Lightweight frames?

[Crowella]

Thought I'd post it here.

We had an interesting discussion yesterday in our 3rd year engineering materials classes at Uni about the need for composite and ultra-light niche materials for cycling frames. Our lecturer put down "fashion" as a reason to use specific materials and gave a racing bicycle as an example.

Debate arose and none of us could draw a conclusion as to whether or not it is really neccessary to have carbon fibre, titanium and the like on a cycle considering the weight differences between them and conventional materials are really small. This was considering the weight of the bike being far less important than the rider + forces of cycling.

So my question is: Is having a lightweight frame from a composite/rare material really worth justifying the cost? I ask this because there are enough cyclists here with a whole array of gear to give a good judgement.

[CLP]

So my question is: Is having a lightweight frame from a composite/rare material really worth justifying the cost? I ask this because there are enough cyclists here with a whole array of gear to give a good judgement.

For my mind, yes.. to a point. I know I'd much rather be climbing a hill carrying as little extra weight as possible. Losing a few kilograms in that instance is quite noticeable.

the other thing to consider is ride quality offered by different materials. Part of this is personal preference, as each frame material has different characteristics. Carbon Fibre for example, is well known to have a relatively "dead" feel, transmitting little of the road shock to the rider (i can verify that this is the case!) .. yet Aluminium frames are known to give quite a harsh ride, usually mitigated by the use of carbon fibre forks and seat post.

hope that helps a bit

Cheers,
CLP

[mrleisure]

I don't know enough on the engineering side of things to answer your question but a good argument for the use of the exotic materials is that the profesionals use bikes made from them . Surely they would be using the best that is available to give them any advantage possible . As for the recreational rider , the diference in weight probably doesn't really matter that much but it's nice to have all the bling

[DexterPunk]

The first thing I thought of, was what CLP mentioned. Rigidity, and amount of flex in the bike I'd say would probably be a higher consideration than the marginal difference in lightness between such materials as carbon fiber, aluminium, and titanium. Which I'm guessing would be what translates into the feel of the ride you get from the varying materials as CLP described. From a photography standpoint, I know it makes a difference in regards to tripods when you want as little movement as possible, and may have a heavy lens being supported.

Even though it was years ago, after doing two great vic bike rides... I definitely say that I'd rather be 500g lighter than heavier when doing 120km up and down hills.

[DarrenM]

The first thing I thought of, was what CLP mentioned. Rigidity, and amount of flex in the bike I'd say would probably be a higher consideration than the marginal difference in lightness between such materials as carbon fiber, aluminium, and titanium.

A lighter material allows you to have a larger diameter tube for the same weight which reduces the flex in the frame, but how much that matters between the light alloys/titanium I don't know. I guess it's down to the manufacturer to choose which materials have all the characteristics they want.

I imagine carbon fibre would take that a step further by giving complete control over the shape of the entire frame allowing designs that you can't get through welding sections of extruded metal tubes together.

Would it be possible to build this out of alloy/titanium with the same weight and strength?

[Crowella]

I did forget to mention flexibility of the materials, mostly regarding stiffness and elasticity. I'll have to find the material comparisons up on our software and have a look.

Wouldn't most of the ride comfort though be dealt with outside the frame such as the saddle and tyres?

I'm not arguing what the result is, I'm just genuinely interested to hear what cyclists think about these frames.

EDIT: This looks like a 4th year project idea.

[Hz-Lab]

Frame geometry would effect ride comfort a lot more than the Materials used. I think Materials would not play too big of a part on the actual comfort level. The way the bike reacts though is a lot different. Carbon bikes in the DH world are a lot stiffer in cornering, an advantage to the good riders, a disadvantage to the amateurs as it's a lot easier to be bucked off. They also don't handle as well at higher speed, but that again comes down to weight as a heavier bike handles rough terrain at speed better.

Carbon fibre is still only relatively new in the Downhill world as it's only just been recently that they have really worked out the right way to build them. Before hand because of the extra strength required in a DH bike, carbon was not an advantage as the bike would end up just as heavy. But recently they have been taking carbon away from sections that dont require the strength to lighten it up. So it's chunky where it needs to be, and thin and light where its not so important.

This bike for example is probably at the forefront of Carbon bikes in the DH world


the Santa Cruz v-10 Carbon. Been a successful bike with World Cup wins and a World Championship win.

It's a one of those polarizing debates in the long travel bike scene. In XC however it seems carbon is where it is at, and this is purely a weight issue. Trying to save the odd 100g here and there.

[CLP]

A lighter material allows you to have a larger diameter tube for the same weight which reduces the flex in the frame, but how much that matters between the light alloys/titanium I don't know. I guess it's down to the manufacturer to choose which materials have all the characteristics they want.

for titanium it's very important as it's well known to flex a bit. The first Ti bikes were essentially copies of the steel roadies that were around at the time, using Ti tubing rather than steel. Most reviews bagged them for having excessive amounts of flex in the bottom bracket under load and i seem to recall at least 1 review that expressed alarm at the amount of backward flex in the Ti forks under braking. Modern Ti bikes use oversized tubing (pioneered by Cannondale with their Aluminium bikes IIRC) to increase frame stiffness and carbon fibre forks to overcome the fork flex.

[CLP]

Frame geometry would effect ride comfort a lot more than the Materials used. I think Materials would not play too big of a part on the actual comfort level.

disagree to a point. but this might come down to the type of bike you ride Hz and the type of riding you undertake.
after 5 or 6 hours in the saddle while riding on the road, a lot of discomfort can occur through the transmittance of road shock and vibration through to the rider. You probably don't experience a lot of that riding off road, with a bike that sports some sort of suspension and wide soft tyres!

