A critical piece of information in choosing frame tubes is the frame size. Deflection is proportional to the cube of tube length (based on the equation for deflection where loading is applied to the free end of a cantilevered beam). This should be a conservative approach, since frame tubes are part of a truss and not really cantilevered and torsional deflection is proportional to tube length. However, we still are not including the effect of increased weight of the rider.
The following chart (Figure 1) shows the rank (from Table 1) of top and down tubes that would be used to match the ride of a frame made of traditional tubing of specified wall thickness (everything else being equal) using the cube of the ratio of tube lengths.
Motorbike Frame Tube Thickeness
The standard tubing usually has a weld seam on the inside of the tube which is visible. This results in a stress riser and is not as strong as a clean smooth finish like the DOM tubing. Since the DOM tubes have a lot of processing required, they are much stronger and more uniform which make them the better choice for structural applications such as motorcycle frames. Because of this extra process during manufacturing, they are usually more expensive as well. I definitely recommend DOM tubes over standard tubes.
All of the frames that we are working on use 1.5" outer diameter tube with 1/8" wall thickness (using DOM tubing). We did some Finite Elements Analysis (FEA analysis) and put together a report showing the differences between the tube diameters and their performances. We can put it up if enough people request it. The FEA analysis that I conducted assumes a uniform material with no welds, which equates to DOM steel tubing.
Choosing what material you want your frame to be made from is one of the key decisions to make when buying a bike.\nBike frames have been made from a variety of different materials over the years, with steel originally dominating. Now the major choice is between aluminium and carbon fibre, although steel and titanium still feature commonly.\nEach frame material has its pros and cons, depending on your priorities as a rider, including weight, budget, longevity and the performance characteristics you want from the frame and, as a result, the bike.\nWhat are the key properties of aluminium, steel, titanium and carbon fibre to consider when it comes to buying a bike?\nWe spoke to two experts to find out:\u00a0Richard Lambert from UK titanium and steel bike specialists Enigma, and Liam Glen, a mechanical engineer who currently works for Airbus, as well as being a former professional cyclist and the winner of the 2021 Highland Trail 550 bikepacking race (we\u2019ve got a gallery of Liam\u2019s singlespeed Stooge Cycles Scrambler).\nAluminium frames\nAluminium is the go-to metal for budget to mid-range frames, providing a combination of low weight, stiffness and affordability that\u2019s hard to beat.\nAlloy or aluminium?\n\n Aluminium frames are often referred to as \u201calloy\u201d, although all metals used for bike frames are technically alloys. Immediate Media\nYou\u2019ll often see aluminium frames referred to as \u201calloy\u201d. That\u2019s because pure aluminium would be much too soft to form into a bike frame, so it\u2019s mixed with other elements to alter its physical properties.\nIn fact, all metal bike frames are made of alloys for the same reason. Steel is itself an alloy of iron, and titanium is predominantly alloyed with aluminium and vanadium.\nWhen it comes to aluminium frames, numbers such as 6061 and 7005 \u2013 the two most common aluminium alloys used \u2013 are a code for the additives (chiefly silicon and magnesium) that are mixed with the aluminium to form each alloy. Every \u2018recipe\u2019 has slightly different properties.\nHow is an aluminium bike frame made?\n\u201cAll metals have quite similar strength-to-weight ratios,\u201d Glen says. \u201cIt\u2019s factors like the width of tubing and its wall thickness that are more important than their strength.\u201d\nIt\u2019s relatively easy to manipulate aluminium tubing to give it different properties along its length and aluminium tubes are usually butted, to ensure stiffness where it\u2019s needed, and save weight where it\u2019s not.\nWhat is tube butting?