Fork Oil Question

My service manual states to use 10W 40 oil in my forks. When I look at Z1Enterprises website for stuff, they list 15W and 20W Fork Oil, which I assume are straight weight oil. I am not sure what I need to use when I replace the oil in my forks? Do we have any fork experts on the site that can set me straight?

what kind of bike do you have?

ive allways just used goog ol 10-40 and never had any problems!goodluck,happy wrenching!

what kind of bike do you have?

I have a 1981 KZ1100. It is listed in my signature.


If 10W 40 is sufficient for the forks, is Fork Oil a gimmick?

Write or call and talk to Jeff @ Z1. He would rather ride a Harley than steer you wrong This is what he does for a living and it's a LOVE of his ( what a lucky guy ).
I am using PJ-1 10 weight in my Z1 forks, but I'm also using Progressive front fork springs. So I don't want too stiff a ride.
Pat

my clymer calls for 10w non detergent oil

We only have 10w and 15w in stock. 20w is too darned thick for most bikes. Most fork oil is just single weight these days - although you can get multi-weight fork oil it's tougher to find and tends to be for the dirt or racing bikes.

Each model is a little different in it's requirements - and the total weight on the bike can influence your choice. What may seem like stiff forks for a 150lb rider may be too soft for a 250lb rider.

You want to make sure you use a non-foaming fork oil - this will be more consistent over bumpier roads

I heard somewhere about using auto transmission oil. Anybody ever try this?

wireman wrote:

ive allways just used goog ol 10-40 and never had any problems!goodluck,happy wrenching!

you use regular 10-40 in the forks? how does it work? handle ok?

ive allways used it ,i used to like to see how long i could stand on the back wheel when i was younger and more fearless,never had any problems with smashed header tubes seemed to do the trick for me!goodluck,happy wrenching!

I have used ATF in the old days before anyone made fork oil. All I can say about it is it worked. Not well but that was all we had back then.

I put automatic transmission fluid, 10-W I think, in my forks years ago and installed fork boots (gaiters) on the tubes. Since then I have never had a fork seal go bad and after sitting for years and years before running again, the front suspension works just fine. Why we changed to transmission fluid I don't know and can't remember, it was a new fad at the time, like the brand new DOT 5 brake fluid or the unheard of practice of turning on your headlight. I do recall the shock of seeing how bright an H-4 halogen headlight could be, they were just coming in to vogue. Funny how things change over more than 30 years. Back then we were still getting used to mandatory helmet laws.