Bent Crank Arm Spider-Sugino 75
05-10-14, 10:20 AM
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Bent Crank Arm Spider-Sugino 75
I got a new frame today and started building it up with components from my old bike. When I installed the crank with the corresponding BB, only one of the arms rubs the chainstay. All the other arms have about 1-2mm of space between them and the chainstay. I did not notice this issue with the other frame and have never had issues because of it. It may have been that way from the get go as well. The cranks are Sugino 75 track cranks. I think I may just need to replace the cranks, but anyone ever slightly bend a spider arm back? Or know how this could have happened? Also, all the chainring bolts were tight and I never had issues with them coming loose. Thanks for all the help!!!
05-10-14, 11:36 AM
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Often, what appears to be a bent crank arm is actually a spindle problem (rare) or more commonly a crank mounted poorly. Sometimes, especially when using with sharp corners on the ends, the spindle shaves the inside of the crank slightly, and the crank is slightly off plane..
So first look inside the spindle hole (no need to remove) and look for any hint of shaving on the crank.
Then, on the off change that something went wrong, remove both cranks, and reinstall 180° around on the spindle. This rarely helps, but sometimes does, and is easy insurance against doing work you shouldn't.
Otherwise, the crank is defective, and you can either return it , or straighten it on your own. I routinely true spiders by levering them with an improvised pry bar using the BB face as a fulcrum.
Do not lever against the chainstay, since that often dents the stay rather than moving the crank.
So first look inside the spindle hole (no need to remove) and look for any hint of shaving on the crank.
Then, on the off change that something went wrong, remove both cranks, and reinstall 180° around on the spindle. This rarely helps, but sometimes does, and is easy insurance against doing work you shouldn't.
Otherwise, the crank is defective, and you can either return it , or straighten it on your own. I routinely true spiders by levering them with an improvised pry bar using the BB face as a fulcrum.
Do not lever against the chainstay, since that often dents the stay rather than moving the crank.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
