Fork oil change

[ldhthept]

Must be snowed in up there in the great white north with little to do in the way of entertainment.

[redjay]

That's what I was thinking Biking season will be here soon.

[Sabre-t]

Originally Posted by degreaser

ok, this brings up a question I have about oil density, because if either of the 10w and 20w oils have different density, mixing the 2 will cause the lighter density oil to float on top of the heavier density oil? which makes me wonder if the oil Viscosity = oil density?

The oils will mix together and stay mixed. Viscosity does not equal density.

As degreaser said, mix them 50/50 then use that mix to fill the forks. You do NOT want to have slightly different weights in the forks because you didn't blend it accurately in separate batches. If it doesn't come out exactly 15W, you really aren't going to notice the difference if you use a purchased 15W the next time around. The first time I changed fork oil, I couldn't find any 15W and didn't want to wait for an order to come in. I blended my own. Couldn't really tell any difference the next time I changed it using a purchased 15W.

[MrMikey]

I'm not a high performance rider by any stretch of the imagination, so keep that in mind. When I did mine last year, I used Dexron 6 ATF. It seems to handle fine for me but as I said, I'm not a peg scraping kind of guy..................M

[Sabre-t]

Originally Posted by MrMikey

I'm not a high performance rider by any stretch of the imagination, so keep that in mind. When I did mine last year, I used Dexron 6 ATF. It seems to handle fine for me but as I said, I'm not a peg scraping kind of guy..................M

It's not about peg scraping, it's about the response from the front end regardless of riding conditions. Personally, I would not use ATF in forks, though I know some folks do.

[BrokeAss]

I use ATF in forks quite often. Forks and automatic transmissions are both hydraulic, and ATF is a darn good hydraulic fluid, especially synthetic. Fork oil comes out black in as little as two years, but ATF comes out as red as the day it was added even years later. Before some marketing geniuses realized they could bottle different weights of hydraulic fluid and call it "fork oil", ATF was exactly what they used in motorcycle forks. ATF is also used in many manual transmissions, including the Mazda transmissions found in F150's. The only downside to using ATF is that its weight when used as a fork oil is not advertised, but it has been found to be ~7wt. If you need 10-20wt oil, then you'll have to spring for fork oil.

[Sabre-t]

Originally Posted by BrokeAss

I use ATF in forks quite often. Forks and automatic transmissions are both hydraulic, and ATF is a darn good hydraulic fluid, especially synthetic. Fork oil comes out black in as little as two years, but ATF comes out as red as the day it was added even years later. Before some marketing geniuses realized they could bottle different weights of hydraulic fluid and call it "fork oil", ATF was exactly what they used in motorcycle forks. ATF is also used in many manual transmissions, including the Mazda transmissions found in F150's. The only downside to using ATF is that its weight when used as a fork oil is not advertised, but it has been found to be ~7wt. If you need 10-20wt oil, then you'll have to spring for fork oil.

Since there is no standard for fork oil weight, it is no surprise that the ATF "weight" is not as advertised for fork oil. The only reliable way to compare fork oils is by viscosity. One brand's 15 weight can be equivalent to another's 10 weight. It is also not surprising that an ATF would be "~7wt" (whatever you consider to be 7 wt) as ATFs are formulated for viscosity stabilization at 100°C. If your forks are getting that hot, you have a serious problem!

I've also read that you should only use ATF if you have a spring damper type fork (open damper), which is stock on most of these bikes. If you have cartridge dampers or are using an emulator, I have read about everything from poor performance to damage to the cartridges/emulators due to some of the characteristics of certain ATFs. I guess it depends on which ATF you use. Personally, I don't know enough about it to risk using an ATF when I can get a properly labeled product that I know will work.

I do prefer Maxima 15 weight (regular, not racing), so I won't be using ATF, anyway. Once you find an oil and like a particular weight of that oil, you should stick with that brand if you want consistent results from change to change.