M1 0w40 as Mountain Bike Fork Oil

Messages
7,550
Location
North Alabama
I just replaced the rebound damping oil in my mountain bike air fork. The fork is a 2003 Manitou Black Super Air, that calls for 10wt. Manitou fork oil. Just for kicks & giggles, I used M1 0w40 instead. I have not ridden the bike since I changed the fork oil. The viscosity of the M1 at 40°C is roughly 2.5X that of 10wt fork oil. What type of performance differences should I expect from the M1 0w40 vs 10wt fork oil?
 
Messages
4,844
Location
Saskatchewan
My buddy and I rebuilt his older Marzocchi (an XC500, I believe) using 5W-30 back in university. I think it called for 5wt or 10wt fork oil. It seemed to work fine. Don't know about long-term or fine-tuning issues though. My Marzocchis see temps of -5C up to +40C (I use a rigid fork in winter), and they certainly stiffen up in the cold. I'm sure the difference in viscosity due to that is much more than by switching to 0W-40. I just open the valves a little more when it gets cold. I'd probably use a 0W too if I did it now to reduce thickening in colder weather.
 
Messages
2,857
Location
DELAWARE
I would have used what was recommended. Motor oils are built with lubrication qualities first and hydraulic second. Hootbro
 
Messages
392
Location
Central Florida
Id say youre heading for a cartridge blow out...fork oil isnt really cheap @ about 10 bucks...but a cartridge is much more expensive...good luck with that! [edit]I just reread your post...its an air fork too? I think youre relaly asking for trouble...I think you would have been much better off with not even servicing it.[/edit]
 
Messages
392
Location
Central Florida
BTW you can ususally goto a motor cycle shop and buy fork oil, for less than a bicycle shop sells it for...usually for less than 10 bucks you can get a full quart of the proper weight youre looking for.
 
Messages
2,187
Location
Arizona
WW; a dirt bike shop should have all kinds of suspension oils for $7-9/qt. I bought some Redline for either $8 or $9 a few months ago from the local shop. A 0W40, if used in dirt bike forks, for example, will slow rebound down immensely and make compression much harsher/stiffer compared with ideal/very good settings with your dialed-in oil weight.
 
Messages
4,844
Location
Saskatchewan
Now that I actually think about it, you guys are right: motor oil certainly isn't the best choice. But what about ATF like Dexron III. The back of this jug (Tech 2000) calls it an "excellent anti-wear hydraulic oil for applications requiring good low-temperature fluidity"? I would prefer to use something that won't thicken as much in the cold as regular fork oil if I can get away with it.
 
Messages
4,844
Location
Saskatchewan
I just came across my Marzocchi service manual and it says:
quote:
Marzocchi oil item 52.5 or Finish Line Shock Oil are the only Marzocchi approved shock oils. Using other mountain bike suspension fork oils or motorcycle fork oil is not recommended and will void the warranty. Many motorcycle oils contain seal additives that will damage the seals and O-rings causing seal failure and possible damage to the fork.
So I guess I'll avoid motorcycle oils for these particular forks unless someone can provide more insight.
 
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