[brianinmaine]

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What if I just use 30W non-detergent as fork oil. What could it hurt? Seems like it would be fine if you can use ATF. Any thoughts on this? I just changed fork seals. 1 was aweful, 2nd was easy/no problems or leaks. First one didnt come apart well- the bottom bushing came right through the top bushing and being lazy/cheap, I put it back together without changing bushings. Mistake! Fork on that side was SHOOTING oil out. Now I get to do it again! Stupid, stupid, stupid me. Oh well. So why not a known viscosity oil like 30W instead of ATF, or do I have to buy fork oil? Seems like it's just the industry pulling a fast one on us all....

 

[twisty]

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brianinmaine wrote:

What if I just use 30W non-detergent as fork oil. What could it hurt? Seems like it would be fine if you can use ATF. Any thoughts on this? I just changed fork seals. 1 was awful, 2nd was easy/no problems or leaks. First one didnt come apart well- the bottom bushing came right through the top bushing and being lazy/cheap, I put it back together without changing bushings. Mistake! Fork on that side was SHOOTING oil out. Now I get to do it again! Stupid, stupid, stupid me. Oh well. So why not a known viscosity oil like 30W instead of ATF, or do I have to buy fork oil? Seems like it's just the industry pulling a fast one on us all....

brianinmaine, sure you could use 30 weight motor oil as fork oil, we have used it for years in our dirt bikes.

Problem is: 30 weight motor oil is MIGHTY thick to use as a fork oil in a road bike. It would probably leave an almost non existent ride quality in cold weather & could foam uppretty easily in severe ride control situations.

There is also a chance you could blow a fork seal in a large bump control situation in cooler weather.

I would think a 15 weight fork oil should work out very nicely with possibly a 20 weight for a front end with severely worn parts & warm weather.

Some of the problems encountered with using motor oil's are: some contain a seal swelling agent to keep seals soft, most canfoam up somewhat when forced through control orifices, most motor oils have a pretty large viscosity spread even in the same viscosity range, unless a premium synthetic the cold pour point is usually much higher than fork oil or ATF.

Twisty

 

[Renegade]

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Thanks Twisty... That's why I use only ATF for forks.. It's what the book recommends anyway..

We also used type A red fluid in large aircraft struts in the military. If it's good for the Air Force, it's good for my MC.

 

[Hobie1]

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Back in March, I re-built my forks top to bottom. I ordered some 15 weight oil from a respected vendor. I received a bottle of Spectra(I think) fork oil. You wanna know what color it is??? RED! Made me wonder a bit. The stuff works ok a little stiff perhaps with the new Progressives but the bike handles great. BTW, the PO apparently had rebuilt only one fork in the past as the oil looked completely different from one tube to the other. Some people, I swear.:baffled::goofygrin:

I don't see why ATF would be a problem as long as you use the same stuff in both tubes in equal amounts. Yes, you don't know exactly what viscosity it is but as long as it works who cares.

Hobie

 

[rcmatt007]

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I've always used atf fluid w/o any problems... just remember progressive springs want you to measure the level of fluid as they are thicker springs.

 

[exavid]

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When filling the forks that have Progressive springs, note the amount of oil it takes and from then on you can change it by volume and won't have to measure again. You'd have to allow a wee bit for incomplete drainage, but it wouldn't be much.

 

[Jason]

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Twisty is right, 30 weight is way too thick for a road bike, even a heavy one like the Wing. 20 weight at the most, 15 is ideal and 10 is too light, all just my experience of course.

 

[brianinmaine]

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OK, I'll just stick with ATF, I guess. Thanks for all the replies!