\n\n Butting helps to save weight where it\u2019s not needed, and improve strength and stiffness where it is. Ribble Cycles\nBike tubing, whatever it\u2019s made of, is usually butted. This means it\u2019s thicker at its ends, where there\u2019s more stress and you need more material for the joints to other tubes, while it\u2019s thinner in the middle to save weight.\nStraight gauge tubes are consistent throughout in their thickness, with consistent properties to match. Single-butted tubes are thicker at one end (for example, at the bottom bracket junction), double-butted tubes are thicker at both ends and triple-butted tubes further reduce the thickness in the middle of the tube.\nButting is only part of the story and you\u2019ll often see premium alloy frames described as \u201chydroformed\u201d, which describes the process of adapting the shape of a tube using high-pressure fluid and a mould.\nHigh-end aluminium bikes are more advanced than ever and this process can help form complex shapes to influence the characteristics of a particular part of a frame, including weight, strength and comfort. Many of the latest aluminium frames also sport aerodynamic design features.\nAluminium tubing is usually welded together to make the frame. A raw weld can be quite bumpy in appearance, but this is often smoothed down after welding for a cleaner look on premium frames. It also helps save a little weight. Once an aluminium frame has been welded, it will be heat treated to return the alloy to its full strength.\n\u201cYou\u2019re applying a lot of heat to a localised area [when welding], which can change the metal\u2019s properties locally and make the welds the weakest area,\u201d says Glen. Tempering after welding helps to alleviate this.\nWhat are the properties of an aluminium frame?\n\n The latest aluminium road bikes can produce a ride to match their carbon fibre counterparts. Steve Sayers \/ Immediate Media\nAluminium is the material used for the majority of cheaper bike frames but it\u2019s still a popular choice for some pricier, performance-focused frames, both on the road and, in particular, for mountain bikes.\nWhile the exact properties of an aluminium alloy frame will vary from one bike to the next, typically it\u2019s relatively lightweight with a high level of stiffness, robust and around a fifth of the price of carbon fibre.\nAn alloy frame can actually be lighter than a carbon fibre one at a similar price, although expensive carbon frames will always be lighter still.\n\n Aluminium is well-suited to the rough and tumble of mountain biking. Ian Linton \/ Immediate Media\nAluminium is much less dense than steel.\nAs a result, an aluminium frame can be made with oversized tubing to achieve a high level of stiffness, with thicker walls, while still being lighter. According to Ribble, the tube wall thickness of an aluminium alloy frame will commonly be twice that of steel, with tube diameters in the region of 20-30% larger.\nAluminium frames historically had a reputation for being uncomfortable, due to the relative stiffness of the material and lack of shock absorption, but the latest frame building techniques, as well the trend towards wider tyres on road bikes, mean many alloy bikes offer a much-improved ride quality.\nWhile aluminium frames offer an impressive balance of strength, stiffness and low weight, aluminium alloys can be prone to long-term fatigue, unlike steel and titanium.\nHowever, aluminium frames tend to be less susceptible to crash or accidental damage than carbon frames. As a result, aluminium remains a popular frame material on all mountain bikes, as well as being a smart option for privateer road racers on a budget.\nPros of an aluminium bike frame\nStiffness-to-weight ratio\nAffordability\nMore durable than carbon\nCons of an aluminium bike frame\nStiffness can result in a harsh ride quality\nAluminium fatigues over time\nDifficult to repair\nSteel frames\n\u201cSteel is real\u201d, as the old adage goes, and was the material traditionally used for bike frames.\nIn fact, steel was the staple of frame building for around 100 years, even at pro level, right up until the mid-1990s, when aluminium alloy frames started to take over \u2013 with only a brief spell in the pro road peloton \u2013 and the first carbon fibre frames were tried out.\nLugged or welded?\n\n Colnago, the masters of lugged frames. Immediate Media\nThere are two main construction methods for steel frames, either using lugs or not.