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Wednesday, March 17, 2010

Frame Materials

Material World

Part of my idea for this blog is to provide helpful information for people biking in Taiwan or people who are interested in biking in Taiwan, including routes and tips. I hope to discuss Taiwan related issues through bicycle metaphors and share historical, cultural and ethnographic information that can help turn the next ride into something beyond simply a route past concrete and rice fields.

Another goal is to touch upon cycling as a sport. I really didn’t care as much about professional cycling until I started spending some time in the saddle trying to improve. All of a sudden, as I evaluated my own improvement, did I gain a newfound respect and understanding for the skills of those gifted enough to make the pro-tour. The amount of guts, grit and finesse is truly worthy of respect.

Lastly, I hope to discuss hardware and all those things that make us figure out complex algorithms to justify spending NT15,000 on 100 grams less bike.

Most of all I hope the information here can be useful in some way to help make cycling in Taiwan more fun and help strengthen our community, which has a tendency to lean toward the petty elitist if we let it. Lots of folks are interested in joining and are afraid to jump in because they lack the information they need to feel good about getting a bike.

I have covered types of bikes and bike geometry, so now I should probably add something about frame materials.

The basic bicycle frame has remained largely unchanged for over 100 years. It is still, essentially, two triangles back to back, creating a diamond shape; triangles being the strongest geometric shape. And for over 100 years bicycle companies have been refining and sculpting these shapes to better take advantage of new developments in materials, production techniques and shaping to create ever better bikes… and largely to convince the consumer that somehow the newest generation is ultimately better than the last and more money needs to be thrown at the latest technology. This is what bike companies do… they sell bikes. Key word SELL. They play on our fantasies and try to convince us that the engine is fine, but with the right, high-tech chassis, we could take L'Alpe d'Huez with the best. Now, I am not a luddite. I love new tech. I just think there is a lot of marketing junk out there that we oh so want to believe. “If I only had X then I could do Y and Z.” Material is not necessarily the best way to accomplish this.

In essence… a frame builder can make a bike feel (fill in your favorite adjective) with the proper geometry and design. A carbon fiber bike can be flexy or harsh. An aluminum bike can feel smooth and forgiving. A steel bike can feel stiff and light. A titanium bike can ride like a noodle or a rocket. If the material is used with its properties in mind… it could be a great bike for anyone. The argument of “identical frames” with different materials is just silly. Anyone who’d copy a design for a steel bike with aluminum should be beaten soundly. There are some great bikes out there for almost every purpose made from each of the major materials. Just because aluminum or steel are not the material de jure, does not mean they are in any way inferior. Still, each material deserves some individual attention for what it can and can’t offer.

Carbon Fiber

“So… carbon bikes are the best… right?"

Willier Monococque Frame

Carbon fiber frames now occupy just about every position of the pro peloton. There is a very good reason for this. Carbon fiber can make some very good bikes… and bicycle companies have brought the cost of producing carbon fiber frames down to the point where the mark up at sale is often many, many times greater than cost. Bike companies know that the consumer will want whatever is under Armstrong’s ass… even if there are no tangible benefits in performance. There are lots of examples of this, like low profile forks and shorter stays.

A carbon fiber or “composite” frame is made from molding different weaves of carbon fiber molded in a matrix that can determine how the frame performs. The engineers can adjust the matrix of carbon fiber types to adjust the characteristics of a given frame. Identical frames can perform in fundamentally different ways based on the weave of the carbon fiber. Carbon fiber offers new frame shapes that could not be achieved with metal tubing. Most builders use either lugged carbon techniques, where the individual carbon fiber tubes are bonded into carbon lugs, and monocoque molding (single shell).

Look 585 lugged carbon fiber

The down side of carbon is that, although it can be light, stiff, smooth or whatever you want… carbon tubing has very poor elongation qualities and thus it can not bend, and when it fails, it fails catastrophically. There have been several instances where unseen damage led to mid-ride catastrophic failure. Another problem is in the bonding. Metal filaments are wrapped up in the carbon fiber matrix at the points of rider interface i.e. bottom bracket, headset etc… There is a potential for the bonding to separate. There are reasons why there are still no carbon fiber touring bikes that need to negotiate the worst roads under stress.

Another down side of carbon fiber is that it does not biodegrade and can’t be smelted anew. There are some programs for recycling carbon fiber components, but the scope and uses for recycled carbon fiber are limited.


“So… carbon fiber is light and stiff and smooth, but not as dependable as titanium?”

Kish Custom Titanium

Titanium is a fantastic metal. I would like my next bike to be titanium. Titanium frames can also be crafted to perform in a variety of ways. They can be built stiff and harsh, they can be springy and forgiving. You can have a titanium frame to ride like it is on a cloud or tuned to feel more of the road.

Titanium is twice as dense as aluminum and yet 56% as dense as steel. Titanium is only half as stiff as steel and thus engineers of titanium frames must take this into account to manage the desired stiffness. When designers try to thin titanium frames out too much they run into the problem of frames getting too flexy. The real advantage of choosing a well-engineered titanium frame is that the elongation of titanium is much greater than the other metals. Titanium can have twice the elongation of steel and three times that of aluminum. Stronger steels and aluminums sacrifice even more elongation for strength.

Titanium and steel both are both great for resisting fatigue. Titanium can undergo repeated flex and the high modulus properties allow it to snap right back so that a titanium frame can feel brand new after 30 years. With carbon fiber, the jury is still out. Nobody has ridden a carbon frame long enough to test the long-term effects. We just don’t what happens after a couple dozen years. Some riders claim their carbon frames feel “dead” after a couple years of riding, or that could be just bike lust. Titanium is a proven winner for longevity.

