Fork oil SAE?

[gfritzmeier]

Changing fork oil on my 2003 Aluminum. I'm changing the old springs to progressive. They sent along a jar of fork oil SAE 15.
My question is: At my age what I really care about is a smooth, comfortable ride. They sent 15 wt. and manual says to use SAE 10.  I'm wondering what weight you guys might use. Taking in account that I'm 72 years old with back problems.  Thanks

[Arizona Wayne]

Do your forks have cartridges like the older Guzzi forks?  If so as I recall then the forks need ATF fluid instead.

[rocker59]

Changing fork oil on my 2003 Aluminum. I'm changing the old springs to progressive. They sent along a jar of fork oil SAE 15.
My question is: At my age what I really care about is a smooth, comfortable ride. They sent 15 wt. and manual says to use SAE 10.  I'm wondering what weight you guys might use. Taking in account that I'm 72 years old with back problems.  Thanks

Ask the folks you bought the springs from.  There may be a reason that they sent you 15wt.

Anyway, yeah.  Heavier oil will increase damping, all things being equal.

But all things are not equal since the springs are new and different.

The good thing about fork oil is that if you don't like the damping provided by the 15wt, you can always change it out to 10wt.

[troyhamilton]

i put trans fluid in my first 850-t. if 15 wts too stiff you can change it out.

[Perazzimx14]

FWIW ATF is approximately 10w and works a treat in many fork applications that call for near that weight oil.

[sib]

Fork oil is probably the only place where the viscosity is entirely up to the rider's preference rather than the manufacturer's spec.  The viscosity will determine the damping range of the fork.  What matters here is NOT what kind springs or the spring rate, but instead what the adjustment range (if any) is on the damping.  If you want less damping and a cushier ride, use a lower viscosity oil, vice versa if you want more damping and a stiffer ride.  That is why specialty companies like Motorex offer fork oils in a range of viscosities from 2.5 to 15.  BTW, unlike the more-or-less universally accepted viscosity specs for motor and gear oils, the viscosities of fork oils having the same SAE number can vary significantly among different manufacturers.

Although many people use ATF oil, fork oil has properties specifically designed to minimize foaming of the oil caused by cavitation.

[rocker59]

Fork oil is probably the only place where the viscosity is entirely up to the rider's preference rather than the manufacturer's spec.  The viscosity will determine the damping range of the fork.  What matters here is NOT what kind springs or the spring rate, but instead what the adjustment range (if any) is on the damping.  If you want less damping and a cushier ride, use a lower viscosity oil, vice versa if you want more damping and a stiffer ride.   

The '03 Cal Aluminum does not have fork compression and rebound damping adjustments.

And, I disagree with you about damping as it relates to spring rate:  If you change spring rate, you usually need to change damping.   Damping setting for a stiff spring is going to be different from the damper setting for a soft spring.  Especially rebound damping.  A stiffer spring will have more rebound than a softer spring and will usually require more rebound damping.

But yes, damping is a personal preference kind of thing...

[Chuck in Indiana]

BTW, unlike the more-or-less universally accepted viscosity specs for motor and gear oils, the viscosities of fork oils having the same SAE number can vary significantly among different manufacturers.

This. I recently put new seals in the Mighty Scura's Ohlins forks. Unfortunately, it takes about .6 Liters per leg, and they only sell it in 1 Liter bottles at 30 bux a whack.  $60 for fork oil?? I paid. (not Guzzi content)
Ohlins 5 wt. may or may not (probably not) equal somebody else's 5 wt. Rather than going through setting up the forks for a different weight oil..and there are no curves here in Indiana to do that.. I just ponied up.

[sib]

...And, I disagree with you about damping as it relates to spring rate:  If you change spring rate, you usually need to change damping.   Damping setting for a stiff spring is going to be different from the damper setting for a soft spring.  Especially rebound damping.  A stiffer spring will have more rebound than a softer spring and will usually require more rebound damping....

The last thing I want to do is start a spring flame war, but from all I know (and I admit I'm not omniscient), if two springs have their preloads adjusted to give the same amount of sag with a given total load (i.e., preload, rider, and bike), then they will behave identically within the limits of their range of travel.  A weaker spring will require more preload than a stronger spring to give the same level of sag, but once the sag is set identically, the springs will require the same amount of damping to give the same ride.  I welcome comments to the contrary, especially if backed by a good technical reference.

[Orange Guzzi]

I have switched the oil types and viscosity in the forks of my 2003.  I could not tell a difference.  I have switched the front fork tubes to Bassa rebound and compression adjustable dampening.  Changing the settings from lowest to highest has very little affect on the suspension's behavior. 

I installed racetech springs and emulators before changing the upper tube assemblies to the Bassa.  I could not tell a difference and adjusting the emulators is a pain in the behind and messy. 

I recently changed the rubber/metal sleeves out of the rear shocks with spherical and needle bearing.  This made the best upgrade to my suspension. This allowed the shocks to rotate freely around the mounting points. 

[rocker59]

The last thing I want to do is start a spring flame war, but from all I know (and I admit I'm not omniscient), if two springs have their preloads adjusted to give the same amount of sag with a given total load (i.e., preload, rider, and bike), then they will behave identically within the limits of their range of travel.  A weaker spring will require more preload than a stronger spring to give the same level of sag, but once the sag is set identically, the springs will require the same amount of damping to give the same ride.  I welcome comments to the contrary, especially if backed by a good technical reference.

Spring Rate.  Stiff springs and Soft Springs perform differently, even when set to the same static sag, and will require different damping settings.  A softer spring can require significantly different preload than a heavier spring to reach the same ride height / sag.  That is a static setting and doesn't factor how each spring will perform when in motion.  For instance, a stiff spring with too little rebound damping can tend to top out on rebound.  A softer spring with too much damping will feel harsh.


Here's a link worth reading, if a person has some time to kill:
http://www.sportrider.com/tech/sportbike-suspension-guide

[ITSec]

The last thing I want to do is start a spring flame war, but from all I know (and I admit I'm not omniscient), if two springs have their preloads adjusted to give the same amount of sag with a given total load (i.e., preload, rider, and bike), then they will behave identically within the limits of their range of travel.  A weaker spring will require more preload than a stronger spring to give the same level of sag, but once the sag is set identically, the springs will require the same amount of damping to give the same ride.  I welcome comments to the contrary, especially if backed by a good technical reference.

Further to Rocker's comments, the new springs (branded Progressive) may also be progressive-rate (likely). If so, you not only have the question of stiffness but of the rate at which the springs progress from compliant to stiff (determined by many factors, such as proportion of the winding rate change and so on). The weight of the oil for a progressive-rate spring is a balancing act that the manufacturer has been performing for a while.

I'd say the best approach is to start with the manufacturer's recommended weight and then move up or down based on experience rather than guesswork - unless someone here already has that specific experience to offer. And yes, fork oils are best compared to other weights from the same manufacturer, as their weights are not directly comparable from one source to another. Pick a well-known brand with a range of choices and you'll be better off...

[bad Chad]

I think the manual calls for 30wt in my breva, but I had the shop put 10wt in and found it works great for fast response, might not be what your looking for though.

[gfritzmeier]

I've decided to put 10 viscosity.  I called progressive and they sent the 15 along. They used specs for Cal. EV as they had nothing for Alum.  What they did say was 10 was OK if I wanted a smoother ride. So there I go.

[93spada]

Fork oil is probably the only place where the viscosity is entirely up to the rider's preference rather than the manufacturer's spec.  The viscosity will determine the damping range of the fork.  What matters here is NOT what kind springs or the spring rate, but instead what the adjustment range (if any) is on the damping.  If you want less damping and a cushier ride, use a lower viscosity oil, vice versa if you want more damping and a stiffer ride.  That is why specialty companies like Motorex offer fork oils in a range of viscosities from 2.5 to 15. BTW, unlike the more-or-less universally accepted viscosity specs for motor and gear oils, the viscosities of fork oils having the same SAE number can vary significantly among different manufacturers.

Although many people use ATF oil, fork oil has properties specifically designed to minimize foaming of the oil caused by cavitation.

Found this today, on another of many, rain days in the NE!!!   Thought I would pass it along to fire up some thoughts and comments.

http://mahonkin.com/~milktree/motorcycles/fork-oil.html

Tried to copy and paste for ease sheet but failed.

I just rebuilt the front dampers on my SPIII. Used PJ1 .05wt. Seems OK but could maybe a little stiffer om 90% of full damp.
Am going to do the rear Koni's when back from an extended road trip (Maybe WNY and VA rallies).
Ikon has an oil they sell with a kit. They call it X HVI 15
 
http://www.ebay.com/itm/IKON-KONI-mc-shock-absorber-rebuild-hydraulic-oil-suspension-fluid-1-liter-/132105668654?hash=item1ec21c882e:g:HnoAAOSwux5YLzP0&vxp=mtr
 
Thoughts for what to use?? I can see why there are so many recommendations.

Thanks
Paul