Hi, I got a used Shimano 105 group for a song, and everything's working great except that the SPIDER of the right crankarm is bent, so the chainrings wobble. I'm definitely sure that the chainrings themselves aren't bent, have laid them out on a flat table and there's no obvious problem, but when I put them on the spider and tighten 'em down, it doesn't lay flat...
Any tips on fixing this? Would bending it back into shape weaken it too much (it appears to be bent about 2 mm)? I imagine I could bend it back into shape with a vise, but what part would I want to try bending? I dunno how to align it properly other than by trial and error, which could be very tedious...
I got a used Shimano 105 group for a song, and everything's working great except that the SPIDER of the right crankarm is bent, so the chainrings wobble. I'm definitely sure that the chainrings themselves aren't bent, have laid them out on a flat table and there's no obvious problem, but when I put them on the spider and tighten 'em down, it doesn't lay flat...
Any tips on fixing this?
Yes, I have an online article on exactly this topic.
Sheldon "Clothespin" Brown +------------------------------------------------------+ | A billion here, a couple of billion there -- | | first thing you know it adds up to be real money. | | --Sen. Everett McKinley Dirksen | +------------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.comhttp://sheldonbrown.com
On Mon, 01 Aug 2005 13:22:18 -0400, Sheldon Brown <[email hidden]>
Quoted message said:
Dan Lenski said:
I got a used Shimano 105 group for a song, and everything's working great except that the SPIDER of the right crankarm is bent, so the chainrings wobble. I'm definitely sure that the chainrings themselves aren't bent, have laid them out on a flat table and there's no obvious problem, but when I put them on the spider and tighten 'em down, it doesn't lay flat...
Any tips on fixing this?
Yes, I have an online article on exactly this topic.
Sheldon! What in tarnation are you doing? Sitting there typing all day, article after article, ready to preempt any stupid bike question anyone might ask.
What freeking orifice are you pulling this stuff out of.
Any tips on fixing this? Would bending it back into shape weaken it too much (it appears to be bent about 2 mm)? I imagine I could bend it back into shape with a vise, but what part would I want to try bending? I dunno how to align it properly other than by trial and error, which could be very tedious...
Bending aluminium: bad idea. Even to keep using it when it's been bent once is probably a bad idea.
Bending aluminium: bad idea. Even to keep using it when it's been bent once is probably a bad idea.
Jasper
A good point. I figure that since the spider arms aren't actually bearing my weight, the worse thing that could possibly happen is that the weakened spider arm bends or breaks again under the load of pedaling... since I'm a poor grad student, the risk is worth it :-)
I'll of course inspect the crank for cracks carefully before replacing it.
Any tips on fixing this? Would bending it back into shape weaken it too much (it appears to be bent about 2 mm)? I imagine I could bend it back into shape with a vise, but what part would I want to try bending? I dunno how to align it properly other than by trial and error, which could be very tedious...
Bending aluminium: bad idea. Even to keep using it when it's been bent once is probably a bad idea.
Jasper
Bent an FSA crank spider. Sent it back under warranty. They just bent it back and shipped it back to me. Said it happens all the time.
Any tips on fixing this? Would bending it back into shape weaken it too much (it appears to be bent about 2 mm)? I imagine I could bend it back into shape with a vise, but what part would I want to try bending? I dunno how to align it properly other than by trial and error, which could be very tedious...
Bending aluminium: bad idea. Even to keep using it when it's been bent once is probably a bad idea.
Not so. I've straightened a bent aluminum crank arm. And an aluminum (non-replaceable) derailleur hanger. And aluminum brake arms. And an aluminum handlebar bag support. (That was one I made and heat treated myself. It's been reshaped many times.) And aluminum rims. And a couple aluminum rear pannier racks... etc.
None of these have caused problems in thousands of miles of riding.
