Lowering links and chain tension

[CFB 4,601]

I know I’ve asked this question before, but can’t find the answer by searching.

After fitting lowering links, should the chain adjustment, slack, be adjusted to be the same as with OE links?

After much head scratching, I just can’t figure all this sprocket/swing arm pivot point stuff out.

[outrunner 4,457]

I should imagine it would be the same tension, set it then get the rider to sit on it and see what the slack feels like then, I could be wrong of course, it would not be the first time.

 

 

Andy.

[trisaki 2,029]

Dont forget to adjust the chain on the tightest part of the chain  , turn it through a few revolutions to find 

[embee 7,288]

Well no, by fitting the lowering links you have effectively moved the wheel part way through its travel already towards the straight line mid-travel point.

The pivot points in alignment thing is pretty straightforward. The chain has the least slack when all the points (gearbox shaft/swingarm pivot/wheel spindle) are in line, as the wheel moves away from the straight line position (either up or down) the distance between wheel spindle and gearbox shaft gets slightly less, so looser chain, because the swingarm pivot isn't at the gearbox shaft position. It would normally be designed such that the straight line is more or less at mid travel of the suspension so that the chain slack variation is minimised.

I've looked for a diagram and this is the nearest I can find. You see the arc with centre S moves the wheel towards the gearbox at the limits compared to the arc centred on G.

 

Ideally you would have a centrestand, put the bike on it, undo the suspension links and lift the wheel until you get the straight line and least slack in the chain. Adjust it at that point to give just a slight amount of slack in the chain (it must not go tight). Then drop the wheel down and fit the links, and see what the slack is at the new extended point and use this as your setting in future.

[CFB 4,601]

Thank you Murray, that makes perfect sense.

[Rick 236]

Very good answer Murray, I always adjust my chain to the widest recommended  measurement and expect that using the standard settings would probably suffice as a little slack is better than tight. 

[embee 7,288]

14 hours ago, Grumpy Meltdown said:

Thank you Murray, that makes perfect sense.

There's always a first time, I better not push my luck. 

[Trumpet 215]

AFAIK Only Bimota recognised this and developed a chassis with the gearbox sprocket in line with the swinging arm pivot, meaning chain tension stays constant throughout suspension movement. If they are offset slightly, the chain either tightens up or slackens as the suspension compresses. Most are not aligned so chain tension varies.

[Urbanfireblade 17]

Hey.

Just for anyone who comes across this post. Best thing is to adjust your chain to the tightest allowed(30mm) before lowering your bike.

Then, after it's been lowered, measure the tightest point again, and note it down. Now you know what is the minimum amount of free play you should allow with your lowered links fitted.

 

For example

 

I've just lowered my 2016 NC750X -20mm at the rear.

My chain tension has tightened 10mm. It was set at 30mm before, now with my lowering links chain tension is now at 20mm.

So I will keep mine between 20-30mm free play which will be equal to the recommended 30-40mm free play at standard ride height.

 

If anyone is interested, the standard rear suspension drop links measure exactly 133.5mm centre to centre.

 

I made my own droplinks +8.25mm longer, so 141.75mm centre to centre, this lowered the bike approx 20mm. 

I lowered the front forks 10mm, bike is still fine on the sidestand......as long as you don't have the rear shock preload on minimum as the rear sits low and the bike is too upright, 2 clicks from minimum the sidestand standard length is fine.

Edited July 13, 2020 by Urbanfireblade
Added info