\nLugged frames see the tubes slotted into cast steel lugs at their joints then brazed together. Frames without lugs feature tube junctions that are welded together or fillet brazed.\nLugged construction used to be common, with classic steel frames often having very elaborately fretted lugs, but welding tends to result in a lighter frame and there\u2019s less clean-up needed than with brazing, which typically results in excess material at the joints that needs to be removed afterwards.\n\n Steel was the go-to option for bicycle frames for more than 100 years. Felix Smith \/ Immediate Media\nOn the other hand, according to Glen, brazing needs a lower temperature than welding, so there\u2019s likely to be less alteration of the steel\u2019s properties, leading to a stronger joint.\nLike the tubes in aluminium alloy frames, steel tubes are typically butted to make them lighter. There\u2019s more variety in tube shapes in modern steel frames, rather than the round sections of old.\nWide variety of steels\n\n Reynolds has been producing steel tubing since 1898. David Caudery\/Immediate Media\nMost performance-minded steel bikes are made from chromoly steel, with high-tensile steel seen on cheap, low-end frames.\nDifferent compositions of steel have different properties. Reynolds 531 is a classic alloy used for bike frames, with the 531 referring to the proportion of manganese, carbon and molybdenum in the alloy.\nThere are plenty more options now, though, from tubeset providers including Dedacciai and Columbus.\nLambert points to the wide variety of different tube compositions and profiles available for steel, which he says is not the same for other frame tubing. That means you can build up a very sturdy frame for touring or one that\u2019s lighter in weight, depending on what\u2019s chosen.\nStainless steels are also an option. On average, they\u2019re weaker than chromoly steels, although specialist stainless steels have been developed for bike making that are as strong as, or stronger than, chromoly, says Glen.\nWhat are the properties of a steel frame?\n\n While aluminium and carbon are now more popular, steel afficiandos still swear by the original frame material. Andy Lloyd \/ Immediate Media\nThe main downsides of steel are its weight and cost. It\u2019s heavier than aluminium and more expensive to manufacture on a mass scale, ensuring aluminium remains the preferred option for most of today\u2019s metal bike frames.\nHowever, while steel is much denser (and heavier) than aluminium, it\u2019s stronger and more durable, too. This means frame builders can use smaller-diameter, thinner-walled tubes and maintain the required level of stiffness, though the weight penalty remains.\nUnlike aluminium \u2013 and, as we\u2019ll come on to, carbon fibre \u2013 it can also be (relatively) easily repaired, if damaged.\nSimilarly, steel also has a fatigue limit \u2013 it can withstand stress below its fatigue limit an infinite number of times without resulting in failure, again unlike aluminium, which will wear with time.\n\n Steel remains a popular option for touring and bikepacking bikes. Duncan Philpott \/ Immediate Media\nThe natural damping properties of steel can result in a \u201cspringy\u201d \u2013 read: comfortable \u2013 ride quality, too, even if it\u2019s not a match for the stiffness-to-weight ratio of aluminium.\nFor all of these reasons, steel is a popular option for boutique and custom bikes, as well as touring and bikepacking frames, where weight is less of a concern. Steel offers better value than titanium, and durability and longevity are key.\nThat said, steel frames, unless made of stainless steel, need to be painted to stop external corrosion and can be coated inside the tubes too in order to stop rust.\nPros of a steel bike frame\nStrong, durable and won\u2019t fatigue\nEasy to repair\nComfort\nMore affordable than titanium\nCons of a steel bike frame\nRelatively heavy\nMore expensive than aluminium\nLess advanced tube shapes than aluminium\nWill corrode if not properly treated\nTitanium frames\nTitanium is often viewed as a luxurious option, partly due to its ride quality and cost, as well as the fact a titanium bike is often touted as a \u201cbike for life\u201d.\nMost metals have a defined number of load cycles before they\u2019re likely to fail. Titanium is far more resilient to repeated stresses and strains, and this means skilled frame fabricators can build frames lighter and with more compliance without risk of failure.