Simple enough question really - I can only think of the cotic rocket.
is it so that you can bend ally into weird wonderful shapes and make it look dead sexy compared to steel?
Or is it that the inherent advantages of steel like a bit more compliance etc become redundant when you start to use full suspension?
Just wondering like.
It's too heavy
theres a downhill bike. k...something I think? (and not knolly, khs, kona)
one or two others I think Ive come across(on the interwebs). Dirt jumpy-ish things
EDIT:
One of which being the DMR Bolt
[125mm rear/120-150mm fork, concentric BB/chainstay mount]
AFAIK: Steel is flexi, when made into tubes small/light enough for a bike frame. You don't want that in a FS, that's what the S is for. You want the frame rigid.
It's too heavy
A kg of steel weighs the same as a kg of carbon. But maybe you are being ironic.
There's even fewer titanium ones I think.
ease of machining bearing housings etc.
alu = lighter stiffer frames
lots of taiwanese factories ready to weld it...
Keewee did one
BMW have done a few
Balfa did half a one
Not many others I can think of, a few smaller companies/one man band affairs but I dont think you can really count those.
I got a keewee chromo 8
indestructable i reckon
but so so heavy... good for uplift days
weight makes it pretty stable 🙂
light steel flexes.... not good for pivots/linkages etc i reckon
would love to try the cotic though
front triangle of a K9 dh frame is steel but not the back. IIRC there used to be an all steel Identiti single pivot dh/fr frame a few years ago too.
A friend of a friend has a BMW (racelink?) and it is well-ard! Weighs more than any expensive bike I have ever handled, apart from my mum's old pashley princess maybe! 😆
Steel tends to be used by bijou manufacturers and they tend to build/assemble hardtails. FS frames tend to come from the larger manufacturers most of whom stopped using steel twenty odd years ago. You've pretty much answered your own question with the two suggestions you've made yourself I'd say.
Steel is far from flexy... for a given volume, steel is about 3 times as stiff as aluminium, although it is also approx 3x heavier... however, it's harder to form into individual and unique shapes for design flair and more importantly marketing purposes, so is left to rust.
(to be fair, I have 3 full suspension steel bikes and whilst the ride characteristics are schweet, and the frames strong the weights are not competitive within the Trail/AM Market, although once you start getting a bit more hardcore (something like a transition bottlerocket) they become more competitive... the DH bike is ahead of it's time and still a respectable weight today (keewee cromo8)
Marketing.
Aluminum is stiffer, lighter and stronger according to the marketing department. In reality there's rarely more than a smidgin in it, otherwise there woudn't be both options.
Specialized prototype their bikes in steel (or certainly used to, I've seen the prototype post monocoque enduro) as it's easy to do short runs with steel tubes.
There was a Raleigh M-trax FS in R853.
Steel is far from flexy... for a given volume, steel is about 3 times as stiff as aluminium, although it is also approx 3x heavier... however, it's harder to form into individual and unique shapes for design flair and more importantly marketing purposes, so is left to rust.
Aluminum is stiffer, lighter and stronger according to the marketing department. In reality there's rarely more than a smidgin in it, otherwise there woudn't be both options.
Which is missing the point that it's not the material but what you do with it, and that it's not possible to do the same things with all materials. Aluminium frames are made stiff by using large diameter tubes. If you used steel tubes of the same diameter as commonly used for alu frames, then either the frame would be a lot heavier than the comparable alu one or the tubes would have walls so thin (1/3 of the thickness of the alu frame) that it would be extremely fragile. If you use smaller diameter tubes as is commonly the case with steel frames then you get a lot less stiffness - the bending stiffness of a tube is proportional to the 4th power of the diameter, so making a tube just 20% smaller in diameter makes it less than half as stiff.
It's not just marketing - an alu frame optimised for stiffness will be significantly lighter than an equivalent steel frame (that or the steel frame will be a lot less stiff). The reason there are both options is actually where the marketing bit comes in!
