I’m just considering a new road frame and would like some clear information on grades of carbon…

3k
12k
T700
T800

high modulous

what does it all mean and what to look for? Am I right in saying the above just represents the type of raw carbon and the resign/assembly method makes a big difference?

Sorry if this has been done before as quick google search doesn’t really answer it.

Cheers

PL

Do you know/worry about which series aluminium your frame/components are made from? If not, I wouldn’t worry about those either…

I always check what aluminium parts are made from. eg a stem can have different alloys for the main body and faceplate. in a frame it is even more important – just like the way people pay more for certain grades of steel.

As for the carbon fibre – is the type of fibres used and how they are presented.

t700 for example is a high tensile strength material – it is used for aircraft, rotor blades etc and is quite common on bikes. It is a good material.

3k and 12k refer to the weave of woven materials and the larger number means a coarser weave due to a larger tow.

The most popular material for bikes seems to be T700 and is used as UD (unidirectional) in the carbon 456 I believe.

You get different grades of fibre which can be used to tailor the material for the application and requirements and obviously some cost a lot more than others but tbh your money is better spent on optimisation through testing and modelling and refining the manufacturing and sticking with the common, but good property fibres and not going for the exotics.

You will see bikes that are made of the same fibres that cost £400 for a frame and some that cost over £2k for a frame. sometimes the expensive ones will say they have an exotic carbon fibre in them and use that as justification – how much of that fibre and where it is used can vary but in a bike application I would put my money and time in the design and testing and worry about splashing out on the expensive fibres later.

Andy – thanks very much for taking the time to type that out, apprecaite it.

I know what my rigid frame bikes are made from as it is one key component of the ride. For example, a mate has inbreds in cro-mo and 753, the latter feels a bit nicer.

>Do you know/worry about which series aluminium your frame/components are made from?

No. But I know what steel and Ti my frames are made from.

No worries.

I would normally go for 7005 alloy for a frame and 7 series alloys for most things but the lower number ones have their places – eg maybe go for lower grade face plate so it distorts through shearing before it snaps.

For carbon, I was asked in a bike shop if there was a material reason why some carbon frames are 5x more than others. tbh not really for bike stuff. You use a decent fibre such as T700 and as I said earlier the money is easily accounted for on the design and development. Maybe some of the really expensive road frames may have expensive fibres but tbh they probably use it in the chainstay and that is about it and it allows them to shave off 20g. On the most part it is probably Bull Sh*t marketing and it doesnt matter what fibres you use if you don’t optimise and develop properly.

The right fibres have their purpose and you need to choose the right one and design for that fibre but I would be happy with ‘run of the mill’ T700. It is good enough for rotor blades so it’s good enough for me.

Ps there is also the resin to consider. Lots of variation in resin. But again their are standard ones that people will design to as they are well documented.

The reserve factors of carbon fibre are so conservative due to the data being conservative and allowances for manufacturing and damage during life (they are designed to age like you would spec solar panels) you will see carbon frames take a hell of a lot of stick before they fail. This is why people shouldnt be afraid of carbon bikes, they can probably take so much more knocks and force and fatigue than most thin walled metal bikes in/near their weight range.

Given the limited number of manufacturers of UHM and HM carbon fibre and the limits placed on exporting these materials into china, I wouldn’t worry too much, as pretty much all the CF frames (which are nearly all made in china/Tiawan) you can get will be medium modulus anyway. Despite what they might claim!

For example, a mate has inbreds in cro-mo and 753, the latter feels a bit nicer.

It’s 853, not 753 and if you really believe that (yes, I have both) then you’d probably best make sure you really do read all the marketing because it’ll clearly affect how the bike rides for you…

No. But I know what steel and Ti my frames are made from.

You also might want to read into what the differences between grades of steel for example are and how that’s not the critical factor in determining how the bike will ride.

I dont even know what carbon fibre is, some sort of wonderstuff I think. I wanted a carbon fibre bike and thats what I bought, I could have been sold anything though, but in my head its carbon fibre and thats good enough. Im sure it’ll do for you too.

Now surely alot of it has just got to be marketing trollocks?!?!

Its not in a manufacturers interest to use sub grade materials as their frames will snap etc, so they all produce frames that they hope will perform as required. Then some marketing person comes along and tries to dupe you all in to thinking that piece of glued together plastic is better than Fred’s glued together piece of plastic.

Surely you better to look at how the frame rides, failure rate, weight, etc etc rather than the actual material ?

It’s black magic David, and who doesn’t want to ride a bike made of black magic!

3k and 12k are the numbers of individual carbon fibres in a ‘tow’. A tow is a bundle of fibres.

T700, T800 and High Modulus are different fibre types.

Different tows and fibre types can be used in different types of composite. The most usual types are unidirectional lay-ups, woven or NCF (Non Crimped Fabric, a halfway house between UD and woven).

What is most important in composite frames, other than the manufacturing technique and tolerances, is the design. In particular what the direction percentages of the fibres are, how the interfaces are designed.

No amount of marketing spiel can give you any indication about the quality of a composite design. I would say that real world experience is the only good way too assess a composite frame. I.e. only buy from a company with a good record.

And a link to the company I work for: Aerocomp. Excuse a few typos and other errors, it’s a spangly new website.