I recently purchased some Fox 20wt "gold" and 4wt Fox oil, expensive stuff (even using the small ebay resellers). The Fox 4wt looks identical in every respect to standard moto cross 4wt oil. Anyone used this before in their fork lower leg services ? (not planning to currently, but interested to know as I believe they are identical products labelled in different bottles)
Wouldn't be surprised after all Fox want about £30 for a socket to change a volume spacer when you can get one without their logo on it for a third of that 🙄
On that subject how come a 5 minute job like that and potentially part of setting up your forks don't they provide the tool considering the eye watering cost of the forks in the first place? Maybe they do on their £1K plus forks I've never been that flush .
Anyway sorry to interrupt 🙄
I don't know if it was motor cross specific, but I've definitely used motorbike fork oil in the past. I also use automatic transmission fluid in my Nexus hub gear instead of the Shimano Panda Jizz infused* stuff.
Interested to know how you found out
The Fox 4wt looks identical in every respect to standard moto cross 4wt oil.
Because the manufacturers are usually very keen on keeping the additive packages a secret from end users.
*There has to be a reason it's SO expensive.
they provide the tool
Well, one good thing is they’ve moved to using a cassette tool for new models.
And just because you can buy a branded tool, doesn’t mean you have to. See also the expensive tool kits you can add on when buying expensive cars.
The Fox 4wt looks identical in every respect to standard moto cross 4wt oil
It even comes in bottles the same shape as Moterex… I wonder why…?
😉
Don't know if it's 'motocross' or not but I use Smith and Allan motorcycle fork oil in my Rockshox forks and it seems to work fine.
It's about a tenner a litre so significantly cheaper than the RS equivalent and available in a range of weights.
yes and its perfectly fine.l MTB branded stuff is a ripoff.
Yep. I've used Castrol 10wt motorbike fork oil instead of Rockshox Dodo Jizz Infused 15wt for a couple of years now in my fork lowers. Absolutely fine.
If it was doing any damping work, I would definitely use the right weight and possibly the 'right' brand. But in the lowers it is only acting as a lubricant anyway.
As above, MTB branded stuff is a rip off.
Fox also charge £100 for a digital shock pump which you can get from Lifeline or Brand-X for 30-40 quid.
Use the motocross oil. I've done it in the past with no issues.
I've always used Silkoline motorbike fork oil in al of my forks and it's been fine
But in the lowers it is only acting as a lubricant anyway.
Not always the case. In the lower on the damper side.
I have suspension fluid from Rock Oil and Motul in my cupboard, I don't believe either are MTB-specific.
So for Rockshox forks I've always used whatever motorbike stuff in the lowers as it's just lubricant. On the fox 36s I have now I did some interneting and it appears the 4wt stuff is used by the damper and allegedly has teflon in it. So for that I bought some of the fox stuff of eBay. For the air side I just used normal motorbike fork oil.
I've used motorcycle oil (Silkolene I think) before with no problems.
Yes Motul - in RS pikes and lyrics. On that note with my low speed compression damping always being at the minimum of adjustment to reduce chatter, would changing to a lower weight oil, move that sweet spot towards the middle of the adjustments from where I can use air pressure, volume spacers and rebound to fine tune things better?
When doing a lower leg service I mean as noticed someone said the oil in lower leg doesn't affect damping (I assumed it all gets cycled through the damper?)
I've always used motorcycle fork oils too...and I make motorbike noises when I ride so the oil doesn't get confused.
The new Fox 4wt which replaces the Teflon infused stuff is just Motorex 4wt:
Lots cheaper than the Fox branded stuff
Always used "alternative" oils. Both rockshox and fox have always used other brand oils. Often the shape of the bottle is a give away, they just change stickers.
I've even used engine oil for the lower bath as they can tend to cling better.
Instead of fix 20wt, I use Supergliss 100 slideway oil
I never liked the idea of fix yet with teflon and used Maxima 85-150 instead.
Even my brakes use Putoline fork oil.
The secret is to ignore "wt" as it's pretty meaningless. I think it was Torco fluid that fox used to use and for no reason at all, they use to change the "wt" reference when they put their stickers on.
Look to match centistokes cSt, This is an actual measure of viscosity, usually at 40°C and 100°C.
https://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid
Is a useful table comparing common oils.
Not always the case. In the lower on the damper side.
You've piqued my interest!
Can you explain, please?
You've piqued my interest!
Can you explain, please?