Think the Rocket is demonstrating one of the good reasons not to use steel- just look how many people say "It'll be heavier than the competition because it's steel" (which it isn't), or "steel is flexy" (when Cy's saying it was chosen for stiffness).
Reality isn't always what sells bikes.
because Taiwan makes aluminium bikes in a certain way. so everyone submits their CAD designs for a frame, The factories churn them out at a low uint cost.
Switching to steel would require expensive modification of the manufacturing process.
well..
Ive ridden one or two steel bikes(!) and they ride smoothly because the frame has a bit of flex built in to it for the reasons aracer so rightly points out. (good summary there aracer)
The swingarm of the rocket is alu.. where the stiffness is needed and theres all the shock pivots to house.
much easier and cheaper to cast or cold forge these in alu, makes sense.
oh an its 853 which is stiffer generally throughout the tube/frame IMHO than the earlier tubesets from reynolds (for example)
now can anyone tell me about the stainless tubesets, Im thinking about trying either an off the peg thing or getting something built.
Ive not ridden one an am looking for an alternative to Ti as I have a habit of breaking things 🙁
cheers
J
Lolz at bigrich
bigrich - Member
because Taiwan makes aluminium bikes in a certain way
LOL. Taiwan or whoever makes aluminium bikes because that's what everyone wanted. If the market reverted back to steel, that's what they'd go back to making (who do you think used to make all those steel frames...)
The problem with steel when designing for light weight is that if you make the tubes small/light enough then the wall thicknesses start to be an issue as they get very thin - they become very easy to dent or do a beer can to - eg crumple.
Steel is a fantastic material if you don't mind a bit of extra weight - on something like a FR bike for instance (the aforementioned Cotic)
Ive ridden one or two steel bikes(!) and they ride smoothly because the frame has a bit of flex built in to it for the reasons aracer so rightly points out. (good summary there aracer)
Depends on the frame design - None of my steel bikes are particularly flexy/springy - certainly not more so once built up than my large Alu tubed Pace RC303 (before it broke 🙂 ) which had a very long seatpost...
The swingarm of the rocket is alu.. where the stiffness is needed and theres all the shock pivots to house.
no, the stiffness is needed in the seat tube, which is steel, and thats the main advantage of the design to my mind.
aracer has answered the questions very accurately.
I'm not buying it for a second that Cotic know better than all of the other (considerably more experienced and skilled) manufacturers.
Not heavy? 7.6lbs for a 16", it's heavier than that Foes Shaver which everyone was saying was heavy lest week (and the foes has more bounce).
no, the stiffness is needed in the seat tube, which is steel
Rubbish! Why would the seat tube need to be stiff on a FS bike!??!?!?!
I don't know if to laugh or cry at some of these responses
Rubbish! Why would the seat tube need to be stiff on a FS bike!??!?!?!
Absolutely, it's obvious to anyone that the pivot mounting points don't need to to be as rigid as possible - everyone wants the back end of their full-sus to not only pivot on the designed plane but also flex laterally and twist... 🙄
thepodge - Member
Would people be interested in getting custom steel frames for under £500?They would be standard 4130 and with a limited spec such as you could only choose 1 kind of dropout (horizontal or vertical) not one of 20 styles of H or V dropout or for head tubes any one of 3 lengths.
Really your main options would be geometry.
I have the chance to work with a frame builder but I don't want to start bothering him with all sorts of questions and ideas unless there is some real interest as there is nothing worse than some one taking up loads of your time and then never placing orders.
Posted 7 months ago # Report-Post
Come on thepodge, wipe away your tears and share your knowledge with us...
Absolutely, it's obvious to anyone that the pivot mounting points don't need to to be as rigid as possible - everyone wants the back end of their full-sus to not only pivot on the designed plane but also flex laterally and twist...
The effect of which is miniscule when compared with the effect of rigidity provided (or not) by the swingarm. 🙄
psling, stop stalking me...
