The Different Types of Bike

Mountain Bikes
Mountain Bikes are designed for off-road cycling on rough trails. They have chunky shock-absorbing tyres usually with a heavy tread that grip the trail for steering control and good traction on slippy surfaces. They have a more upright sitting position than conventional race / road bike so that you can see trail ahead. They come with a wide range of gears which that make hill climbing a lot easier.
Hybrid Bikes
This type of bike combines the mountain bike's comfortable sitting position and low gear ratios with the race / road bike's lower rolling road resistance, by using larger wheels, with not such a heavy treaded tyre. They are an excellent compromise if you will be mainly on the road or on light trails or canal paths.
Sport / Race Bikes
If you are looking for speed then it's got to be a race bike, they have skinny tires with large diameter wheels which give a very low rolling resistance, they also have a more aerodynamic sitting position, which means you are sitting in with your head forward.
Kid's Bikes
This section of bikes covers a large age group, from 2½ right through to 12 years of age. The smallest bikes come complete with stabilizers and have easy to reach brake levers, which can be adjusted to suit even the smallest hand. They also have real pneumatic tires and non slip pedals. As the bikes get bigger stabilizers can be added. Once you get on to the 11 inch frames they start to come with Shimano gears, 5 to start with and then increasing to 15.
Gears
There are no prizes for having the most gears, it's having the right gears that matter. Cross country and trail riding requires a wide range of gears, including the low ratios to ease you uphill, high ratios to deliver speed on the flat, and mid range for technical control. For a road bike, on the other hand, speed is of the essence and rolling resistance is lower even on the hills, so you need fewer gears, closer together.
Gear Shifting
All gear shifters are mounted within easy reach, so you can change gear without lifting your hands from bars or brakes. There are several systems, each designed to provide optimum performance for a particular model, and it's worth looking at the differences.
Rapid Fire
Specified on top of the range models, the Rapid Fire shifter provides a bar-mounted total control unit, fully indexed for fast, positive changes across the full range of gears.
E-Z Fire
The shift is indexed, so for each fire of the lever, you're guaranteed one clean and positive multiple shift, and the system is ergonomically designed: shift up with the thumb and down with the forefinger.
Gripshift
The original rotational gear shifter descended from motorbike technology. The gear shift is integrated into the handlebar grip and indexed for smooth movements up or down through the gears.
Revoshift
A rotational shifter with an optical display which tells you what gear you're in so you can make a quick and accurate gear selection. Revoshift is designed with reduced spring tension for smoother, easier action.
Thumbshift
This is the original indexed gear system. The back 5/6 gears are indexed, but you have to feel for change on the front gears.
Brakes
Plunging down a steep, muddy forest trail in a blizzard requires something different of a braking system than pulling up at the fifth set of traffic lights on your morning to route to work.
Disc Brake
This is the latest in the range, the ultimate multi-condition braking system descended from motorbike technology. Designed to handle punishing descents, the system eliminates the risk of 'fading' (caused by heat build-up between conventional brake pads and rims) and delivers long-term braking efficiency.
Power Brake
This also gives a great positive action, providing extreme stopping power and control in all conditions. Technically, the design increases the length of the cantilever arm, so that the pull from the lever is transmitted with more power, yet without diminishing sensitivity.
Cantilever Brake
This was a whole leap forward from the original 'centre pull' brakes that inspired them. Individually mounted to achieve the optimum contact angle between pad and rim, the cantilever pull delivers equal pressure to each side of the wheel rim for smooth, safe braking.
Suspension
When you need a bit more shock protection, these are your options.
FS
This stands for Full Suspension, which means the bike has front shock absorbing forks and a rear suspension system which are tuned together to give a smooth free ride performance and totally controlled decent.
HT
This abbreviation is short for Hard Tail or front suspension only. A suspension front fork is tuned to a responsive frame with a rigid rear end for enhanced cross country climbing.
Suspension Seat Post
This is the third option, designed to soak up unexpected rear end shock.
Frame Materials
The best material for each model is selected according to the hammering it's likely to receive, as well as ride priorities like speed and performance. Strength, weight, response and durability are all considered: Steel is tough, workable and responsive. Aluminium is ultralight, so strength & style can be combined in oversize frames.
Tube shape is important too, designed to cut weight and air resistance without compromising on strength.
Tires
From knobbly mountain bike thickies to slick tarmac burners fitted to road bikes, the choice of tire depends on how much adhesion you need. Remember that adhesion = friction, so city riding on mountain bike tires is harder work than it need to be.
There is also a third way: knobbly outer tread and semi-slick centre tires offer performance on virtually any surface.