On the down side, titanium is welded with argon gas and fabricators must be careful during the welding process or risk brittle welds. Machining is also difficult, so the price to produce high quality frames is relatively high. Another factor is the environment. Titanium takes greater energy to extract and process. Environmentally minded people may consider this a problem. Then again, a bike that lasts 30 years may make up for that over the environmental cost of buying one bike every 3 years, like the big bike corporations would like you to do.


“So aluminum is an obsolete frame material that will just wear out in a couple years.”

Cannondale CAAD9 Aluminum

Aluminum frames really hit the scene in the mid-80’s when Cannondale started selling their notoriously stiff frames with oversized tubes and a thickness that was overcompensating. I remember riding around on these things. Tooth chatteringly rigid.

The aluminum frames on the market are alloys, usually 6061, 7005, 7000, 7075 and others.

Aluminum is has 1/3 the density of steel, which means it is really light and yet some alloys are just as strong as steel. SO a strong, low density metal, but a low modulus, so it can be light and stiff. The oversized tubing allows for a good, light bike with plenty of stiffness. Sounds like a climber. As the diameter of the tubes increases, so does the stiffness.

Unlike titanium and steel, aluminum’s elongation isn’t as great. This means that under load, stressed enough times, aluminum will fail.

Merckx Team SC Scandium Aluminum Alloy

This does not mean aluminum frames are throwaways. Engineers design aluminum frames with these factors in mind and butt the tubing to ensure there is enough aluminum in the spots that are put under stress to take advantage of its properties. This type of well thought out engineering, shaping and design can produce an aluminum bike that can last a very long time and ride like a dream. Some of the best bikes ever produced are aluminum. It can be argued that the Merckx Team SC, scandium alloyed aluminum is one of the greats. Best of all… aluminum can be inexpensive. Why pay an unnecessary amount of money if you can get an aluminum bike that rides like a dream. Just because it is AL does not mean it is not as good as any other material.

Scandium and other alloys are often added to aluminum to achieve better results and lighter bikes. When scandium is added to 7000 series aluminum it changes the structure of the aluminum grains to be smaller and more refined. This adds strength and allows thinner tubes to be drawn for a smoother feel. It also helps strengthen the welds for frames that often rival carbon in weight.

The ecological downside is that aluminum is costly to refine and recycling is not very energy efficient.


“So steel is an ancient frame material that weighs a ton and was retired long ago except by artisans and romantics. You can’t make a fast steel bike”

Speedvagen Steel Road Bike

The obituary for steel has been written many times over the years at yet it keeps sticking around like a bad rash after a college party.

The steel crowd loves to repeat the maxim, “steel is real”. I don’t buy that it is any more real than titanium, aluminum or Swiss cheese. A lot of steel’s big proponents can come across as elitist hipsters who like to imagine their bikes forged by magic elves in the furnaces of Mordor, like a scene from some fantasy rock song of the 70’s. But there is a reason why steel has its die hards (ouch…the puns!)

Bikes have been made of steel for 100 years, and despite the age of the technology, steel has continues to evolve to remain competitive with other frame making materials. Now, a frame maker can choose from CrMo, Reynolds 851, 951, Tru Temper OX Platinum, S3, Spirit, Life, Zona etc… these are all great steel tubes with some approaching titanium’s strength to weight ratio.

Steel is more dense and therefore the same amount of material weighs much more. Despite this, steel is very stiff. Steel holds twice the stiffness of titanium. This means steel tubes can be drawn smaller to compensate for the weight.

Steels used in bike frames can hold vastly different properties and therefore each should be looked into (not here, not now).

Basically, steels have pretty good elongation numbers and can withstand a lifetime of pedaling.

Steel can be repaired, welded, and cold set. It is durable and with proper care, it can last forever. Steel can be made light and many companies still sell fast racing bikes.


“So, which frame material is the best?”

Despite what marketing departments will tell you… they are all great materials that each have a lot to offer and each can be designed to deliver a whole variety of characteristics. The weight differences between quality frames from each material is so insignificant to most riders it can mean as much as a 20 second difference in a hill climb, but then the next 5 hours can be a tooth-shaking, back aching hell. The best thing is to try them all as equals and choose the one that works with you. The speed and performance will not come as much from the frame materials as from how those materials are used and the geometries they are designed with. A fast climber can be smooth and does not have to be too stiff. Long stays and space for 28c tires does not make a slower bike. Comfort will not come from the frame as much as it will come from a good set of wheels.

Bike companies pull a slight of hand. They want to move bikes and they offer some good looking deals. High zoot frames with recognized names on the gruppo, but upon closer inspection the wheels are crap. In almost every complete bike… the wheels are going to be crap. Pardon my caveman metaphor, but customers are quick to get distracted by the tits and the ass… the frame and the gruppo… and don’t notice the personality, which largely comes from the wheels. Shops are aware of this and will often adjust tire pressure to provide a desired ride. The pricier bikes will ride better and smoother with proper inflation and the lower end they will over inflate to create harshness. The saddle should also be comfortable. Brooks makes nice saddles, but Selle Italia and Fizik and others are great too. Saddles are like shoes… some just don’t fit. Geometry determines the handling characteristic… and lastly… fit. If the rider doesn’t fit the bike it’ll never feel great. Speed can come as much from comfort as stiffness. If a bike is too stiff a rider can’t take advantage of the properties. I know I go slower when overinflated. This is similar to a stiff bike with short stays.

The best thing any rider can do is to get a more efficient and stronger engine. The material can often be an excuse for one's own failings in training and conditioning. It is too easy to just blame the bike.

So go don’t discriminate and try ‘em all. Find the one that sings to you. You may be surprised what works for you.