I'll have my first frame through in a couple of months (curse you transportation by sea) then I'll know what kind of quality is on offer, there has been talk of previous frames being a bit "slap dash" shall we say
I know bugger all about engineering and material science but all the bike mag articles on bike frame materials I've read over the years suggest pretty much what aracer said.
No idea how factually correct those articles are mind.
Thing is, the material is somewhat irrelevant to us, the end users.
The frame components of a full sus need to be stiff enough to tie the various mounting points together without flex compromising the bikes performance, and it needs to be tough enough to survive the usage it's likely to be put through over a reasonable lifespan. How it's achieved is the bike designers problem. We're only interested in how the finished product rides.
For an abuse friendly 150mm bike, there seems to be relatively little difference in weight between steel and ally frames, not so sure about carbon stuff thats appropriately stoutly constructed, rather than built to be superlight. Also bear in mind that on a slack 150mm bike, wheels and tyres (and other components) need to be relatively strong to cope with the kind of riding that kind of bike encourages. A few g +/- on the frame is irrelevant.
I've spent about 10 hours on a Rocket (and only the chain stay and droplink are ally, the front triangle and the seatstay are steel). One of the least relevant things about it is the frame material. It's way stiffer than my Uzzi. It handles beautifully and it munches technical climbs for breakfast. The demo bike was 5lb lighter than my Uzzi (which is as light as I can get it without compromising performance). About the only relevance the frame material has that I can think of is that the downtube is slightly less likely to get covered in dinks from rock strikes.
Thing is, the material is somewhat irrelevant to us, the end users.
You'd think so, but material and wheelsize are things used to sub divide categories in bicycling. It's the way it is.
People look for "853 frames", "650B bikes" rather than "bike to ride across X".
Read cy's lengthy and informative blog on the issue, that tells you everything you need to know
One of the least relevant things about it is the frame material
Which brings us neatly back to the OP's original question. To the designers and manufacturers it obviously does have some relevance, and to Cy (of Cotic fame, an engineer) it was relevant enough to specify steel tubes as part of the design. But why? To be [i]different[/i]?, to improve performance? cost?
Edit: I should obviously stalk you more quickly thepodge (rather than actually work between posts) 8)
The effect of which is miniscule when compared with the effect of rigidity provided (or not) by the swingarm.
If you're a mechanical engineer then please let me know what you've designed so I can avoid buying it! And if you're not, then maybe you should stop disagreeing with one because your arguments are totally flawed. Do the words "leverage" and "torsion" mean anything to you? Or maybe the phrase "second moment of area"? Honestly...
thepodge -
Member
Read cy's lengthy and informative blog on the issue, that tells you everything you need to know
Obviously that'll be a completely un-biased view from a guy who is trying to sell steel bikes 😉
You'd think so, but material and wheelsize are things used to sub divide categories in bicycling. It's the way it is.
People look for "853 frames", "650B bikes" rather than "bike to ride across X".
It's the same in most market sectors. With musical instrument amplification it's speaker size / configuration, magnet material, open/closed/ported, rather than X loud and with Y tone.
Partly due to the tribal leanings of human behaviour, partly due to buzzword marketing, partly due to journalistic inaccuracy driven by the previous point.
Cy's explanation of why he chose Steel for the Rocket: http://www.cotic.co.uk/geek/steel-full-suspension
Legend, he'd have to design them before he could sell them
He used to sell alu frames, he's not ruled out selling them again
Read the blog and then come back and tell us which bits are just marketing or biased
[i]Do the words "leverage" and "torsion" mean anything to you? Or maybe the phrase "second moment of area"? [/i]
Ooh, I love it when you talk dirty...
Do the words "leverage" and "torsion" mean anything to you? Or maybe the phrase "second moment of area"?
You've just given me a flashback to my first year at uni. Not the good bits either.
The only reason steel is frowned upon by the large makers is because they invested years of marketing bullshit to convince the buying public that Alu was "better" than "heavy steel".