\nTitanium alloys\n\n Titanium has a timeless appeal as a frame material. Matthew Loveridge \/ Immediate Media\nLike aluminium and steel frames, titanium is an alloy and there are also different grades available to frame builders.\nThe AL3 2.5V alloy (containing 3% aluminium and 2.5% vanadium) is the most common grade used for titanium frames. 6AL 4V tubing is notably stronger \u2013 and more difficult to work with, as a result \u2013 and is sometimes used for high-performance frames or individual areas where stiffness is key, such as the head tube and bottom bracket sleeve.\nEnigma, for example, uses the stiffer, higher-grade 6AL 4V alloy, also known as grade five titanium, for its performance bikes, rather than the 3AL 2.5V alloy (or grade nine) in its more compliant Etape frameset.\nTitanium alloys are also highly fatigue resistant, which means that they can flex without failing. Moots, for example, uses flex in the titanium chainstays to provide pivotless suspension at the rear of its Mountaineer and Routt YBB framesets.\nWhat are the properties of a titanium bike frame?\n\n The latest titanium frames can be designed to offer a stiff, sporty ride. Robert Smith \/ Immediate Media\nTitanium has distinct advantages over other metals for a bike frame. It\u2019s less dense than steel so a frameset can be lighter while still having thicker-walled tubes. A titanium tube is half the weight of a steel tube of the same tensile strength. Enigma\u2019s titanium tubesets typically are 0.9mm thick at their thinnest point, against 0.5mm for steel.\nThat makes it harder to dent a titanium frame and, since titanium doesn\u2019t corrode, the frame doesn\u2019t need painting, so scratches and chips aren\u2019t an issue either. The raw finish typical of titanium frames looks great too, although there\u2019s no reason why a titanium frame can\u2019t be painted.\nOn the other hand, titanium is a lot more difficult to work with than steel, according to Enigma\u2019s Lambert. \u201cYou have to be careful over cleanliness and control of the welding process, in particular purging oxygen, for which Enigma uses argon gas,\u201d he says.\n\n What\u2019s not to like about details like this? David Caudery \/ Immediate Media\nIt used to be that there were few titanium tubesets available and they weren\u2019t designed specifically for bikes. This gave titanium frames a reputation for being over-flexy. Lambert says that\u2019s not an issue now, as there\u2019s more choice of bike-specific tubing, while design features such as tapered steerers and wider bottom bracket standards mean that titanium frames can be designed to be as stiff as the application demands.\nThat said, titanium still has a reputation for offering a comfortable ride quality in the hands of a good frame builder.\nThe flip side is that titanium is the most expensive metal option, often eclipsing the price of a carbon frameset.\nPros of a titanium bike frame\nStrong, durable and won\u2019t fatigue\nLighter than steel\nRide quality\nRaw finish or painted\nCons of a titanium bike frame\nHard to work with\nNot as light as carbon or high-grade aluminium\nExpensive\nCarbon fibre frames\nEver since Lance Armstrong won the 1999 Tour de France on a Trek 5500 OCLV, carbon fibre has been the go-to material for high-performance bike frames.\nAnd for good reason. Carbon fibre is a highly-adaptable wonder material that can be shaped and fine-tuned to precise requirements, balancing stiffness, comfort and aerodynamic performance.\nCarbon isn\u2019t without its downfalls, though. Carbon fibre bike frames are expensive \u2013 well into five figures at the top-end of the market \u2013 and can be more susceptible to crash damage than other materials.\n\n Carbon fibre really came to the fore in the early 2000s. Tim de Waele \/ Getty Images\nHow is a carbon fibre bike frame made?\nA carbon bike frame is made up of layers of carbon fibre (fibres woven into sheets) embedded in a matrix of epoxy resin. The carbon fibres give it strength, the resin holds it together.\n\u201cCarbon has the highest strength-to-weight per ply,\u201d says Glen. \u201cBut that\u2019s only in one direction, so it\u2019s stacked at multiple angles in a bike frame. That means that its strength-to-weight goes down a little, but it\u2019s still higher than other materials.