Gear problem or frame flexing.......

robz400
robz400 Posts: 160
edited July 2010 in Road beginners
I have a Carrera Virtuoso that I've had for a couple of years now. I set the gears up when I bought it and since then in 4ish thousand miles its only ever needed minor adjustments.

They still work perfectly but if I start really pushing hard, eg out of the saddle climbing or sprinting to keep up with traffic it will jump from gear to gear....

Is this a setup problem or is this just the frame flexing and therefore I am clearly far too strong and powerful and the ultimate excuse to buy a new bike?????

Comments

  • schweiz
    schweiz Posts: 1,644
    4000 miles on the same chain and casette?

    I'd hazard a guess and say they were worn and needed replacing
  • robz400
    robz400 Posts: 160
    Ahh, didn't think of that, it is still on the original cassette and chian, how often should they be replaced then?
  • Pross
    Pross Posts: 42,437
    It depends but you can get a tool that measures how much your chain has stretched and when it needs to be replaced. The cassette (and front chain rings) should last longer but if you continue to ride with a stretched chain it can make those wear out more quickly. Might be worth changing the gear cables too.
  • schweiz
    schweiz Posts: 1,644
    when they're worn!

    It's not time/distance based. wear depends on many things including lubrication (chain lube, chip fat, WD-40), riding style (spinning/mashing), gear choices (not running crossed gears), cleaning (personally, I don't use degreaser, I just wipe the chain down with a rag)and where you ride (off road/on road) and when you ride (winter/summer)

    typically a chain is considered worn when it has lengthened by between 0.7% and 1%. If you replace a chain at this point, in my experience the cassette will be okay and last for 4-5 chains or even more.

    http://www.sheldonbrown.com/chains.html

    If your chain is badly worn, then change the cassette too.

    Then there's two schools of thought on what to do next. You can ride the new chain and cassette to the condition they are in now and replace again in 4000 miles remembering that at the same time the chain rings are wearing out faster and will need replacing sooner.

    Or replace your chain more often in future, making your cassette and chain rings last longer. As chains are generally the cheapest part of the drive train, then that's usually seen as the most cost effective over time.
  • robz400
    robz400 Posts: 160
    Thanks all.

    New chain it is. I realise they come in different widths for 8,9 or 10 speed but are the lenghths standard, so any 8 speed chain will fit.

    Oh and do I need a special tool to get the old one off or will my trusty angle grinder be sufficient?
  • alfablue
    alfablue Posts: 8,497
    Chains come with more links than you need so they will require cutting to the right length. See the instructions on chain length here: http://sheldonbrown.com/derailer-adjustment.html#chain

    You will need a chain tool like this

    http://www.chainreactioncycles.com/Mode ... delID=1625

    If you fit the chain just as it comes it will be too long and the rear mech will lie so the chain runs over itself in some gears, and it will flap about.

    KMC or SRAM chains are good because they have a quick link for removing them and refitting them without tools (useful for cleaning), though you still need the chain tool to cut it down to size.
  • PeeDee
    PeeDee Posts: 88
    You need a special tool to set the chain length. They are available at any bike shop for a couple of quid upwards. Basically it pushes the pin out from one of the the links in the chain, the chain then falls into two pieces.

    To join the chain you do the same in reverse. Better, is to buy a "quick link" which is a nifty little spare link that you can insert in the gap to allow you to take the chain off again in the future without any tools.

    If its your first go I would get a local bike shop to show you how its done (little private shop is best, not Halfords etc).

    Finally, 9 speed chains are thinner than 8 speed, 10 speed are thinner still. The rule is that you can use any chain that is not too thick, e.g. 9 speed chain will work on 8 speed gears, but not the other way round. Bear in mind a thinner chain will wear quicker, so try and get the right size if you can.

    If you need to change the cassette as well then you will need more special tools to do this.
  • owenlars
    owenlars Posts: 719
    I change chains every 1500 miles, that seems to generally coincide with the 0.75% wear mark on the chain wear gauge.

    New cassettes every 6000 miles or so so seems to be a fairly good rule of thumb as well, so my experience agrees with Schweiz.
  • robz400
    robz400 Posts: 160
    Thanks, very helpful :)

    Is there a single job on a bike that doesn't require a specail tool!!! I've been working on my motorbikes for years with nothing but a socket set and so far every job I've done on the bike requires new tools!

    Still good excuse for buying stuff :)

    Thanks again
  • PeeDee
    PeeDee Posts: 88
    Get one of these so that you can replace you chain before it gets too worn and damages the cassete and chainset...

    http://www.chainreactioncycles.com/Mode ... elID=42815

    In the long run it will pay for itself many times over.
  • PeeDee
    PeeDee Posts: 88
    You can make your own special tools. Much more fiun!

    Split the cain by clamping the chain sideways onto the top of a heavy vice with the jaws open by 3mm or so. Drive the pin though with a hammer and a thin parrallel sided punch.

    To make a cassette remover get an old socket and use your trusty grinder to make a series of notches in the top (like turrets on a castle tower) the right size to fit the lockring on the cassette.

    Make a chain wrench from 20cm of flat steel bar and a length of old chain. You need this to stop the cassette spinning round while you are trying to undo the lock ring.

    Go on, you know you want to :)

    Best to have a good supply of Germaline and stcking plasters handy too.
  • robz400
    robz400 Posts: 160
    The vice idea is genius, only problem is that I would have to buy a vice!

    So far i've changed wheels, bottom bracket and forks so have bought most things. I'm guessing this is the last tool i'll need until its time to replace the headset bearings!!

    I've heard thats a pricy one, so any clever ideas for making my own one of them from a washing bottle and empty toilet roles????
  • PeeDee
    PeeDee Posts: 88
    A length old plastic waste pipe makes a good tool for fitting a new crown race over the steerer (a wood chisel gets the old crown race off.). A length of threaded bar from B&Q, some nuts washers and a couple of large sockets makes a headset press for fitting the cups.. An old washing up bowl and boittle filled with parafin (re-filled from an oil fired central heating tank) is handy to have around for cleaning components.

    The best use I have found for a toilet roll is hanging beside the loo to put the paper on. I must admit that now I'm older and more affluent I tend to buy tools rather than make them (except for the trick with the toilet roll, which we still use regulalry). :)