Slightly OT: As an engineer I will never understand why bearing mounts and housings are made of Alu. Alu can be quicker to machine, not always easier, but the part you are trying to protected is made of softer / weaker material than the disposable bearing you place in it.
If you're a mechanical engineer then please let me know what you've designed so I can avoid buying it! And if you're not, then maybe you should stop disagreeing with one because your arguments are totally flawed. Do the words "leverage" and "torsion" mean anything to you? Or maybe the phrase "second moment of area"? Honestly...
Oooooh big man use big word.
So the seat tube which is welded either end and exposed for about 300mm and also 35mm in dia is going to flex more than the swingarm is it?
The only reason steel is frowned upon by the large makers is because they invested years of marketing bullshit to convince the buying public that Alu was "better" than "heavy steel".
dogshit.
I think a more interesting question if we are talking in terms of materials most appropriate to the job(s) is why aren't more FS bikes produced using a greater mixure of materials?
Again there are some notable exceptions the Rocket obviously, Balfa BB7, a few others but in most cases it seems frames are manufactured exclusively from one material or another (commonly Aluminium or Carbon composites these days), I'm not saying that this is "Wrong" as such but considering the different jobs each member in a frame has to do, coupled with any constraints on the design and the balancing of manufactureability, cost, weight, strength, stiffness and marketability issues I'm suprized we don't see more widely mixed material designs.
Nailing your colours exclusively to one material is probably not that wise, as much as I love bikes like the Chromo-8 and Race-link they are relatively blunt tools for an increasingly precise job...
For example I'd be intersted to see a Steel front/composite rear 'AM' type bike and if/what it might deliver in terms of a Ride/weight/cost tradeoff... Discuss...
Come on guys play nice. This is a great thread don't spoil it.
Other steel full suss bikes include the Super Co DH bike which is. Dry like the Brooklyn Machine Works Racelink and I think is built by an ex employee of BMW.
Where you see steel in FS frames they are always low volume niche manufacturers (Cotic, K9, BMW, Super Co). That large manufacturers tend to prototype designs in steel suggests that steel is easier and cheaper to work with which is critical for low volume manufacturers.
The cotic rocket looks great and i would love to ride one but you really can get away from its weight. It is heavier by about 1lb over equivalent frames. That's a tricky 'sell' to most people especially when it's not just 1lb heavier than the mean but 1lb heavier than the next heaviest equivalent. My Nic is the same weight as the rocket but it does offer the option of 20% more travel should I set it up that way. I wouldn't worry about a full build being 30lbs but lots of other people will.
I like Aracers response though because he seems, like someone else pointed out, to be reflecting the materials science I've read in the last.
Who remembers the cannondale 3.0 frame from the early 90s? That had huge tubes and super thin walls that would dent if you even squinted at them. It didn't impair their performance (to a degree) but who wants big dents in their frame?
For example I'd be intersted to see a Steel front/composite rear 'AM' type bike and if/what it might deliver in terms of a Ride/weight/cost tradeoff... Discuss...
I know a very talented engineer and equally talented bike rider who has built exactly that as a home made bike. Steel front with high single pivot carbon fibre swing arm and an idler to neutralise chain torque. 150mm travel super low BB slack HA and he rides it faster than anyone else I've ever ridden with. It was featured on the Dirt website around September last year.
It was pretty heavy but it was a prototype and way over built as such. The swing arm on its own was something like one kilo. But he made it in his garden shed.
wrecker - MemberNot heavy? 7.6lbs for a 16", it's heavier than that Foes Shaver which everyone was saying was heavy lest week (and the foes has more bounce)
Actually, it isn't- both Foes and Cotic claim 7.8lbs for the medium. And the Foes has less rear travel, and is recommended for a 150mm fork with a max of 160mm. Very comparable frames. Pretty much the same as a Covert, both lighter than an SB66
legend - MemberObviously that'll be a completely un-biased view from a guy who is trying to sell steel bikes
Yes that's right, Cotic found themselves with a load of steel frames in the warehouse one day, then made up an explanation for why you should buy them. Or, maybe not.
