If you are looking for a new bike, you may be debating what frame material to choose. There are three main choices, steel, aluminium or carbon. Carbon is expensive and is mainly reserved for pros and grown men in lycra but if you are on a budget we will be looking at the most accessible of the three - steel and aluminium.
Some steels are more equal than others
First, you should know not all steel is equal. Two of the most common types of steel in bicycle frames are High Tensile steel and 4130 Chromoly steel. Let's not get into science to why are they called that and how are those names representing the chemical compounds and structure but let's get the basics clear what you must know to choose the rigt bike.
High Tensile steel, also widely called Hi-Ten steel is the most basic of them all. It is generally heavier and softer compared to the 4130. 4130 ChroMo steel due to its chemical compounds is lighter and stronger. Yes, also slightly more expensive. It doesn't leave the HiTens without credit though. If weight is not an issue you could as well go for the cheaper option.
Aluminium has its tricks too
6061 and 7005 are two of the most common aluminium compounds used in frame building. Although the 7005 aluminium show better results in the lab for strength, 6061 aluminium is much easier to work with allowing manufacturers to produce lighter frames cheaper. The difference in strength is measured in such far-fetched numbers you wouldn't ever reach in real life anyway, unless, of course, you plan a parachute jumping stunt with a bike without a parachute.
So is steel still real? Or will alloys take over?
It is a widely known misconception that aluminium bikes are light and steel is heavy. Although the HiTens steel is, some 4130 steel bikes can be nearly as light as aluminium. Of course, aluminium is lighter per the same volume but often aluminium frames have to be bulkier to keep the same strength and in the end, it all comes together with the frame building technique.
You can see in the chart below that double butted 4130 steel frame can compete with a straight gauge aluminium frame due to less steel used in the building process. Aluminium frames generally still tend to be lighter but also more expensive.
Quality of Ride
We determined aluminium is lighter, so does it ride better? This section will be all about flexibility.
Flexible is good if you ride on the road, in the city with bumps and curves. Flexible is comfortable. This is steel for you. Steel will absorb the roughness of the road and will result in a smoother, more pleasant ride.
Stiff is good for speed, for track and for edgy controls. This is aluminium. A stiff frame will help you with all that but will also transfer all vibrations from the road to your seat and handlebars. Although lighter and potentially faster, you will compromise on comfort.
Strength and Durability
No doubt, there isn't anything more durable than steel. It will take scratches, dents and rides home from a pub without largely damaging the structural integrity. Steel is flexible and it "gives in" on damage flexing it out. Steel frames are extremely durable and in many cases will last a lifetime.
Aluminium, though, is not far behind. With latest material science aluminium has become extremely strong too. It will withstand a lot of damage but it's biggest weakness is it lacks flexibility. It withholds an extreme pressure but once that border is crossed, it breaks rather than bends.
We are, of course, talking extreme forces here. Generally, both materials have their own advantages and disadvantages. Let's wrap it up here:
Although slightly heavier than aluminium, some steel frames can still be very light and they are much stronger and durable giving a more pleasant ride on a daily basis.
Lighter and faster than steel, the frames are chunkier and stiffer giving advantages for speed but making you feel all bumps on the road. Very strong but breaks rather than bends under extreme pressure.
Hi-Tens steel bikes
4130 ChoMo steel bikes
Reynolds 520 steel bikes
Columbus steel bikes
6061 aluminium bikes
6066 aluminium bikes
7005 aluminium bikes