Carbon Fibre Wheels Anyone?

So, in the past there has been some debate about the usefulness, expense, fragility etc of any material other than steel as a substitute when making a wheel.

Well I follow the Koenigsegg feature on drive and I simply marvel at the technology these guys are using and stuff they produce. Its not a bike, but wheels are wheels and their latest Carbon Fibre wheels just seem incredible.

Here's the video on how they're made (kind of) and addressing some of the common arguments against the use of this material:

Forget the argument of expense, I would LOVE to have some made for my bike! Discuss!!!

[Grant66]

CF has too many other issues to be considered useful for mass produced vehicles.

Having worked for the last few years on an aircraft programme which uses CF for structural components; I would be hesitant to want to have wheels made from it on my vehicle. The use of CF on an aircraft wing cost/benefit is negligible, on a vehicle its just a gimmick.

The layup process is critical, as is the temperature and pressure in the autoclave. Get these wrong, which change dependent on the resin or carbon used and you have minor defects which are very difficult to assess in terms of both fatigue and stress. These minor defects lead to cracking and splitting and are likely to affect the structural integrity before becoming visible. If your only making a handful of these wheels a year, then you can NDT each one to look for these manufacturing defects, this wouldn't be feasible for mass production.

Damage repairs also produce 'issues' and where a simple blending of metalic is possible, with CF it isn't if you break the fiber strands. Yes, you can fill with resin, but you can't be sure of the integrity of the repair without further expensive testing.

Weight saving can be achieved with super plastic forming or additive layer manufacture using metal, which although won't give you the CF look will remove the through life maintenance issues.

So to sum up, if you can afford a half mill for a car, you can afford the additional maintenance cost these wheels will cause. If you can't stick with metal.

I understand its not really a mass produced option, but surely if you watch the video it shows the potential is there to improve this process for all vehicles? The post was to use Koenigsegg's own example, so lets assume they got the measurements and autoclave process right. Therefore, he is essentially saying there is a structural and performance benefit.

40% weight savings on a critical unsprung part of the car which is most prone to centrifugal force seems like a pretty good benefit to me. This is not really directly comparable with a plane wing in that context.

I did also say, cost aside - as this is clearly the biggest obstacle to mass market. In fact, lets turn that around. If they could be manufactured for half the cost of cast wheels, who wouldn't choose the CF option? Break it, buy another!

Its a fair point to use super plastic forming as a counterargument but where is this in mass made motorcycles? I'm more intrigued by his arguments that they are actually more durable than forged alloy and significantly lighter & more balanced. Cost is always going to be the biggest factor as its not easy to make or replace. But 40% weight saving on a motorcycle is just such a good number

Originally Posted by Runako

Forget the argument of expense,

Well once you forget that there really IS no argument.

Originally Posted by Spank86

Well once you forget that there really IS no argument.

How useful is this to the discussion? "CF cost a lot of money!" Yes. Should we stop building things because its costly? No. Should we keep trying to innovate? Yes. Can innovation bring the cost down? Yes. They've made 20 sets of wheels. Not much at all. But really, the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

Originally Posted by Runako

How useful is this to the discussion? "CF cost a lot of money!" Yes. Should we stop building things because its costly? No. Should we keep trying to innovate? Yes. Can innovation bring the cost down? Yes. They've made 20 sets of wheels. Not much at all. But really, the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

What I'm saying is that apart from weight there is no argument against a wheel which is lighter and stronger than current technology, unless of course youre feeling lazy and want to wait for one made out of carbon nanotubes (or graphene, seems like they wanna make everything out of graphene sometimes.

Originally Posted by Runako

I'm more intrigued by his arguments that they are actually more durable than forged alloy ...

I'd say that's a statement that could be more or less true depending on how you want to measure durability.

Originally Posted by Spank86

I'd say that's a statement that could be more or less true depending on how you want to measure durability.

Did you watch the video all the way through? I am no engineer but he gives examples. Believe or not, up to you. But why is it any less believable than what Toyota tells you? (2.9 million vehicles recalled in 2014)

Originally Posted by Spank86

Well once you forget that there really IS no argument.

Originally Posted by Spank86

What I'm saying is that apart from weight there is no argument against a wheel which is lighter and stronger than current technology, unless of course youre feeling lazy and want to wait for one made out of carbon nanotubes (or graphene, seems like they wanna make everything out of graphene sometimes.

Ah, apologies.

Originally Posted by Runako

the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

I suppose you could make the argument that CF is simply unsuitable for mass production but then the same has been said for a lot of things and time and money normally prove that theory false.

If it provides sufficient benefit then someone will work out a way to mass produce it.

Originally Posted by Runako

Did you watch the video all the way through? I am no engineer but he gives examples. Believe or not, up to you. But why is it any less believable than what Toyota tells you? (2.9 million vehicles recalled in 2014)

I don't disagree with what he's saying, He's the expert but what he's saying is that that the wheels either fine, or in bits.

I've hit a curb hard enough to put an inch deep dent in a steel wheel and driven the car home (with rather a lot of vibration), Now he may argue that that's not an example of durability but the car was still drivable (at quite some speed). It's clearly a good material for a sports focused vehicle where weight is the main consideration (although interestingly that's truer at lower speeds [not necessarily the same as low speeds]), I'm not however sure that even if it became available for all vehicles it would be good for all of them. Certainly I don't think it would be so suitable for the offroad market and possibly not for your average suburban runabout.

It's all very well saying if it suffers complete collapse you just get another one (money no object) but wheel replacement "costs" more than simply cash.


All that said I'd definitely love to know what motorcycle racing teams think about the possibilities, a car is one thing but in terms of bike racing this sounds like ti has the potential to be as big (or bigger) than the move away from spoked wheels.

[Grant66]

Originally Posted by Runako

so lets assume they got the measurements and autoclave process right. Therefore, he is essentially saying there is a structural and performance benefit.

CF is no stronger, no lighter and no more resistant to damage than metalic. The benefit in aircraft construction is its fatigue resistance, its not as susceptible to bending moments causing material instability.

Originally Posted by Runako

40% weight savings on a critical unsprung part of the car which is most prone to centrifugal force seems like a pretty good benefit to me. This is not really directly comparable with a plane wing in that context.

Aside from there being no such thing as centrifugal force, the wheel will be subject to vibration and impact (small defects in the road surface) forces. CF needs to layered to absorb the impacted forces to minimise the likelihood of layer separation.

Originally Posted by Runako

If they could be manufactured for half the cost of cast wheels, who wouldn't choose the CF option? Break it, buy another!

But your cast wheel will show visible cracking before breaking, without routine NDT testing the first indication of CF wheels failing will be as your sliding along the road on you brake discs.

Originally Posted by Runako

Its a fair point to use super plastic forming as a counterargument but where is this in mass made motorcycles?

Addictive Layer Manufacturing when perfected will surpass CF, we're already making small parts for use on test aircraft,
This process can produce repeatable identical complex parts, can be automated and uses a material that doesn't have any of the negatives that CF has. It has the potential to be cheaper than making complex machined parts, but will never be used to make wheels for expensive cars as it won't look bling.

Originally Posted by Grant66

Aside from there being no such thing as centrifugal force

Originally Posted by Grant66

CF is no stronger, no lighter and no more resistant to damage than metalic. The benefit in aircraft construction is its fatigue resistance, its not as susceptible to bending moments causing material instability.

Doesn't it have a better tensile strength (for it's wight) than Titanium?