Fork Oil Confusion

A conversation on another thread jogged my memory about a thread I wrote on another forum about my experience with finding the right viscosity fork oil, which as you will read has nothing to do with the W number.

Before I started researching fork oil I didn't know much about it other than it was oily.

So I suppose you could say I knew fork oil about fork oil.

The searching started when I took my first ride after fitting my newly sealed forks.

They were stiffer than a stiff thing on a stiff day. In other word they were 'king stiff.

I had already purchased the oil before I sent them off so Ernie put it what I had sent him.

The manufacturers W numbers bear no resemblance to the viscosity.

The Yamaha manual recommends Yamaha Suspension Oil M1 or Ohlins R&T43.

Both of which seem pretty scarce in the uk. A US site tell me that Yamaha M1 is a zero weight oil but no viscosity figures. The Ohlins site however was more helpful giving a viscosity of 19 mm2 Centistokes @ 40°C. So I had a reference point to aim for.

I contacted Opie Oils for some advice and Tim (very helpful) set about finding me some suitable oil.

His first recommendation was for any 5W oil until I pointed out that it was the viscosity that was the critical factor as the 5, 7.5, 10W etc bore no resemblance to the viscosity. Telling him my aim was a viscosity of 19. He came back again with a recommendation for Motul Light 5W Factory Line Motorcycle Fork Oil which has a viscosity of 18, so close enough for me. I then set about finding others that were in the same range so I had a choice.

Fork Oil recommendations for the Yamaha FJR 1300A

Centistokes @ 40°C

Millers Suspension Oil 2.5 NT 17.2

Motul Factory Line 5W Light (Synth) 18

Motul Expert 5W Light (Semi Synth) 18

Red Line Light Weight Suspension Fluid 16

Silkolene 02 17.94

Yamaha M1 18.7

Yamaha 01 15.3

So as you can see from the figures above the W number bears no resemblance to the viscosity.

The oil I supplied to Ernie turned out to have a viscosity of 47.4, no wonder it was bloody stiff.

The right oil is on its way from Ernie. I will use Opie next time I need fork oil, Tim, you are a top man.

Good info there Rae

There is a lot of bad information out there on fork oil especially on forums where people have their own opinion rather than researching.

When I changed the springs to hyperpro on the FJR they came supplied with fork oil and I will buy the same oil when it comes to changing it as they are the guys who know what they are on about and thats the oil made to work with those springs and forks and I must say it all works rather well.

Another thing that is always misinformed is the mixing of oils, most people think if you mix two oils 50:50 you get a figure in the middle, however it's not as simple as that. When I was doing this research I had a long chat with one of the chemists at Silkolene and he gave me a mix ratio to obtain the viscosity I was looking for. In my case looking for a viscosity of 18.7 Centistokes @ 40°C he advised me to mix a 2.5W with the 5W in a 1/3 to 2/3 ratio respectively which gave a viscosity of 18.85 Centistokes @ 40°C, close enough for me.

He started talking about molecular structure and how the two different weights react with each other, even though I have a laboratory quality control background this was way above my pay grade, so I just took his word for it.

It's nice that they gave you the time to explain it

I have always found the tech guys at most companies are willing to chat. I had a very informative chat with a guy from Castrol about the BMW oil they used to supply to BMW this was the 5W-40 verses the 10W-40. And his parting shot believe it or not was "any oil is better than no oil"

I have always found the tech guys at most companies are willing to chat. I had a very informative chat with a guy from Castrol about the BMW oil they used to supply to BMW this was the 5W-40 verses the 10W-40. And his parting shot believe it or not was "any oil is better than no oil"

Its funny you say that as when I had the TL there was owners in the US of A that would only use the cheapest wallmart oil they could buy and just change it every 2k

One of them had over 200k on the bike and he stripped it to rebuild it and it was perfect inside! He just put new gaskets on and put it back together

I have always found the tech guys at most companies are willing to chat. I had a very informative chat with a guy from Castrol about the BMW oil they used to supply to BMW this was the 5W-40 verses the 10W-40. And his parting shot believe it or not was "any oil is better than no oil"

 

Its funny you say that as when I had the TL there was owners in the US of A that would only use the cheapest wallmart oil they could buy and just change it every 2k

One of them had over 200k on the bike and he stripped it to rebuild it and it was perfect inside! He just put new gaskets on and put it back together

I've always stuck to frequent oil changes and last time I took my car engine to bits at 130k it was like new internally. I only dismantled it because that engine had a reputation for snapping timing chains and self destructing.

There are not many places that refine oil so even your bog standard Wilko's oil is from a reputable source. The issue is the additives. It's the detergents which break down first so frequent oil changes keeps fresh detergents in the engine so it stays clean.

Great info there

What oil did you originally use giving you the viscosity of 47?

This was a while ago so the memory fades but it was a 10W oil can't remember the brand it might have been Silkolene.

I suppose the problem then is getting hold of the technical guys from within the inner company circle in the first place. I'm doing some work on my Nc30 forks at the minute and so I've been genning up on fork oil and stuff again.

I've got a load of motul factory and expert knocking about and it's quite similar to the genuine "Honda Pro Ultra Cushion" oil... But it doesnt come in as nice a can; I want it just to sit on the shelf.

I know fork oil about this subject.

Oi, using my jokes? Stick to your day job