FSA's New High-End Crankset Skips the Carbon - Taipei Cycle Show 2019

Mar 29, 2019 at 1:32
by Mike Levy  
Taipei Cycle Show 2019
FSA's aluminum KFX crank arms are machined in two separate pieces before being glued together.


If you want lightweight and high-end components, and especially cranks, the usual answer is carbon fiber. But FSA, who have plenty of fancy carbon things in their catalog, is going a different route with their upcoming aluminum KFX arms.

There are countless alloy cranks out there, though, so what's so interesting about these? Instead of machining them from a single piece of aluminum as per usual, they're made in two halves before being glued together. Yes, they're glued.


Taipei Cycle Show 2019
Taipei Cycle Show 2019
See those ridges and channels? They slot together very precisely to create a single unit.


Now, if know Cannondale well, that process might sound a bit familiar; they do a similar thing to make their impressive Hollowgram Si arms. The idea is that by machining them in two halves, FSA can remove as much material from the inner face of each arm as possible, making for a hollowed-out structure that's said be relatively lightweight yet strong enough for downhill and enduro use.

One arm is left with very precise channels cut into the mating face, while the opposite arm gets thin ridges that slot into said channels and, with the help of some powerful glue, make for a single crank arm.


Taipei Cycle Show 2019
Machining the arms in two pieces lets FSA remove material from inside that they otherwise wouldn't be able to reach.


I was told that they'll weigh in at around 520-grams (arms and spindle) so while they're certainly in the svelte category, they aren't the lightest around, either. FSA doesn't have any plans to move away from carbon fiber, they told me, only that they wanted a solution that's relatively lightweight but without the sometimes fragile nature of carbon. There's no word on an MSRP yet, but you should see them on shelves by late-summer.


87 Comments

  • + 66
 Looks like the new Pole crank.
  • + 105
 waaay too short for it to be Pole.
  • - 4
flag jaame (Mar 29, 2019 at 2:10) (Below Threshold)
 @WAKIdesigns: au contraire. Pole have been experimenting with 94mm spindle, 120mm cranks in order to maximise control through rough, high speed turns.
  • + 3
 @jaame: I saw an article once from Leo talking about crank length and how he was testing 135mm cranks but for the life of me I can't find it, you don't perhaps know the one, or have a similar article laying around somewhere?
  • + 12
 @jaame: some people at Pole need to learn to ride instead of trying to find solutions to problems that do not exist. Then stop justifying sht they do by showing videos of Isaak Levisson who can send stuff on Hillbilly fest on a shopping cart and BTW moved to a "too short" Canyon and is having the best season of his riding career. Waiting for them to jump on "attach heavy sht to BB" train. BMX racers run 180 and even 182.5mm cranks (due to start gate sprint) and try to beat them on a pumptrack where short crank length is supposedly most favorable of all discilpines.
  • + 12
 Ha ha ha! I made it up, but it looks like it's pretty close to the truth!
  • + 1
 @jaame: Yeah, I was surprised too. My point was merely that the cranks were made out of two machined halves fixed together. My favorite cranks for a mountainbike would probably just be tubular steel cranks like I have on my BMX. Simple, smooth and do the job. I get that with triple chainrings or extra wide bottom brackets (because boost) people would want narrow cranks for everything to fit, but my bb is just 73mm and I'm still running a single ring (with a taco instead of bashring these days) so there is more than enough room for simple tubular cranks that just do the job without a fuss. Unfortunately I haven't found oval chainrings and tubular cranks that are compatible.
  • + 3
 @WAKIdesigns: A pole is still has two wheels like any other bike, it has nothing really that different. its still a bike. It has a slightly longer wheelbase and might be considered slack by some. Are pole really saying that they are providing solutions to problems?? I would think they are offering a product which is not exactly the same as the others, it would make business sense no?? What makes them that much different from the bike that you own and ride? I think the answer would be the material its made from and the few centimetres in the wheelbase. meh.
  • + 0
 @WAKIdesigns: you speak the truth. The Loam ranger constantly talks about how the crazy long wheelbase has saved him from his hack riding.
  • + 6
 @puddinghead: I like their bike, i like that there is an option like that, just their accusational marketing is worthy of biggest bullshitters in the business like Trek and Sram.
  • + 1
 I thought that... Keep it bare and it would look good on a machine. To be fair, Pole's geometry is getting less and less extreme as every time anyone brings out a bike it's longer than the last and Pole have stayed the same.
  • + 1
 @agnostic: you’re damn right it has! (Don’t forget to like and subscribe) Wink
  • + 1
 @rob-chambo: Someone commented that the new Poles are getting shorter a couple of weeks back. Bushranger review perhaps.
  • + 1
 @vinay: get a 4 or 5 bolt spider from profile and run any ring you want.
  • + 1
 @MikeGruhler: Yeah, good idea!
  • + 29
 Last week I made a crank entirely out of two pieces of glue which were then machined and sandwiched together with metal. But I put it in the bin filed away under; may come in handy as a disengenuous online anecdote
  • + 27
 Now there’s a creek in my crank..
  • + 27
 Simple way to stop it...Get a beaver.
  • + 7
 @loopie: It'll stop the creek and lengthen the crank...win win
  • + 1
 @loopie: Dam it!
  • + 22
 hey PB: find out what glue they use. It's always impressive hearing about how good modern adhesives are that they meet structural requirements.
  • + 6
 This^
Apparently it's a pain in the ass to glue aluminium because of the thin layer of oxide layer that severely weakens the bond.
  • + 10
 The glue is probably some sort of epoxy and the surfaces are etched with some mix usually containing sulfuric acid. There are several off the shelf solutions available. I would not expect a manufacturer to share his process though.
  • + 12
 There are some really good glues out there. The challenge is to be able to tell whether the bond is (still) good or not. Back when Fokker made aircraft, they also glued their panels whereas others used to rivet them. No/less rivets meant less drills so that basically implied fewer weak spots. They developed the "Fokker Bondtester" to inspect the glued bonds. There were downsides too though. American Airlines doesn't paint their aircraft which implied there shouldn't be any glue stains. They spent so much time cleaning these aircraft that they probably made very little money off them.

