I have a Sugnio GP 170mm crankset that i picked up used. and Im pretty sure the drive side is bent. The pedaling feels all wonkey after installing them. Same pedals feel fine on another crankset/bike.

Is it possible to bend a fordged arm or could it be a bad casting?
If i eyeball the crank it seem like it might be bent just before the pedal hole threads.

I was surprised to see this because the arm itself if flawless. Maybe before i got it, it had one hell of pedal strike or something else where it tweeked the arm but its an odd spot for bend too. I guess thats the risk you run buying old parts.

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conceivable problem could be in spider rather than arm proper

it is quite rare but sometimes there can be an error in the way the tapered opening for the spindle is formed

a bent spindle would be another possibility; if you pull the arm you can turn the spindle from the non-drive side and watch the spindle end


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Sugino is good stuff. I highly doubt such a crank has ever left their factory in that condition. Pedal strike seems much more likely. Bending it back to straight is probably possible but not recommended. I would fully expect the crank to break at the twice bent region in the next few thousand miles. So, sadly, I'd call this a learning experience. Too bad. I have many thousands of miles on Sugino cranks. On 5 of my 6 bikes now.

BB is new/sealed so i dont think it would be that. Maybe it is the spider. Its very frustrating .....i do know that.
I will make sure its not the spindle just to be sure.

I guess the spider seem straight in that it tracks the ring gear fine from what i can tell. Spinning it seems to stay nice and straight in relation to a fixed object (judging from the downtube).

Yeah i have another set of AT cranks and i have probably 10+k on those. No issues.

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good detective work!

sounds like you have it narrowed to bent arm


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At least on some hot-forged cranks like 600 Arabesque, I've taken the 18" adjustable wrench and just torqued on the pedal eye after diagnosing the direction of the bend and twist that I was dealing with.
It was easy to get things feeling normal, though I can't say how straight it really ends up.

If you ride the one bike with a bent crank long enough, it will eventually feel 100% normal.

Sometimes it's just the pedal spindle that is bent (note any wobble while the spindle is being threaded in and out).

At my weight, I wouldn't fear giving the 18" wrench a modest tug on a forged arm, as there is always some "recovery" stress-relieving that occurs initially at relatively low force levels.

It is possible to bend a forged crank arm. Many years ago, I got side-swiped by a van and my 1st-gen Chorus crank arm ended up with a bend.

Your bend could have been caused any number of things Backing into something with bike on a rear car rack might do it.

I would want to test if the pedal axle is perpendicular to the seat tube and parallel with the ground/other pedal axle when threaded onto the crank arm.

My initial instinct is to say junk it. My secondary is to say 3 points pressure could push things back to normal.

I did this with a Nervar square tapper bitd, with my dad’s vise. I felt I was successful. I know now it was not a wise move with the Nervar being cast. Now I wouldn’t even think about with the casted cranks.

forging is not the same as casting, although in the process of forging there is casting involved...and some more.
You might get away with bending a forged crankarm where a cast arm would just crack, and when it does...Da Ya Go!
The game is over

Yes, I just did that to a donated bike at the charity shop where I volunteer. Somehow, the non-drive side crank arm got bent such that it no longer cleared the chain stay. I removed the pedal and crank arm, clamped the crank arm in a bench-mounted vise, and slipped a long steel pipe over the arm, using the increased leverage to pull the arm straight again. Worked fine.

Same story here. Bought an SR Apex 86 bcd crankset and after installing it the NDS pedal was slightly off. About what you’d get from pedal strike.
Rode it that way for a while but eventually put it in a vise and used one of those Park unbending tools to remove the twist.
More than ten years later, it’s still running just fine, has been on multiple tours as well as Cino.

Hot-forged or cast cranks are much more amenable to being straightened, because their grain structure allows planar sliding within the grain (as opposed to a forging's disrupted and thus more interlocked grain structure).
A cast crankarm will generally have larger cross sections so that bending or fatigue don't occur at too low of a force level, making it feel stiffer at stress levels below the yield point.
Note that some aluminum alloys and casting processes produce parts that are less tolerant of yielding (and of corrective yielding) than others!