Some dampers are designed to ingest oil from the lowers and then bleed it back out of the top of the damper if they become over full. This is why you never cycle the likes of a grip 2 damper while it's out of the fork.
Yeah, that.
Marzocchi DBC (Dynamic Bleed Cartridge) and the Grip damper, that coincidently (yeah right) Fox developed and put into use when they bought the Marzocchi name, cycle a small amount of oil between cartridge and fork lower, so you need the same oil in the cartridge and the damper side lower.
[ duplicate post removed ]
Well, I never knew that.
Isn't it a bit risky for a damper to take oil from a lower where, presumably, there's a higher chance of it getting dirty?
In any case - thanks for the answer. 👍
Potentially, yes. Hence the service schedule. This was an answer to dampers not being designed to take in excess oil. If they did by accident, they would split. They used to run a bidirectional seal which was higher friction. Now, as the fork compresses and the pressure builds in the damper, the sealing edge is put to work. In rebound, the internal pressure decreases and due to not having a lip in this direction, runs the risk of sucking in a tiny amount of fluid from the lowers.
It's not a full circulating open damper. It's a closed damper designed to deal with a real world problem rather than trying (and failing) to battle that real world problem.
Think of BikeYoke dropper posts. Rather than solve the ifp/air ingestion issue, they just made bleeding it off super easy.
for rockshox any 10-20w will be fine, for fox, you need to use the same fluid as in the damper in the damper side.
I used to just get rock oil or silkoline for my shocks, but I've got motorex 4wt for my fox 34's
https://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid
was something mentioned i a previous thread, there's a chart listing oil viscosities for some of the (maybe older) common shock oils and it's clear that just because it says it's a certain wt oil, doesn't necessarily mean it'll behave the same.
I've used motorbike suspension oil in my forks. Prior to that I used bottle jack oil which worked well.
I use Motorex in the lowers and the damper. It's motorbike fork oil and It's what Manitou recommend.
Up to a point, anything will work in the lowers. I've used Castrol engine oil in Rockshox before.
As Onzadog says though, it's the Cst that matters more than anything else. Not all oils are equal and some have far higher lubricity despite being technically the same (5w40 or whatever).
As above you can often ID the oil. Fox Red used to be Silkolene RSF Pro, you could recognise the bottle, they just put a Fox sticker on it which apparently cost £10. Fox Green was Torco iirc. Rockshox is definitely Maxima though I don't know for sure if there's an identical product.
Grip damper is a funny one, it's a really clever sort of self-bleeding design but also, they said it was only compatible with their ptfe oil and that you must never use anything else under any circumstances then they stopped selling it and went lol, no we lied, ps only use our 4W oil, definitely don't use any other oil from any other manufacturer and certainly not Motorex which is literally the same oil but less than half the price. Fox stickers have got more expensive, the latest ones cost about £18
Pretty sure rock show lower fork oil is just engine oil …. Heads off to find link
The last few posts suggesting you can use any old shite, (I'm paraphrasing, but jack oil? Really? That's for hydraulics) I don't subscribe to. This comment comes close to the issue.
Not all oils are equal and some have far higher lubricity
It's because you're not just buying oil, there's an additive package in there too. The higher lubricity ones for example contain a friction modifier. There may also be anti foaming agents, likely no extreme pressure, (EP) additives, and something that can cope with water drawn in through the seals. I don't exactly know, but that's my point really, the manufacturers keep these blends a closely guarded secret. Do you even know if you are buying synthetic or mineral oil? Which is needed?
Qualification - I look after lubricant supply at work. Thousands of litres per year of many types in multiple applications from gas turbines to high voltage electricity distribution systems. I'm not an expert by any means but know enough not to balls it up and who to ask for better advice.
So you're saying I can't use baby oil?
That's a shame, I bought more than I needed for my paddling pool.
So you're saying I can't use baby oil?
Not in your forks, but it will stop your brake disks from corroding and prevent squealing. Might not prevent screaming, but that won't be from the brakes. 😁
One thing to mention for the Fox GRIP forks - that 4 wt/teflon oil they recommend does end up in the damper - I used fox gold at one point, assuming it was the same, forks felt awful. You definitely want the right weight in the damper side lowers
jack oil?
I couldn't afford the correct stuff and I had some leftover jack oil which I had used in a trolley jack. It displayed similar properties as the dirty oil I removed from the stanchions on my manitou forks plus it could handle 2ton of trolley jack abuse so I guessed it would be able to take my weight and a few bumpy trails! It did a good job and the forks live on 15years later with the same oil 🤔 as I'm pretty sure my brother hasn't changed the oil in the years he's had the bike? 😄
The last few posts suggesting you can use any old shite, (I'm paraphrasing, but jack oil? Really? That's for hydraulics)
What is a fork but a hydraulic damper?
