I need 230ml of fork 7.5 wt oil and have 500ml packs of 5 and 15.

How much in ml of each do I need to have to get 7.5?

Ta

Different chemically isnt it, different ‘weight’ hydrocarbons/polymers – i.e. not like diluting pop?

Are they the same brand?

Some will mix, some won’t.

Are they the same brand?

Yes, and specifically says on the bottle it’s ok to mix weights.

I once rang tech services for silkolene (i think) to ask them same question. They said it was 1/3 and 2/3 but I can’t remember which way around. 7.5wt isn’t a standard measure though so feel free to go by trial and error.

77ml of 15wt 153ml of 5wt.

57.5ml of 15wt
172.5ml of 5wt

By my calculations (1 x 15 plus 3 x 5)/4 = 30/4 = 7.5

1/3 and 2/3 would give you (1 x 15 plus 2 x 5)/3 = 25/3 = 8.33333

assuming it can be caluclated along the lines of

5x + 15y = 7.5 x 230

then you need 172ml of 5xt and 58ml of 15wt.

No idea if this is how you actually calculate it though!

Cheers, Rich

Fully synthetic usually mixes fine, with predictable results – in this case a 7 parts 5w to 3 parts 15w will give you 8w.

I don’t think it’s proportional though – as in, 5wt and 10wt in equal portions doesn’t make 7.5wt

Yes, all above assumes that it does mix proportionately, if not then it’s obviously much more complex.

If it is proportional, the easy practical way to do it is to mix an equal amount of 5 and 15, then take that mixture, and mix it with an equal amount of 5wt again.

If you start with 57.5ml of each and don’t spill any, you’ll end up with what you need.

That’s what they told me, it’s not a linear conversion.

what are you using it in?

If it’s for an MTB fork an approximation of the weight is fine. You might err on the side of lighter or heavier depending on your preference. If it’s for an engine of some kind I’d rather a more scientific approach i.e. monitor the oil pressure and temperature.

what are you using it in?

Marzocchi 44 RC3 Ti

It’s Rock Oil SVI fork oil.

http://www.widman.biz/English/Calculators/Mixtures.html

A 70/30% mix roughly.

i just redid my Lyriks with fox 5wt oil instead of 7.5wt as stated. Will I die a fiery death soon?

Only if you set fire to your forks.

noted.

A linear guess will be very close to right. Strict linear would give 7.5w at a 3:1 ratio using 5w and 15w. You could go 7:3 for 8w or 8:2 for 7w depending on if you feel like the fork is under-damped (too active) or over-damped (not active enough) respectively. In any case all three of these options will be close enough to the original spec. “w” commonly referred to as “weight” is a very subjective marking anyhow – every manufacturer determines it differently.

Just chuck the 5w in. I doubt you’d notice much if any difference, you might need to turn up the damping a couple of clicks.

^ Yup, I’ve regularly done this, usually with improvement in small-bump performance.

What would Bruce Willis do?

What would Bruce Willis do?

the 44 RC3 Ti works best if you hand mix something a little different.
you will need to work out your average (fully kitted) riding weight and take it from there. i’ve eventually settled on a 8.7wt oil in the lowers on mine.

bung in some 5wt and compensate with the rebound adjuster if necessary