Skylark Posted February 25, 2014 Share Anyone try 2.5wt damper oil in Rockshox Forks, just to clarify thats approx 7 cST @ 40 deg fork oil, Rockshox factory oil is Maxima Racing Fork Fluid 85/150 5wt Fork Oil 15.9 cST @ 40 deg. I have found some Putoline HPX 2.5wt 6,74 cST @ 40 deg for R140 a Litre at the local Hoda-Wing motorbike shop. Some say if you are not to heavy its a good way to tune the fork, I'm 70kg, it allows the forks to respond faster making them feel smoother over small chatter. From what I understand 2.5wt will speed up both rebound and reduce compression damping, mainly on the low speed side of things. Anyone actually tried it? Edited February 25, 2014 by Skylark Link to comment Share on other sites More sharing options...
Brighter-Lights Posted February 25, 2014 Share I've been using Castrol 2.5w fork oil in forks and rear shocks for 5 years - no issues.. main reason was to have more responsive suspension for a lightweight rider without modifying the shim stacks. BTW the Castrol was R25 for I think 900ml at auto store. Link to comment Share on other sites More sharing options...
Skylark Posted February 25, 2014 Share I've been using Castrol 2.5w fork oil in forks and rear shocks for 5 years - no issues.. main reason was to have more responsive suspension for a lightweight rider without modifying the shim stacks. BTW the Castrol was R25 for I think 900ml at auto store. I couldn't find castrol below 10wt and it was R80 for 1L, where did you find it - R25 is the bee's knees! How did the forks respond with 2.5 compared to 5wt, what modification did it do to the travel, I'd think better small bump low speed response, how does it affect the big hit response when the fork is under hard compression further up the travel? Edited February 25, 2014 by Skylark Link to comment Share on other sites More sharing options...
Hairy Posted February 25, 2014 Share Anyone try 2.5wt damper oil in Rockshox Forks, just to clarify thats approx 7 cST @ 40 deg fork oil, Rockshox factory oil is Maxima Racing Fork Fluid 85/150 5wt Fork Oil 15.9 cST @ 40 deg. I have found some Putoline HPX 2.5wt 6,74 cST @ 40 deg for R140 a Litre at the local Hoda-Wing motorbike shop. Some say if you are not to heavy its a good way to tune the fork, I'm 70kg, it allows the forks to respond faster making them feel smoother over small chatter. From what I understand 2.5wt will speed up both rebound and reduce compression damping, mainly on the low speed side of things. Anyone actually tried it?Heard very good things RE the Putaline ... PING Droo Link to comment Share on other sites More sharing options...
droo Posted February 25, 2014 Share 7 cst is super light. You're correct in thinking you'll speed up the low speed compression and rebound without making much difference to the high speed. You should notice better small bump sensitivity if you're a light rider, but it may affect your lockout and you may find yourself blowing through your travel. Hairy 1 Link to comment Share on other sites More sharing options...
Skylark Posted February 25, 2014 Share What is the relation of the damper fluid weigh to sag/rebound/compression damping? What does it do to the tune of your fork? Edited February 25, 2014 by Skylark Link to comment Share on other sites More sharing options...
G00SE Posted February 26, 2014 Share Shouldn't affect the sag - that's determined by the air pressure in the air spring.It will affect rebound and compression, But I think droo answered that one already. Link to comment Share on other sites More sharing options...
Skylark Posted February 26, 2014 Share I'm sure sag is affected to some degree by the rate of compression damping?How would going 2cST higher affect things? Yamalube 5wt is the closest to factory weight I can find and it's 2cST heavier than factory spec. Edited February 26, 2014 by Skylark Link to comment Share on other sites More sharing options...
droo Posted February 26, 2014 Share I'm sure sag is affected to some degree by the rate of compression damping? Nope. Air pressure affects sag. The end. (Unless you're locked out, in which case nothing will affect it.) How would going 2cST higher affect things?Yamalube 5wt is the closest to factory weight I can find and it's 2cST heavier than factory spec. Bel-Ray 5wt @ 17.1 works great, as does Motul 5wt @ 18.2. RS factory oil is Maxima 5wt @ 15.9. Link to comment Share on other sites More sharing options...
