RADBMX.CO.UK
Technical & Reference Section => Tech and Restoration => Topic started by: OrgasmDonor on August 28, 2007, 11:45 AM
-
every build i build the chain has tight n slack points when the chainring is turned
the chainrings are not bent, the c/ring bolts are tight and aligned, the chain ring is as lined up to the freewheel as possible but when built i take it for a thrash round the block and the chain goes tight n slack, i always use izumis,
whats happinin dudes? its doin me fookin head in
oh yeah, i aint a fat knacker either 11 1/2 stone, but could the initial test ride cause this?
wadya reckon?
daz :)
-
cos ure fat and have lead feet lol
mine stretch too mate
and im not very slim
-
the "tight n slack" on chains is usually cos the chainring isnt perfectly centered on the BB spindle, or cos of the "freewheel float". There is always a gap in the freewheels 'open / looseball' bearings and the gap moves round with the freewheel (I think cassette hubs have less freewheel float). Its not usually to do with the chain its self.
Im no help as to how to stop it tho, sorry.
-
the top hat washer holding the c/ring in place was not a perfectly tight fit, would say about 1/2 mm out, would that be enough to cause a huge difference in tension d'ya reckon?
-
What cranks chainwheel and freewheel are you using Daz?
-
the top hat washer holding the c/ring in place was not a perfectly tight fit, would say about 1/2 mm out, would that be enough to cause a huge difference in tension d'ya reckon?
Quite a small offset on the chainring could cause quite a big difference in the tension. An offset of say, 0.5 mm is added to one side and taken away from the other so it could be 1mm out. Hold a spanner or screw driver still against the chainstay of the frame near the chainring teeth, and then spin the chainring (look out for the crank arms!). This will show you how much it is moving by. You can also see the freewheel float if you hold the cranks still and spin the wheel forwards. You will see the freewheel teeth moving up and down as the wheel spins inside it.
-
could be a bent rear axle. had to replace mine not long ago to cure the same problem! frreewheel/casette will bob as its not spinning true! hence the tight spots in the chain
-
What cranks chainwheel and freewheel are you using Daz?
gt profiles, mirage power disc, mcs chainring
the hubs are brand spankers and almost definately not bent
will check freewheel float n stuff later, and will report back if i find anything,
thanks for now dudes :daumenhoch:
-
I think if you tried a one piece chainwheel (profile etc.) with a snug top hat washer the problem will go away, in my experience ols school spiders aren't great with more modern cranks. That's just my experience however, i'm often wrong!
-
I get the same problem on my race bike, it gets pretty critical because the chain gets so slack. I replaced the freewheel but no change, I think Alex nailed the point with the slight offset on the chainring causing a magnified effect on the chain :(
I just cant seem to align them perfectly for love nor money :rant:
-
chains do give, and like laz said, a two pice spider, no matter what make or quality, is never going to be coc'k on, and as alex said, freewheels arent built to be micrometer perfect, three variables coming together is going to cause tight and loose spots, no matter how good your builds are.
cest la vie
Dave
-
chains do give, and like laz said, a two pice spider, no matter what make or quality, is never going to be coc'k on, and as alex said, freewheels arent built to be micrometer perfect, three variables coming together is going to cause tight and loose spots, no matter how good your builds are.
cest la vie
Dave
hey, my builds are shite but i like em except this one, this build is horrendous, i had an idea in my head used all the best parts and it should have been cool, fook me its horrible, i'll post picks later, i blame generallee for sending me oddy1000s with GOLD nipples and not chrome :LolLolLolLol: