Type of oil to use in forks

[waldo877]

Looks like SAE 15 is what goes into the forks of my bike, but I can't seem to find 'fork oil' anywhere, at any autoparts store. Seems the bike dealers close before I can get to them as well. Anyone know a large chain type store that would carry this? Hydrolic oil work?

[67fire]

I just use 10W-30 Synthetic motor oil.

Eric

[waldo877]

And that works well for you? No swelling of the seals, or foaming?

[TheCafeKid]

I just use 10W-30 Synthetic motor oil.

Eric

No. DO NOT use MOTOR oil....

Use oil designed specifficly for putting in your forks. Oddly enough, its called "fork oil" and you can pick it up at just about any motorcycle shop worth its salt enough to have you walk thru the door. Remember, the oil in the forks ISNT for lubrication so much as its for DAMPNING. motor oil simply isnt viscous enough to adequately do the job, plus it WILL foam. The manuals suggest, if you CANT find fork oil, either a mix of ATF and motor oil (in the early manuals) or straight ATF (later manuals) I would rather go straight ATF than mix any motor oil in it. However, with as easy as it is to find fork oil in both 10w and 15w, I would suggest using the stuff intended for the purpose...

[Larry D]

Get fork oil.
Have some family, a friend, a neighbor go to the bike shop and get some...

[Steve]

Yep, fork oil all the way.

Order it online, if you have to.

Depending on your style of riding and your degree of gravitational attraction, you might want to choose between 10w or 15w. While you are in there changing the oil, make sure you have the proper amount of preload in your springs. This helps assure that you have the proper amount of travel in your suspension to absorb the nasty stuff that a road can throw at you.

.

[rustybronco]

order it online!

or you can also mix dexron-III (mercon) and 20 Wt engine oil. you'll end up with a combined Wt of 13.5 'ish.

[waldo877]

Trying get the forks a little stiffer. Changing the oil in the first place because one of the seals is just junk. So, 10w or 15w, which will net me a little bit of a stiffer ride? And, when changing the seals, how do I tackle the allen bolt at the bottom without making one of those t-handled 'tools'? Not sure I understand the purpose of it after reading that tutorial a bunch of times.

[TheCafeKid]

Trying get the forks a little stiffer. Changing the oil in the first place because one of the seals is just junk. So, 10w or 15w, which will net me a little bit of a stiffer ride? And, when changing the seals, how do I tackle the allen bolt at the bottom without making one of those t-handled 'tools'? Not sure I understand the purpose of it after reading that tutorial a bunch of times.

You either have an air impact ratchet, or the tool, or you dont do it. Those will have some pretty nasty "loctite" equivalent on them, so your hand strength likely isnt going to break them loose. Read the tutorial again. those are what keep the dampening rod attached to the lower fork tube...

[Steve]

OK, "stiffer", related to the forks, can mean several things.
1) your springs are weak, allowing the bike to droop, you need 'stiffer' springs to hold it up.
2) your spring rate is OK, but the forks move too easily, you need more-viscous oil to increase the damping.
3) everything else is OK, but you just plain ride it hard and the forks are flexing under the stress. You need a fork brace to 'stiffen' it up.

Start with proper springs. You can pretty much assume that the stock springs in the bike are worn out and were barely adequate to start with, 25+ years ago. Progressive Suspension sells fork springs that make a world of difference in ride and handling. With them, you don't need to add any air to help the springs, they start out with the right rate. They (Progressive) recommend using 15w oil with their springs, but they are also rather performance-oriented. For those of us that are more sedate riders, a 10w oil will track irregularities in the road better.

Now that you have the proper springs, determine how big a spacer you need to add to bring the bike up to the proper ride height. A length of PVC tubing works well as a spacer. You want the front of the bike to settle no more than 1 to 1.5" with you on the bike, ready to ride. This will leave 4.5 to 5" of travel, assuming you have the stock 6" of travel.

Once you have all that, add the proper amount of oil, close it up and ride.

Concerning the seal change: hvae you done any searching for "changing fork seals"? I haven't either, but here is the tool I made:


A detail from one end:


It's just a piece of 5/8" all-thread rod with two nuts jammed on each end. There is a damper tube at the bottom of the fork that the nuts will fit into. Having some thead stick out past the nuts like that will help center the tool in the tube. You need to hold that tube in place while you loosen the Allen-head bolt on the bottom of the fork. Some have reported success by using an air impact wrench, but not everybody has one of them laying around.

.

[waldo877]

Awesome, thank you steve. and the size of those nuts are 19mm correct?

[Steve]

Sorry, I keep forgetting which tool I made for which bike.

The tool with the 5/8" rod is for my son's Venture Royale. You need to use 1/2" rod.

The nuts that fit the 1/2" rod use a 3/4" wrench, which is 18.75 mm, which is pretty darn close to 19 mm in my book.

.

[lurch12_2000]

Looks like SAE 15 is what goes into the forks of my bike, but I can't seem to find 'fork oil' anywhere, at any autoparts store. Seems the bike dealers close before I can get to them as well. Anyone know a large chain type store that would carry this? Hydrolic oil work?

Freedom Cycle in Concord is open late on Thu nights. If you can't find 15w then buy 10w and 20w and mix a half bottle of each in a 3rd container for 15w. Then you'll have a choice of 10w, 15w, or 20w leftover for the next change out.
FYI, I found 20w a little stiff, especially riding in the colder temps (under 40F). And I used the $6/qt Spectro stuff not the $20/qt stuff!

[Nessism]

If you look though the various Suzuki manuals they call for using SAE oil and/or using a mix of oil and ATF on various models. For example, the GS1000 manual calls for SAE 10W/20 oil. I take the SAE reference to mean motor oil although fork oil should also be fine for obvious reasons. I’ve heard people talk about the anti foam properties of fork oil but it seems to me that motor oil operates in a harsher environment in terms of getting churned up so I don’t think this is a significant consideration. Personally, I use fork oil but I wouldn’t hesitate to use motor oil if the proper weight is available.

[rustybronco]

Don't forget atf has very good anti-wear and anti-foam properties.
just don't use type "F" fluid, it has metal particles in it. ( used originally with metal clutch discs )