Morning All,

I’m in the middle of servicing my forks (08 Float 140mm RL) and was planning to use the half bottle of 7wt fox fluid I had left over from a previous pair of forks. When I checked the amount I needed on the Oil Volumes (no. 25) chart I realised that the forks I currently have require Fox green 10wt fluid not 7wt 😮

What is the difference in the wt figures, am I right in thinking its a measure of viscosity? What would be the effect of using the 7wt oil instead of 10wt, would it affect the performance of the forks?

Is there anything else I could use as a viable substitute?

Cheers 🙂

it will have less damping using the “thinner” oil

Try the seven you’ve got. They might compress a little quicker but you should still have enough adjustment on the rebound. If you don’t like it, try some heavier fluid. Just be aware that not all ten weight oil is the same viscosity.

Recently bought Fox oil for my forks at my LBS…as per the instructions mine require 7wt. Anyway apparently they don’t do 7wt anymore and the Fox oil I was sold was 10wt. Checked with Mojo and they confirmed…if Fox don’t think it’s a problem that mine will have 10wt, can’t see it’s a problem yours will have 7wt.

it will have less damping using the “thinner” oil

So would that mean that the fork stroke would be softer/spongier as a result of using “thinner” oil and if so could this be compensated by using more rebound or air?

Failing that would 10wt synthetic motor oil be used as a substitute?

EDIT: Onzadog, have just seen your reply

nuke: have you noticed any difference in the feel of your forks using “thicker” oil and if so was this easy to remedy using rebound/air?

So would that mean that the fork stroke would be softer/spongier as a result of using “thinner” oil and if so could this be compensated by using more rebound or air?

Damping is not the same as spring rate, You get less damping so you need to turn the rebound adjuster to get back to the same level of damping otherwise it will be bouncy

It will have less compression damping as well this means it will dive a bit quicker on the brakes and in compressions. Hardly likely to be practicable tho –

If you want thicker oil get motorcycle fork oil – don’t use engine oil

Air isn’t the answer. That will just alter your spring rate. I doubt you’d notice the difference in compressing. Although you might prefer it! It doesn’t hurt to play about with it. You’ll not do any damage and you’ll not die. Well, one day you will but it will have nothing to do with fork oil.

I’ve often tuned forks using oil weight and height. I’ve even tweaked the internals on my float fork to make them more linear and I’ve also shortened the travel on some vanilla 140 mm fork when told it couldn’t be done. Don’t be afraid to play around with them.

OK that makes sense. I hadnt thought about using motorbike fork oil, just get some 10wt of that instead?

Onzadog: ahh the Dr Peppers approach, sounds like a plan to me and also means I dont have to walk to the otherside of the world, or at least town, to halford 😉

Not all suspension fluids are equal. If you really want to mimic the 10 st oil that fox use, have a look a pvd on Wikipedia. He has a list of all fork oils by true viscosity. You can then buy the stuff fox use without paying fox prices for it. I think their ten wt is a silkolene product anyway. Seven wt and float fluid are torco products.

I had a quick look on pvdwiki but it didnt list any base product for Fox which is a shame but will give it a proper read later on tonight.

I think for now I’m just going to use the 7wt and see how they go from there.

Thanks for all your advice 🙂

nuke: have you noticed any difference in the feel of your forks using “thicker” oil and if so was this easy to remedy using rebound/air?

Nope, can’t say I did. TBH after confirming it was fine with Mojo, I didn’t really give it another thought. So many potential variables with fork setup that if I had noticed a different ‘feel’ to that fork, I doubt I would have been conclusively able to pin it down to the fact the oil wt was slightly different.

Actually, thinking about it, I loomed into a picture of a bottle of fox ten weight oil for the specs then used the pvd site to find the nearest mate and actually found the exact one

have used shell 7.5wt fork oil with no issue in my fox shox instead of 7wt and it was cheap as chips from a local Ducati dealer.