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Bent middle chainring on my Acera Triple?

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Bent middle chainring on my Acera Triple?

Old 06-07-20, 01:00 PM
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DanBF
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Bent middle chainring on my Acera Triple?

I have a 2013 Fuji Absolute with an Acera triple crankset. I've been experiencing chain drops at random times. I noticed that the middle chainring seems to be bent. I'm pretty sure this is abnormal but I wanted to check with you guys before I attempt to straighten it. I took a video so you can see what I'm talking about (please disregard the reathing noises lol)
Fixing this looks pretty straightforward but I've never removed a chainring before. Do you have any tips or advice?
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Old 06-07-20, 02:16 PM
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Is the bens associated with the middle ring's shift gate? Sure looks to be a bend from over aggressive pedal pressure when shifting, this time with the left foot forward.

For an experienced wrench this is not hard to improve. straightness wise. Maybe not like OEM but better. The trick is to focus the bending back pressure right at the peak of the bend and do so with no other ill effects or chance to slip and create a big OOPS. The first possibility I would consider is to brace the DT with a fairly large flat item (and not one that has burrs) This item will be the foundation for a prying lever that acts on the ring at the right spot. Not having tiny fingers on a third hand to help locate all this taping the foundation item against the DT helps. I often use ire levers or other plastic block for this. Then the lever can be a stiff long tool, like a screwdriver or pedal wrench. Practice the set up before applying real pressure. An alternative is a hammer and punch to focus the bending pressures. But i find a lever slows down the forces and reduces the OOPS quickness. Andy
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Old 06-07-20, 05:47 PM
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I have had good success using a long-nosed Vise-Grips pliers like this: https://www.amazon.com/VISE-GRIP-Ori.../dp/B0000BYD9A to straighten bent chain rings without removing them. I find it helpful to remove the chain (I use quick links) to be able to more easily move the crankset back and forth to visualize how I am progressing. I agree (as I usually do) with Andrew Stewart that oiveragressive shifting is the likely cause; an impact would be more likely to damage the big ring.
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Old 06-07-20, 06:11 PM
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Originally Posted by DanBF View Post
I have a 2013 Fuji Absolute with an Acera triple crankset. I've been experiencing chain drops at random times. I noticed that the middle chainring seems to be bent. I'm pretty sure this is abnormal but I wanted to check with you guys before I attempt to straighten it. I took a video so you can see what I'm talking about (please disregard the reathing noises lol)

Fixing this looks pretty straightforward but I've never removed a chainring before. Do you have any tips or advice?
You probably canít remove the chainrings. Acera level cranks tend to have riveted rings. You might be able to straighten it without removing the ring but itís going to be a bit harder.
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Old 06-07-20, 08:52 PM
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Originally Posted by dsbrantjr View Post
I have had good success using a long-nosed Vise-Grips pliers like this: https://www.amazon.com/VISE-GRIP-Ori.../dp/B0000BYD9A to straighten bent chain rings without removing them. I find it helpful to remove the chain (I use quick links) to be able to more easily move the crankset back and forth to visualize how I am progressing. I agree (as I usually do) with Andrew Stewart that oiveragressive shifting is the likely cause; an impact would be more likely to damage the big ring.

I, too, have used large jawed slip joint pliers to bend back ring sections. The trick is to isolate the force to only the ring bent.

If all three rings have the same "wobble" then the spider is likely the issue and bending all three rings with force on the spider arms' "bolts" (or rivets/spot welds) is the first approach. Bur when only one ring is bent that one needs to be dealt with independent from the other(s). Placing a stiff item (a cone wrench barely meets this, a open end wrench is better) across the outer (or inner) ring to spread out the reactive force is a neat trick. The slip lock pliers jaws would be on that stiff brace and the bent ring's bad point.

This is a type of repair that needs creative thinking and consideration to both what's "good enough" as well as what's going wrong Andy
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