FSA 3 bolt cranks

Tiffster · **Posted:** Fri Apr 17, 2009 11:34 am

I know there was a thread on this somewhere but i cant find it.

New 3 bolt cranks from FSA:

FSA also showed off their latest range of 2x9 mountain bike cranks which use a proprietary ‘386’ spider configuration (three bolts, 86mm bolt circle diameter) instead of the previous version’s 94m pattern. According to FSA, this allows for smaller and more versatile inner ring sizes than before and the new cranks will be fitted with 27/40T or 27/42T sizes.

FSA will offer the new cranks in K-Force Light carbon fibre and Afterburner hollow-forged aluminium varieties, both in either standard 68/73mm threaded or BB30 bottom bracket configurations. The K-Force Light model will include ceramic bearings as standard equipment, a slightly narrower 164mm pedal stance width and a trick outer chainring with extra-thick sculpted mounting tabs that yield extra stiffness for improved shifting."

Looks wicked if you ask me, weight is claimed 680 grams for the BB30

Pics/info courtesy of Cyclingnews.

Kayba · **Posted:** Fri Apr 17, 2009 12:52 pm

I wonder what chainline this crankset will be. Based on the close distance between chainring and chainstays on the pic, I would say approximately 48 mm.

welcomdmat · **Joined:** Sat Apr 23, 2005 3:17 am **Posts:** 358

I just don't understand the 3 bolt setup. I know that Middleburn has had some sucess with this (I say that only because they have continued to produce them and not because of any real knowledge), but why not go with a 104mm bolt circle? Chainrings can get plenty small enough with a 104 (and really with a 110 or even a 130 you can get that small, so the bolt circle change to get a ring smaller then 44t smells of bs to me but there could be an engineering benefit to the design :roll:

). Will the Middleburn rings fit the FSA crankset? The outer ring is very expensive on the K-Force to replace once you grind it down.

GrahamB · **Posted:** Fri Apr 17, 2009 2:18 pm

welcomdmat wrote:

Chainrings can get plenty small enough with a 104 (and really with a 110 or even a 130 you can get that small, so the bolt circle change to get a ring smaller then 44t smells of bs to me but there could be an engineering benefit to the design :roll:

).

Ah, the smallest you can fit on a 104 is 32t. I think the point is to be able to mount both rings via the same bolts, like a conventional double. You can't mount 27-XX like that on 104mm, best you can do is 30-XX using an expensive Extralite inner ring and filing your spyder to get chain clearance.

However I agee that using a 104/64 gives you plenty of range, the ability to use readily available rings in any size you could imagine, and less strain on the bolts (more of them and at a larger radius for the outer ring). It doesn't help FSA make money, otoh :lol:

2 wheels · **Joined:** Tue Mar 21, 2006 12:56 am **Posts:** 4890

These cranksets are to replace FSA's current '494' 2x9 cranksets with 4 bolt 94mm BCD. These have 44/29T chainrings.
With the new smaller '386' 86mm BCD they are able to use a smaller 27T inner chainring that could not fit on the larger 94mm BCD.

http://cyclingnews.com/mtb/2009/apr09/s ... a_otter091

Quote:

FSA also showed off their latest range of 2x9 mountain bike cranks which use a proprietary ‘386’ spider configuration (three bolts, 86mm bolt circle diameter) instead of the previous version’s 94m pattern. According to FSA, this allows for smaller and more versatile inner ring sizes than before and the new cranks will be fitted with 27/40T or 27/42T sizes.

FSA will offer the new cranks in K-Force Light carbon fiber and Afterburner hollow-forged aluminum varieties, both in either standard 68/73mm threaded or BB30 bottom bracket configurations. The K-Force Light model will include ceramic bearings as standard equipment, a slightly narrower 164mm pedal stance width, and a trick outer chainring with extra-thick sculpted mounting tabs that yield extra stiffness for improved shifting.

Claimed weight for the complete BB30-compatible version is around 680g and suggested retail pricing is right around $1 per gram. Given the roughly two-hour machining time per outer chainring, replacement costs will be pricey there as well at around US$200.

The Afterburner version will offer far better value at about US$270 and just over 700g in BB30 (MegaExo versions will still weigh under 800g). Pedal stance width is a more common 170mm or so and the outer chainring is made from conventional aluminum plate.

Both cranks will be available around the end of June.

