Bottom Bracket Slipping

jaqian

The last week or so I've noticed a bit of slippage. I'll be stopped at the lights pedal raised, ready to go. As soon as I push down on the pedal, its slips about an half-inch/inch before the bike moves. Also happened this morning trying to cycle up a small hill (Broombridge in Cabra) and it kept slipping so much so I had to get off and walk. It never seems to be a problem once I'm cycling.

Any idea what could be causing this and what can I do to remedy it.

Cheers,
Rob

bcmf

any noises?
Doesnt sound like a BB. A BB should get very noisy. Did you try and spin the pedals/cranks off your bike.

IM0

its nothing to do with the BB, its your rear hub's freewheel is on its way out, heed it and replace before you get stranded somewhere :embarrasement:

jaqian

No, no noises. If its the freewheel, that makes sense as the threads are a bit fecked. Have new cassettte waiting for a new wheel, which I'm getting off Rothar this Friday. If its the freewheel then problem sorted

ednwireland

errr cassette and freehub body are seperate unless you have a old fashioned screw on cassette and freehub

freehub



cassette


if the prob is as you describe its probably the freehub

Single Malt

Could be an excessively worn chain cassette or chainrings.

jaqian

Mine isn't a freehub but rather a freewheel and I've been reliable informed that both it and the cassette are fecked. Hopefully the new wheel and cassette will sort the problem as funds are low and don't want further expense as in a new BB.

Will let yis know if the new gear sorts the problem

kona

jaqian wrote: »

Mine isn't a freehub but rather a freewheel and I've been reliable informed that both it and the cassette are fecked. Hopefully the new wheel and cassette will sort the problem as funds are low and don't want further expense as in a new BB.

Will let yis know if the new gear sorts the problem

Id get a second opinion .

doozerie

An issue with the bottom bracket alone couldn't cause the problem you are describing. The rotation of the cranks is limited by the chain, which in turn is limited by the freehub/freewheel - for the cranks to rotate while you are stationary (i.e. without rotating the rear wheel) either the chain is slipping on the front chainring (= need new chainring, and almost certainly new chain and cassette too), the chain is slipping on the cassette (= need new chain and new cassette), and/or the freehub/freewheel is slipping internally (= new freehub/freewheel). It could also be that your crank is slipping on the bottom bracket axle (= new crankset) but if this were the cause it should show up a lot more of the time and a loose fitting crank should be very noticeable anyway.

If it slips in all of the rings on your rear cassette/cogs, it is more likely to be the internals of the freehub/freewheel slipping. If it happens in some gears only (your most frequently used ones) it is more likely to be excessive wear on the rear cassette/cogs + chain. You might be able to narrow it down by standing beside the bike with both brakes applied and pushing hard on the right pedal - watch the cassette/cogs to see if they spin (while the rear wheel doesn't) if/when the slippage occurs - if they do, its the internals, if not it's external wear.

If you have a threaded freewheel rather than a freehub+cassette right now, then presumably it's an old rear wheel - most (all?) manufacturers moved to the freehub design many years ago now, which can make finding a new freewheel tricky these days. By the way, if you are getting a new wheel and cassette then you should also fit a new chain at the same time otherwise your worn chain will accelerate the wear on the new cassette.

Of course, your bottom bracket could also be worn to the point where it needs replacing too, but that issue wouldn't show up in the way you describe above.

kona

doozerie wrote: »

If you have a threaded freewheel rather than a freehub+cassette right now, then presumably it's an old rear wheel - most (all?) manufacturers moved to the freehub design many years ago now, which can make finding a new freewheel tricky these days.

Considering all BSO use freewheels, they are probably more abundant than bikes with cassettes and freehubs. There is certainly no issue in getting the part.
Anything under e300 is gunna have a freewheel and even some over e300.
Part is around e20 and the labour around e15.

doozerie

kona wrote:

Considering all BSO use freewheels, they are probably more abundant than bikes with cassettes and freehubs. There is certainly no issue in getting the part.

Fair point, I haven't worked on a BSO in a long time, and any recent ones I've seen have been at the 400euro range and above and had freehubs.

Last time I tried to source a 7-speed freewheel for an old wheel of mine, a few years back, I had real trouble finding one, but I limited myself to two or three brands and specific ranges within those brands. If I was less fussy maybe I'd have found one easily enough.

kona

doozerie wrote: »

Fair point, I haven't worked on a BSO in a long time, and any recent ones I've seen have been at the 400euro range and above and had freehubs.

Last time I tried to source a 7-speed freewheel for an old wheel of mine, a few years back, I had real trouble finding one, but I limited myself to two or three brands and specific ranges within those brands. If I was less fussy maybe I'd have found one easily enough.

What supplier did you use. Suntour still do em, you can get them through raleigh no problem.

doozerie

kona wrote:

What supplier did you use. Suntour still do em, you can get them through raleigh no problem.

Thanks. I tried a few local bike shops at the time, and one of them eventually managed to source one, by luck more than anything else according to what they said. Not long after that the hub axle snapped though and put an end to the best hub I've had - RIP. I can't complain though as it lasted about 15 years up to that point. Interestingly, I read somewhere since then that one of the motivations behind the design of the freehub design was to eliminate broken axles and that it had been very successful in that.

kona

doozerie wrote: »

Thanks. I tried a few local bike shops at the time, and one of them eventually managed to source one, by luck more than anything else according to what they said. Not long after that the hub axle snapped though and put an end to the best hub I've had - RIP. I can't complain though as it lasted about 15 years up to that point. Interestingly, I read somewhere since then that one of the motivations behind the design of the freehub design was to eliminate broken axles and that it had been very successful in that.

yea it spaces the bearings better so the load is spread more even over the axle

jaqian

the new wheel and cogs seem to have done the trick, no more slipping Btw I got me 7-speed cassette from ChainReactionCycles, its Shimano.

Thanks for all your help and suggestions.