GoLefty!! Posted February 26, 2014 Share 7 cst is super light. You're correct in thinking you'll speed up the low speed compression and rebound without making much difference to the high speed. You should notice better small bump sensitivity if you're a light rider, but it may affect your lockout and you may find yourself blowing through your travel. depending on the prefered settings, the oil may also cavitate which will wreck the shim stack. this oil will only loose viscoity as it warms up. What is its VI? Link to comment Share on other sites More sharing options...
GoLefty!! Posted February 26, 2014 Share I'm sure sag is affected to some degree by the rate of compression damping?How would going 2cST higher affect things?Yamalube 5wt is the closest to factory weight I can find and it's 2cST heavier than factory spec. compression damping will only affect how fast maximum sag is achieved.Compression damping can affect the upper end of your spring rate curve but you're not interestd in that while you stnding still unless you like to bounce your frint wheel and fork in the parking lot to show everyone how "plush" your set up is :Rollseyes: 2cSt higher means nothing if you don;t know the VI of the oil. The fork oil is only at 40C at the start of the ride. the momoent its starts workign the tmeperature in the oil will start to climb uless you have a heat exchanger in there somewhere What is the viscosities of the Yamalube at 40 and 100? what is its VI...? Link to comment Share on other sites More sharing options...
droo Posted February 26, 2014 Share depending on the prefered settings, the oil may also cavitate which will wreck the shim stack. this oil will only loose viscoity as it warms up. What is its VI? Also true. From the Putoline data sheet, VI is 458, making it 3.01 cSt @ 100. Maxima, which is what RS uses as factory spec, is 15.9 @ 40 and 3.51 @ 100, VI 150. Your thoughts on the cavitation issue with these numbers? As far as I understand, VI isn't nearly as critical in forks as it is in shocks due to larger oil volumes - although there's not a whole lot of oil in some cartridge dampers - but RS dampers take around 120cc depending on the model. Can't find any data on the Yamalube stuff beyond what's been mentioned already. Link to comment Share on other sites More sharing options...
GoLefty!! Posted February 27, 2014 Share 3cSt at 100 is on the low side but shoudl still provide sufficient cavitation protection. I am assuming the Putoline has an antifoamant in the additive package?One last aspect to consider is the water shedding ability of the oil. A lower viscosity at 100 will shed any water easier. this but this can also give rise to cavitation snce the water component will boil off at 100C depending on whether the fork is extended (pulling low pressre on the oil and boiling point of water reduces. Designof the shims stck is also a factorso best bet is to try the 2.5 out; down a few Dh runs with it and strip and inpect the shim stack. When developing fork oil years ago I picked up cavitaiton in MX forks with viscosities below 3.5cSt at 100. theffect was largely dependant on the compression damping circuit. Some forks showed problems others not over a 100 hr test Link to comment Share on other sites More sharing options...
Skylark Posted March 4, 2014 Share Can someone correct me if I'm wrong, from my google searches this what I have found about fork oil weights and your forks tune: If at your required fork sag, say 25%, you blow through the travel too quickly then use a heavier wt oil, if you can never get through your travel at your required sag then go lighter wt oil. Does that sound right? Link to comment Share on other sites More sharing options...
Skylark Posted March 5, 2014 Share Just checked with Castrol SA , they don't sell 5wt fork oil anymore due to low demand only 10wt.The cST on the castrol 10wt is 22 compared to the RS spec oil of 15,9 - how much will that difference affect things? Link to comment Share on other sites More sharing options...
droo Posted March 5, 2014 Share Can someone correct me if I'm wrong, from my google searches this what I have found about fork oil weights and your forks tune: If at your required fork sag, say 25%, you blow through the travel too quickly then use a heavier wt oil, if you can never get through your travel at your required sag then go lighter wt oil. Does that sound right? True for orifice dampers, but less so for shim stack dampers. RS dampers are hybrid, with orifices controlling the low speed and shims controlling high speed. So you'll boost low speed compression and rebound but without affecting the high speed too much, which is what would stop you from blowing through travel. As for using a 22 cSt oil, it won't do much more than move your rebound adjustment range a bit to the slower side and firm up LSC a bit. Try it out and see what happens. At worst you've spent a buffalo on an experiment. GoLefty!! 1 Link to comment Share on other sites More sharing options...
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