Synthetic Fork Oil?????

[DennisDarrow]

Time to change the fork oil and bleed the brakes. Yes, I understand about getting a NEW container of DOT 3 or 4 brake fluid for my 75 R90/6. So no problem there.

Went to get fork oil at the local MC supply outfit. They are an independent with a very great rep with advice and mechanical work on all types of bikes. Anyway, all they had for fork oil is "Fuchs Silkolene" synthetic. They advised that it is the best available.

The question is: For me, on these older type engines, trans, gaskets, etc, that some folks report seepage/leaks past seals and stuff when they switch over to synthetic. This ol thing never leaks a drop of anything so am wondering what is thought about synthetic fork fluid and seals.

Any thoughts would be welcome, as I am not gonna add until tomorrow; but do have it draining right now.............Thanks guys.......Dennis

[ccolwell]

I would, but then I use synthetic in the engine, trans and drive train. Don't ride the R90S enough to make any claims to knowledge, but I used synthetic in the same places on my '84 R100 and never had a problems.

[alkoivisto]

I've been using locally produced synthetics in my '81 R100 and my old Brit bikes for just about four years now without any problems. Doing engine oil changes every 6000 miles on R100. All other lube changed once a year. R100 does about 15,000 miles per year. When I pulled plug on final drive at end of last year it was absolutely clean. Zero leaks anywhere as some predicted. My son's '71 R60 had final drive spline area leak which actually disappeared after a couple thousand miles of synthetic use. Go figure. Brit bikes another issue as they just leak faster than they did before. OEM anti-corrosion feature I guess. I am going to extend oil change interval and get sample tested mid season to find out condition.

BTW, my son works for this local manufacturer so I was pretty much stuck using it. Old wive's tales about synthetics now tossed out the window.

[DennisDarrow]

Guys.........My mind is already convinced about sticking with dino in the engine and driveline....................

Am asking about the synthetic useage in the forks..................thoughts there.......???????????

Surely not to start another inane thread about Dino vs Syn..............Just have never seen discussion here about the forks..........Surely dont want leakage that doesnt exist now........Have been using ol Castrol stuff for years but it is all gone now.............

Thanks.........Dennis

[alkoivisto]

Guys.........My mind is already convinced about sticking with dino in the engine and driveline....................

Am asking about the synthetic useage in the forks..................thoughts there.......???????????

Surely not to start another inane thread about Dino vs Syn..............Just have never seen discussion here about the forks..........Surely dont want leakage that doesnt exist now........Have been using ol Castrol stuff for years but it is all gone now.............

Thanks.........Dennis

Right-O. Absolutely am not diving into Dino/Syn. Been there, done that here at home.

I've used Shell Rotella in years past and still use it my 225,000 mile Suburban, tractor and other equipment. Good stuff.

I guess I meant forks also. I change yearly also. No problems to date. My observation fork action more consistent from hot weather to cold weather. Can't detect any real difference in stiction. My own personal opinion is a seal in borderline condition can control lubricants that maintain viscosity over wider temperture range, that is when it's cold, seal lip can still scrape off oil.

My experience only.

BTW, synthetics in my Norton forks made a world of difference.

[alkoivisto]

Like...????

There is absolutely no good reason that will warrant the higher cost of synthetic oil in the forks. You are going to run 5W or 10W in the forks and it will probably last five-some years. I have never met anybody who changes fork oil every year.
And IF you would, it makes even less sense to spend the money on synthetic.

Re: Norton forks. I own two 1972 Commandos. Side by side comparison with one having 20 wt synthetic and other with 20 wt Belray, MY experience PERIOD, fork action was superior with the synthetic. I've rebuilt forks on both and conditionwise they are identical. The extra cost for synthetics versus standard lubricants is negligible in the whole scheme of things. If I really wanted to economize I'd drink cheap beer and cheap scotch anyway.

Regarding fork oil changes on my R100, no seal is absolutely perfect. If they leak a little bit, they're going to suck a little bit. You have constant extreme pressure changes while in operation, especially up here on northern Mn area roadways. For me to ride 75,000 miles on same oil would be crazy. After 15,000 miles it is definitely crappy looking. Your fork is basically a little hydraulic system without a filtration system. That little bit of oil does a awful lot of work in one the most important parts of the bike. No place to go cheap! I myself know of no one around here who does not change their fork oil on a annual basis. You are certainly free to do as you wish.

Besides, like I said earlier, my son works for the local mfr and this enables me to get it at his discount. Keeps the money local and supports local jobs.

There, I've said my piece.

[riderR1150GSAdv]

Since you will more than likely replace the old seals, I think that Syn fork oil would work for you. The question really is if you want to spend the extra $$ on the syn oil?? Only you can answer that.
YMMV

[lostboy]

What is the brand name of that "locally produced" synthetic?

