FRM is known for their lightweight parts, and now they’ve got a $4,900 frame made with Dyneema and carbon, and only a light clear coat. The result is this striking full suspension bike, complete with Dyneema-enhanced cockpit parts and other tricks to deliver a bike that’s under 10kg (22lb) complete. Claimed frame weight is just 2kg (4.4lb) with shock.
Why Dyneema? It’s strong, but it also removes vibrations.
Wonderful material innovation. However, they need to update their molds. Most of the folks I know who have purchased a FRM full susser have ended up getting rid of them within a year, because the geometry is pretty outdated for today’s standards. The most common commentary about them is how uncomfortable they are.
You know many people with a FRM… ? and they said the geometry is outdated and the bike not comfortble… ? sure… wonder where you live? these things are super rare in italy and you are defiitley not italian, so the changes are you never actually seen one. These are racing bikes, not general consumer, the angle is normal for a racing bike.
Cheese, spokes are flexible but they don’t stretch so they help to absorb flex. Don’t take it out of context and expect it to make sense. Each spoke is in tension tuned to all the other spokes in tension so when placed in compression it translates to the opposing spokes as tension absorbing and relieving compression, comprehend?
The spokes are flexible, so they dampen the vibrations well. As for wheel stiffness, the normal pull strength for the spokes is so high that under any hit possible there’s no way the force is gonna change from pulling to compressing. With proper tension, the wheel flex is all about the rim and spoke spacing.
The spokes aren’t flexible, any more than any other spoke is flexible.
From the specs, Dyneema is more “elastic” than steel, yet has a much, much higher ultimate strength. So you get very nice stretch of the spokes for a given tensile stress (more than steel). This keeps them from going slack. May also result in a more forgiving wheel. I don’t think one can really take advantage of the very high ultimate strength due to rim limitation. These properties also make it great for “catching” things…like bullets. They’ll stretch, but takes a lot to break them.
It seems dyneema also dampens well which is a different set of properties.
What they don’t tell you is that Dyneena (a.k.a. “Spectra” in the US) is very heat sensitive. Get it hot, like inside a car on a hot day, and it “creeps” (stretches permanently). It’s not particularly abrasion or cut resistant, particularly when it’s under tension. It was used extensively for bowstrings back when I was competing in archery and we had to learn to deal with it’s properties, or suffer the consequences. I certainly wouldn’t want it as spokes, especially for a bike that’s going to be used off-road, where abrasion is likely.
I can see it as having some benefits as a buffer/damping material in the frame, but it’s polyethylene, which is notoriously difficult to bond to, so I wonder how well it will hold up long-term.
They have changed formulas now. I used to use it as leader material when flyfishing for pike and yeah the older stuff used to get that heat creep, I stopped using it for a long time. It seems the newer formulas have addressed that issue at least for fly leaders so I would just be assuming the same for other Dynema/ spectra materials as well.
if you look at how the spoke material is threaded through the holes of the hub it looks like a shoelace through the eyelet of a shoe. it doesn’t look like it is properly mounted on the hub nor like it would hold up to actual stresses of riding around banging on the bike. I find that people who are obsessed with ultralight are the theoretical physicists of bicycling. while they may have some cutting edge ideas this bike looks very much like a fragile study in materials science and I doubt it would hold up under normal mtb conditions much less if used in a full torque full load racing environment. it looks like a temperamental study of a bike.
Josh, these spokes are Berd Spokes and they are properly mounted. The hub connection can withstand over 300 kg, which is stronger than most steel spokes. Wheels built with Berd Spokes typically outlast the best metal spoke counterparts in fatigue tests, and are absolutely suited for racing. See http://www.berdspokes.com for more information.
Of course it’s not going to fatigue, but it’s sensitive to heat and it cuts, and abrades pretty easily. It would have to be made stronger than a steel spoke in order to survive for any length of time in the real world, as it’s bound to get damaged. It’s also UV sensitive and will degrade over time when exposed to sunlight. The bottom line is that spokes are a poor application for this material.
As it goes, because spokes don’t bare load, but tension instead, it’s an outstanding application for the material. Dyneema, Cuban fibre, Spectra, whatever you call it. If you imagine that your spokes aren’t like pillars to lean on, but are there to maintain the shape through tension. It stands to reason then that a fibre as insanely strong as Dyneema, would be used in this way as not only is it hugely UV resilient (even before resin), but can bare 15X the load of steel. (Have a look at the tension strength abilities through its use in shipping industry ropes on youtube). Given it’s a lighter wheel as a result, it’s stronger, it’s more UV resilient, it’s already an incredible fibre to use.
Add to that the fact that is dampens vibration as well, and you’re able to create a wheel, which frame geometry designers can go wild with because it also reduces twitch in the handling.
(Oh and try breaking a bag for life just for fun to see how strong this stuff is!)
Yes, they are! See http://www.berdspokes.com for more information.
Is using tensile strength really relative? Knots are well known to drastically reduce the strength of the structure….only as strong as the weakest link. Just gonna drop this here:
