to do?? There are two options to this fix...a wider rear hub (170mm) or an offset wheel where the wheel is not symmetrical.
THe problem with a wider 170mm hub is that there are few people who make one and therefore they are expensive. The upside is that the wheel can be built and installed without having to include spacers for offsetting the wheel.
The upside to the 135mm offset option is that the rear hubs are readily available and cheaper - the downside: you have an offset wheel...
At this point it starts to become personal preference - snow bikes were originally built with tons of modifications and that 'standardization' in the industry is continuing to sort itself out. It is almost like when full suspension bikes first came out and there were lots of designs and it took several years before things started to normalize and frames started to use similar designs. That is still happening at a fast rate in the snow bike industry where companies are starting to get closer to standards which is great for the consumers because it is less work in regards to modifications and not having to go dig for hard-to-come-by parts.
The wider wheels definitely create for some interesting challenges as it impacts the drive-train. It has been fun to learn about all this and I still feel it is the proverbial tip of the learning iceberg for me - there is a ton to think about when buying a snow bike as whatever choice a person makes in the snow bike world, it will impact the downstream future buying decisions based on availability of parts and upgrades.
I've heard those phat wheel bikes are fun, but you'll forget all about them when you see this:
ReplyDeletehttp://www.youtube.com/watch?v=63usXn-4oQo
am really jonesing to test ride a phattie - wonder if those ktrax ever got anywhere??
ReplyDelete