What matters in frame materials?
There are numerous factors to consider when choosing a frame material, which fall into four broad categories:
- weight
- longevity
- rigidity
- strength
Weight
The lighter it is, the easier it will be to propel, especially up hills. However, too light and the bike might snap on the first pothole you hit. So we're looking for low weight without compromising strength.
Longevity
If you are hurtling down Alp d'Huez, with another 15 hairpins to go, you need a bike that will get you to the bottom in one piece. You need to be confident that the bike you ride today is in the same shape as when you bought it, 2, 5 or even 10 years ago.
Rigidity
The less a bike flexes under torque the more forward motion you are going to get for the effort you are putting in.
Comfort
You might be comfortable sitting straddling a pailing fence, but for the rest of us, not sitting on a pailing fence is definitely more preferable. Buying a bike that doesn't feel like a pailing fence to sit on is also more preferable.
Raw Materials
There are four main materials available today to choose from in bike frames; steel, aluminium, carbon fibre and titanium.
Steel
Twenty years ago, virtually all bikes were made out of steel. Nowadays things are a little more different. What changed? The good thing about steel is that it was easy for a frame builder to work with, was durable, and had great strength and good shock adsorbtion properties. The problems start when you want to build a lighter steel frame; as you reduce weight, you also reduce strength and rigidity - most steel bikes are therefore reasonably heavy by todays standards.
weight: fairly heavy if preserving strength
longevity: high, but stiffness tends to reduce over years
rigidity: heavier frames will be stiffer than lighter ones
comfort: reasonable to high
Aluminium
Most lower end bikes today are made from aluminium, and manufacturing has improved in leaps and bounds since the earliest frames produced in the early 90's. A good Al frame will have low weight and high rigidity, perfect for a fast accelerating machine. Longevity is not as good, as bumps, knocks and stresses are more likely to cause an issue - if you want to be riding the same bike in 10 years time, choose a different frame material.
weight: light
longevity: lower, difficult to repair
rigidity: high, excellent power transfer
comfort: reasonable
Carbon
Carbon is the material of the 21st century, very light, strong in one direction, and relatively easy to work into complex shapes, carbon has become one of the most used materials for bike frames. Its only drawback is being fragile under side impact conditions, and that it provides a harsher ride under some frame conditions.
weight: very light
longevity: variable. Difficult to repair
rigidity: varies considerably depending on design
comfort: varies, heavier frames with more resin usually more comfortable
Titanium
Titanium is not often found in a frame due to the cost of and difficulty in working the material, however, it makes an excellent frame choice - light, strong and usually results in a comfortable frame. With the added benefit that a Ti frame will not rust, you have a recipe for a very long lasted machine (as long as you don't hit something!).
weight: very light
longevity: high
rigidity: high
comfort: high