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help with changing a chainring please

Old 03-26-14, 04:35 PM
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help with changing a chainring please

hi,

I'm new to servicing my bike. I've always let the shop do it but I have decided that I needed more frustration in my life so here I am!

I have worn components and need to change my chain and a couple of chainrings on a shimano triple FC4603 crankset. I'd blush if I had to admit how much reading I've had to do to even come up with the basic plan here....

my question is this....do I have to remove the crank to replace the middle chainring on this unit?

It seems to me that I do. I can get the outer/larger 50 tooth ring off no prob of course but the middle seems to have to come off from the back which would require removing the crank. Here is the spec for the unit I need to service:
https://techdocs.shimano.com/media/te...9830746319.pdf

I'm asking this in case there is some trick I can't see.

thanks
-Conor
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Old 03-26-14, 04:39 PM
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You don't have to remove the crank.
The middle chainring is attached with the same bolts as the large one.
Just remove the large chainring and you will see.
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Old 03-26-14, 04:56 PM
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+1, the inner ring's diameter is too small, and cannot be removed over the mounting arms (aka spider), but the middle can easily be maneuvered over one arm at a time, and a new one mounted the same way.

When installing the replacement, be sure to keep the inside in, and outside out. Usually it's easy because the inner (toward the bike) surface has counterbores to recess the nuts of the mounting bolts.

BTW- you may need a chainring nut wrench (or may not) to hold the nut while you turn the bolt with a 5mm hex or torx key. The nut wrenches aren't always needed, but can be if the crank's old and there's rust or corrosion in the threads.
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Old 03-26-14, 05:10 PM
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With an HT2 crank, the process for removing the crank is so quick and simple, it makes little sense to leave the crank on the bike if attempting to remove the middle or outer rings.

Removing the crank would also allow you to clean any debris in-between the crank arms and BB which is normally pretty inaccessible, and will avoid any potential scratching of the arms on the chainring removal/install.
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Old 03-26-14, 05:17 PM
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great! thanks for the replies. I'm ordering the parts and will give it a go so. Something tells me you haven't heard the last of me
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Old 03-26-14, 05:22 PM
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Originally Posted by fahyc
great! thanks for the replies. I'm ordering the parts and will give it a go so. Something tells me you haven't heard the last of me
Is that a threat? (maybe it's a treat)
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Old 03-26-14, 08:49 PM
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The trick you can't see is that the bolts attaching the rings to the spider are super tight. Whether or not you take the crankset off the bike to do the changeover, you might want to consider loosening the bolts (Breaking them loose) while the cranket is still installed on the bike, as this configuration gives you much more stability and leverage. Same with final tightening after you're done.
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Old 03-27-14, 07:54 AM
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One specific with the FC-4603 crank is that the 30T granny chainring is bolted to the middle 39T chainring, not to a separate bolt circle. So, to remove the middle chainring without pulling the crank, the granny ring must be unbolted from it first.
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Old 03-29-14, 03:58 PM
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great guys. thanks. components are in work so must see can I get them tomorrow and give this a go.

...and no that wasn't a threat (unless you are sick of me already ..... in which case I guess it was!)
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Old 03-29-14, 07:31 PM
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the 3rd one is the buggar .. inside of a double would come off , arm in place..
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Old 03-29-14, 07:37 PM
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Originally Posted by ClarkinHawaii
The trick you can't see is that the bolts attaching the rings to the spider are super tight. Whether or not you take the crankset off the bike to do the changeover, you might want to consider loosening the bolts (Breaking them loose) while the cranket is still installed on the bike, as this configuration gives you much more stability and leverage. Same with final tightening after you're done.
Also, leave the chain on the big ring while you break the chainring bolts loose. That way, if your hand slips, you'll be less likely to stab yourself.
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