M1 0w40 as Mountain Bike Fork Oil

[wavinwayne]

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?

 

[bruce381]

I'd guess very stiff ride.
bruce

 

[wavinwayne]

bump

 

[rpn453]

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.

 

[Hootbro]

I would have used what was recommended. Motor oils are built with lubrication qualities first and hydraulic second.

Hootbro

 

[ShortBuSX]

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]

 

[wavinwayne]

You guys have scared me. I'm dumping the M1 tonight & putting the recommended stuff back in.

 

[ShortBuSX]

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.

 

[ShortBuSX]

Only problem with that is whats the weight? Most MTB suspensions call for 7, 10 or 15 weight.

 

[bulwnkl]

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.

 

[wavinwayne]

I drained the 0w40 & re-filled the fork with Suzuki 5wt fork oil. Ahhhhhhhhh, now I'll be able to sleep tonight.

 

[rpn453]

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.

 

[rpn453]

I just came across my Marzocchi service manual and it says:

quote:

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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.

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So I guess I'll avoid motorcycle oils for these particular forks unless someone can provide more insight.