Bit of techinical advice please

Discussion in 'Beginners' started by funnymummy, 7 Jun 2008.

  1. funnymummy

    funnymummy A Dizzy M.A.B.I.L

    While out with a mate last week my chain came off, something thats not ever happened before & as I have a full chain guard we had a bit off a job getting it back on.
    My friend noted how 'wobbly' my pedal/arms where, to be honest thye been like for ages & although I had noticed I just assumed some movement was normal, he reckoned my bearings had gone & the next day he replaced them for me, whih seemed to do the trick, but after a couple of day they started to wobbly again.
    I've been out today & relised we wouldn't get home until getting dark & i'd not put the lights on the trailer so i popped into a nearby bike shop & bought some cheapies.
    I mentioned the wobble & bearings, the chap looked at my bike & seemed puzzled...He said I have a sealed unit & it shouldn't be possible to change just the bearings, he advised I should get a whole new bottom bracket fitted & could do it for £30 ish or more for a better quality one.
    I looked on Ebay & can buy the same as I alreday have (Prowheel 28/38/48) for under £15 inc PP
    Although my technical knowledge is quite limited I am pretty good at picking things up & fixing stuff as long - as I have a rough guide/manual to follow LOL.
    Any advice on whats best etc would be muchly appreciated - cheers guys xx
  2. longers

    longers Veteran

    I'm not so technical myself so will only say what I think I know to be true.

    The Prowheel item you found on e-bay is the chainset. This is the bit which carries the chain and the pedals. It'll have the three chainring on it and the arms (cranks) where the pedals fit.

    The bottom bracket is the hidden bit in the middle of the bike that you attach this to. It sits at the bottom of where the tubes meet at the bottom of the bike and will have a small spline sticking out of each side. It is on these splines that your chainset attaches.

    Is this making sense? ;)

    If you have wobbly cranks then it could be the fitting of these onto the splines that is the problem or it could be a problem with the bottom bracket itself.

    if the former then they might need tightening with an allen key in the centre and if it's the latter then a new bottom bracket is possibly required.

    I think they are not really designed to be serviced nowadays but may well be wrong on this.

    I don;t know the price of them and you will have to weigh up the cost of buying the tool to do it yourself against how infrequently you could be required to do it.

    If someone wants to correct any of this please fell free.
  3. Fab Foodie

    Fab Foodie hanging-on in quiet desperation ...

    Longers is pretty much correct. You need to determine whether the pedal crank-arms (or chainset) are loose on the bottom bracket splines OR whether the bottom bracket bearings are loose.

    If the crank-arms are loose on the bottom-bracket axle, then there will be some rotational play in the crank arms i.e, If you hold the left one rigid there may be some rotation in the Right one (or keep the right rigid and check for rotational play in the left). It's unlikely that both crank arms are loose, it will be one or the other. It may tighten, but it may not if there is too much damage.

    Alternatively if the bottom Bracket axle that connects the 2 crank arms to the bike is worn you should be able to hold both crank arms and detect up and down play between the pedals and the bike (and a knocking/graunching sound) BUT only the axle shaft should be seen to move. If the whole bottom bracket assembly is loose, then you will see the axle shaft and it's housing move relative to the bike frame.

    Older bikes will have a simple cup & cone bearing system which is not a sealed unit and these can develop play over a lot of years usage.

    I hope this makes some sense. Frankly I'd tootle along to the nearest decent bikes shop and ask their opinion. Any remedial work will require specialist tools anyway and a mistake will be costly.

    If it is a new Bottom Bracket required then £30 to supply and fit seems OK.

    What bike btw?

    Oh, and welcome to Cycle-chat!
  4. HJ

    HJ Cycling in Scotland

    Auld Reekie
    You are probably best off getting a new bottom bracket, my LBS would do it for £22.95 Fitted, so £30 is a wee bit expensive but not extortionate. You could probably do it your self, but it does require a special tool to do it. Instructions given here and here. Hope that helps.
  5. bonj2

    bonj2 Guest

    whack a hollowtech all in one job in and have done with it.`
  6. OP

    funnymummy A Dizzy M.A.B.I.L

    Cheers for the answers, i'm not averse to gettingg me hands dirty but as you all seem to mention i'll be needing a special tool, that i obiuolsy wont have, I think I will let a pro deal with it LOL!
    The shop I called in today was miles from home so i'll toodle down my LBS on Mon & see what they say - The guys there are really great.
    Fab Foodie - My bike (her name is Gilly!) is a Giant Expression DX.
  7. longers

    longers Veteran

    The tool is probably something like this.

    Simple enough in theory and not too dear but I speak from a little experience when I say that it can be a little bit awkward to get your BB out. You may want to let your LBS take the strain.
  8. longers

    longers Veteran

    Of course you may have "the knack". I don't ;).
  9. Steve Austin

    Steve Austin The Marmalade Kid

    To fit a new BB, you 'll need a crank puller and a BB tool, so you'll possibly spend £20ish on tools, and another tenner+ on the BB, so £30 seems ok.

    I always suggest folk try to fix their bikes themselves but when its a one-off job like this, its really worth using a bike shop. Your bike has got a VP cartridge BB, which was a cheap unit to begin with so any replacement should last a good while.

    Happy riding
  10. RedBike

    RedBike New Member

    Beside the road
    Bottom brackets vary in price depending on which model/make you go for; but you're normally talking about £15 ish. Therefore £30 to fit it isn't bad at all.

    (Espeshailly as they have a habbit of 'welding' themselves into frames)
  11. OP

    funnymummy A Dizzy M.A.B.I.L

    Cheers for all your help on this.
    I called into my LBS this morn & they can sort me out for £25 fixed n' fitted.
    Only downside I will have to wait a few days - the shop really isn't a bike shop anymore, it used to be a bike shop that also sold the odd electric bike or those bloody things that grannys zoom around on, but it got bought out & now only does the powered thingies.
    It's still the same staff & they can do all the work, they just don't actualy have the part I need in stock so he ordered one in for me.
    Fingers crossed it'll be ready for the weekend - my kids are off to their dads for the day on Sunday & I can feel the urge to have a real blast over the downs coming on!!!
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