Bicycle Mechanics - How do I test to see if a crank is tweaked?
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Recently, I picked up a 1988 Trek 400T with a Sr Sakae triple crank (Oval Tech chainrings) and need a little help.
When I cranked it around it appeared a tad "out of whack" so I pulled the big ring off and it has 5 teeth worn down to nubs (presumably from a wicked crash as there are scrapes all over the aero bars as well) but lays flat against a table.
I grabbed the crank itself and tried to pull it side to side to see if it was loose in the shell but it's tight...SO,
I need an easy way to check the crank arms themselves before I spend a bunch of $$$ buying new rings, etc.
Thanks for the info as always,
Exactly what appears "out of whack?" The chainrings or crank?
10-12-03, 11:04 AM
Out of whack meaning cracked? Your cranks seem ok from what you've described so far...
When I look down from the top (i.e. align the f derailleur and the chainring) and spin the crank it appears there is a side to side wobble in the rotation. I pulled the big ring off and it lays flat against a table so I was trying to eliminate the parts before replacing the whole.
It just doesn't seem normal that there would be a wobble like that. The ring looks straight other than missing the teeth.
Nothing is cracked.
10-12-03, 04:58 PM
maybe the bb spindle is bent.
10-13-03, 10:52 AM
Pull the crank off and reinstall. Check again.
10-13-03, 12:18 PM
How do I test to see if a crank is tweaked?
Well, you could test his blood to see if meth is present.
I could be mistaken but most rings unless CNCed have a small amount of side to side movement. The rings are stamped and are not perfectly straight.
If you remove the chainrings and they all lay flat, then fixer's advice is sound. If they still have side to side movement and rub the der cage then change the b.b. spindle. Those older spindles bent pretty easily and they are not that much to replace.
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