When for example it says 4cm of free play, which of the below examples of measuring is correct? In image 1 the chain’s movement is through a 4cm ‘window,’ and in image 2 the chain’s upper edge is free to move upwards by 4cm. I hope you get what I mean?
The bottom image, but reversed, if you get my meaning. You should measure mid way along the bottom run of the chain at its tightest point, ideally with you sat on the bike so the suspension is loaded as it would be when riding.
StuartT595 Yes no stupid questions here in the asylum. And answered quickly thanks to Yorkshireman. Joe.
If you are talking about the T120 I'm afraid Yorkshireman is wrong ,just checked my handbook which says to check the chain with no weight on the bike (section 1 page 100).Assume that means without anyone sitting on it. If I've made a total prat of myself and it's different model, then, many apologies to Yorkshireman.
Chain slack specs are usually with the bike upright but unloaded, ie, no one sat on it. The spec allows for the chain tightening during riding and will (should) give a min and max chain slack figure. Don't know the measurements for your bike but an example would be between 20 and 30mm so 15mm will be too tight and 35mm too slack.
What I do on each new bike and it only needs doing once.. Support the bike upright and remove the shocks. Tie up the swinging arm or put spacers below it until the three axis are in perfect alignment. Tighten the chain adjusters slowly whilst rotating the wheel to find the tightest spot. Once found back off the adjusters until you get 5mm or running slack measured at the midpoint. Refit the shocks and leave bike on side or centre stand without rotating the wheel and measure the slack. I prefer to pull down as hard as I can and push up as hard as I can to gat an easily repeatable minimum measurement. Write this figure down! This may take a couple of hours to get your minimum figure but you’ll never run an overtightened chain again.
I would have thought image 1 would be correct, being 4cm total travel from being pushed up to being pushed down This is how I have been doing it for 25 years since I was shown at what was my local bike shop I have not had any issues with the chain being too tight doing it this way, as always enough slack for when the rear suspension is under load and the chain would be at its tightest. Have I been adjusting it too tight for 25+ years! If it is too slack I find gear changing gets clunky and the chain snaps tight when put under load (2010 Speed Triple btw)
Neither image is quite right. Image 1 is closest, but is indicating the distance between highest position of the top of the link and lowest position of the bottom of the link. What should be measured is the range of movement of a single feature - either the top edge of the link or the bottom edge.
I use a small piece of stiff white card, one for each bike, with the correct min-max marks so no need for a ruler. Checking takes seconds. No point in marking the chain for it's tightest spot either as it will change as the chain wears.