Analysis Paralysis or the inability to make a choice due to an overwhelming amount of information is extremely common in the bike world. There is endless information available about every little piece that bolts onto a bike, never mind the bike as a whole. One of the topics that comes up frequently is frame material and since this is one of the defining features of a bike that you cannot change, I thought I would talk a little about each common frame material here.
Aluminum (Aluminium for the Brits)
Aluminum is probably the most common material to make bike frames from. It is easy to work with, light weight, and not too expensive. Hydroforming and other advanced manufacturing techniques allow for extensive shaping of the frame tubes to optimize the weight and flex characteristics of the frame. Early aluminum frames were often quite harsh to ride as the engineering was not as well understood and manufacturing was not as refined. A modern aluminum frame is not usually significantly harsher than any other material
Pros:
Recyclable
Inexpensive to manufacture
Relatively light
Cons:
Easier to damage than Steel or Ti
Not as light as carbon fiber
Carbon Fibre
AKA magic. Carbon is kind of a wonder material as far as its strength to weight ratio is concerned. Manufacturers can make some truly amazing shapes out of Carbon that are impossible to replicate with other materials, while also being astoundingly light. Due in part to the freedom to make frames in whatever shape you can dream of, carbon bike frames are also able to me made to be as stiff or compliant as the manufacturer would like, often the frame can be stiff in one direction while being able to flex in another, making a frame that is both responsive and direct, while also being comfortable. The downside to all this is that carbon frames are very labour intensive to produce, leading to more expensive frames.
Pros:
Very light weight
Precisely engineered
Extremely long fatigue life
Cons:
Not recyclable
Expensive
Steel and Steel Alloys
Steel is the original material to make frames from, with distinctive thin tubing and a classic profile. Steel is extremely easy to work with and very strong, making it a favored material for small manufacturers and home builders. A common characteristic of steel bikes is a comfortable ride, typically due to the small diameter, thin tubing that steel frames commonly use. This can lead to a lot of undesirable flex or high weight if not engineer carefully. Steel frames have a distinct feel and are often coming from very small companies that have a lot of passion.
Pros:
Strong
Easy to modify or repair
Comfortable ride
Cons:
Heavy
Can be flexy
Rusts without proper care
Titanium or Ti
Another wonder material, Titanium is renown for having similar ride characteristics to steel, while being far lighter. Ti is notoriously difficult to work with making frame costs quite high, often similar to carbon fiber. Titanium frame tubes are usually a little larger diameter that steel tubes, but not as large as aluminum. Titanium frames are often regarded as a "buy it for life" sort of item and are easy to spot with their usual polished finish.
Pros:
Light weight
Great ride feel
Your friends jealousy
Cons:
Expensive
Difficult to make complex shapes from
There are excellent frames available made from every material here which doesn't help picking so here are some examples of why you would pick each material.
Aluminum
Budget conscience
Not worried about a little extra weight since performance is similar to carbon fibre
Concerned about the environmental impact of carbon fibre
Looking for the best value (the highest spec alloy bike in a companies lineup is often the best price/performance ratio)
Carbon Fibre
Want the lightest bike
Wanting the most optimized frame flex and comfort characteristics
Steel
Interested in hardtails with a classic frame shape
Want to support a local builder
Wanting custom geometry without spending a fortune
Want a bike that will last a lifetime and take you around the world that can be fixed at any roadside workshop
Titanium
Wants a classic looking frame with out the corrosion concerns or weight of steel
Wants a bike that turns heads and the you will be asked about frequently
Wants a bike that will last a lifetime without any special care requirements
I hope this helps a little and please come by the shop if you want to delve deeper into any of these subjects as we are huge nerds that love this stuff.