[DennisDarrow]

Thanks Alkovisto for the thoughts, concerns, and reality............

RiderR1150.......Am not planning on having to change out the seals right now, that is the purpose of this thread, to see if I could use the synthetic without having a bit of leakage......I guess we shall just see..........

imarnr....Mike........I dont pretend to have a stable of motorcycles at my disposal; but I do quite a bit of maintenance on farm equipment here, and the thing that I have found that keeps these old jewels running is to not think that I know more than the engineers that designed them. Page 24 of my owner's manual advises, "oil change every 10,000 miles or each year." At any rate, do what YOU do and thanks for the thoughts even though I am gonna follow what the engineers advise when it comes to maintenance.

Actually, I was hoping that Paul Glaves might pipe in here or a couple of the guys that truly know what is going on and dont just post to see themselves in print...........

Guess I will go ahead and forge on with the synthetic. Thanks anyway guys...........God Bless.......Dennis

[Rod Sheridan]

Like...????

I have never met anybody who changes fork oil every year.
And IF you would, it makes even less sense to spend the money on synthetic.

Hi Mike, my name is Rod and I change fork oil during spring maintenance, every year.

Regards, Rod.

P.S. I agree, I don't use synthetic oil.

[alkoivisto]

What is the brand name of that "locally produced" synthetic?

Amsoil.

[R80andR100RT]

I'll sacrifice and pay for the good old BMW fork oil. In my R80 I last replaced seals in 1986 which leaked because I put Shell Aero in them. Since then I have used only BMW fork oil. Added boots in 1993 and still no leaks 23 years after the seal replacement.

[alkoivisto]

Front fork oil has no lubrication duties???? What do you have for bearing surfaces?
You're saying I can run without any fork oil at all and result will be just a bouncy ride?

BTW, I've been twisting wrenches since I was a kid. I have designed and built hydraulic systems since that part of what I was trained to do in early 70's. I formerly worked as mechanical draftsman and designer. I also learned from my dad, a retired heavy equipment mechanic who in the 50's built one of the first all hydraulic pulpwood loaders in the area.

So there...!

[alkoivisto]

Wow!! I hope all you guys who change your fork oil every year also buy a new helmet every three years (because it is unsafe to use it any longer, the "engineers" who design them say)
I really must not read my service manuals right but I can't find a recommendation to change the front fork oil every year in any of them.
Here are some other thoughts: I appreciate the short tutorial about the "hydraulic system" that is a front fork. I do know them well, I work in power steering:violin
Both hydraulic brake and power steering systems differ significantly from a hydraulic fork, however, inasmuch as they are hydraulic work systems and a fork is a damping system. In a brake and power steering system, the fuid is "compressed" (fluids are non-compressible, btw) to perform work. In a fork, the fluid is moved through different diameter orifices to slow down a piston. By pushing the fluid through small holes it is resisting the piston's axial movement. Anybody any idea what the pressures actually are?? The are no "extreme pressure" cycles in a front fork! A power steering system sees 2,500 PSI max and each pumping cycle under no steering load gets the fluid continuously up to 70-80 PSI plus the heat generated through losses in a pump can reach 230F. In spite of this, we frown on frequent fluid changes because the debris introduced by disturbing a closed system does more damage in the long run. Brake fluid is supposed to be changed every year because it attracts moisture and the temperature cycles that occur due to pad friction are the bad part.
In a hydraulic system that has no or little lubrication duties (e.g.; a front fork) the advantages of a synthetic fluid over mineral based fluid can not be substantiated and there is no characteristic of a synthetic fluid that would cause or support this.
How does a 10W synthetic fluid dampen different than a 10W mineral oil based fluid?
A final question: As the rear shocks are basically the same system as the front fork, are you changing them also every year because the fluid in them is really "crappy" :scratch :scratch



Wasn't my intent to turn this into a argument. I'm simply stating what has worked for me. I'm not trying to change your mind. A close friend of mine is a retired municipal fleet mgr and feels synthetic lubricants are all garbage, yet local fleet owner ( + hundred over the road semis)we do work for swears by synthetics. I will go my way and you can go yours.

[alkoivisto]

Reading sometimes helps: ..or little lubrication duites (e.g.: front forks)..and what bearings exactly do you have in a front fork that need lubrication by the fork oil???

Sliding or plain bearings, sometimes known as a bushings, similar in operation to a shell type bearing such as a rod or main bearing. I'm assuming you've had forks apart? There are some exceptions such as my T-160 Trident where aluminum fork lowers bear directly on fork tubes. Try that without oil.:scratch

[fabiox]

no synthetic oil use only mineral