That's great and all but my issue with carbon wheels isn't their impact resistance, it's sustained load. Especially lateral "across the grain" load. Carbon fiber like aluminum or magnesium will flex to a degree with no adverse effects. See how much that wheel bounces? A metal wheel would just dent, but it could be repaired back to perfection. However resin is more brittle than metal, and in time will flex to a breaking point, and once it's compromised the wheel is completely junk. We used to pressure test aluminum sleeved, carbon re-enforced hydrogen fuel cells up to many hundreds of psi and found that if we spiked the load the cell would take it and flex back with no damage. However if we pumped up and held the tank at a slightly lower pressure the load on the units would eventually cause fissures and a subsequent blowout failure. If during a street ride you hit a bump that could damage a wheel with a metal one you will feel the issue if it's big enough but your wheel won't tear itself apart on you. I've dented rims but not bad enough to affect the bead of the tire or cause a bouncy ride, and I only noticed it when doing a tire change hundreds or thousands of miles later. With a carbon wheel you could ding it and cause damage but not know it. It will absorb the hit, crack, and flex back. If you're lucky it will be visible on the surface, but that's not guaranteed to be the case. Now you have a wheel that is structurally unsound and the rotational inertia and lateral g-forces you put through it are slowly making it worse to the point of catastrophic failure. Let's not forget these things are attached to 400lb bikes with another couple hundred pounds of rider pressing down on them! You probably won't feel anything until a second or two before the wheel shreds apart as it de-laminates. As we all know corner exit acceleration and hard trail braking put a LOT of force through the wheels. More than enough to tear apart a compromised spoke that's only a couple layers of material thick. The RBX wheels are structurally much safer. Their larger spokes will absorb and distribute load more efficiently and will have a higher tolerance before irreversible damage is caused. But for the money is any carbon wheel really worth it? I've held a 6" BST rear at the same time as a forged magnesium Marchesini and a forged aluminum Carrozzeria. The Marchesini was exactly the same weight in my hands, and the difference between the BST and the Carrozzeria was barely noticeable. Obviously at speed the centrifugal force will increase that difference exponentially but we're talking about a pretty minimal difference in terms of feedback to the rider. Something a very good rider on a modern bike might notice but not make a real difference at the end of the day. I'll keep the peace of mind, and more money in my pocket, and stick with a metal wheel. Just my 2c EDIT - For what's it worth the rider was OK, but his bike was absolutely destroyed as a result.
That happens everyday with thousands of bikes all over the world wearing these wheels, why would you want to see a video of that. If you want to see a bike fitted with these wheels, sans tyres and tossed 30ft in the air, then you're missing the point... You can't drop ANY metal wheel from more than knee height without causing structural damage but no matter what some people see, theyre determined never to understand them. That works for me, if everyone had these wheels I wouldn't feel so special about mine.
I'm not suggesting they should hold up if you're tossing them in the same way or at the same height with a motorcycle mounted to them, but to suggest that what they're doing even remotely approximates the forces you see on a wheel in the real world, where the force is exerted through the hub, is just silly. You were suggesting that the video showed the rigidity of the wheels, right? I'm suggesting the forces on a mounted wheel are very different, both in the location, direction and volume of force being applied.
Don't think anyone is suggesting that is a real world scientific test but it was interesting to see them hold up to abuse that they were probably not even designed to withstand.
If crosswinds were an issue on solid wheels, Tour De France bikes wouldnt use them. Id love to get my hands on a set of those RTBs, they look sick to me!
Depending the the wind and the course they don't use them. Gusty winds from the side can blow you off the road. Constant wind at the right angle will give you a sail effect and make you go faster easier.
the only time i think wind might have some different effect w/ those rbx wheels as compared to one w/ 'standard' spokes is when they are sitting on a paddock stand. once your wheels are spinning, i dont think the wind just blows right through them... you know, turbulent flow and all due to the spoke spinning has to be significant. you might even be able to argue that the relatively aerodynamic x-sectional shape of those big spokes is beneficial: less turbulence. vince
Not at all, hence my posting "Just for giggles....." before the link. Sorry, I should have spelt that out. If it were up to me I'd mount a wheel on a solid spindle through the hub, then apply both constant pressure and a sharp pressure through the rim and measure deflection and return, up to destruction. I don't need to do that though, the relevant agencies that approve the wheels already do that and to an extent, so does every rider of every bike fitted with them. I'm sure if I did that though mainly all I'd get were responses along the lines of "You used the wrong temperature to test in", "The colour of the press was wrong", "you should have filmed it in HD" etc... Some people are determined never to accept any form of 'proof'. That video just shows one thing you can do with carbon wheels which you can't with metal, and as a FACT does prove they're more resiliant to at least being tossed 30ft up in the air over metal ones. That is all. Oh. My. God. Hence why I didn't even bother to respond... Next time your bike is on a dyno or even a paddock stand if you're happy running the bike on it, presuming it has conventional spoke pattern wheels, blow an airline through the rear wheel while it's spinning... Now try that on a near solid spoke one.
