dura ace cranks - how freely should they rotate?

jonathan2
jonathan2 Posts: 78
edited April 2012 in Workshop
Hi, I am currently building up a TT bike (my first build) - it is a mix of new and second hand and new equipment. I have just installed a second hand dura ace crankset / chainset. I have used a torque wrench etc.. However, when I come to spin them (without the chain fitted) I am a little surprised by the levels of 'friction'. They rotate smoothly and are what I believe to be in good condition, there is no 'grity-ness' but they do not spin 'continuously' like a wheel does when you give that a 'spin'. I can give a crank a firm flick / push and it only rotates about 3/4 of a complete rotation. is this normal? -

Comments

  • centimani
    centimani Posts: 467
    Take the chain off, you'll be amazed how freely it will spin.
    If it doesnt then, there may be something too tight.

    Edited to say...disregard, shoulda read the post properly :(:D
  • jonathan2
    jonathan2 Posts: 78
    Hi, thanks for the reply and for seeing that; indeed, the chain is not fitted. By your reply, I guess you think something is wrong, however, I cant think what? - the only thing I can think of is that I tightened the left hand 'cap' too tightly before tightening the bolts. I shall 'experiment' now. If this does not work, I guess there might be a problem with the bottom bracket bearings?
  • turnerjohn
    turnerjohn Posts: 1,069
    guessing the BB is DuraAce ? FSA and Shimano are very slightly different. You haven't put any spacers in have you ? If the BB torqued in good and tight ? were the BB threads "chassed"....I'm guessing if its a DuraAce BB its not fitted in the frame correctly.
  • trekvet
    trekvet Posts: 223
    When you fit any chainset, well years ago, you would nip it up all the time feeling the slack when pushed to and fro towards the chain stay. When all free play was just gone, a tiny fraction more and that was it. Spin the cranks and you have to grab them to stop before they bash your eye out or your shin. Any friction would be down to the grease. Ah, those were the days (abt. 1960).
    The Wife complained for months about the empty pot of bike oil on the hall stand; so I replaced it with a full one.
  • jonathan2
    jonathan2 Posts: 78
    Cheers all. I have taken all off, checked, double checked and very carefully put it back together again. It is correctly fitted. However, when just turning the 'bearings' while just holding the cup/s, they feel smooth but stiff. I believe it to be dura ace bb and I have done a little 'research' on the web and it seems that this is 'common' for shimano and I am not as worried. I think I will give it a try and see how it feels when riding.
  • unixnerd
    unixnerd Posts: 2,864
    I have Dura-Ace cranks I bought used with the bearing, but whilst the bearing is Shimano I'm not convinced it's Dura-Ace. All fits fine and is smooth but it does show a little bit of friction when turned. Don't forget that whatever grease is in it will normally be running at a slightly higher temperature after a mile or two pedalling, you're looking at it cold. If it were free flowing now it might be too thin once on the road. Bearing in mind the amount of power being put through your cranks I'd not be surprised if that grease heated up 20C in use.

    My tourer's Truvativ cranks are the same.
    http://www.strathspey.co.uk - Quality Binoculars at a Sensible Price.
    Specialized Roubaix SL3 Expert 2012, Cannondale CAAD5,
    Marin Mount Vision (1997), Edinburgh Country tourer, 3 cats!
  • centimani
    centimani Posts: 467
    TBF, new bearings are 'tight', mostly due to fresh grease being packed in there, the grease causes a lot of friction.
    As an example...FSA BB4000 overhaul i did a couple years ago.
    Standard bearings, no chain, spin the cranks and they spin just just a couple revolutions.
    Then I fitted some low friction seal bearings, spin the cranks and they spin..and spin..and spin. Tremendous difference.

    Again, to highlight the friction effect grease has...once low friction bearings were fitted, i decided i'd slop a layer of grease in the outer shell, between the bearings and the outer dust seal, to prevent water ingress to the cartridge bearings.. it instantly slowed it right down again.
  • fortyone
    fortyone Posts: 166
    A year ago I fitted a Dura Ace 7700 Octalink bottom bracket and set it up just right. However, on 2 occasions it gradually became much tighter without any adjustment from me. The chainset didn't spin very freely. Those bottom brackets are adjusted like the old style ones. I got rid of it and replaced it with an Ultegra one, which doesn't need adjusting, and those are different, with sealed bearings installed. The 105 bottom brackets are the same as Ultegra.
  • bus_ter
    bus_ter Posts: 337
    I think this is normal. My older bikes with Sora/2300 and other low end cranksets spin very freely. I recently bought an Ultegra 6700 full groupset and found the crankset to be much stiffer in comparision. I believe it's because of extra seals and thick grease that cause a slight amount of friction. However this extra friction is negligable in use. I can still spin my crank with my little finger and hardly any pressure. You're talking the tiniest fraction of a watt to overcome the friction. On the up side you have a much better sealed unit that after thousands of miles will be spinning just as smooth when the cheaper stuff gets all gritted up and dirty.

Categories