I know a very talented engineer and equally talented bike rider who has built exactly that as a home made bike. Steel front with high single pivot carbon fibre swing arm and an idler to neutralise chain torque. 150mm travel super low BB slack HA and he rides it faster than anyone else I've ever ridden with. It was featured on the Dirt website around September last year.It was pretty heavy but it was a prototype and way over built as such. The swing arm on its own was something like one kilo. But he made it in his garden shed.
I've seen it on the dirt site and it got me thinking at the time, I'll admit is was in the back of my head when I posted above.
I have a couple of my own home brew ideas I'm working up right now in a not disimilar vein...
It was the approach I liked, materials/manufacturing methods chosen, based on available resources/expertise, final product looked very good IMO...
Oh and just to echo geetee1972; this isn't really the right thread for trying to bitch-slap each other, take it elsewhere please Ladies...
There can be quite a bit of flex in a seat tube under hard pedalling or cornering loads, part of the twist along a frame that means flexy frames can run wide on corners. But any frame flexes as a system, the forces going through it don't really change as the design changes, just where they concentrate and how the frame handles it. Beef up the seat tube and the top and down tube and swingarm may flex more. etc. So all parts are important, needs balancing.
Anyway, my answer to the OP would be that the global brands sell into markets that don't have the attraction to durable steel products that we do. There's no reason for them to use steel where it could be an option. It's more about fashion / styling and low weight. The UK is different/odd/irrational/unique depending on who you talk to. Being different in this market helps you survive against very well resourced companies with larger R+D and marketing depts. It can also result in some pretty cool/interesting bkes.
theres a downhill bike. k...something I think? (and not knolly, khs, kona)
Keewee?
always nice to see the armchair engineers come out to play
(leaving the real ones actually get on with engineering things 😉 )
Love the "armchair engineer comments", hark at thee! I've heard more guff here from "I'm an engineer" types than those knowledgable about bikes.
geetee1972 - MemberWho remembers the cannondale 3.0 frame from the early 90s? That had huge tubes and super thin walls that would dent if you even squinted at them. It didn't impair their performance (to a degree) but who wants big dents in their frame?
tubes on high end Principias could be visibly compressed by hand! Rode great tho!
AM bikes need to be a bit more crash-resistant I guess.
Because steel is real and doesn't need the skill compensation of full sus
Love the "armchair engineer comments", hark at thee! I've heard more guff here from "I'm an engineer" types than those knowledgable about bikes.
I'm not an engineer, I just find these threads amusing as it invariably starts with a genuine question and then degenerates in to hearsay, hyperbole, misled-by-marketing comments, and bad science used to justify peoples pre-conceptions.
Yes that's right, Cotic found themselves with a load of steel frames in the warehouse one day, then made up an explanation for why you should buy them. Or, maybe not.
Ah ****, I've just read an article by Dave Weagle saying that alu and the DW-link are the best for trail bikes. Now I'm confused, or one if them is wrong, or something.
It's almost like brands need a USP....
amedias, Engineers need lunch breaks too you know!
I've seen it on the dirt site and it got me thinking at the time, I'll admit is was in the back of my head when I posted above.
It is an incredible bike for being made in a garden shed. I was with Adrian and his fiance in Verbier last year (with Bike Verbier of course) so got to see him ride it the whole week. Apart from Adrian being incredibly talented on the bike, it was amazing to see a home made bike perform. He had some problems with the idler set up, as you might expect; there's a lot of torque going through a relatively small axle and the bearings take a real hammering. But other than that the whole thing was so solid. I think it weighed in around 34lbs with DH tyres so it wasn't light but but it was light enough.
Adrian was very keen on the high single pivot saying it made the suspension work really well but obviously you needed the idler to make it also pedal well.
Rubbish! Why would the seat tube need to be stiff on a FS bike!??!?!?
