[Closed] Different components, different materials, why ?

steel has been used for stanchions. Pace, Cheap RockShox, it is heavy but it is durable.

basically comes down to fit for purpose. design parameters, material properties.

sliders tend to be cast you have to create the bridge somehow, so aluminium and magnesium make sense, steel doesn't. Seatposts have often been made of steel at the cheap end of the market,

Titanium has been used for hubs, partially, Hope Ti Glides;Spokes, Union/DT; Handlebars lots.

Have you been sniffing glue??? Most of the things you think you can't get, you can!
Also why would anyone want steel bike components? If you want steel one's buy a 'supermarket special' bike.
Have you thought that the reason most things are made from what they are is because it might be the best materials for the job? 🙄

basically comes down to fit for purpose. design parameters, material properties.

d45yth, I refer you to [url= http://singletrackmag.com/forum/topic/why-does-stw-forum-attract-so-many-of-lifes-losers ]an earlier thread[/url].

d45yth - Member
Most of the things you think you can't get, you can!

Also why would anyone want steel bike components? If you want steel one's buy a 'supermarket special' bike.

my new forks have steel stanchions.

for: they were about £100 cheaper than the ally stanchion version (which weren't even in stock anywhere in europe/the world), the chrome steel is very durable (important in a bearing surface exposed to abrasive filth)

against: they're a little bit heavier (it's not much so i don't care).

my new forks have magnesium legs.

for: it saves a lot of weight vs aluminium or steel.

against: it's very soft, they'll get a bit scratched and scruffy if i'm not careful with the car-packing. (i can live with that)

Look, to be quite honest I think you're being a bit of a troll with the original post and wasn't even going to comment. I've seen plenty of your posts on here and it doesn't seem like you're thick. So why is it that so many folk ask for advice and answers to their questions on the internet, when there is a perfectly useable search bar at the top of their screens?
Another thing, believe me I don't say anything on a forum that I wouldn't say to someone in real life.

MTG, how long have you been riding for? Just curious, cos though it's less prevalent these days, more and more you used to find the things you say about in weird and wonderful materials.

Ti spokes are and were made by DT... Why not common? Cos they're about £10 per bloody spoke! That and Ti, an inherently elastic material, is a bit too flexy really for a spoke. You need more of it to make a stiffer wheel, hence thicker, hence heavier and less aerodynamic. Though obviously they'll make very resilient wheels as it will be hard to get them to yield elastically.

Steel has been good enough for fork stanchions for a long time. On cheaper forks, sub £200 say, just about every fork will have steel stanchions. Also, back in the day, Pace used to use steel stanchions too, but of a much higher quality, and they were actually quite light. Obviously motorbikes on the whole still use steel stanchions too, but weight is less of an issue there. Mainly ally tubes are used these days though, cos they can be made light and stiff for a given cross sectional area, and that's the most desirable qualities in a fork stanchion.

Mag is good for fork lowers mainly cos they need to be cast, and of a fairly thick material to keep everything in. Mag alloy is perfect here cos its pretty light. For crank arms, it would be nowhere near stiff enough, as Mag alloy is a pretty soft material to be honest.

Ti hubs? Go back to the 90's... All Hope hubs used to have a Titanium sleeve with 2 alloy flanges bonded to it. There are hubs out there machined from a single billet of ti also, but they're very very expensive. Also, Ti is heavier than ally by about 50% or so by volume, and ally is more than strong enough for a hub material. Why make it out of a heavier, more expensive material, when a lighter cheaper one is more than up to the job?

Ti handlebars? Personally, I like just about everyone else I can think of, like my forks to do the flexing, and my bars and stem to be as stiff as possible. Ti is much less stiff than ally or Carbon (unless you use a lot of it) and this isn't so desirable IMO. Some niche mongers will have ti bars on their niche ti bikes, mainly for aesthetic reasons, but I'm not a fan.

It's all about the inherent properties of the material, and their suitability to an application... Materials science and all that! I remember once though someone asking why spokes weren't tubular, as surely that would be much stiffer than a thin strand of wire when they must be under so much "compression" on a bike... Had to facepalm at that one!

but that doesn't explain why there isn't a steel seat post that wouldn't look out of place on a £1000 Reynolds 853 frame.

There are.

You've just got to search for them, and not on CRC or in your LBS.

Oh, and forgot to mention (particularly relevant with this one), there's also economies of scale. It's much cheaper to make something in volume than it is in isolation, even if using quite expensive materials. I can tell you a nice steel seatpost (probably Reynolds 853) will cost you a lot more than a high end carbon, or Titanium one, and will also be heavier than either!

Do you all not think that someone with a bike that fills so many niches as the OP's doesn't already know a lot of this? 🙄

Do you all not think that someone with a bike that fills so many niches as the OP's doesn't already know a lot of this?

Do you not think MTG's maybe a bit lonely and just fancies a nice chat?

Not trolling, it was a genuine question. Maybe I should have made it clearer that I was referring to good quality components widely available from the likes of CRC or Wiggle, for example.

I used to have steel BullsEye cranks on a Pace RC200. they were regarded as comparable to aluminium cranks at the time, yet the idea of steel cranks never took off and, [i]as far as I know[/i], no one else makes good quality steel cranks. Why not ?

Why doesn't anyone make a good quality seat post out of Reynolds or Columbus steel tube ?

Wheel rims are effectively an odd profile hollow tube wrapped round in to a circle. Why not make them out of titanium or steel, like frame tubes ?

Crank arms look like the ideal part to cast or forge in magnesium, so why are they always aluminium ?

Do you all not think that someone with a bike that fills so many niches as the OP's doesn't already know a lot of this?

I'm not in a position to assume. Though I have met him a few times, and know he rides LOADS (and a fairly unique/niche bike), it is why I asked how long he's been riding as if he'd been riding as long as me, he'd certainly be able to answer his own questions.

He's posting links for me, telling me I'm one of lifes losers. Isn't he the one that likes to start new posts and sits behind his computer getting a chuff on when it gets to so many pages long?

Yeah maybe uncalled for... Though asking if he'd been sniffing glue was probably a bit provocative a first statement.

Cross posted, so I missed this.

I can tell you a nice steel seatpost (probably Reynolds 853) will cost you a lot more than a high end carbon

What's a "chuff on" ?

I used to have steel BullsEye cranks on a Pace RC200. they were regarded as comparable to aluminium cranks at the time, yet the idea of steel cranks never took off and, as far as I know, no one else makes good quality steel cranks. Why not ?

Weight and complexity

Steel cranks [i]could[/i] be made light enough, but then they'd be very expensive. MUCH cheaper to mass manufacture them in ally.

Of course though, you could always fit some Profile BMX race cranks to your bike as you either run SS or a Rohloff so you don't need 3 rings, which are tubular 853, and profile do an MTB fit BB, and they also do a Ti axle. Will cost you a few quid, but that will be a VERY stiff and light setup for you!

Why doesn't anyone make a good quality seat post out of Reynolds or Columbus steel tube ?

Again, they do... Just not from your LBS or CRC. You gotta search

Wheel rims are effectively an odd profile hollow tube wrapped round in to a circle. Why not make them out of titanium or steel, like frame tubes ?

Ally rims have very low wall thicknesses. To get Ti or steel rims of anywhere near comparable weight, they'd have to be so thin they'd be like paper. It's why carbon is a good material for a rim (except for cost), as it's less dense and can have a greater wall thickness for a given weight.

Crank arms look like the ideal part to cast or forge in magnesium, so why are they always aluminium ?

You've stated tubular steel is a good material for cranks (it can be) and then cast magnesium? 😕

I'm confused Graham... Cast Mag is sooooooooft and not all that strong. Certainly not very stiff. No good for cranks in any way shape or form, unless the crank arms were huge!

Why ? There's a few companies making good steel frames at a sensible price, why can't they make seat posts as well ?

Much less of a market for them...

You want a 300g Reynolds 853 Seatpost for £100?

Or a Thomson that weighs 250g for £50?

Cast Mag...anyone remember the Kirk Revolution? I think they all broke?

hmm, fork legs/lowers are almost always cast magnesium...

so i'm thinking out loud here:

it's easy enough to make a lightish bike frame from thin walled tubes, so a cast frame would need to be thin section to be competitive.

thin section castings aren't famous for their strength.

maybe we should start making fork legs/lowers from welded tubes?

clearly, i need to think about this more, or maybe less...

The key parameters when choosing a material are:

Modulus (ie how stiff it is) - steel ~ 200Gpa, al alloys ~ 70Gpa, composites variable as you align the fibres but they will be >70Gpa typically in the direction that matters. Modulus does not vary much with different grades of steel, aluminium etc so can be assumed to be pretty much constant.

Strength - NOT the same as stiffness. Varies a lot due to the alloy and how the material is treated and formed.

Density

Manufacturing methods

Corrosion resistance

Toughness - ie for impacts etc

Abrasion resistance - for parts that get worn against (not the same as toughness)

Cost - to buy, machine, treat etc

For stiffness you can either choose a stiff material or a stiff shape - or a combination of the two. eg like an A4 sheet of paper is floppy one way but stiff another.

For strength you either choose a high strength material or increase the cross sectional area.

Titanium is actually not very stiff/high modulus so they would have to be thicker. They would also then be expensive, higher drag, impact on hub and wheel strength as bigger holes etc etc.

Aluminium is very good in places where you need to make something bulky or can make something bulky to make it stiff.

Steel is very good where you want something strong but want to make it quite compact (eg narrow frame tubes) so it can flex.

Geometry has a greater impact on stiffness than modulus as it is a power relationship compared to a linear one.

It is all trade-offs and optimisation.

Steel stanchions are used on cheap forks. They are not optimum for weight V stiffness but they are cheap and reliable and can be chrome plated for long life with minimal maintenance but won't be quite as slick.

Seat posts out of steel are not popular because to get the weight down to acceptable levels the wall thickness went too low for strength. But you can get a competitive steel seat post out of some of the expensive steel alloys. It will just cost a lot.

Also when making tubes etc out of high stiffness/strength but high density materials, ie steel, you have to make the walls thin. This creates problems with stability and impact resistance as even though globally the part is stiff enough for the loads locally it can get deformed or crushed or dented so is unsuitable. eg thin walled steel tubes can dent easier than thick walled aluminium ones of the same weight.

Cast Mag...anyone remember the Kirk Revolution? I think they all broke?

Whilst they were being boxed in the packing dept. in the factory! 😉

Certainly were very light, but think they had a useable lifetime of a few hours...

Mag is no use really anywhere in a high stress area. Mag rims are used on racing cars yes, but then they're thrown away after a relatively short period of time. Mag is good for fork lowers cos it gets a very easy life there, but no good anywhere you want any strength.

matt at 18 bikes makes 953 seatposts

[img] [/img]

Thought i would throw this in, a light stiff ti crank, but look at the welding used to make it, Steel would be as bad. Welding and mass market cranks doesn't really work

I seem to remember that XT and XTR seatposts were steel? which probably made some sense in 27.2 but less so for 31.9, in that gave some stiffness for the smaller diameter long tube that forms a mtb seat post.

There is a basic principle in economics called cost utility, in esssence is the analysis of increased benefit from increased cost. In engineering this translates in a cost versus strength versus weight. In this context strength encompasses all physical factors such as toughness, flexibility, durability eg corrosion or abrasion resistance etc.

The three factors are codependent you generally cannot affect one in isolation. Eg increased strength will result in increased weight for the same cost or increased cost for the same weight. In reality bikes and components are built to a price point, once that parameter is set there is a tradeoff between strength (or other desirable physical properties) and weight.

The trick is therefore through materials engineering and good design to optimise desirable physical properties at minimum costs.

To answer your original Q, things are made of what they are because they provide the best balance of factors at a given price point. The reason other materials aren't used are because they woul be too expensive, heavy or wouldn't be strong enough and (the absolute key point to all engineering) nobody would buy them.

This is a maassive oversimplification - but hopegully illustrates the point.