Fork oil capacity 2000 RT

[mrduck]

Changed out the fork seals,new oil at the local tech recomended level, , now something doesn't feel right, feels way too stiff. Tried loosening every thing up,pumped the front up and down, still feels the same.

Anybody know how muck oil is called for in each leg?

 

 

 

 

Thanks

Don J

[ianboydsnr]

it should have 0.47 litre of oil in each leg.

[T__]

Changed out the fork seals,new oil at the local tech recomended level, , now something doesn't feel right, feels way too stiff. Tried loosening every thing up,pumped the front up and down, still feels the same.

Anybody know how muck oil is called for in each leg?

 

 

 

 

Thanks

Don J

 

 

 

 

Don, assuming you got all the old oil out then installed the correct amount of oil (.45 liter) there are a couple of reasons the front end could be stiffer..

 

The first would be the new seals are gripping the fork tubes causing a drag or stiction on the fork tubes.. It doesn’t take much seal drag to cause a harsh ride on a somewhat smooth road.. If your problem is more pronounced on smooth road than over larger bumps probably suspect a seal drag problem or fork alignment problem..

 

If your problem is more noticeable on larger deep bumps (like large swells or large raised bumps) then maybe you ended up with too much air in the forks above the oil.. Or too much oil in the forks.. In either case the air compresses as the forks near jounce & can cause the spring load to rise considerably near full travel.. ..

 

Maybe try loosening the front wheel axle slightly then riding the bike up & down your driveway while braking the front wheel.. That will help center the forks & hopefully remove some side load off the fork bushings..

 

If you added air to the front tire while working on the bike maybe re-check that against a KNOWN GOOD gauge..

 

Twisty

 

[smiller]

Maybe try loosening the front wheel axle slightly then riding the bike up & down your driveway while braking the front wheel.. That will help center the forks & hopefully remove some side load off the fork bushings..

This would be good advice for bikes with a standard fork front suspension but on the 1100RT the forks are rigidly mounted to the plate at the telelever ball joint and can't move in relation to one another no matter how loose the axle is.

 

I would guess that you either have trapped air or too high a fluid level. Also the fluid should be of very low viscosity as it has (or should have ) nothing to do with damping, it's there just for lubrication and not much else.

[Andy Johnston]

You have to "bleed the forks of any vacuum or pressure in the no load position after installation" quote from Haynes manual.

[Anton Largiader]

It's still good advice, but you can go farther. For one, the axle should spin freely in the sliders when the pinch bolts and end bolt are loose. If the axle was installed incorrectly you may see the fork legs spring apart a bit when you do this. Also, I always fit the axle, spin it while snugging the pinch bolts and THEN tighten the fork brace bolts. There is a bit of slop in the position of the brace, and you can bolt it into an unnatural position if you do things in the wrong order. Then the forks can bind.

 

As for oil level, 470 is the spec (and I do use 470) but really I think it doesn't need to be anywhere near that much. Due to what I suspect is a mixup in specifications, many R1100S owners are using an old, much lower fork oil level and I don't see people wearing out those fork tubes due to lack of oil. Some bikes take even more than 470; that's at least a pound and a half of unsprung weight.

[T__]

Seth, well BMW doesn’t feel that way as they do suggest stroking the forks a couple of time before tightening the axle attachments..

 

The fork bridge attachment is only as good as the parts are machined to mate with each other.. If there is any angular discrepancy the lowers won’t be at the correct angle to follow the uppers through full stroke.. I think the idea behind the stroking is to force the lowers to move a little on the axle to obtain the correct spacing to allow smooth stroking..

 

That fork bridge isn’t exactly a well secured piece with only 2 screws on each side ( a pretty good hinge there yet).. Plus if the fork lower spacing isn’t controlled when the bridge bolts are tightened who knows what the lower spacing is at assemble time..

 

 

 

 

From the manual----

- Apply a light coating of Molykote paste to the

quick-release axle/install it.

-Tighten retaining screw (1).

-Press forks down firmly several times.

-Tighten clamping screws (2).

-Install brake calipers.

-

 

 

 

 

 

Twisty

[T__]

Anton, probably not so much that the oil level will damage anything but the amount of oil effects the volume of air above the oil in the fork.. That air volume is part of the spring package as it effects spring load as air volume decreases at or near fork compression..

I would imagine you are looking at a pretty decent air pressure across the area of both fork tubes at or near fork compression..

 

Twisty

 

[smiller]

Mea culpa, it is possible to bind the legs if you really mess up or ignore the tightening procedure (but it must be fairly difficult as I've never managed to do it in countless changes. ) Regardless, if you're experiencing binding bad enough to be obviously felt after fork installation and don't loosen the fork bridge bolts as well (as Anton describes) then I don't think messing around with the axle alone will be very effective. What I meant to communicate but did a poor job of it.

[Anton Largiader]

Assembled properly, there is no internal pressure under full compression. Assembled improperly, it's a really small component. Maybe five pounds of force per fork leg? It's easy to simulate when the fork is apart.

[T__]

Anton, there has to be pressure build at compression as neither fork is vented to atmosphere.. Unless they are initially bled at full compression there will be an air volume decrease with corresponding pressure increase as they compress..

 

Twisty

 

[Selden]

True, but depending on where in the suspension stroke you close the bleed screw, you can have anything from negative to positive pressure. BUT, it's hard to believe that the seal would be so perfect that, over time, there would not be enough leakage for the internal pressure to equalize with external. Certainly this is the case with my wife's old VTR 250, which has air caps on the forks; air pressure has to be checked periodically, just like with a tire.

[Anton Largiader]

I do bled them at full compression and surprisingly that partial vacuum remains for a long time.

 

But as I said, anyone who wants to assess the spring force component of the air chamber at various configurations can test it very easily. Keep in mind that when the suspension is compressed there is probably 500+ pounds of spring pressure at work plus the hydraulic resistance within the shock (which I think is even greater than the spring) so you might have to think really hard to come up with a scenario in which the air chamber has an effect.

 

Yes there are some forks where the air chamber is a designed part of the suspension, and they are even pressurized to specific levels. I haven't seen anything indicating that these forks (with their no-tech internals) fall into that camp.

 

However, I don't mean to say that changing the air pressure or the fork oil level won't have an effect. I know of one case where a racer felt that the bike turned in better with less fork oil, due to less air chamber. I suspect there was more to it than that, since the air chamber can be eliminated by other means and less oil will mean less internal fork friction, but I wasn't there for the testing.

[mrduck]

Thanks to all for the advice,

we found that simply taking the brace across the top of the fender and the pinch bolts on the fork leg loose, then bouncing it a few times did the trick.

 

 

Thanks again

Don J