Measure rider sag without a mate

[Mike5100 2,061]

I have just worked out a way of doing the rear static and dynamic sag on my own.  All you need is a metre steel rule and an iphone (or a camera with a delay shutter)

And the results have come out spot on to the sag measurements done by the specialist firm near York.

 

First use the meter rule as a radius for the arc of the axle bolt.  So put the rounded end with the hole over the rough position of the swing arm pivot and hold your fingernail of the other hand at the centrepoint of the axlebolt.  Now swivel the meter rule upwards until it contacts an appropriate part of the bodywork.  Make some kind of mark there.

Now take the rounded end of the meter rule and lightly gaffa tape it so the hole in the end is over the mark you made on the bodywork.

Then you can rest the rule on the rounded part of the axlenut.  If you check the photo below you will see that rule forms a tangent with that circle and the point of contact does not move as the suspension is loaded.  You have to fiddle about with the balance of the bike to stop the rule sliding off the nut and this is more difficult to do when you are checking rider sag - ie sitting on the bike but I will come back to that.

Now find a suitable height box and stand your iphone on it to take a closeup pic of the axlenut and ruler.  If you have a centre stand you can do the first one without any shutter delay - and the static sag one but when you come to the rider sag you have 10 seconds to get on the bike, put the rule back on the axlenut and then get your feet off the ground and steady the bike before the shutter fires.

But it got my readings at 24mm static and 50mm rider sag.  The specialist got 25 and 55 but i put all my riding gear on at his place (probably an extra 9kilos)

The stiction effects on my bike were 1mm rear and 2mm front so I have discounted them but it would be more problematic to do the rider sag if you have a lot of stiction in your shock.

.... so pretty chuffed

Mike

[Derek_Mac 1,404]

Necessity is the mother of invention.

[Guest bonekicker]

Clever bugger 

 

Sorry Mike thanks for that 

Edited October 13, 2016 by bonekicker