\u201d\nMost frames are made by layering up many sheets of carbon fibre\/resin material, called \u201cprepreg\u201d, with different grades and orientations used in different places in the frame. Look, for example, says that its 795 Blade frame is made using over 800 different pieces of prepreg.\n\n An oven is used to cure a carbon frame in production. Octavio Passos \/ Getty Images\n\u201cThe resin gives the frame impact tolerance and compression strength,\u201d says Glen. \u201cThere are relatively few companies making prepreg and many frames are made by third parties, so most frames will be made with the same resins. It\u2019s the lay-up that bike makers specialise in and that also gives their frames their different qualities.\u201d\nThe need to master lay-up adds another layer of complexity to carbon frame design. Bike brands also don\u2019t know how individual end-users will ride their frames. That leads to a degree of over-engineering of carbon frames to ensure that they can handle abnormal loads, says Glen.\nMonocoque or tube-to-tube construction?\n\n Colnago is one of the few brands to use a lugged construction for a carbon fibre frame. Jack Luke \/ Immediate Media\nOnce the different layers in the frame have been assembled, which is done by hand, the frame is placed in a heavy metal mould and heated under pressure to bond the different layers together.\nIn a monocoque frame, a different mould is needed for each size of bike, making setup for a new frame design expensive.\nThe alternative, which is used for a few custom frames, is tube-to-tube construction, where pre-formed carbon fibre tubes are cut to length and either wrapped in extra carbon fibre at the joints or glued into carbon fibre lugs. The Colnago C64 is a classic example of the latter method of construction, while Condor\u2019s carbon framesets use tube-to-tube construction.\nA very limited number of bike manufacturers have used machines to weave their own carbon fibres into tubes. It\u2019s a process which has been used for some BMC and Time framesets.\nWhat are the properties of a carbon fibre frame?\n\n Carbon frames can be moulded into complex aerodynamic shapes. Orbea\nA key difference between carbon fibre and all metals is that the composite nature of carbon fibre makes it anisotropic, which means that its physical properties are different in different directions.\nAn everyday example of an anisotropic material is a piece of wood; you can easily split it lengthways, but it\u2019s a lot harder to break across the grain.\nIt\u2019s the same with carbon fibre, which means the layout of different pieces is crucial to how the frame rides and how strong it is. It\u2019s why you\u2019ll repeatedly find references to \u201clay-up\u201d in marketing materials for carbon bikes.\nThe other important factor is the modulus of the carbon fibre used. Higher modulus fibres will be stiffer, but they\u2019re also more brittle, so even a frame marketed as \u201chigh modulus\u201d will be made of a mix of different grades of carbon fibre. Higher modulus carbon fibre is also more expensive, but the end result will be a lighter frame for the same strength.\n\n Carbon fibre is a wonder material when it comes to frame design, but it\u2019s not without its drawbacks. Russell Burton \/ Immediate Media\nYou\u2019ll sometimes find other materials incorporated into carbon frames, too. An example is Bianchi\u2019s Countervail technology, used in many of its frames, which integrates a layer of viscoelastic material into the carbon lay-up, which Bianchi says helps to dampen vibrations.\nThe advantages of carbon fibre are well known, given the propensity of bike brands to sing the praise of their all-conquering, high-end carbon frames.\nThe ability to carefully curate the properties of each part of the frame means carbon frames can be designed to meet the specific demands of the bike and the type of riding it\u2019s designed for.\nCarbon fibre can be used to make a frame that\u2019s extremely light and extremely stiff, with the option to wrap the carbon into complex, aerodynamic tube shapes, while still considering ride quality and comfort.\nIt\u2019s not all good news\nThat will cost you, though, and carbon fibre isn\u2019t always the best option for cheaper frames, where more affordable aluminium options can offer similar \u2013 or better \u2013 ride characteristics, for less money.\nAnother disadvantage of carbon fibre over metal frames is that it can\u2019t be reamed or tapped to provide threads to allow components to be screwed in. That means bearings typically have to be pushed into the frame, or a metal insert needs to be added to house threaded bearings.\nPress fit bottom bracket bearings, in particular, have a reputation for creaking, while metal inserts will add weight to a bike and may introduce alignment issues if not done right.\n\n Carbon frames can be susceptible to crash damage. Kenzo Tribouillard \/ Getty Images\nCarbon fibre is also quite easy to crush, so it can be easily damaged in areas such as quick-release drop-outs. That\u2019s why carbon bikes often have metal drop-outs or inserts for thru-axles, or include metal protectors for these areas.\nBangs and bashes can also cause damage to the interior of frame tubes, which may not be visible from the exterior and which can cause a frame to break unexpectedly. If your carbon frame has a bash or a heavy crash, you should get it inspected before riding it again. It may require ultrasound or X-ray inspection to detect internal damage.\nIf you do break your carbon frame, there are limited options to recycle, whereas with metal frames that\u2019s easy. The value of titanium, in particular, means that it\u2019s unlikely to end up in landfill.\nPros of a carbon fibre bike frame\nExcellent stiffness-to-weight ratio\nHighly adaptable\nCan be moulded into aerodynamic tube shapes\nCons of a carbon fibre bike frame\nExpensive\nProne to wear and crash damage\nWhat other frame materials are available?\n\n A bamboo bike? You bet! Oli Woodman \/ BikeRadar\nWhile carbon fibre, titanium, steel and aluminium are by far the most common material used for bike frames, there are a handful of rarer options, too.\nYou\u2019ll sometimes see frames described as scandium. It\u2019s far too rare an element to be used for an entire bike frame though, and scandium frames are actually an alloy of aluminium with a small percentage of scandium, along with other metals. The scandium content is there to up the strength of the alloy tubing.\nSome bikes and bike parts have been made of magnesium alloy and it keeps threatening to make a comeback, with niche frames made from the material. Magnesium alloy is lighter than aluminium and also stronger, although it\u2019s less stiff. It had its heyday in the early 1990s when the Kirk Precision bike frame was raced at the Tour de France. The Pinarello Dogma was made of magnesium as late as 2006. Vaast also produces a range of magnesium frames, including the Vaast A\/1 gravel bike.\nNatural materials have found a niche in bike frames. Several brands sell bikes with frame tubes made of bamboo. Riders report that it\u2019s comfortable, doing a good job of damping road vibrations. It results in a bike that\u2019s a bit heavier than other materials and, although the bamboo tubes boast great eco credentials, they may need lugs and resins to join them that are less environmentally sound.\nFlax has also been used as a component of bike frames, usually in combination with carbon fibre, as it\u2019s claimed that it absorbs vibration better than carbon alone. It\u2019s used in the LOOK 765 endurance bike range and was also featured in a series of bikes launched in the mid-2000s by racing legend Johan Museeuw.","image":"@type":"ImageObject","url":"https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2021\/11\/Bike-frame-materials-1-12ca49e.jpg?quality=90&resize=768,574","width":768,"height":574,"headline":"Bike frame materials explained: carbon vs aluminium vs steel vs titanium","author":["@type":"Person","name":"Paul Norman"],"publisher":"@type":"Organization","name":"BikeRadar","url":"https:\/\/www.bikeradar.com","logo":"@type":"ImageObject","url":"https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/cropped-White-Orange-da60b0b-04d8ff9.png?quality=90&resize=265,53","width":182,"height":60,"speakable":"@type":"SpeakableSpecification","xpath":["\/html\/head\/title","\/html\/head\/meta[@name='description']\/@content"],"url":"https:\/\/www.bikeradar.com\/advice\/buyers-guides\/bike-frame-materials\/","datePublished":"2021-11-08T15:00:00+00:00","dateModified":"2022-10-21T16:45:27+00:00"}] Bike frame materials explained: carbon vs aluminium vs steel vs titanium How to choose the right frame material for your next bike 2ff7e9595c
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