FSA SLK Tandem crank issue
10-02-22, 05:06 PM
#1
pan y agua
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FSA SLK Tandem crank issue
The newer 4 arm spider FSA SLK tandem crankset uses FSA’s modular crank system.
Today on a gravel ride, the drivetrain was a bit noisy, and it was slow to shift to the big ring. Then the drive train just locked up. Figured out it was chain suck. Got it unstuck, and it happened again, and then again.
Turns out the spider( and thus chainrings were loose with about 3/8ths inch of play. No way to fix it in the field, we ended up walking uphill and coasting down back to the car.
Today on a gravel ride, the drivetrain was a bit noisy, and it was slow to shift to the big ring. Then the drive train just locked up. Figured out it was chain suck. Got it unstuck, and it happened again, and then again.
Turns out the spider( and thus chainrings were loose with about 3/8ths inch of play. No way to fix it in the field, we ended up walking uphill and coasting down back to the car.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
10-02-22, 05:11 PM
#2
pan y agua
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The problem was the modular lock ring which holds the spider in place had come loose allowing all the play in the spider and chain rings.
having not worked on this type FSA crank, had to figure out how to fix it. First you remove the drive side crank arm with a 10mm Allen wrench. With the crank arm removed, you can access the modular lock ring and tighten it with an FSA lock ring tool, or a Park LRT-3 tool.
having not worked on this type FSA crank, had to figure out how to fix it. First you remove the drive side crank arm with a 10mm Allen wrench. With the crank arm removed, you can access the modular lock ring and tighten it with an FSA lock ring tool, or a Park LRT-3 tool.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
10-02-22, 05:16 PM
#3
pan y agua
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The problem is not really field serviceable, at least without carrying some pretty heavy tools. Removing the crank arm, which is tightened to 40nm or so takes at least a large 10mm Allen wrench, and likely a breaker bar. Then tightening the lock ring takes the lock ring tool which is fairly heavy, and a very large wrench. ( it’s torque spec is 36 nm, and the portion that the wrench fits on is too big for many crescent wrenches.)
So just another reason I don’t much care for FSA carbon tandem cranks.
To reduce the likelihood of a repeat, I’m going to use Locktite, and make sure the lock ring is fully tightened to the torque spec.
So just another reason I don’t much care for FSA carbon tandem cranks.
To reduce the likelihood of a repeat, I’m going to use Locktite, and make sure the lock ring is fully tightened to the torque spec.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
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10-15-22, 09:42 PM
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Luckily we have not had that issue. I have to think the lock not was not torqued high enough when put together.
A really nice thing about their system is the ability to customize chainring and crank length. For our setup I removed the spider and put in a 46 tooth big ring which mates to a 30 inner. With a 10-42 cassette our gear range matches our old triple. And we are a backwards team so I was able to put the 170 crank arms front and 175s rear - despite FSA saying it could not be done!
A really nice thing about their system is the ability to customize chainring and crank length. For our setup I removed the spider and put in a 46 tooth big ring which mates to a 30 inner. With a 10-42 cassette our gear range matches our old triple. And we are a backwards team so I was able to put the 170 crank arms front and 175s rear - despite FSA saying it could not be done!
10-16-22, 07:12 PM
#5
pan y agua
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I think you’re likely right that it wasn’t properly torqued to start. Calfee assembled the bike, but I’m betting the crank came from FSA with the spider already attached.
The other possible explanation is that a decent number of off road miles vibrated it loose.
At any rate, now properly torqued, and the addition of some locktite, I’m hoping it doesn’t repeat.
The other possible explanation is that a decent number of off road miles vibrated it loose.
At any rate, now properly torqued, and the addition of some locktite, I’m hoping it doesn’t repeat.
__________________
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.
10-21-22, 10:46 PM
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Not a proper field repair, but can you get a finger tip to it enough to get it spun most of the way in? I doubt it would stay that way long, but in other circumstances it might be better than walking or calling for four wheels.
I'm always amazed at the number of not so well installed fasteners I find, even in critical areas. Six or seven years ago we got a 15-50 lathe at work. The 4 jaw chuck was bought new, with backing plate installed, from a well respected domestic company. The second time we used it we noticed that none of the screws holding the chuck on were more than finger tight and the entire thing was wobbling around. We're talking screws the size of my thumb holding a 150 pound object spinning at 2000 RPMs unguarded in front of a live human.
I'm always amazed at the number of not so well installed fasteners I find, even in critical areas. Six or seven years ago we got a 15-50 lathe at work. The 4 jaw chuck was bought new, with backing plate installed, from a well respected domestic company. The second time we used it we noticed that none of the screws holding the chuck on were more than finger tight and the entire thing was wobbling around. We're talking screws the size of my thumb holding a 150 pound object spinning at 2000 RPMs unguarded in front of a live human.
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