Fork oil volume?

[Crisis management]

Does anyone know how to calculate the air volume for a fork? I'm rebuilding the NZ250s forks and rather than just guessing (worked ok last time) the oil / air volume of the forks I though I may apply a bit of science. The forks are old (1986) damper rod units, so how do I calculate the oil height in the legs?

Wild guesses and useless suggestions are also welcome, I'll distill the good stuff from it!

[Henk]

Fork oil height is usually listed in the manual but since you are asking I guess you don't have one.
I'll have a look in the FXR manual and see what they suggest tonight 220mm comes to mind but also seems wrong.

[Crisis management]

It's not an FXR Henk.....

[Henk]

It's not an FXR Henk.....

I know but fork length should be quite close so similar air gap should work.

[Crisis management]

I know but fork length should be quite close so similar air gap should work.

You're smarter than you look aren't you?

That's good thinking, thanks, I'll get that off you when I pick up the slicks tonight.

[F5 Dave]

an old rule of thumb was 6" from the top compressed with no springs. Then add a bit if its too soft on bottoming.


bit like all generic rules, its pretty crap.

[Crisis management]

an old rule of thumb was 6" from the top compressed with no springs.

Ok, so thats 9 & 27/64ths of a fluid ounce per leg then?










It appears I am overthinking this, I've been reading too many White Power manuals lately. :crazy:

[RDjase]

100mm? + or - 10mm seems to work ok in my RD350 with 32mm forks, the KR150 with 33mm forks and the FXR with 33mm forks.

1mm of height is about 1cc of oil with these size forks

I make spacers to set the sag and muck around with oil heights to suit bike weight, rider etc Get your rebound feeling good by the fork oil weight/grade and do the compression/dive by the oil/air level

Pretty sure its 100mm . been a few years since I have done much on them. Spent alot of time getting the KR150 Streetstock set up for Tyler

[pete-blen]

Does anyone know how to calculate the air volume for a fork?


Yes I do...
Forks are hard to get a true volume from a calculation because of all
the componets in them displaceing volume...

3.1415927 x radius x radius x length = volume in CCs.

try filling one with oil then tipping it into a calabrated bottle or what ever..

[tri boy]

As others have said,
100mm + or - a bit should be fine.
More importantly, if your on the track, and you are running last, we need pics:nya:

[Crisis management]

As others have said,
100mm + or - a bit should be fine.
More importantly, if your on the track, and you are running last, we need pics:nya:

Thanks everyone... especially this prick.

Ya bastid, how did you know I was last, who's been telling? :mad:

Wait till next month Brett, I've got the inaugural R80 on Pukekohe adventure, what can possibly go wrong?

[davebullet]

Probbaly too late but the Suzuki GT125 service manual says 125mm and the stanchions are 30mm diameter

[Akzle]

i always crank the volume to 11.

[jasonu]

i always crank the volume to 11.

Do you even know what a motorbike is?

[Akzle]

Do you even know what a motorbike is?

what's a is?



(fuck you yankee doodle)

[crazy man]

what's a is?



(fuck you yankee doodle).......Donut