terry26rims Posted April 19, 2010 Report Share Posted April 19, 2010 Replaced my 22t chain ring and bought a new chain but am still feeling a knock when i do revolutions on my cranks. Thought it might be the bottom bracket but when there is no chain it doesn't do it! When i lift the rear wheel off the floor and push the cranks round with my hand the chain seems to move up and down a couple of mm's making it look blurry, this isn't normal is it? What's causing it? Also the chain has come off in the past but not recently. Quote Link to comment Share on other sites More sharing options...
Canardweb Posted April 19, 2010 Report Share Posted April 19, 2010 Could it be your crank hitting your rear brake slave cylinder? Quote Link to comment Share on other sites More sharing options...
Ben John-Hynes Posted April 19, 2010 Report Share Posted April 19, 2010 It'll most likely be the chain/new sprocket bedding in/meshing together. Quote Link to comment Share on other sites More sharing options...
terry26rims Posted April 19, 2010 Author Report Share Posted April 19, 2010 nope that's not it. Quote Link to comment Share on other sites More sharing options...
Ben John-Hynes Posted April 19, 2010 Report Share Posted April 19, 2010 Could be a stiff link in the chain? Possibly the link you put back together when you fitted the chain. Quote Link to comment Share on other sites More sharing options...
terry26rims Posted April 19, 2010 Author Report Share Posted April 19, 2010 no it did it before thats why i bought the new bits to eliminate the chainring and chain from the problem. Quote Link to comment Share on other sites More sharing options...
Ben John-Hynes Posted April 19, 2010 Report Share Posted April 19, 2010 Hub/freewheel? Crank on magura slave? Pedal bearings? Bottom bracket? Quote Link to comment Share on other sites More sharing options...
dirt jumper jake Posted April 19, 2010 Report Share Posted April 19, 2010 no it did it before thats why i bought the new bits to eliminate the chainring and chain from the problem. Its the bottom bracket, i had the exact same problem with my jump bike. there bearing are probably shot but only make a sound under enough pressuer which explains why it knocks when you are pedalling but not when you just crank it with your hands. Quote Link to comment Share on other sites More sharing options...
terry26rims Posted April 19, 2010 Author Report Share Posted April 19, 2010 Hub/freewheel? Crank on magura slave? Pedal bearings? Bottom bracket? I know pedal bearings are not quite gone but are not any where close to perfect. Bottom bracket is my thoughts but what about the chain fluctuation? Maybe thats causing the chain to not land properly within the teeth i don.t know what to try any more. I don.t know too much about bottom bracket or have any tools to remove it or replace it. Get a shop to look at it time? Quote Link to comment Share on other sites More sharing options...
josh barker Posted April 19, 2010 Report Share Posted April 19, 2010 if you have vertical dropouts, it will more than likely be the tensioner Quote Link to comment Share on other sites More sharing options...
terry26rims Posted April 19, 2010 Author Report Share Posted April 19, 2010 Its the bottom bracket, i had the exact same problem with my jump bike. there bearing are probably shot but only make a sound under enough pressuer which explains why it knocks when you are pedalling but not when you just crank it with your hands. You've hit in the nail on the head i think can't do bottom brackets myself so that will be next on the list to change. Thank you everyone for your thoughts. Quote Link to comment Share on other sites More sharing options...
Muel Posted April 19, 2010 Report Share Posted April 19, 2010 It's can't be the BB, because you said it doesn't do it with the chain off? You just replaced the sprocket, so it's most likely chain suck because the chain is old. New chain will most likely sort it. Turn the pedals back and forward, when you here the clunk does the chain jump or vibrate? If so you've got chain suck, new chain time. Quote Link to comment Share on other sites More sharing options...
Mr Motivator Posted April 19, 2010 Report Share Posted April 19, 2010 BB and or cranks could just be loose. Take the chain off, jump on one side of the cranks and then the other; does it make a noise then? Also, chain too tight? Quote Link to comment Share on other sites More sharing options...
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