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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?