Cheers,
CLP

[norbs]

I dont know that I am good enough of a rider to know the difference to be honest. I know that my current aluminium bike is lighter, therefore easier to ride than my old steel framed MTB, but I think that is also to do with the 29 inch vs 26 tyres.

I doubt that given the chance to ride a road bike made from CF, Ti, Aluminium, Steel, Bamboo or any other exotic material, I could tell them apart. I may be wrong.

[Hz-Lab]

Yeah i guess that would come in to play a lot more with roadies. Ok, well with that in mind then, how much does Geometry effect handling on road bikes? Not comfort, but the actual handling. In MTB'ing, the Geometry is the be all and end all, with the head tube angle being a very defining point as far as cornering goes.

[CLP]

Yeah i guess that would come in to play a lot more with roadies. Ok, well with that in mind then, how much does Geometry effect handling on road bikes? Not comfort, but the actual handling. In MTB'ing, the Geometry is the be all and end all, with the head tube angle being a very defining point as far as cornering goes.

Geometry is pretty important from a handling point of view. Good example is the Giant TCR and OCR range. The TCR series are designated racing bikes and their geometry dictates that they are generally quite twitchy to ride. They also tend to put the rider lower over the bar (So there is a comfort factor involved there). The OCR range on the other hand can/are made from the same materials but have slacker tube angles which make them more stable to ride, but less responsive. So the geometry in a road bike has pretty much the same effect as it does on a MTB.

[Duke]

Hurtz, Road Geometry is just as important for road feel & handling as the MTB scene.
Just like a MTB can be a cross-country, freestyle or downhill monster a Road bike can be specific to a certain type of event via changes in geometry.
Read & digest as much as you can here: http://www.cyclingtipsblog.com/2011/02/ ... -handling/" onclick="window.open(this.href);return false;

As for the topic of this discussion I will just say that in pro-roadcycling power to weight is king. So any material that reduces weight will be used & refined to gain that competitive advantage considering most riders are already down as low as 6-7% body fat (some lower).
Truth be known many a rider uses many a bike in a season, it's no secret many frames break very quickly in the pro-scene. So it's little surprise that the same happens to many rich recreational, mature & overweight riders who try to mimic their heroes a little too much.
It's fine if you undertand the expensive lightweight stuff isn't designed to last 5-10yrs any more.

As for which materials work best for which applications I suggest you grab the latest issue #51 of RIDE Cycling Review as they have a great article on the original topic of this thread.

[Crowella]

That might be worth taking a look at.

I have no doubt that each material has definite advantages or disadvantages but it's good to see what the general view is on these materials. I can understand the professionals using them but I feel as if the most benefitial thing would be the fitness of the cyclist rather than some fancy frame.

I could be wrong. Might be a nice thing to test in the labs.

[mrleisure]

Interesting article , hope it helps .

http://www.calfeedesign.com/tech-papers ... ite-paper/" onclick="window.open(this.href);return false;

[DexterPunk]

That might be worth taking a look at.

I have no doubt that each material has definite advantages or disadvantages but it's good to see what the general view is on these materials. I can understand the professionals using them but I feel as if the most benefitial thing would be the fitness of the cyclist rather than some fancy frame.

I could be wrong. Might be a nice thing to test in the labs.

If you are as fit as you can be in the time you have each day to ride etc or exercise, and still want a bit of an advantage, I can see it helping. As I mentioned before, think of riding over 100km up and down hills. The few hundred grams may not be hugely significant when you start out, but by the end of the day, I'd rather have the lighter bike under me. I agree that improving the fitness of the rider would probably be more beneficial in most cases, but thats not always possible. And even if you did get fitter and stronger.. and you knew there was a lighter and better bike out there to make your rides easier or faster, why wouldn't you want it? Otherwise we'd just all stick to penny farthings.

[Crowella]

Gave that article a good read and it's very interesting to hear about all this stuff. I might have some considerations ahead regarding a material designs assignment probably along the lines on different materials used. Would go well with the uni racing car development too

It starts to become a little clearer now as to why the expense goes out to the racing side of it all.

[Crowella]

Bringing back an old thread, turns out our 3rd year material science selection assignment is... based on bicycles of all things. That statement the lecturer said was obviously to get us riled up for it

The 6 different bicycles and allocations are:
i) A sprint bicycle (watch some Olympics footage to see them in action) Group 1
ii) A road race bicycle (e.g. as in the tour de France) Group 2
iii) A mountain bike Group 3
iv) A BMX stunt bike Group 4
v) A touring bicycle for backpacking around Europe (assume mountainous terrain) Group 5
vi) A motor assisted bicycle (possibly folding) Group 6

The components available for analysis are:
i) The frame (including assembly)
ii) The front forks (may include suspension if fitted)
iii) The wheels (hubs, spokes or discs, rims)
iv) The pedals and cranks
v) The gears
vi) The control systems (brake and gear levers & cables or hydraulic system)
vii) The drive system (usually a chain)
viii) The Brakes (discs, rim brakes, hub brakes? choose the most appropriate for the application)
ix) Headstock assembly and bearings
x) Handlebars

Thank god I got into group 2

The basis I have gathered from starting this assignment is that i need to forget what I know about bicycles and work from the ground up

I'll come back to you guys with our results from the assignment in 2 months time. It'll be good to see what bicycle theories get translated into.