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Discussion Starter · #1 ·
stock is 10 WT

I have zero mods to my front forks or rear shock

I weigh ~210 with gear

Read on the forums someone put harley davidson extra heavy fork oil in one leg which wasn't the greatest but still an improvement over stock.

Should I go with 15WT in both, 20 WT in both or harley heavy fork oil (they dont make extra heavy anymore) in just the one leg? Anyone play around with changing the oil as a budget suspension mod to improve dampening?

gotta love budget racing :D
 

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10 WT, 15, 20, etc doesn't tell you ****. You need to specify actual oil for a proper comparison. Google fork oil viscosity chart and look through the table. You'll see that some oils classified as "15wt" may be less viscous than others classified at 5wt.

The Ohlins R&T oil that's 5wt which I use on my zx6r is 19 cSt (centistoke...unit of viscosity measurement) at 40 degrees C. Traxxion Dynamics recommends using Maxima fork oil 15wt in their instructions that come with their damper rod kit. That oil is actually 46 cSt....much thicker. Generally a good rule of thumb is to use what's recommended.

If you're planning on using this for racing, I strongly recommend just upgrading your suspensions, not just the oil. The stock ones are junk!
 

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10 WT, 15, 20, etc doesn't tell you ****. You need to specify actual oil for a proper comparison. Google fork oil viscosity chart and look through the table. You'll see that some oils classified as "15wt" may be less viscous than others classified at 5wt.

The Ohlins R&T oil that's 5wt which I use on my zx6r is 19 cSt (centistoke...unit of viscosity measurement) at 40 degrees C. Traxxion Dynamics recommends using Maxima fork oil 15wt in their instructions that come with their damper rod kit. That oil is actually 46 cSt....much thicker. Generally a good rule of thumb is to use what's recommended.

If you're planning on using this for racing, I strongly recommend just upgrading your suspensions, not just the oil. The stock ones are junk!
I learned this when I modded my old N650 forks. Went with intiminators the first time then did a full zx6r fork swap after. There are a few charts that compare the different brands and how they would really rate viscosity wise.
Here's a question for you guys that I have never actually messed with other than just ponder the theory. Do you remove the legs when you measure fork oil? All the guides and install pamphlets from various kits say remove them. I've thought about just pulling caps and measuring them while on the bike. If you think about it, and I could be wrong, but the angle of the forks while installed should have no effect on the measurement of the oil level. Being a liquid, the oil will level itself out.
 

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I learned this when I modded my old N650 forks. Went with intiminators the first time then did a full zx6r fork swap after. There are a few charts that compare the different brands and how they would really rate viscosity wise.
Here's a question for you guys that I have never actually messed with other than just ponder the theory. Do you remove the legs when you measure fork oil? All the guides and install pamphlets from various kits say remove them. I've thought about just pulling caps and measuring them while on the bike. If you think about it, and I could be wrong, but the angle of the forks while installed should have no effect on the measurement of the oil level. Being a liquid, the oil will level itself out.
It absolutely changes if you use something like the motion pro measuring device, which is just a graduated rod stuck to a ring that rests on the top of the tube. That rod is not going to be in the dead center of the tube most likely so depending on where it is in the tube, it'll measure something different because the oil level won't be parallel to the ring. You can do the math based on a rake angle of roughly 25 degrees. A quick calculation I made yields a difference of almost 17 mm between having the measuring rod all the way to the front vs all the way to the back inside the fork tube.

You should remove it and hold it as vertical as you can. I actually have one of mine in the vise right now since I was about to install the Traxxion Dynamics damper rod kit...then I realized I forgot to order the oil :/

A cheap way to "stiffen" up your forks is to increase the oil level. Or if you want to soften them up more, remove some oil. That's the equivalent of changing fork springs...I would do that before messing with a different viscosity oil than what the fork cartridge was intended for. Your compression and rebound damping will change drastically with different viscosity oils.
 

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Discussion Starter · #5 ·
thank you sbk1198 I did some research and now am leaning toward adding in 10cc of oil to help stiffen the forks before my next race this weekend

my question is would it be ok if I open the caps and just squirt in 10cc or do I need to remove the fork legs and do the whole thing with the special level tool?

sorry for the newbie questions
 

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thank you sbk1198 I did some research and now am leaning toward adding in 10cc of oil to help stiffen the forks before my next race this weekend

my question is would it be ok if I open the caps and just squirt in 10cc or do I need to remove the fork legs and do the whole thing with the special level tool?

sorry for the newbie questions
Yeah you can do that. If all you're doing is adding oil, and you have a syringe or something to squirt it in the tube that works fine. A syringe is helpful because it also makes it easy to measure out volume pretty accurately. Go in increments of 10cc in each fork, try it out, and see how it changes. Then keep adding if you need more.
 
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I changed my OEM fork oil after the first 500 miles and it came out like whale snot. If you still have that crap in your forks, then the time to change your fork oil is now.
 
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