If you say so! Sorry but I'll believe the engineers who've taken home JEC Composites awards by beating out Porsche's R&D department over the opinions of an anonymous guy on a forum and some journalist. You're entitled to your opinions though. Hypocrisy at it's finest Carbon wheels are banned at the highest levels of motorsport for a reason, and that's because they cannot consistently handle the loads exerted on them by a MotoGP bike, F1 car, etc. It is a structural safety issue. The 125 and 250 GP bikes got away with using them because the bikes weighed nothing and neither did the riders.
Ah fantastic, so you've got the engineers reports testing both BSTs, numerous other wheels and RBx wheels together? Well why didn't you say so and post up the report?! That'd answer a lot of questions. Until then, saying that offers absolutely zero credibility to anything you have to say. Exactly the same as me. How's that for hypocrisy? Show me anywhere that the governing bodies say they won't allow carbon wheels in top level motorsport due the reasons you stated above, which you just read from other completely unfounded internet posts? All they say that I've managed to find is they're not allowed. Personally when I spoke to a member of Sterilgarda's Yamaha team about them not being in MotoGP he said it was due to the temperature of the carbon brakes on both MotoGP and F1... That and the politics created by the largest company supplying wheels and brakes to most of the MotoGP paddock. By your reckoning that RBX wheels are so much better than either BST or Dymag offerings, are you suggesting we could see them in MotoGP? No, didn't think so. How's that hypocrisy thing working out for you?
Like I said, personally I am a happy BST customer. IIRC, Tim Hunt used a set all year when he was chasing that big Honda payout a couple of years ago and had no issues. BST's have been around for a while and I am yet to see nor hear of a failure during normal use "normal" being defined by racing or even street use. The thing about the internet, is that you never hear the good because "the good" isn't entertaining. There could be 10,000 satisfied BST customers and you might get 1 or 2 (like in this thread) people who make a thread or post simply to say "no problems here, I like them". But yet you have 1 person have a bad experience (with anything, not just wheels), and they will ensure the whole e-world knows about it within seconds. For the record, I am not sponsored by BST, I paid for them like everyone else. I am simply giving my opinion. As far as the RotoBox...yes, they are ugly. Would I use them...yes...if they were given to me. Would I buy them, no. Am I that vain about how my shit looks? Yes. If I were given a set, I would run them, give them a back-to-back comparison to the BST's and expressed my thoughts.
Please find the text that explains that carbon wheels are banned in MotoGP. Brembo supplies wheels (Marchisini) and brakes to every OEM. They also make VERY good racing products. Sometimes business relationships are more important than simply what is the best part to use....especially when everybody is using the same thing. Carbon Fiber is a commonly accepted structural material in everything from Motorcycle wheels to airplanes (Boeing 787). Its silly to say it is not safe to use them as wheels.....as long as they are built correctly. BST has been making carbon wheels for at least 10 years (that's when I saw my first set). We sell the wheels, we have hundreds of customers with the wheels, and there are set on the bike I ride all the time. I have never seen a failure. Due to this sample size and my access to the kind of customers in the US that use this type of product, I believe that BST makes a good wheel. I would go as far as to say that there is probably more to this story than what is being reviled and this is not a far reaching problem with BST wheels as a whole..
No they don't. There are no universal standards and no certification processes for motorcycle wheels; there is no agency that tests motorcycle wheels for DOT or other certification. It's a self-applied label based on the assumption that a company has done the appropriate testing.
Correct, but BST don't test their own wheels, a company over here do it. They've no interest in BST other than performing those tests. You think if the wheels failed they'd be willing to put their name to the tests?
I happen to have two engineering degrees, and one of them is in Materials Science. So keep on believing what you want...
We've seen the photos of the wheel. Photos of the rest of the bike will tell those of us who have been doing this longer than a day what happened.
At this point the only thing you will learn about the bike is that it is wadded up. Based on the condition of the wheel, I'd say the bike took a pretty good football tumble...
I'm going to bet the order of events was football tumble...resulting in destruction of wheel and not what the bike owner is claiming happened.
