…Why not?

The thread discussing Cotics new bouncer the other day got me thinking, why hasn’t steel really been generally considered the optimal mateirial for FS bikes?

I know it’s a generalisation but I can only think of a handful of FS bikes that used steel:

Keewee Chromo 8
BMW Mini/Race link
DMR bolt
Balfa BB7 (did the Avent version still use a steel back end?)
Curtis Thumper cross? (Rissie racing aluminium back end?)

They all seem to have been intended for more Ruffty Tuffty Gnarcore/DH riding too.

Given that steel HT frames have come back into favour over the last 8-10 years or so, can anyone offer a compelling reason why Steel bouncers don’t seem to have so much appeal?

I would imagine that they’d be bloody heavy! Also, isn’t the main argument for steel that it has a bit of give so is more comfortable? On a FS you have a shock that deals with that so I’d imagine it’s not an issue.

I can’t think of a single reason why you would use steel in a full suspension bike.

Xprezo have a range of them.

Really just like that then, a total non-starter for most people then?

I’d have thought that steels ability to offer some compaliance was an advantage, no shock is perfect (well some might be).
It’s (arguably) more easily repaired than aluminium and has a very good strength to weight ratio.
I was under the impression you could still make a sensible weight HT frame from steel, why not an FS?

It just seems strange to me that the massive Lob-on people have for steel HT frames doesn’t extend to FS bikes…

I’m just questioning the recieved wisdom that steel is not the appropriate material for building FS bikes…

Some people get a ‘lob-on’ for steel for its supposedly magical ride properties (which only a few steel bikes actually have to any real degree). The other major benefit is it’s typically cheaper. The former is irrelevant if you’re designing a FS, the latter arguably less so too if you’re already spending £1k on a frame.

A FS frame made of steel would typically be very heavy or flexy, neither of which are really desirable 🙂 If you used the lightest steels, then you could get the weight down a bit but it’d then be seriously expensive.

I can’t see a problem with it but I don’t know why anyone would buy one unless there was a significant cost benefit. Steel is cheaper to buy and weld isn’t it?

Some of the statements on this thread are wrong, just plain old wrong. You could do with signing up to the Cotic newsletter as Cy has done a wonderful explanation of why he has used steel for the Rocket. His logic is exactly the same as why we have used it for our full sus, although we have the added benefit of ease of manufacture in small runs/custom applications.

Steel does make sense for several reasons but only for certain types of frame. If you want an ultra-lightweight short travel frame then steel is not going to be the best option, but then again neither are most of the other materials available depending on what other criteria you throw in. Carbon is too expensive and can’t be recycled (easily), aluminium isn’t light enough, ti is too expensive. I don’t think anyone (Cotic, Us or any of the other manufacturers mentioned) are trying to say that steel is the best option for a full sus frame, it can be in certain situations and is just another alternative

Matt

Steel gives more options for custom build (no heat treatment etc)

I think this is what you want:-

http://www.wiesmann-bikes.de/

I always wondered the same about that Litespeed Sewanee: could they have made it rde just the same and weigh just the same if they had used an aluminium alloy?

Excluding al the argos and motorworld specials, there was also an all-steel identiti dh bike a few years back.

The back end of the K9 dh bike is steel IIRC. If there wasn’t such a stigma around welded/repaired frames (of any material) I wonder if a lot more DH frames could/would be all steel, or have steel in the parts of the back end that are more prone to failure from prolonged radness.

I believe the K9 is the other way round actually, steel front and aluminium rear end

I’d have thought the cost of casting/machining steel for pivots etc and weight involved in that would be the killer?

Also easier/cheaper to make stiff light frames in alu – letting the shock do the job, not the material.

clubber,
I disagree. Aluminium frames are now cheaper than quality steel frames to produce. This is the major reason for their predominance.

The other reasons stem from marketing rather than engineering.
It is a complete fallacy about the stiffness of aluminium.
Steel is both stronger and stiffer than aluminium. The key to aluminium frames’ percieved stiffness is the tube diameter, not the material.

edit: just read the posts between, and pretty much agree with what they’ve already said

It’s amazing how the preconceptions people have about certain materials (mostly due to marketing bo**ocks..) shape their views isn’t it…

Rather than actually looking at it from a materials/physics/engineering point of view and the *actual* properties of the materials in question and then how those properties change when you arrange them in certain ways.

It is never as clear cut as:

Alu = stiff = harsh = light
Steel = bendy = comfy = heavy

There is a LOT more to it than that, and you can show any number of frames/designs where the opposite is true, or at least the lines are blurred.

(EDIT – looks like a few people already replied while I was typing that ^)

sunn radical:

yeah, steel bouncy bikes are crap.

(if you don’t know anything about the radical, go and do some homework)

Beaularks to all that mechanical engineering stuff. The best thing about steel is that you can clearcoat over the raw welds and end up with a frame that looks like it was forged on Vulcan’s anvil. 🙂

aluminium isn’t light enough

but steel is????

anyways, I’d like one of these when I win the lottery:

but steel is????

