Filebase article using motor oil in forks...

guitargeek wrote:

No, that's backwards. As the oil heats up it becomes thinner, not thicker.

hwms wrote:

???????????? Not the way I learned.

That is true under normal operating temps, exceed the temp range of the oil though, and you can cook it into a thick sludge.

Simple test (being wintertime here), try pouring the oil out of a quart oil bottle when it is 10 degrees F, then heat it to 100 degrees and try it. I think you will find it is a lot thinner at 100 than it is at 10

Harry, read my post above again, multi viscosity oil does not get thicker, it just does not get thinner as soon as a single viscosity (one with a number matching the lower number). Again, it's simple to demonstrate, just do the test I described above.

Or, if you want to be more in line with the official teat, do it at 10 and 200 degrees F.

Post edited by: steell, at: 2005/11/25 01:14

oil gets thicker as it gets thicker,thats why you run heavier oil in racing motors to make up for looser bearing clearances,i mean oil gets thicker as its heated,darn that public school ed!

Post edited by: wireguy, at: 2005/11/27 18:12

thats why you run heavier oil in racing motors to make up for looser bearing clearances

That is a common misconception. A heavier weight oil is used in racing engines so that enough lubrication will be provided at the elevated temps that such engines run. That's also the reason for the increased clearances.

More oil info, in case anyone is interested:

www.mr2.com/TEXT/OilFacts.txt
www.nordicgroup.us/oil.htm
motorcycleinfo.calsci.com/Oils1.html
www.usc.edu/CSSF/History/2003/Projects/J1531.pdf
serendip.brynmawr.edu/sci_edu/farber/pdf/viscosity.pdf

And I still have not found the one I'm looking for

Post edited by: steell, at: 2005/11/25 02:09

Motor oil used to be used in forks - all my Brit bikes called for motor oil in the forks. Today, why would you not want to use an oil specifically made for use in forks? Seems foolish not to take advantage of the technology.

Personally, I can't imagine using anything heavier than a 15 weight fork oil, I weigh ~240 lbs and use a 50/50 mix of 10 and 15 weight fork oil. I find that works best for me, the front wheel absorbs the bumps instead of bouncing over them and loosing traction, and does not bottom out (and I like to get the bike in the air).
I would not even consider using a regular motor oil, especially when fork oil is cheap.

it says in that filebase article that the oil will not thin out below the higher number when heated,thicker oils are used in motors with looser clearances to make up the the clearances,would you run 15w40 or 5w30 in a motor with a lot of miles on it?id be willing to bet most people would go with the thicker oil