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Chain too tight after doing up axle nut?

Discussion in 'Maintenance and Servicing' at netrider.net.au started by Speed Dealer, May 30, 2014.

  1. Whenever I adjust my chain, I find the perfect amount of slack, but then after tightening up the the axle nut, the chain is way too tight. This means I have to undo it again and adjust again. When doing up the axle nut, I make sure to push the tyre forward hard against the axle adjuster bolts.

    Any reason for this?
  2. I've heard of this, but never noticed it until my present bike. It definitely occurs , though I'm quite certain not all bikes are so afflicted. I'm sure I would have noticed it. Here is my pet theory - it could be wrong.

    Wide swing arm mounts make the swing arms nearly, if not actually parallel. Squeeze them together and if anything, the distance centre to centre (axle to swing arm) would reduce. If the mount of the swing arm mount is narrow and the arms angle outwards, then squeezing the swing arm would have the effect of lengthening it slightly. My old bikes all had a tessellated nut and hole in the axle, through which one would put a cotter pin to secure it. There was no need to do the axle nut up hard. The pin would hold it. On my present bike - 1250 Suzuki Bandit, there is no such arrangement. The nut is held on by the friction of the threads, so I'd guess I probably do it up a bit tighter, squeezing the swing arms together a little. The swing arm mounts are narrower than the distance between the swing arms at the axle end.

    If you doubt this would have an effect, just stand on the floor with your legs parallel, then move them apart a little. Do you get taller or shorter as you spread your legs?

    With a chain, very small variations in axle position are apparent in chain tension changes.
  3. It happens. Eventually you develop a feel for how much slack to allow before leaning on the breaker bar so as to leave the perfect amount once everything's tight.
  4. What you need to do is sit a bit of rag over the bottom of the chain, spin the wheel so the rag gets between the chain and sprocket at the rear (pulling the chain tight), then tighten the axle with the rag there, roll the wheel again and the tension should be spot on
  5. other trick is to position the bar so you push down rather than towards the back.
  6. Generally still gets tighter though, the rag method is the best bet
  7. I have noticed that some axle's have a taper between the shaft and the threads. The shaft might be 30mm, but then taper down to say 26mm threads. If you undo the nut too much then the axle shaft might slip out of the chain adjuster, so that the threads are sitting inside the adjuster instead of the shaft. Now it might not make much of a difference if the nut is on the disc side, but if the nut is on the sprocket side then it could make a couple of mm difference when the axle is tightened, causing your problem.
  8. I always put a small screwdiver (the one from your bikes tool kit will do) between the rear sprocket and chain, the rotate the rear wheel so the screwdriver starts to go partway around the sprocket. This forces your rear wheel forward, while you tighten the axle nut. (Of course, then remove the screwdriver :)).

    Another thing to consider, is it is better to have your chain slightly loose, rather than tight. Because a tight chain puts undue force on your countershaft(C/S) sprocket, which can cause internal problems or C/S seal to pop-out. And more chance off snapping a chain. Most chains tighten further as you ride over bumps. Ideally, tighten the chain to the recommended manual spec, but if in doubt, go on the loose side.
  9. That's the rag method but instead using a screwdriver, a rag is a lot healthier for the chain/sprockets....

    The 2nd half of the post is worthwhile though, so many people don't get it that too much slack is better than not enough
  10. I think if you can fit a screwdriver between the chain and sprocket and rotate it, the chain at least is stuffed.
  11. Yeah, and even trying too isnt really a good idea anyway, hence the rag method being the best
  12. A thin screwdriver between the chain and rear sprocket, is very common at most MX meets, I have been doing this for years, with all my bikes.
    As the screwdriver, will only go part way around the sprocket, which is plenty to apply forward pressure on the wheel when tightening the rear axle. ( I am not saying to apply excess force to make the screwdriver rotate right to the rear)
    Normally, the screwdriver will not rotate right to the rear of the sprocket, unless the chain is extremely loose. Regarding damaging the chain/sprocket... I have never had a problem, and still get good life from both. If this was to damage the chain/sprocket, I suggest buying better quality kit.
    Whether you use a rag, stick or screwdriver.... this is a better method than trying to hold you foot against the rearwheel when attempting to tighten the axle nut.
    Just ensure you check the chain tension when the rider is onboard.
    • Agree Agree x 1