Fork fluids whys why nots

Famous racers like homeslice have compliled a list of many decidated fork oils to definitiely state no company rating seems to match any other and almost none of them match the vicosity on label so its trial and error selection rather than much logical number following. I've tried a few alternatives in Peel modified Roadholders, fork oils 20 to 10 grade too stiff then ATF a tad too thin for off road so settled on brake fluid for the most intense flings in my life. I tried DOT3 in Trixie but too bouncy/jaring and found brake fluid is so hydrophilic internals rust to restrict so put in Rotella 15/40 and happy with that long term in factory roadholders. Except for the rust preventives *has any one run into any downsides of non-fork fluids? I'm thinking maybe air compressor oil might be worth trying. I've also mixed up fluids like the 20+10 for 15ish grade w/o issue in case others so tempted. No one grade can fit all fork internals, surface conditions or pilot mass.

My understanding of fork oils and its only thru recently taking up classic racing is:
1: the W number in most fork oils refers to weight and engine oil and has little to do with what forks do.
2: The action of the damper forcing the oil thru small holes causes foaming and foam does not damp, that's whay ATF and engine oil does not work for long.
3: twin tube shocks are not very good as the oil is in contact with air and gets contaminated when hot.
4: damping is converted to heat via the fluid
4amper rod forks have a fixed damping orifice and cannot cope with variable bumps.\
5: I am a convert to twin Ohlins shocks on my BMW racer and Nitron shock on my 900ss, for the Commando the Ikons will do for a road bike.

Hobut No one grade can fit all fork internals, surface conditions or pilot mass

very correct !!! a fat bloke will always require more damping than a thin one

i think you are searching for the perfect solution to a problem that changes on each and every surface you ride on

have you experimented with synthetic fork oils vs minerals

you can purchase 5/10/15/20W fork oils in Europe and most are available in both synthetic and mineral base
i would think synthetics are used to reduce friction levels and be less hydroscopic

Most racers accept that their suspension is set up and is only a compromise between the good and the bad. Tarmac racing has different forks / springs compared with an off road setup, which usually has a longer travel and softer springs e.t.c.
Fork oil is a matter of “try it and see” it is almost impossible to set the forks up for every bend, road surface e.t.c.
Some manufactures, like the Japs recommend ATF in some of their forks, and straight 10/12.5/15/17.5/20W oil in others.
Generally I find it slightly better to have too soft springs and pack them with spacers to suit myself, as I can also add or subtract 10cc of fork oil to suit.
Mixing equal amounts of 5 and 10w sae to obtain 7.5 w is OK but you can get them sometimes like;

http://www.ebay.co.uk/itm/Juice-Lubes-P ... 258b2742a9

http://www.ebay.co.uk/sch/i.html?_odkw= ... w&_sacat=0

Kal-Gard Smooth Stroke fork oil with moly has been my fave for 35 years. Unfortunately it's out of production. I found some 30wt, great in July/August, but too firm for spring/fall temps 40/50'sF.

Stateside ebay.com a quick search for Bel Ray shows weights of fork oil 2.5 to 30. No relationship
with Bel Ray just used their name as I know they make fork oil.

72combat lays down the college test cheat sheet to be pensive if getting one of em wrong.

Bernhard down and dirty guidence is more useful for my inquiry as tested Dextron II and liked it expect off road as much which could be the cavitation/areation 72 list high lights. Both reviews ease me and concurs to trial/error w/o much concern of hurting anything till just about right. I don't know that I can tell rebound from compression dampening just what scares me the least to test more till too much again.

Btw what good does an air pocket do in Roadholders if it just pumps down in a min or so? D/t this pump down its dicey to really find optimal level as just fill then bucking broncho.

from what I gather " packing out the springs" only adjusts the height/preload, the spring rate would remain the same.... :?:
I bought the Racetech Bible to get a better understanding of suspension, its pretty good.
Says stuff like there is not real standard for so called fork oil.
The air pocket acts as a damper as air can compress.
Lots to experiment with :mrgreen:

One of my Commando manuals recommends 5W30 for the fork oil which got me thinking: Why don't more forks call for a multi viscosity oil? Seems like it would take care of the difference in damping between hot and cold. Also might be less affected by hot and cold weather.

Foaming is a big problem in a lot of mechanical conditions and ATF is particularly good at not foaming up. Honda used to call for ATF in a lot of their forks - especially Moto Cross. I have seen hydraulic systems that call for 20W50 motor oil in them and then last for years and years. (Bobcat Zero Turn lawnmower drive system)
And, The "W" in multi viscosity oils stands for "Winter."

I plan to try some 10W40 in my forks and 20W50 as well. I'm sure someone else has tried this so any warnings won't be rejected.
Dan.

Yep sir on the good ole W not meaning weight so viscosity is actually a "grade" number. As fork oil don't get engine frying pan hot, all the oil listed above will not act like mulit grade just the lower cold thin viscosity grade number/value as poured out the can, ugh nowadays plastic jug. Its was such a bugger to add new fluid I put two holes in Peels alu fork caps, one for a tube off a big calibrated cattle syringe and the other to vent the displaced air bubbles out. I guess most of us won't ride much below freezing but I hope too play snowy hill climbs w/o gelled oil inside.

72Combat said:

from what I gather " packing out the springs" only adjusts the height/preload, the spring rate would remain the same.... :?:
I bought the Racetech Bible to get a better understanding of suspension, its pretty good.
Says stuff like there is not real standard for so called fork oil.
The air pocket acts as a damper as air can compress.
Lots to experiment with :mrgreen:

Click to expand...

Yes sir, quite right, but if you think about it for a minute, if the spring was too hard there is nothing you can do about it except change to a softer spring. A hard spring will just bounce over the bumps and not absorb the bump, whereas if you have slightly softer springs than you need, you can preload them to suit and they will still absorb some of the bump, without going over hard. (Without going to the added expense of obtaining harder springs.)
as you say, Lots to experiment with :mrgreen:[/

ATF is specified in quite a few forks by various manufacturers. I use it in my Fauth-modified Norton forks and have been very pleased with it. I had several Ducatis (900 SS, 916, 999) and ATF was the recommended fluid.

mike996, appreciate ATF feedback in Fauth fork kit as that's 2nd best I found in Peels after brake fluid. After seeing the rusting down side of brake fluid in factory Trixie forks I now think reason I liked it a bit more was less friction lowering than ATF so help dampening on Peels extremes of use. The reason I think such thin fluids work well in Greg's kits is the thicker damper rod in tighter damper cap. So far I'm only one I know of that's tappered the rod section that moves in cap at loaded sag level and about an inch above/below this for nil dampening of ~2" road nuance texture absorbing. Thinner the fluid the faster forks can react both ways. As little as we hear online about Fauth Fork Kits he's told me a few years ago the kit price had to go up as world wide supply of Ford 8N/9N valve springs sold off so only new production left. One could trial/error other spring spacers of course.

Anyone know the fluid grade of the hi end race elites?