In the bicycle industry, a good example of course is the glued connection between the CFRP tubes and the titanium lugs of the Atherton/Robotbike frames. It doesn't go anywhere. That said, I think the Robotbike process is better thought out. They have a hole in the lug for air to escape so that the glue covers the entire surface it needs to cover. From what I see here, chances are pockets of air can't escape pushing back the glue from where it needs to go. But that's just armchain engineering of my part of course. It may just work out fine Smile .
  • + 9
 Polaris snowmobiles have been “gluing” there bulk heads and a arms together for the past six or seven years. Sure they had some issues but at this point are really reliable. If “glue” is good enough for a machine that weighs 500 pounds and builds up to 200 horsepower I’m sure these cranks will hold up just fine.
  • + 4
 @vinay: If air is an issue, they may use a vacuum, as a crank is rather small so it won't be a hard thing to do.
  • + 5
 @Lambert45: came here to post the same. Polaris uses Lords epoxy. I’ve used it to build and repair a couple Polaris sleds and it’s impressive.

The sleds are just over 400 lbs now with 150ish HP.
  • + 1
 @ZigaK13: I agree, but on the other hand there is pedal screw down and and bottom bracket on the other side even if the glue lost its power, it should be fine

(just make the hole bigger so we can store a cliffbar in cranks)
  • + 1
 @faul: Yeah, they probably cure it in an autoclave. Not sure whether high or low pressure would be the way to go. Low pressure (vacuum) may "suck" out the excess air but if the bubbles just expand and as they evacuate, drive some of the glue out as well I'm not sure if that is of any help. There is nothing driving the glue into those tight corners are the air goes in the other direction. I was actually thinking of curing it under overpressure. This will shrink the bubbles and drag the glue deeper in there. Sure once everything is cured and you're back at ambient pressure there may be some tiny bubbles in there at a slight (1 bar max) overpressure but that shouldn't be much of a deal. That said, maybe these interlocking ridges weren't meant to be glued anyway and they apply the glue to other mating surfaces which are designed with air evacuation in mind.
  • + 2
 @meathooker: Well of course, if they're using the Lord's Own Epoxy, it'll hold just fine.
  • + 2
 They microwaved marshmallows and used that.



Seriously, microwaved marshmallows is a powerful glue, we stuck a potato to a plate! (They also expand like crazy in the microwave)Smile
  • + 1
 @vinay: I think it depends what type of adhesive they are using. If they are using a 2 part that needs to be mixed you would typically mix it and then put it under vacuum to remove any air bubbles that you generated. Curing under vacuum can cause larger voids depending on the geometry because under vacuum the adhesive will basically be boiling and driving it out of the bond area. If I were to do it I would use a two part epoxy, prime the bond area, degas the epoxy and then bond under pressure (clamp the two parts together) and heat. That should give you a very strong part.
  • + 1
 Whatever it is I’ll have what they are having. They most certainly are huffing glue to try and sell something like that.
  • + 15
 The Lotus Elise aluminium chassis is also glued, and they stated that the glue was stronger than the aluminium. The bonds on this looks incredibly strong with all the area for adhesive. The design is very nice too.
  • + 2
 Most all "supercars" as well.
  • + 13
 FSA makes Cannondale cranks, so hardly anything new for them

The question is when does the patent run out, I seem to remember it doesn’t cover Europe so fair game....