To stop the seat wobbling of course!
theres a downhill bike. k...something I think? (and not knolly, khs, kona)
You're thinking of Katipo I suspect.
http://katipobikes.pinkbike.com/album/Katipo-bikes/
legend - MemberAh ****, I've just read an article by Dave Weagle saying that alu and the DW-link are the best for trail bikes. Now I'm confused, or one if them is wrong, or something.
Or possibly they're wanting different characteristics from their bikes? Crazy idea I know. Turns out, some people even like bikes with no suspension at all!
You're thinking of Katipo I suspect.
I've never heard of or seen that brand before. Interesting looking bike. It's basically a Sunn Radical and why not? That was clearly an awesome bike and worked really well.
materials science,
engineering,
production scale,
marketing,
Economics.
Take your pick, all are relevant to some extent.
Some more so than others to different parties (producers and customers), but hard to ignore any one of them.
IMO, the first four combine to make mass production of allu framed bikes more economically viable, so there are more of them. That's not to say they're better or worse.
Actually, it isn't- both Foes and Cotic claim 7.8lbs for the medium. And the Foes has less rear travel, and is recommended for a 150mm fork with a max of 160mm.
Actually, Cotic state that the small is 7.6lbs. The small Foes is 7.4lbs.
The Cotic has 150mm rear travel, the Foes 5.75" (146mm). Foes also recommend forks 120 - 160mm.
Neither are light bikes. But if you want stiff, strong and light; buy carbon.
I found this.........
Aluminum vs. Steel: the truth about stiffness
Apr 09 '01 Write an essay on this topic.
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The Bottom Line Flex is good
You have all heard the hype about aluminum, how it is ligher faster and better than steel. Accept this for what it is hype. Aluminum bikes are only marginally lighter than steel bikes. The lightest production aluminum frame I know of is the Cu92 Giant XTC frame at 3lbs and only a third of a pound lighter than a 3.3lbs Ritchey P-21. Therefore weight should not be a big concern.
That leaves stiffness. Aluminum frames are supposed to be faster because they are stiff, because they do not flex, so they are therefore more efficient. This rides on an assumption that flex is inherantly inefficient which is not totally correct. Think back to high school physics, you probably did an experiment with a spring and a weight, you put a small amount of energy into the system and it would go for minutes. It was a really flexy and really efficient system. The only reason it would come to a stop is due to material damping, that is throught the energy moving through the material some of it went out as heat. Ineffecieny in flex is due to the materials damping characteristics.
So how does this translate to bike frames. Materials like steel and titanium have very low material damping characteristics, meaning that relatively littel energy is lost to heat. That makes sense becuse we make almost all of our springs out of steel or titanium. When you are building up a frame out of these materials you are actually building a spring. On the other hand when one builds a frame out of aluminum they are making the stiffest structure possible, imagine an I Beam. So when you think of flex you shoudn't think of effiency but rather of the ride of a spring vs. an I beam.
Imagine a trapoline next to a wood table. Put one person on the trapoline and ask them to jump, do the same with the person on the table. The person on the table will spend the same huge amount of energy everytime trying to jump higher whereas the person on the trapoline would jump much much higher whith the same or less energy expenditure. That is because the person on the trapoline has a temporaily store energy and then use it later when it is more needed. The person on the table can't do this.
Now forget about the trapoline and get on your bike on some nice twisty singletrack or a sweet road decent. You lean your bike into a corner, carving a nice right hand curve. Now up ahead you see a tight left hand corner coming up. On the aluminum bike you would need to physically lift the front ent up and over to get it to go the other way, however on the steel bike one simply needs to release the spring to have that energy released, boinging the rider into the left hand carve. A faster and less tiring act than the rider on the aluminum frame. Ride a couple of bikes side by side you'll see that it is immensely more difficult to hande the really stiff frame.
