Front Fork Oil Level

[Strada-Stu]

Hello All,

Can anyone tell me the recommended oil fill level for a Strada's forks?

I appreciate that the manual indicates 200cc of oil is required per leg but I'm hoping to simply check and if necessary, top up the legs without draining the existing oil.

Thanks in advance.

SS

[MarkB]

Hi Stu

It is indeed 200ml. I used 10w with the original springs but after fitting Hagon progressive ones I found that I needed to go to 20w to damp out the pogoing under braking. Unless you know that the oil in the forks is nice and clean, I'd always drain them and get rid of the revolting sludge that is probably lurking there.

Regards, Mark

[Strada-Stu]

Thanks for your response Mark.

As the bike was very recently built by a reputable dealer, I'm hoping in the first instance to simply check the fork oil levels by measuring from the top of the fork tube.

Can anyone confirm the procedure for checking the existing oil level in situ?

Thanks in advance,

SS

[EVguru]

There is no official procedure for measuring the oil level. If you're happy with the way the front end feels now, you could establish your own known level.

Too little oil would cause the rebound damping to fail towards full extension. Putting more oil in changes the rate and progression of the air spring that exists above the oil and is a standard suspension tuning tecnique. Many, many different sets of fork internals were fitted at different times so the oil viscocity that works for you may be different to the book figure, HLP80 (in the 'Blue Book') is equivilent to SAE-30 fork oil, but most people are running something in the SAE-5 to SAE-20 range.

[morison]

Hi all,

I'm new to this forum. So as they say where i'm from. G'day.

I don't measure fork fluid anymore and instead I use the measure from the top procedure. It's quite easy. Remove the springs carefully and then by using some wooden sate type squewers you can measure the "air gap". On 38mm Marzocchi's this can be anywhere between 120mm and 150mm. Depends on whose recommendation you following. I use 120mm. I put a mark on the squewer with a pen and dip it in. It's very easy to see how much each leg is out then it's just a matter of equalising them.

Cheers
Chris
76 350 Sport and ex owner of a 500 Sei (should never have sold her)

[Strada-Stu]

Thanks for the feedback guys.

The existing oil level is 400mm from the top of each fork tube which means it is level with the top of the slider and the mudguard. In other words the springs don't sit in any oil. Does this sound about right or on the low side?

The forks feel pretty soft - there is a fair amount of diving on braking.

[3potjohn]

I'd still go with draining and refilling the oil-then you can check the level when you've added the oil as a reference and see what contamination you have in the old oil.Only a few minutes work and if you select the appropriate roasting tin from the kitchen it won't go everywhere.

[EVguru]

The forks feel pretty soft - there is a fair amount of diving on braking.

Read the following article for a description of how a damper rod fork works;
http://www.sportrider.com/tech/146_9408_tech/index.html

NOTHING you do with the oil viscocity will have any effect on the amount of dive, it will only change the speed of dive and going to too heavy an oil will stop the suspension working properly over bumps at speed. The level of oil will have some effect because it changes the air spring above the oil.

Changing the spring rate does affect the amount of dive, but again going to stiff will stop the suspension from following road imperfections properly. The original springs are often rather tired, not to mention probably having been chosen for a slim Italian youth. New springs, ideally matched to the riders' weight often make a difference and progressive springs are frequently recommended to improve damper rod forks.

As a last comment, many riders seem to 'grab' the brakes, rather than applying them in a smooth linear fashion and then complain about excessive dive.

[Strada-Stu]

Thank you again Paul and Jon for that very useful information.

I have a light touch so am not guilty of grabbing the front brake. I'm also not much bigger than the average 1970s Italian youth.

I will experiment with different oil levels and viscosities in the first instance to see if the dive effect can be reduced/slowed without adversely affecting the higher speed handling and will report back.

Cheers,

SS