That gets me thinking!
  • + 2
 Most of the thinking is done long before somebody comes along and copies a product / manufacturing technique.
  • + 2
 I’ve just had a look and it appears all the aluminium crank patents have lapsed today. Don’t quote me on this as I’ve only had a brief look through the list.
  • + 3
 Other side of the coin is that everything has been done many times before. We had someone try to sue us because they had a “patent” for a quick release.

Most patents are actually there for tax reduction reasons rather than new inventions @justanotherusername:
  • + 2
 @SuperstarComponents: Many things have been done before, of course, but there is a difference between development and blatant copying.
  • + 2
 Who said anything about copying? That’s a bit of a presumption there.@justanotherusername:
  • + 7
 Pinkbike: Hollowgram cranks are made by FSA. They are finally using that technology with their own brand, and I hope their will be as good as Hollowgrams since I never liked Cdale's stupid price. Cheers
  • + 8
 FSA are also showing their take at improving gear range, using 2 chainrings!!??
  • + 4
 First ride today with newly installed 2x.....Ahhhhh, that's better Smile I missed you 2x
  • + 2
 @loopie:
Maybe better not to say that out loud, people will think you are crazy. (you’re right though...)
  • + 1
 @cvoc: A year ago..you'd get nailed to the cross for suggesting 2x. Which is exactly when I bought 2x crank/shifter/der for so cheap cuz no one wanted them. But riders in certain terrain are starting to see the light Smile
  • + 5
 Shimano has been doing this for quite some time now with there road cranks. These do come apart at some point in some cases so i would like to see how the FSA holds up.
  • + 0
 I won't ride Shimano road cranks for this reason. Seen too many fail at the adhesive, both online and in person.
  • + 2
 I've broken two of the older 6700 series Ultegra cranks due to separation of the driveside crank arm. One was quite catastrophic and it damaged the driveside chainstay. The other I caught before complete failure. In both cases Shimano warrantied the crank, and the latest failure they replaced it with the R8000 crank, its only been about 9mos but its holding up. Both of the 6700 cranks failed after about 18mos.
  • + 6
 Has it got proper sized bearing friendly 24 mm axles or 30mm junk
  • + 5
 Weld weld weld wot av we are.
  • + 4
 "If know Cannondale well"
  • + 3
 same process and keyed teeth as cannondale SISL2, which means its the same supplier. big breakthroughs guys
  • + 3
 Magic motorcycle cranks. Machined and bonded cranks was done successfully in the 90's.
  • + 4
 The Magic Motorcycle crank is the grandfather of the Hollowgram.
  • + 1
 @nozes: I broke 3 of those MM Cranks. Pretty but needed some FEA analysis. But maybe they wouldn't be as light then?
  • + 1
 @chasejj: Tdf, most cranks in the early nineties were not that good. Imagine if you had those cranks now, they would sell for big money!
  • + 1
 Cannondale has been making the best cranks in the world like this for years. Even the glue interface is copied, talk about a stolen design.
  • + 1
 So I didn't know the patent expired, I guess be wary when you have a sub contractor make your patented design.
  • + 1
 Cannondale does not make cranks. FSA has made SI cranks for Cannondale. Most likely, FSA had an exclusivity agreement with Cannondale to make that design for C years. Now, that time is up and they are bringing the truce and true cranks to AM offerings. Jeez people, it’s amazing how y’all jump to haterade when you actually like the design! It’s just allowing more people to access the option. No one is “stealing” no one is “copying” no one said it was a breakthrough NEW design... just new to FSA AM offerings. Lol.
Trolls, ya’ll too funny!!!
  • + 2
 Look up thanksshimano on Instagram to see what happens to glued together cranks...
  • + 1
 It's the same structure as the Cannondale SI crank arm.......There are patents in the U.S., Korea, and Japan in this way. Smile
  • + 2
 Same weight as RF Turbines and probably 2x the cost
  • + 1
 i like them but cant come up with a reason to swap out my descendant cranks (yes shimano cranks are better, but still)
  • + 1
 I hope they don't use the same glue as Shimano Dura Ace
  • + 1
 Look, now Pole makes cranks!
  • + 1
 That’s a good looking crank!
  • + 1
 FSA, please offer a polished version
  • + 1
 Very cool. Taking cues from Pole bikes I see!!!
  • + 1
 Why can't they friction weld the 2 halves together?
  • + 1
 heavier than XTR, I don't get it.
  • + 1
 Good. And its a thing of beauty!
  • + 1
 This is getting pOLeD already
  • + 1
 Do you mean pØŁęD?
  • + 1
 Love it.
  • + 1
 Looks deadly!!
  • + 1
 2x?
  • + 0
 Thats very cool!
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