Fork Oil Change

I do like Cowboy says. You have to undo the top to fill them anyway and if it does spin use a long piece of wood dowling to hold it back in position. The same piece of dowling can be used as a measure of the old oil level before you drop it out,giving you an indicator as to the level of the new oil.
Much easier than removing the forks

[timwilky]

From memory, when I did a mensuration module in the 70s, so may be wrong

viscosity of a fluid is measured by how long it takes a bearing to fall through a tube of the fluid. Obviously the diameter of the bearing/tube are fixed.

So as others above have it is really a measure of the shear capability of the liquid, the ability of liquid to move. "Thickness" and weight are not really an indication of viscosity. Weight as applied to fluids is the SAE interpretation of viscosity.


edit, whoops the above is for the stokes unit so is the drag. the viscosity is measured in poise and is the ability of the liquid itself to flow through a tube.

[yorkie_chris]

Originally Posted by timwilky

From memory, when I did a mensuration module in the 70s, so may be wrong

viscosity of a fluid is measured by how long it takes a bearing to fall through a tube of the fluid. Obviously the diameter of the bearing/tube are fixed.

So as others above have it is really a measure of the shear capability of the liquid, the ability of liquid to move. "Thickness" and weight are not really an indication of viscocity. weight is the SAE interpretation of viscosity

Yup I've done that. I've seen apparatus that measures it with a cylinder rotating in a cylinder, torque required for a certain rpm, and from that you can find viscosity. There are other types that use flow through an orifice, or a rotating cone and plate. I don't think the ball bearing method is in common use, but I'm not sure.

Drag is connected to viscosity. Definition of viscosity is resistance of a fluid to shearing.

[timwilky]

Originally Posted by yorkie_chris

<snip> I don't think the ball bearing method is in common use, but I'm not sure.

A quick google, remember I did this in the 70s found this

Originally Posted by Dicky Ticker

I do like Cowboy says. You have to undo the top to fill them anyway and if it does spin use a long piece of wood dowling to hold it back in position. The same piece of dowling can be used as a measure of the old oil level before you drop it out,giving you an indicator as to the level of the new oil.
Much easier than removing the forks

Is this possible?
Bikes only done emm around 8-9K, and the front is goosed.
Going to change the oil first, as the springs shouldn't need changed at this low mileage.
What is the cubic capacity of each fork?
My mechanic is doing this, as I don't want to make a mess of anything les than 2 weeks before the GMII.

[yorkie_chris]

It's measured by air gap generally.

The springs don't realy wear, but unless you are very light they'll probably be the wrong rate.

Wow, how weird, I did a search for this thread this morning to look at that table, and now it has been reborn

A 1L bottle of fork oil is enough to do both forks, as they contain just under 500ml each but as yorkie said, its the air gap you worry about.

Forgot I bought a Haynes.
488cc per fork.

mechanic guy is taking them off..
I got confused.
Got 10W oil and still the OEM springs..
Wrong side of 14 stone, so not light

I have 15W oil in mine (was 10W) and its still the same springs after 70,000 miles, don't stress to much.