Might do odd things to the damping depending on viscosity but it will not damage it
Ok, you have it your way. I've explained my reasoning and basis for my knowledge above, and stand by it.
Still wrong tho. How will a hydraulic fluid damage a fork? It might not work as well but it will still work fine
Do you even know if you are buying synthetic or mineral oil? Which is needed?
Makes no difference in dampers. Completely cross compatable
Okay.
I've been reading recently that Rockshox's current lower leg oil flavour of the month/year, Maxima Plush Dynamic Light, is formulated far closer to a vertical slideway oil (or may well just be a vertical slideway oil).
Motorex Supergliss is often talked about as an alternative, but doesn't appear very cost effective.
However, many other vertical slideway oils exist, and something around ISO 68 appears to be the go to for lowers. These are machine tool oils, have excellent lubricating properties to limit stick-slip, and are 'tacky' which ensures they in place longer on vertical surfaces. These features sound exactly like what you'd want in the fork lowers.
Some slideway oils specifically mention suitable for plastic coated slideways, which I would imagine won't be too dissimilar to the coated bushings in forks.
My next lowers service will be using a slideway oil.
I've been reading recently that Rockshox's current lower leg oil flavour of the month/year, Maxima Plush Dynamic Light, is formulated far closer to a vertical slideway oil (or may well just be a vertical slideway oil).
Motorex Supergliss is often talked about as an alternative, but doesn't appear very cost effective.
However, many other vertical slideway oils exist, and something around ISO 68 appears to be the go to for lowers. These are machine tool oils, have excellent lubricating properties to limit stick-slip, and are 'tacky' which ensures they in place longer on vertical surfaces. These features sound exactly like what you'd want in the fork lowers.
Some slideway oils specifically mention suitable for plastic coated slideways, which I would imagine won't be too dissimilar to the coated bushings in forks.
My next lowers service will be using a slideway oil.
I managed to find the SAE grade for the Plush Light oil, but not the Heavy variant - any ideas?
For context. The Maxima Plush oil specs (for light and heavy variants):
For context. The Maxima Plush oil specs (for light and heavy variants):
Interesting data.
The light variant viscosities would indicate it's close to a 0w-20 engine oil. Castrol and a few other brands oil of that grade appear to fit quite well.
A 46 grade slideway oil would also sit fairly close.
Might do odd things to the damping depending on viscosity but it will not damage it
How do you know?
Does jack oil contain EP additives? Do forks have any bronze fittings in them? What about seal swelling agents? Jack oil may well have some of those to keep your old trolley jack from leaking, they won't do your fork any good at all though. What about it's ability to cling to surfaces like bushings? Jack oil probably wasn't developed with that in mind. Detergents? Anti-foam? Newtonian flow characteristics? Temperature stability?
often the shape of the bottle is a give away,
If it looks like a duck, lays eggs like a duck, swims in the water like a duck, eats invertebrates like a duck, then it might still be a platypus.
Motorex who have the expertise and facilities to blend and package a fork oil may well make the Fox stuff, doesn't necessarily follow that it's exactly the same stuff.
Because its a hydraulic oil therefore will not damage a hydraulic system.
Unless it does / doesn't contain any any one of a number of additives that would break / enable a fork to do it's job.
By your logic why not put jack oil (or even fork oil) in an engine? After all it's just a hydraulic pump and some bushings? Why not put EP90 in your BSA gearbox? It's gear oil after all? The reason you don't (shouldn't?) is that EP90 can have additives that attack yellow metals (e.g synchro rings), but then not all EP90 does (GL4 less likely than GL5 but even that isn't set in stone). There's dozens of reasons why the wrong additives or no additives would cause issues in a system.
It MIGHT work, in the same way I MIGHT not break a leg jumping out of a window. It might even depend on the specific fork and window! But with the ludicrous prices of forks these days why would you use something that even with a modicum of knowledge about oils and additives could be very wrong?
Remember when I said I was no expert, but knew when to get better advice? ☝️
Very good TINAS.
Motorex who have the expertise and facilities to blend and package a fork oil may well make the Fox stuff, doesn't necessarily follow that it's exactly the same stuff.
In this case, it definitely is the same stuff. Same with the silkolene.
