replace middle chainring on Ultegra 6603 triple

ben-----
ben----- Posts: 573
edited August 2016 in Workshop
I've just come to replace the middle 39t chainring on my Shimano Ultegra 6603 triple (10 speed). Having undone the chainring bolts it appears I'm not going to be able to get the middle chain ring over the cranks 5 prongs, then over the pedal. So it appears I need to undo the whole cranks from the bottom bracket? Yikes. There's something on these cranks which says 'don't undo'. What tool do I need for this? How to do? Damn it. Was planning to go out for long ride today but looks like this is going to stop me :(

Comments

  • ben-----
    ben----- Posts: 573
    Is this the answer?: http://www.madegood.org/bikes/repair/re ... -crankset/

    Undo one of the individual cranks, the left one, not the bottom bracket. That looks like it might be it.
  • ben-----
    ben----- Posts: 573
    I'm going to try that.
  • keef66
    keef66 Posts: 13,123
    That's exactly what you do.
    Undo pinch bolts from NDS crank, retrieve them with their washers, and the little plastic safety tab that sits in the slot.
    Remove the plastic preload cap from the end of the spindle
    Drop the chain off the inner ring and sit it on the BB shell (or remove it completely if you're taking it off for cleaning or replacing it)
    Push the spindle out of the BB towards the DS. Can require a bit of a whack; soft faced mallet or use a block of wood to protect the end of the spindle if using a metal hammer.
    Note the location of the plastic spacers on the triple chainset. If it's the same as my 105 there'll be a wide one with a bevelled edge on the NDS and a plain one on the DS that will in all probability remain stuck on the spindle behind the spider.

    Once the chainset is out it can be easier to undo the chainring bolts if the whole thing is clamped in a workmate or similar.

    Make sure you note which way the chainring faces so you can install the new one the same way round. Grease the bolts on reassembly.

    Reinstall the crank by reversing the above. Give the chainset a good whack to ensure it is properly seated in the BB.
    Stick the NDS spacer back on.
    Grease the splines and slide the NDS crank on to the spindle
    Tighten the plastic preload cap only finger tight. It's just to preload the bearings, it doesn't keep anything on.
    Insert the pinch bolts, washers and safety tab as before, ensuring the pin goes into the hole in the spindle. Tighten the bolts alternately, if possible with a torque wrench.
    (I don't have a suitable torque wrench so I rely on allen keys and guesswork. Pretty tight I'd say. Never had a crank drop off anyway)
    Chain back on.
  • ben-----
    ben----- Posts: 573
    Thanks very much for this. Excellent description. I went off and managed to do it before seeing it though. I basically managed OK. I think I may not have the middle ring in the right position, having seen this SI_1G30E_001/SI_1G30E_001_En_v1_m56577569830616000.pdf. But basically I manage OK in the end. I'd just never dealt with that bit of a bike before (cranks, bottom bracket area), at least not undoing/taking them off.
    Thanks, Ben.

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