The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Sunbeem on July 19, 2008, 08:35:56 AM

Title: Fork oil, R100RS.
Post by: Sunbeem on July 19, 2008, 08:35:56 AM

Haines says SAE 3 local dealer says  SAE 10 could anyone cast some light on

Sunbeem.

Title: Re: Fork oil, R100RS.
Post by: Bob_Roller on July 19, 2008, 11:24:50 AM

BMW fork oil is 7.5 wt at least on the R65's, I don't think that going to a 10 wt would cause any problems, especially if you don't have a local source for the BMW oil.

Do you have the BMW owners manual for the bike, it has the specification for the oil in there.

Title: Re: Fork oil, R100RS.
Post by: montmil on July 19, 2008, 11:27:50 AM

I'm running the BMW-branded 7.5wt and it feels a little "weak". But then again, I've been pushing the scooter pretty good since I got new tires. I plan to upgrade to at least a 10wt on the next change.

Title: Re: Fork oil, R100RS.
Post by: Crossrodes on July 19, 2008, 12:44:04 PM

Whoops!  I put Belray 5 weight in mine.  We'll see how it works after I get it back on the road.

Title: Re: Fork oil, R100RS.
Post by: montmil on July 19, 2008, 01:30:54 PM

Quote

Whoops!  I put Belray 5 weight in mine.  We'll see how it works after I get it back on the road.

Five weight? It'll probably be fine... unless you wear hockey pucks in the knees of your jeans.  8-)

Title: Re: Fork oil, R100RS.
Post by: Barry on July 19, 2008, 01:50:08 PM

You can only realistically compare fork oil viscosity for oils from the same manufacturer. The reason is that the 10wt or 7.5wt rating is the oils viscosity at 100 deg C which is obviously nonsense for front forks.  You want to know the viscosity at 40 Deg C or lower and that will be different from one manufacture to another depending on the oils viscosity index.  The link below is the best explanation I’ve seen although you might want to skip the maths and look at the table at the bottom of the web page.


http://www.peterverdonedesigns.com/lowspeed.htm

Title: Re: Fork oil, R100RS.
Post by: montmil on July 20, 2008, 07:37:48 AM

After wading through the "oil chart" info, I don't find "our" BMW fork oil. Any idea whose manufacturer's product is really in the BMW fork oil jug?

Title: Re: Fork oil, R100RS.
Post by: Barry on July 20, 2008, 03:23:28 PM

I don’t know if BMW provides viscosity values for current fork oils but Snowbum has a specification for the original BMW fork oil. If you compare this with the table it was pretty thin stuff. It must still be a good reference when selecting another manufacturer. Some (Castrol for one) list viscosities on their web sites.  

http://bmwmotorcycletech.info/frontforks.htm

Title: Re: Fork oil, R100RS.
Post by: Bob_Roller on July 20, 2008, 04:19:07 PM

Quote

After wading through the "oil chart" info, I don't find "our" BMW fork oil. Any idea whose manufacturer's product is really in the BMW fork oil jug?

Spectro Oils is the manufacturer for BMW branded oil, so I'd got out on a balsawood limb and say they are the manufacturer.

I'll check tonight when I get home from work at about 23:30.


I checked the container, and Spectro Oils is the manufacturer of BMW branded fork oil.

Title: Re: Fork oil, R100RS.
Post by: Sunbeem on July 20, 2008, 05:46:55 PM

Thanks folks, you've convinced me that it's not as straightforward as I thought.
I'll ignore the SAE values, and test until I find something that suits me.
Today I tried ATF, (simply because I had some on the shelf, and my BSA liked it).
My previous bike (Armstrong MT500) had wonderful suspension, so I may be hard to please,
but I found it a bit harsh.
I'll try a 7.5, and then a 5, and see where that gets me.
Thanks again,

Sunbeem.