Which oils for Fox ...
 

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[Closed] Which oils for Fox 36 lower leg service?

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Reposting in Bike forum as no response on Chat.

So looking at the fox Oil charts for the 2021 36’s they now spec different oils to last time I did a LLS =
Damper side for Grip2 – 5wt Teflon infused (40cc)
Air side = Fox 20wt 10cc

From previous advise (probably on here) I’m currently holding various Torco Oils with some notes on them –
Torco MTF (trans fluid) – Fox Foam Rings
RSF (medium) – Fox
RFF 7 = RockShox 5wt
RFF 20 = RockShox 15wt

Any advice on which to use where on the current fork? I’m thinking use the two RFF fluids. Since these are simple bath oils and don't do anything to the damping I'm slightly puzzled they use different weights in each leg anyway.


 
Posted : 02/02/2022 11:33 am
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The Grip2 damper is not a sealed damper, it’s more like a open oil bath with an IFP, with oil bleeding off above the IFP into the lower leg and refilling the damper from the lowers oil.
Whether mixing the oils will effect the damping is another matter.


 
Posted : 02/02/2022 11:42 am
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I'd want the fox 5wt in the damper side, and not be too bothered about what's in the other side.


 
Posted : 02/02/2022 11:44 am
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The 5wt Teflon-infused isn't just bath oil - it's also the oil used in the Grip2 damper and there's a mechanism in that that dumps excess oil into the lowers/sucks up additional oil.

The 5wt in the damper side and the 20wt Gold in the air side have always been the oils for the 36 Grip2 (or at least that's what it has been since 2018).

I wouldn't use non-5wt TI in the damper side. Actually - I wouldn't use non-20wt Gold, either.

You can buy small quantities off of Ebay - cheaper than bulk in the short term, and TF Tuned do 35mm foam rings for a few quid a pair.


 
Posted : 02/02/2022 11:48 am
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Thanks. Have done a bit more research on the back of this -
https://us.wplbike.com/blogs/news/suspension-oil-comparison-wpl-vs-fox-and-rockshox

Teflon infused anything seems to be a bit of a snake oil thing and RS 5 is very close to Fox 5. So I'll end up with slightly thinner Lube oil in the air spring side but basically the right stuff in the damper. They'll get a full service in another couple of months anyway but they feel a lot smoother to how they did before. I'll stick the shockwiz on and see if it thinks the damping has changed...

Fox Grip2 damper:
https://cyclinic.com.au/blogs/suspension/fox-36-fit-grip-2-updates-into-2019

"The IFP system is a good thing is due to it's dampening consistency and reliability. It allows the damper to perform much like the RC2 FIT damper, but when the damper is getting 'worked' with either long hard 'shuttle runs' and general heavy use, it can self-regulate its damper pressure by 'spitting' excess fluid from the damper, back into the lowers for re-circulation. It does this via a spring-loaded piston (the IFP) towards the top of the damper that seals fluids from escaping in normal riding conditions. Under heavy riding conditions / heavy use, the piston moves upwards towards the top of the damper as the oil pressure and volume increases. At a point in which the spring-loaded IFP moves up along the inner damper shaft, it meets a 'scalloped' out section of inner shaft (see pic below) that allows the excess oil to flow past. A small bleed hole in the high-pressure outer chamber tube then allows this fluid back into the lower leg 'bath'."


 
Posted : 03/02/2022 11:41 am

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