Fork oil weight?

[dschult2]

O.k. I've tried searching for it and I can't find it. I am planning on changing my fork oil soon and am trying to find out the proper weight for me. I weigh 170lbs with my gear. What weight oil should I use, 10 or 15 or something else. Also where is the best place to purchase, from the dealer or somewhere else? Thanks.

 

[outasight20]

Stock oil weight is 0 or 2.5wt, very light. You can go thicker, but at the expense of front end compliance over bumps. The heavier you go, the more you'll feel every bump in the road, although front end dive under braking will be slowed and handling on smooth roads improved. I got my fork oil at the dealer, but any shop will have it. I actually was running 10wt and went back to 5wt because the roads around here are too bumpy.

 

[Carlos840]

I might be wrong, but i don't think that rider weight influences the choice of oil that much.

It's not like spring rate, which is entirely dependent on weight. Compression and rebound is what oil weight influences, and there is more room for personal choice than with spring rates.

Either way, i think it is important to match the compression/rebound of the front to the rear.
Since you cant tune anything it makes no sens to go super heavy in the front and have a rock solid front and a wobbly rear.
Using 15w oil i think that i get a pretty decent match, the front and rear move more or less together when hitting a bump and it really makes the bike feel that much better.
It also really helps cure the head dive under hard braking, but doesn't make the bike uncomfortable.

Basically, i would say either one could work for you, and would be an improvement over the OEM water they call oil.

(i am 185 lbs with no gear, rear shock on 5, 32mm of rider sag in the front with 0.90 springs and 28mm in the rear)

 

[Erci]

If I'm not mistaken, Yahama uses what they call 0, which equates to everyone else's 5wt fork oil (don't ask me why).

The issue with heavier oil in a fork where a damper handles both compression and rebound: you'll certainly reduce dive under braking, but at the cost of slowing down rebound. Where would this matter? Leaned over going over washboard type of surface.. you may end up with less traction than with stock oil (each bump compresses the fork, but due to slower compression it may not fully extend to soak up next bump).

If you put in firmer springs, that's another story.. definitely would make sense to go with thicker oil.

For OP, weighing 170 with gear, I'd go with 5wt Maxima oil.

 

[ltdillard]

Is there a good "how-to" on changing out the fork oil?
Thanks.

 

[Carlos840]

Is there a good "how-to" on changing out the fork oil?
Thanks.

Just google FZ6 fork oil change, it gives you a lot more hits than using the forum search.

This is a good place to start:

HOWTO: Forks: Seals, Bushes and Oil. in Fazer hints and tips Forum

 

[dschult2]

5wt it is. Thanks guys.

 

[ped]

20wt for the street, 25wt for the track. 15wt is the absolute minimum viscosity that should be used. I build suspensions for racers including AMA riders.

you don't get hydraulic locking in a way that is a practical issue. If it's severe enough to lock the forks up you'd definitely be avoiding it anyway and if it's in a corner you'd crash no matter what. It's really a non-issue that comes from racetech misinformation.

when you're setting up a front end rebound is the key issue. Any thinner oil will give you too much bounce. It's also not a good idea to match the rebound with the rear for chassis balance if the rear is way out of whack....which it is.

 

[FinalImpact]

I don't see the stock forks packing down with 10 wt but to some extent that depends on rider weight and the terrain one encounters. As an example; of their 4+ inches of travel, nearly 35% is consumed just by sitting on it (w/185 lb + gear) as that progressive spring simply starts out at too light of rate (0.75 kg/mm) so the bikes rake angle is compromised right out of the shoot with excessive sag.
Anyway - they make 7.5 wt and I would not hesitate to start there vs 5 or 10.
That said, 20 or 25 wt seems a tad excessive. But I've never tried it so I can't comment but it seems some are happy with 15 while others say that's too harsh.

Depending on your expectation of the bike, you can really transform it with better equipment up front. Although fresh fork oil can't hurt. :thumbup:

 

[outasight20]

20wt for the street, 25wt for the track. 15wt is the absolute minimum viscosity that should be used. I build suspensions for racers including AMA riders.

you don't get hydraulic locking in a way that is a practical issue. If it's severe enough to lock the forks up you'd definitely be avoiding it anyway and if it's in a corner you'd crash no matter what. It's really a non-issue that comes from racetech misinformation.

when you're setting up a front end rebound is the key issue. Any thinner oil will give you too much bounce. It's also not a good idea to match the rebound with the rear for chassis balance if the rear is way out of whack....which it is.

Maybe on really smooth roads... I would not want to ride around here with 20wt fork oil. Break my wrists in half...

 

[ped]

nope 20wt is putting it slightly more loose than a basic general setup.

anyone who's put R6 forks on and had a suspension guy tune it will have about a 20-25wt equivalent setting.

it's getting you to normal.....

 

[FinalImpact]

nope 20wt is putting it slightly more loose than a basic general setup.

anyone who's put R6 forks on and had a suspension guy tune it will have about a 20-25wt equivalent setting.

it's getting you to normal.....

IMO we cannot compare stock FZ forks to anything adjustable. Its apples and oranges with regards to oil weight for damping control.

I think I'm following you but I don't agree with the suggestion of 20 - 25 wt. With the stock OEM forks the metering is fixed for both compression and rebound. Changing the oil impacts both compression and rebound.

Although your last sentence above may in fact be true in many cases ("20-25wt equivalent setting"), it cannot be applied to the stock suspension as the end results is simply too harsh on the compression side. Hence the reason you see no owners stating "I used 20 to 25 wt oil and the outcome was awesome."

In cases where people install emulators, this changes everything. In that case, the OEM metering for both comp and rebound are modified. The suggested drill size for rebound oil flow coupled with the oils wt now control the rebound rate while the emulator takes over the compression rate which the owner can adjust.

It really comes down to personal preference. I stopped at 10 wt as I was not getting the results I wanted so I replaced the forks with adjustable ones. FWIW: my forks had 4500 miles on them and 10 wt was too harsh. Forks with 25,000 miles on them, this may be OK as they wear and leak internally.