FSA also showed off a new 2x9-specific mountain bike crankset with a proprietary 3x86mm bolt circle diameter.
Photo ©: James Huang/Cyclingnews.com

The top-end K-Force Light version uses an extra-beefy outer ring that starts out as a 10mm-thick aluminum plate.
Photo ©: James Huang/Cyclingnews.com

Chainring bolts enter from the backside and thread directly into the outer ring.
Photo ©: James Huang/Cyclingnews.com

The Afterburner 2x9 is definitely a better value costing just over a third that of the K-Force Light and weighing less than 100g more.
Photo ©: James Huang/Cyclingnews.com

http://velonews.com/article/90713

Quote:

FSA launched a new bolt circle diameter at Sea Otter for double mountain cranks, called 386. (Three bolts - 86mm BCD design.) Two models will be available, Afterburner and K-Force. | Photo: Matt Pacocha

The 386 cranks are available in MegaEXO and BB30 options. Both cranks are 9-speed compatible, with a 10-speed version undergoing testing. | Photo: Matt Pacocha

Megaclocker · **Joined:** Wed Dec 17, 2008 5:39 pm **Posts:** 132

Why still no 5 bolt 94/58 crank... 29/42 with a 11-34 (or even 11-36 these days) is plenty.

Those new standard are useless. Poor guy that bought the 4bolt fsa kforce light crank. Good luck to get new plates in 2-4years....

Dan Gerous · **Posted:** Fri Apr 17, 2009 6:06 pm

Nice, the 27t possibility is good for some but 200$ for a big ring? :shock:

I'll stick whit my still lighter Hollowgram SL.

welcomdmat · **Joined:** Sat Apr 23, 2005 3:17 am **Posts:** 358

Whoops -- I wasn't thinking about the small ring

Baulz · **Posted:** Fri Apr 17, 2009 8:30 pm

If Shimano had come up with this idea people would be freaking out, why is it ok for FSA to do?

I'm still happy with my 5 bolt 94mm cranks/rings.

Megaclocker · **Joined:** Wed Dec 17, 2008 5:39 pm **Posts:** 132

Baulz wrote:

If Shimano had come up with this idea people would be freaking out, why is it ok for FSA to do?

I'm still happy with my 5 bolt 94mm cranks/rings.

Shimano is not that stupid... I hope...

What is the point to make beefier chainring to be able to use 3 bolt... 3 bolt have absolutely no advantage.

200$ proprietary chainring sucks.

2 wheels · **Joined:** Tue Mar 21, 2006 12:56 am **Posts:** 4890

Megaclocker wrote:

What is the point to make beefier chainring to be able to use 3 bolt... 3 bolt have absolutely no advantage.

200$ proprietary chainring sucks.

The outer chainrings does not cost $200 because it's beffed up to use only 3 bolts, becuase the Afterburner chainring using the same BCD is much cheaper. What makes the K-Force Light chainring expensive is that it's milled out of a solid peice of alloy. (They claim it takes 2 hours to mill this - no wonder it's expensive if it's true it takes so long time).

It's impossible to make a crankset using non proprietary chainrings if you want the 27T inner and 40/42T outer ring to fit on the same BCD.
It would be proprietary no matter how many bolts they use, 3, 4 or 5 bolts makes no difference it would still be proprietary because of the smaller BCD.
The only way to make a 42+27T crankset non proprietary is to use two different BCD's with each their screws for inner and outer chainring.

But if other manufacturers will start making 2x9 cranksets using the same '386' BCD then it wont be proprietary anymore. Someone always have to be the first to introduce a new standard - or what might become a standard in time.

BB30 was also a proprietary standard until recently when it was made an open standard and other manufacturers like FSA and SRAM also started making BB30 cranksets.

2 wheels · **Joined:** Tue Mar 21, 2006 12:56 am **Posts:** 4890

Megaclocker wrote:

Poor guy that bought the 4bolt fsa kforce light crank. Good luck to get new plates in 2-4years....

ControlTech still makes the Double Play 2x9 crankset with 4 bolt 94mm BCD, same as the current FSA. They do however have a special shap near two of the bolts to make a smooth transistion with to spider.
http://www.controltechbikes.com/test/pr ... ?pro_id=59

http://www.singletrackworld.com/2009/04 ... report-one

njee20 · **Posted:** Sat Apr 18, 2009 10:17 am

That Afterburner looks really really cheap and nasty.

The K-Force looks nice, but the price of rings and the fact you're forced to use theirs would put me off!

2 wheels · **Joined:** Tue Mar 21, 2006 12:56 am **Posts:** 4890

Maybe Spécialités TA or Stonglight will make some compatible chainrings if the crankset becomes popular.
At $200 it should be possible to make some cheaper aftermarket chainrings.

JustusA · **Posted:** Sat Apr 18, 2009 4:21 pm

2 wheels wrote:

BB30 was also a proprietary standard until recently when it was made an open standard and other manufacturers like FSA and SRAM also started making BB30 cranksets.

Nah, BB30 has been an open standard all the time, it is just that others than Cannondale just have caught on. FSA has actually made BB30 cranks for a while though.

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