I was meaning compared to carbon. It is perfectly possible to build a steel frame that is the same weight as an equivelant aluminium frame, but only in certain frame types. This is why the steel full sus out there is generally longer travel as the benefits of steel really come into play and the drawbacks are reduced. If wieght is your main concern, buy carbon, if it’s not, buy something else

clubber,
I disagree. Aluminium frames are now cheaper than quality steel frames to produce. This is the major reason for their predominance.

The other reasons stem from marketing rather than engineering.
It is a complete fallacy about the stiffness of aluminium.
Steel is both stronger and stiffer than aluminium. The key to aluminium frames’ percieved stiffness is the tube diameter, not the material.

OK, the cost thing may now be not the issue.

As to the other I fully understand the ‘stiffness’ of aluminium but the problem here is that in getting a big tube with steel at a reasonable weight and price, you’re talking very thin tubing which then becomes fragile from loads outside of actually riding. Basically, you take one of the benefits of steel (eg the ability to design more flex in without premature fatigue failure) and turn it into a disadvantage – at least according to conventional suspension wisdom where you want stiff frame/linkages and all the movement to be provided through the pivots.

oh, and this:

It’s amazing how the preconceptions people have about certain materials (mostly due to marketing bo**ocks..) shape their views isn’t it…

Rather than actually looking at it from a materials/physics/engineering point of view and the *actual* properties of the materials in question and then how those properties change when you arrange them in certain ways.

It is never as clear cut as:

Alu = stiff = harsh = light
Steel = bendy = comfy = heavy

There is a LOT more to it than that, and you can show any number of frames/designs where the opposite is true, or at least the lines are blurred.

is spot on

I agree with that actually and if you look through my posts (and even my first comment on this thread) you’ll see that’s the case. I suppose the only caveat I’ll add for clarity is that my initial comments are directed more at the less-gnarlcore end of the riding spectrum. As stated above, if weigh is less of an issue and strength is critical then steel can have a role to play and in some areas be advantageous.

It is never as clear cut as:

Alu = stiff = harsh = light
Steel = bendy = comfy = heavy

and even that’s wrong:

steel is stiff.

aluminium is flexy.

(i’m sorry, but someone had to say it…)

Exactly. Kind of 🙂

getting a big tube with steel at a reasonable weight and price, you’re talking very thin tubing

You don’t necessarily need a big tube, though. Because the material’s stiffer.

Also, what is considered a ‘big tube’ for steel would be a small tube for aluminium so even though we are using a huge (by steel standards) downtube for our full sus, it still looks small compared to most aluminium frames. The weight gap is not as big as people imagine it is so a steel frame can end up being stiff enough, plenty strong enough and still at a weight that is acceptable

RudiBoy – Member

cool didn’t know Brooklyn did folding bikes.

The main point of titanium FS bikes, as far as I can tell, is that they are made out of titanium. This is a property that no other material has. No other material other than Titanium lets you make a titanium bike.
Steel is similar to this in many ways.

😆

The main point of titanium FS bikes, as far as I can tell, is that they are made out of titanium.

Aren’t they going to be pretty light but plenty strong and able to shrug off rocks strikes (all other things being equal) and generally be around for quite a while?

Hellish expensive tho yeah.

Or am I believing marketing hype (again)

The weight gap is not as big as people imagine it is

my ali FS bike is already “too heavy” so even if it’s a small gain I don’t want to be pedalling it around all day, not as much of an issue for more gravity stuff I guess. Haven’t lusted after a steel FS since the orange X2 (I was young and stupid)

You guys are missing another big factor! Life cycle. Aluminium frames have a much shorter life cycle, ive cracked several over the years. Steel frames are for life. If you put a crack in it re weld it and get out on it again. Yes, you can re weld alu but there’s all sorts of issues about heat treating, etc. Steel is for life!

I don’t have any experience of the bike industry, but I have spent plenty of time looking at materials substitution across many industries using structural metals. It’s actually quite a complex discussion, and the trade off’s are likely to be between manufacturing aspects and bike performance..

But if you can get a handle on the engineering aspects of your steels, titanium alloys and aluminium alloys, and decide which are the msot important for your application/market/cost base, such as (and this is not an exclusive list):

Material grade
Density
Tensile modulus
Yield strength
Beam bending
Effect of change of section modulus on Specific stiffness
Fatigue
Corrosion
Available finish
Fracture toughness
Heat treatment
Weldability
Effects of welding on yield stress and fatigue
Post weld heat treatment
Machinability
Formability
Cost and availability of raw materials
Cost of manufacturing process (material and grade chosen will have a large effect on this.
Experience/training of manufacturer/workforce

and finally
FASHION.

Then you will be able pronouncements on which is better.

