A Guide To Steel MTB Frames

A good steel mountain bike frame is as relevant today as it was when the first ‘safety’ bicycle was invented in the late 1800s. While there are different, more modern and lighter materials available (including aluminium, titanium and carbon), most mountain bike riders will still choose a good quality steel bike over these relatively new materials.

But what is steel and how has this material been used throughout the history of the mountain bike? In our guide to steel mountain bike frames, we aim to dispel the myth that steel MTB frames are poor quality, heavy and ill-suited for this purpose. So keep reading, the info may surprise you.

What Is Steel?

According to the World Steel Association, steel is:

“the world’s most important engineering and construction material. It is used in every aspect of our lives; in cars and construction products, refrigerators and washing machines, cargo ships and surgical scalpels.”

So why not use it in MTB bike frames?

Steel comprises a large component of iron combined with small traces of carbon (max 2%), and small quantities of other various elements including manganese, chrome, silicon, phosphorus, sulphur and oxygen. How these elements are combined has a huge impact on how the steel performs. So just saying a bike has a steel frame gives little information about the actual quality of the frame and how the different steel frames will perform.

So What Are The Different Types Of Steel Used In MTB Frames?

While there is a wide variety of steel out there, MTB frames usually fall into 2 different categories; the cheaper ‘high-tensile’ steel used on low-end frames and chromium-molybdenum otherwise known as ‘chromoly’ steel used on ‘premium’ frames.

High-Tensile Steel

Hi-Tensile or carbon steel is an alloy made with iron and carbon which is strong and very resistant to bending and breaking. It is a very durable and tough material which makes it perfect for everyday use. Hi-Tensile steel is the most common material for lower-end bike frames as it is easily manufactured. Plus it is the choice for smaller, independent bike manufacturers who are looking for inexpensive materials that are strong and easy to use.

It is a good option for people who want to ride a bike daily without breaking the bank.

Chromoly Steel

Chromoly steel is an alloy of steel made with iron and small amounts of chromium and molybdenum. This combination makes chromoly steel lighter, and more durable than high-tensile steel. Generally, bikes made from this material are more suited for people who are using their bikes in tougher conditions like mountain biking. Chromoly steel is more expensive to manufacture, which makes chromoly mountain bikes more expensive. However, these bikes are lightweight, extremely strong, have more flex which makes them more comfortable to ride in tougher terrains.

What To Look For In A Steel Mountain Bike?

A good steel mountain bike is all about the quality of the steel tubes and how they have been put together.

First, let’s take a look at the tubes. Most performance steel mountain bikes are made from chromoly steel, with high-tensile steel used on cheaper, low-end frames. Different compositions of steel have different properties.

The UK company Reynolds is the classic manufacturer of steel bike tubes (founded in 1841 as a maker of nails) - the Reynolds 531 is a classic steel alloy used for bike frames, with the numbers 531 referring to the proportion of manganese, carbon and molybdenum in the alloy.

Every steel bike will have a bike decal (or sticker) at the base of the upright seat tube with information about the quality of the steel - with Reynolds the higher the number, the better the quality.

Today there are plenty more options for tube set providers, including Dedacciai and Columbus. The leading Italian brand Columbus (founded in 1977) denotes its quality with its own branding, so there doesn’t seem to be an industry standard for labelling tube quality. But the information is there.

Secondly, let's take a look at how these tubes are put together. There are two main construction methods for the tubes of steel frames to be connected - either by using lugs or by welding.

Lugged frames see each tube slotted into a cast steel socket (or lug) at their joints which are then brazed or soldered together. Frames without these lugs feature tube junctions that are welded together or by using a technique such as fillet brazing.

Lugged construction used to be the most common, with classic steel frames often having very elaborately fretted lugs, but welding tends to result in a lighter frame and there’s less clean-up needed than with brazing.

How Your Riding Style Affects Your Steel MTB Frame Choice

Mountain bikes have evolved over the years and there are now a variety of different disciplines that fall under the MTB umbrella:

With cross-country and enduro riding the bike frame’s weight becomes very important - the lighter the better.
Trail bikes are mostly a bit heavier and can be used as a good all-rounder.
Downhill bikes need to be overbuilt and aggressive to go downhill in the roughest terrain, and as fast as possible - crazy!
Hardtails are your entry-level MTB frames, probably your first MTB. The quality of the frame is not so important here, so even high-tensile steel will do the trick.
Dirt Jumpers are a type of hardtail MTB. A dirt jumper is a cross between a BMX and a traditional mountain bike. The frame is heavy which means that high-tensile steel will do the trick.
Even fat bikes can be classified here, but the frame has to fit the tyres.

Iconic MTB Models

While many cyclists want the latest titanium or carbon frames, steel has been the professional choice for many years. Some iconic models of steel mountain bikes throughout history include the following:

Team Marin
Trek Single Trak
Kona Explosif
Diamond Back Axis
Raleigh Special Products 853
Rocky Mountain Blizzard
GT Psyclone
Orange Clockwork
Specialized Stumpjumper
Nishiki Alien

If you are lucky enough to find one of these iconic models on the market, you’re welcome to bring it to Bike Sanctuary for a radical restoration or dream rebuild!