/5 fork oil?

Hi, I've searched several times, can't seem to find any info here (I have found lots elsewhere) - what weight/brand fork oil do you use for your (SWB) /5? My forks have standard springs and had been rebuilt a few years ago. Would synthetic work? And do you change it once a year? I just did all my fluids and was shocked to how dirty all the oil was...and I don't ride that much.

thank you, Chuck

The original specifications called for the equivilent of 3wt fork fluid. I think that is too thin for adequate damping. When I had a /5 I liked 5wt with 10cc or so extra oil in each fork.

Probably more info that you want!

https://bmwmotorcycletech.info/front-fork-oils-amounts.htm

As Paul said, try the 5wt...possibly consider adding more to reduce the air volume. I've never done that on my /7. I've ended up using 7.5wt, maybe 10wt...whatever was available from BMW. I'm not sure what the change interval is, but it's definitely more often than I do it. I wouldn't do it by time...consider mileage, maybe every 10K or 20K miles? If 20K miles is 10 years, then that's probably too long.

thank you Paul and Kurt. I did read Snowbums articles, or skimmed more like it. And I was stumped. I had seen references to 7.5, then to 10...I'll read more and make a decision.

Regards,
Chuck

front fork oil, amounts, etc

Seeing this thread prompted me to finish a bit of article rework I had started awhile back, so, today I uploaded a few changes to my explanations for the article, and the article and revision will be dated (at bottom) as 07/15/2020.
https://bmwmotorcycletech.info/front-fork-oils-amounts.htm

I suggest not changing fork oil viscosity unless you are SURE the forks are in alignment, and that stiction has been eliminated as best possible. Stiction can be from improper tightening of the axle; improper fit of the fender attachment and/or any improperly fitting fender brace....

Once the forks are known good in alignment and stiction minimized, then oil amount and viscosity can be played with, if once has a real reason.
The /5 front forks are easy to modify for such as racing or really aggressive street riding. Most shouldn't do more than stiction work and oil not over 10W.

Snowbum

For laughs ... the specification used to be AeroShell. I often wondered if I could go to the local general aviation airport and buy some. I think you used to be able to buy custom bottles of it from Motobins in the UK. It's red (and not ATF).