Why do I always have to change both the cassette and chain?

danielsbrewer
danielsbrewer Posts: 123
edited August 2011 in The workshop
Every time I change the chain on my bike, the gears start to slip, in certain gears (the ones I use most often), and I have to replace the cassette as well as the chain. I change the chain when it has a stretch of 0.75 according to a chain stretch measuring tool I've got (checking most weeks). From what I have read here, if you change it at
0.75 then you shouldn't have to change the cassette every time, but not in my case. Also from my eye the cassette doesn't look worn either. I thought it might be the cheapo components that I was using on my last bike but its just happened on my new one too (tiagra coimponents). This is really doing my head in, and I could do with your
assistance.

When do you change your chain? I am wondering whether I should bother changing it at 0.75 if I am going to have to change the cassette any way and wait until the cassette starts playing up, but then that might mean having to change the chain rings too which could be pricey.

Any other ideas why this might happen? The bike started off with a shimano chain but the replacement is a KMC X93 one, but I wouldn't have thought that would have been a problem? Riding style? Not cleaning the chain often enough?

Comments

  • andrewjoseph
    andrewjoseph Posts: 2,165
    I've had this a few times, but only if I've let the chain get too worn.

    perhaps your chain checker is worn? a bit fiddly but a ruler and measuring 12 links should be a foot, chain is worn when 1/16 over (I think, can't remember the details of hand).
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • bails87
    bails87 Posts: 12,998
    I had exactly the same problem. I just put it down to using certain cogs much more than others.

    Maybe buy 2 or 3 chains and rotate them every few weeks to spread the wear?
    MTB/CX

    "As I said last time, it won't happen again."
  • nicklouse
    nicklouse Posts: 50,675
    yep 1/16"

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

    BUT if you are only using a couple of cogs on the rear they will be wearing more than normal.

    maybe look at your gearing and possibly change the ratios so you more of the cassette.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • danielsbrewer
    danielsbrewer Posts: 123
    Yes I tend to use about 2-3 cogs on the back during my commute using the largest ring at the front. It is a 12-25 tiagra cassette and I think I use cogs 2-4, where 1 in the smallest. Maybe I just need to be more disciplined in changing down when I stop at a junction.

    Good idea about rotating the chains, I can see how that might work and would also help me to remember to clean the chain every week.
  • wgwarburton
    wgwarburton Posts: 1,863
    Hi,
    You could consider simplifying your gearing. Modern drivetrains are set up to give you lots of closely spaced gears but the trade-off is that they use thin sprockets and narrow chains. If you're using the bike recreationally and also using a wide range of gears that's not an issue (the wear gets spread between sprockets) but if you are constantly using a small number of sprockets the wear will get concentrated.

    Maybe you'd be better served by a simpler setup where you have fewer but more robust gears- the extreme being a single speed or fixie, with hub gears or lower sprocket count derailleur setups offering an "in-between" solution.

    One other possibility is to get bigger chainrings- the reason chainrings outlast sprockets is that the load & wear is spread across more teeth. The same principle applies to the rear sprockets, so if you have a bigger front chainring you'll use a bigger rear sprocket to get the same ratio and hence it should last longer.
    You don't say what your chainring sizes are but say you're using a 44T front against your 14T rear on a 26" wheel, you have roughly an 81" gear. Move to a 52T front and you''ll get about the same gear ratio with a 17T rear sprocket (79")... but with 20% (3!) more teeth at the rear to take the wear.
    That's probably not a practical example, as it may not be trivial to swap in a big 'ring like that to your setup, but you can see the principle that's at work.

    Bottom line- have a think about how you can best meet your gearing needs with better durability, bearing in mind that enclosed drivetrains, big sprockets and wide chains generally offer better durability.
    If it's going to be too difficult or expensive to change then adjust your shifting habits, if you can, and accept that, ultimately, these are consumable parts that need to be budgeted for....

    Hope that's helpful.

    Cheers,
    W.
  • Blue Meanie
    Blue Meanie Posts: 495
    Counter Intuitive, but you shouldn't over clean / lube your chain.

    I wipe mine down with an oily rag and lube, then wipe again to remove excess. Only gets a proper degrease every month or so.

    Current chain is about 3k miles old, cassette about 1k.
    FCN16 - 1970 BSA Wayfarer

    FCN4 - Fixie Inc
  • CiB
    CiB Posts: 6,098
    I buy two chains and rotate them every 1500 miles or so; got about 7500 miles out of the original rings + cassette so far. You could try using more gears too instead of sticking in the same few cogs, if that fits with your fitness, ability & environment.
  • rolf_f
    rolf_f Posts: 16,015
    Blue Meanie wrote:
    Counter Intuitive, but you shouldn't over clean / lube your chain.

    I wipe mine down with an oily rag and lube, then wipe again to remove excess. Only gets a proper degrease every month or so.

    Current chain is about 3k miles old, cassette about 1k.

    I clean my chain every time it gets mucky - avoids the dirt effectively sandpapering the drive train. Causes no problems and keeps it running much more smoothly. You can't over clean your chain :wink:*








    * IMO of course!
    Faster than a tent.......

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