It may be that one's old bike is simply worn out and in need of replacement.
Alternatively, it could be that a new bike has a better design and features.
Finally, it could be that a new bicycle is more suited for certain purposes, like mountain bikes for off-road trail riding.
Upgrade There are multiple arguments for why a bike upgrade might be justifiable.
If your old bike is lying around with flat tyres, rusting in a shed, then there must be a reason for it.
Hopefully it's not for having lost the desire to ride altogether.
It may be that the bicycle you own no longer serves its prior purpose.
It could be that it's too old, too uncomfortable or simply too hard to fix.
One needs to consider whether attempting to revive an old bicycle to a rideable state is worth the effort or expense.
New Design While it is a shame to get rid of an old bicycle, if it no longer meets the needs and requirements of the rider, then one is better off doing away with it.
Newer bikes have continually enhanced designs and features to satisfy the modern bike rider.
Suspension on mountain bikes is one example.
It was a rarity in times gone by, but is now becoming quite common on more modern models.
For the comfort it provides the serious mountain biker, it may turn out to be indispensable.
Quick release skewers are another enhancement that are now sometimes used to conveniently detach and re-attach parts of the bicycle, such as the wheels and seat.
For someone who needs to work on their bike regularly, such an advancement may save a lot of hassle with bolts and spanners.
Practicalities An impractical bicycle is one that is probably rarely ridden.
In such a case, an upgrade to an appropriate bicycle is probably warranted.
For example, trying to ride a road bike on a farm may be fraught with difficulty.
A trade in for a mountain bike or BMX will probably mean happier riding.
In a world of rising fuel prices and environmental concern, some keen cyclists may consider riding to work.
If public transport is required for part of the journey, a folding bike could be handy to squeeze into peak hour trains.
Such a bike is also more easily stored once one arrives at their place of work.
If it's a difficult decision to part with one's old bike, but a new bike is needed, one might consider keeping both.
One bike could be used for daily use, and another for its specific purpose.
An old bike might be suitable as a runaround, or for riding to the train station, but could be left at home in place of a racing road bike for more serious biking pursuits.
Whether it's for a new smoother running bike, a better or more comfortable design, or for a bike that's simply more practical to one's current situation, it's always nice to upgrade to a new bicycle.
A range of BMX bikes, mountain bikes, road bikes and specialty bikes give the consumer plenty to choose from.