This concept reiminds me of a saying in the Italian motorcyle industry "If something is too perfect you tire of it quickly" That is often true of aluminum frames, they are too perfect. In order to make the bike go as fast as it is supposed to go the rider must apply energy at the perfect times in the perfect direction. pull on the handlebars a certain way while cranking with a certain amount of power, and having your butt on a certain perfect point on the seat. This is really difficult to do.
The Moral of the Story FLEX IS GOOD. You wouldn't buy a ski or snowboard or golf club or hockey stick that didn't flex why a bike frame? I still accept that some people really like the ride of aluminum but most of us are not given the choice. The most popular offroad pricepoints between $850 to $2000 have no steel or ti bike. CALL THE MANUFACTURER AND TELL THEM YOU WANT A CHOICE, THAT YOU WANT STEEL.
***RESPONSE TO GIOVAGNS "FRAME MATERIALS"****
Giovagn expressed a rather elloquent and well written rebute, however I will maintain my original stance that the overall "real" speed in almost all riding conditions of steel and titainium is near equal to that of aluminum and that the advantage of aluminum is primarialy psychological in that it has a greater percieved speed.
There is one fundemental flaw in Giovagns argument and that is the idea that flex is primarily a function of the vertical plane, sort of like a full suspension bike. While this flex does occur it is really marginal, second off if you were to lose a race because of too much flex on the vertical plane you would have lost the same race on the basis of bad technique. If the net force of your two legs is primarily in the downward direction you are only using one leg at a time, and we all know this is a bad idea.
To clarify things one must understand that the flex that I talk about is the twisting that occurs between the handlebars and the bottom bracket, not vertical flex. When one views flex in this way the rebound of the frame is concurrent with the efforts of the rider. The onlw real difference then is the "pop" of the frame, that energy transmitted in that "split second" in a sprint. I will say that the amount of difference in "pop" between steel and aluminum is not a major determining factor in the outcome of a sprint, in which the major factors are raw power over time, timing and position.
What the difference between the materials would be psychological, do you like the flavor of steel or aluminum, pretty simple.
I found this.........an old artical but aren't we all 😉
Aluminum vs. Steel: the truth about stiffness
Apr 09 '01 Write an essay on this
The Bottom Line Flex is good
You have all heard the hype about aluminum, how it is ligher faster and better than steel. Accept this for what it is hype. Aluminum bikes are only marginally lighter than steel bikes. The lightest production aluminum frame I know of is the Cu92 Giant XTC frame at 3lbs and only a third of a pound lighter than a 3.3lbs Ritchey P-21. Therefore weight should not be a big concern.
That leaves stiffness. Aluminum frames are supposed to be faster because they are stiff, because they do not flex, so they are therefore more efficient. This rides on an assumption that flex is inherantly inefficient which is not totally correct. Think back to high school physics, you probably did an experiment with a spring and a weight, you put a small amount of energy into the system and it would go for minutes. It was a really flexy and really efficient system. The only reason it would come to a stop is due to material damping, that is throught the energy moving through the material some of it went out as heat. Ineffecieny in flex is due to the materials damping characteristics.
So how does this translate to bike frames. Materials like steel and titanium have very low material damping characteristics, meaning that relatively littel energy is lost to heat. That makes sense becuse we make almost all of our springs out of steel or titanium. When you are building up a frame out of these materials you are actually building a spring. On the other hand when one builds a frame out of aluminum they are making the stiffest structure possible, imagine an I Beam. So when you think of flex you shoudn't think of effiency but rather of the ride of a spring vs. an I beam.
Imagine a trapoline next to a wood table. Put one person on the trapoline and ask them to jump, do the same with the person on the table. The person on the table will spend the same huge amount of energy everytime trying to jump higher whereas the person on the trapoline would jump much much higher whith the same or less energy expenditure. That is because the person on the trapoline has a temporaily store energy and then use it later when it is more needed. The person on the table can't do this.
