fork oil ? after spring upgrade

[busa dave]

My fork seals are leaking. So i ordered everything to do the job myself. I'm also upgrading my fork springs to better suit my weight. I'm 280 pounds. My question to you suspension guru's is what would the preferred fork oil weight be. I have been told lighter fork oil is like a poor mans gold valve. but I'm a little concerned that with the added spring pressure the lighter oil wouldn't be sufficient. I've heard 2 different things. some tell me the factory oil is 10w others say it's 5w. I can't decide what to use and I'm doing the job tomorrow. Thanks ahead of time for your help.

Dave

 

[BlondeOnaBusa]

The weight of the oil is really of little consequence, you can control the valving with your rebound and compression settings.
You'll need to cut (shorten) your pre-load spacer if you increase the load rate of your spring.

Chances are that your rear spring might need to be changed as well.

What you want is that the bike to be balanced, front and rear - when you 'bounce' it, that the front compresses at the same rate as the rear and that in turn, that it bounces back up, front and rear, at the same speed.

Its not black magic, but you have to twiddle with the nobs to get the gist of it.

If you have any more questions PM LA Busa. He will be able to walk you through it.


Good luck!

 

[Lamb busa]

BOB is right on.

 

[rusheriv]

With the spring change, I'd recommend sticking with the 0w-5w oil. If you find that you still run out of adjustment then go to a heavier oil, maybe a 7.5w or 10w. On OEM Kayaba cartridges (forks) the factory fills with a 0w (pt# 99000-99044-L01) which is the equivalent of other manufacturers' SAE5w.

Should you go with a heavier oil? That would depend upon the type of riding you do and what your current rebound and compression settings are. If you're doing a lot of hard riding (i.e. track days) where the forks get really hot, so much so that your rebound and compression settings are turned all the way in (clockwise) or almost fully closed, then you might want to go with a slightly heavier oil. Keep in mind though, there will be a difference with the new springs and if you go with too heavy of an oil you may end up with a suspension that's too slow. Slow is not good! With a slow/hard compression the suspension can't react quickly enough to compress over bumps and will skip and chatter and will tend to drift wide in corners. Likewise, if the rebound is slow the wheel will carry over imperfections in the road and stay compressed longer causing it to turn too quickly. If the suspension can't react quickly enough to extend again it may pump down until it bottoms out. Again, not good!

Good reading on suspension tuning, the hows and whys can be found right here in the Maintenance and Do-It-Yourself forum.
Or here and here.

 

[Tufbusa]

Your stock fork oil is indeed 5w. There is a reason they come stock with 5w.

I use Maxima Fork Fluid 125-150 7wt which meets all of suzuki's specs perfectly.

All of Suzuki's forks seem to be a little slack on rebound with the stock 5wt. The downside of heavier oil is it takes longer to heat it up to operating temperature. Yes, the fork oil does act differently when it's hot. This is why it's very important to set your suspension up when the oil is hot!

 

[busa dave]

Thanks for the input guys. I'm going to give 5w a try and see what happens. I do alot of aggressive street riding and track days. so I'll find out how well it works and if need be I'll change it out.

 

[busa dave]

Ok guy's started and finished the install after work. took almost 4 hours, but we stopped to eat dinner and had a couple beers. Very easy project. All I can say is WOW. Why did
I wait 3 years to do this? What a difference. I ended up going with 10w. I called traxxion dynamics because that's where i bought the springs and their tech recommended 10w It seems to be perfect.

 

[mike1180]

Congrats!

 

[BlondeOnaBusa]

Great job!