I have no doubt that you could easily make a steel FS frame as good as an aluminium one but I would wager that the major reasons why aluminium is more prevalent are:

1) Fashion/marketing
2) Fashions knock on effect in the industry where most production outfits are geared up for aluminium manufacturing, so to make a production run of quality, competitive steel FS bike will be more expensive as the availability of mass production machines/workers/facilities is less..

Oh and this

brant – Member
The main point of titanium FS bikes, as far as I can tell, is that they are made out of titanium. This is a property that no other material has. No other material other than Titanium lets you make a titanium bike.
Steel is similar to this in many ways.

😆

shrug off rocks strikes

just zip tie a bit of tyre to your down tube if you’re worried.

Steel frames are for life.

Jeez… who wants a frame for life? Doesn’t sound much fun. Buying new things is FUN.

How much do the 18 bikes steel FS and cotic rocket frames weigh (w/shock)?

Never said I wanted it for life..
Would be nice to be able to sell it on rather than scrap it.
Im sure that’s partly why big manufacturers make them from Ali. Short life cycles = sell more frame = more $$$$.

Steel seems to be very much in vogue at the moment, a lot of people like the look of skinny tubes and having just bought a steel hardtail, the ride characteristics are a revelation to me, so I don’t see why a properly designed steel full suss shouldn’t be viable.

I agree that fashion/marketing is the driving force however.

ska-49 I used to think the same way about steel lifetime, but as Brant once said in response to my pushing this idea on this forum: (I’m paraphrasing from memory) he has never known of a bike frame that was designed below the fatigue limit, it would be very heavy if it was.

Therefore the lifetime argument is not relevant here..
Potentially this also means the steel feel argument is also a red herring..

See also

I often wonder why no one presses things in steel ,well I dont but it would be nice for some things.

Can we readress the old chestnut ? chinese manufacturing thing they do things in a certain way

I have a clever calculator that does just what CY explained in his little write up you can simply compare tubes.

Comparing an apple to an apple steel tube x dia and y wall against a carbon tube x dia and y wall doesn’t give you a carbon tube that has any advantages to get the same properties as an 853 down tube your wall is 3.5 times thicker in the centre compared to the thinnest section(in fact for certain fibre types steel is stiffer at the diameters being used in steel frames)

The weight gap is not as big as people imagine it is so a steel frame can end up being stiff enough, plenty strong enough and still at a weight that is acceptable

So it wont be as stiff, strong, or light as an aluminium frame?

for certain fibre types steel is stiffer at the diameters being used in steel frames

I think the point is you can’t make a 4″ diameter steel downtube like you can an aluminium (or carbon) one. So while steel is stiffer on paper you’re forced/able to use much smaller tubes, which aren’t as stiff.

Steel gives more options for custom build (no heat treatment etc)

[quote]Yes, you can re weld alu but there’s all sorts of issues about heat treating, etc. Steel is for life! [/quote]

In MTB’s we seem to have been drawn towards 853 by the marketing, look at BMX’s (and some dirt jump frames) and a lot more frames make a bigger deal about the headtub/dropouts/BB beeing heat treated, or the whole frame being 100% post weld heat treated.

Yet we’re also convinced that aluminium must be heat treated, when IIRC it’s only certain alloys that do and plenty of popular frmes have been built from alloys that haven’t required this. (Mountain cycle and 6000series alloys spring to mind but don’t quote me on that).

I’d buy a cotic rocket if I didn’t already have a similar FS and could justify the premium(ish) price. But then I’d also buy a gaff rigged sailing boat, or a rigid 29er mountainbike, knowing that there are better performing options, but sometimes it’s the little things and the quirks that make you happy.

That’s more like the debate I was hoping for.

My original point was that with some rare, notable exceptions, the entire history of FS bikes has been Aluminium and more recently Composites.

Many other industries have been the complete reverse of this Steel has only been partially displaced in Automotive and Civil engineering relatively recently, and the work done there to create strong, light efficient structures using steel has been very significant.

I’ll be honest it wasn’t a well phrased opening question really, I’m not expecting anyone to tell me the next Anthem will be made from steel, but like I said in my OP the Cotic Rocket was the frame that got me thinking again, probably because its a 7.2Lb, 150mm, Trail/AM type bike made ~70% from steel (or at least from what I can gleen), to my mind it sounds like a reasonably good bike on paper…

We’ve sort of become the natural home of the Steel HT (The UK I mean) in recent years with a few companies popping up who’ve built some expertise in the design and construction of bikes made out of the steel; I’d contend that the little bit of knowledge/experience over which stock tube has the right balance of wall thickness, and diameter to give you the flex/stiffness, weight and weld area for a given application is sort of dropping off the radar for many bigger companies where it’s become more and more Hydroformed Aluminium or CF monocoques and big batch numbers, I think it’s where we might have a chance to excel and dare I say it lead, so I wouldn’t discount applying those expertise to an FS bike or two…