Now forget about the trapoline and get on your bike on some nice twisty singletrack or a sweet road decent. You lean your bike into a corner, carving a nice right hand curve. Now up ahead you see a tight left hand corner coming up. On the aluminum bike you would need to physically lift the front ent up and over to get it to go the other way, however on the steel bike one simply needs to release the spring to have that energy released, boinging the rider into the left hand carve. A faster and less tiring act than the rider on the aluminum frame. Ride a couple of bikes side by side you'll see that it is immensely more difficult to hande the really stiff frame.
This concept reiminds me of a saying in the Italian motorcyle industry "If something is too perfect you tire of it quickly" That is often true of aluminum frames, they are too perfect. In order to make the bike go as fast as it is supposed to go the rider must apply energy at the perfect times in the perfect direction. pull on the handlebars a certain way while cranking with a certain amount of power, and having your butt on a certain perfect point on the seat. This is really difficult to do.
The Moral of the Story FLEX IS GOOD. You wouldn't buy a ski or snowboard or golf club or hockey stick that didn't flex why a bike frame? I still accept that some people really like the ride of aluminum but most of us are not given the choice. The most popular offroad pricepoints between $850 to $2000 have no steel or ti bike. CALL THE MANUFACTURER AND TELL THEM YOU WANT A CHOICE, THAT YOU WANT STEEL.
***RESPONSE TO GIOVAGNS "FRAME MATERIALS"****
Giovagn expressed a rather elloquent and well written rebute, however I will maintain my original stance that the overall "real" speed in almost all riding conditions of steel and titainium is near equal to that of aluminum and that the advantage of aluminum is primarialy psychological in that it has a greater percieved speed.
There is one fundemental flaw in Giovagns argument and that is the idea that flex is primarily a function of the vertical plane, sort of like a full suspension bike. While this flex does occur it is really marginal, second off if you were to lose a race because of too much flex on the vertical plane you would have lost the same race on the basis of bad technique. If the net force of your two legs is primarily in the downward direction you are only using one leg at a time, and we all know this is a bad idea.
To clarify things one must understand that the flex that I talk about is the twisting that occurs between the handlebars and the bottom bracket, not vertical flex. When one views flex in this way the rebound of the frame is concurrent with the efforts of the rider. The onlw real difference then is the "pop" of the frame, that energy transmitted in that "split second" in a sprint. I will say that the amount of difference in "pop" between steel and aluminum is not a major determining factor in the outcome of a sprint, in which the major factors are raw power over time, timing and position.
What the difference between the materials would be psychological, do you like the flavor of steel or aluminum, pretty simple.
I know Sunn use steel in a few of their FS bikes- the Charger, an enduro bike has a alu front triangle & a cromo back end, I think their downhill bike (the radical?) has a similar setup. On that note, does anyone actually sell Sunn bikes in the UK? Loving the look of the charger..
Imagine a trapoline next to a wood table. Put one person on the trapoline and ask them to jump, do the same with the person on the table. The person on the table will spend the same huge amount of energy everytime trying to jump higher whereas the person on the trapoline would jump much much higher whith the same or less energy expenditure. That is because the person on the trapoline has a temporaily store energy and then use it later when it is more needed. The person on the table can't do this.
Eh? I'm imagining trying to jump on a trampoline and not getting very far at all.
I think crc do sunn bikes, they aren't as good as they used to be though
thepodge - sunn stuff is great, owned a couple of their bikes recently. They even do a full-sus with a steel rear-triangle.
lipseal - that article you've copied/pasted is utter pish.
I'd seen a few mediocre reviews of their more recent stuff
It's nothing earth-shattering, but good kit for much cheapness.
They've gone bust (again!) but have been bought out by Look, so next year's bikes should be interesting.
We had the Kern LT as our rental bikes and they were excellent - gave the Alpine 160 a very tough run for it's money!
The Sunn Modular S2 looks nice.
Its such a pity that they cant follow their former glory
Anyone made a frame from inconol or other superalloys? How about the some of the metal composites that are around? Theres always someone with too much money who would by one.
lipseal - that article you've copied/pasted is utter pish.
Got to keep the forum standards up you know. 😆