Ok, I have done several searches and keep coming up with different numbers. Also, some of the links that were in the old threads are gone. So, I need to know how much fork oil to put in each tube. I am just using the stock springs. I found the 380ml's amount but that seems like a lot.
Is 380ml for each side correct?
Also, I want just a little stiffer than stock feel on the front. A friends dad, who is a very reputable bike mechanic/builder, suggested using 10w-30 motor oil, as he says it give just a little better performance feel than regular 5w or 10w fork oil.
So what would be a good weight of oil for me to run?
I am not track racing or anything, but want a sportier feel than stock.
Any help is appreciated. Thanks!
David
service manual says 382 ml. Yes, that's for each side, or per fork. You can also get the old oil out somehow and add fluid until it is 3.9 inches from the top of the fork. It's important that the fork is compressed all the way when you measure. That way you don't have to worry that you didn't get all the oil out and overfilled it.
Never heard of using car oil. :dunno_white: Stock oil is 10wt.
Alot of people (including me) use 15wt and it slows down the compression and rebound a noticable amount. (less bottoming, less like a pogo stick)
Depending on the year, though, your springs might be way too soft and the weight of the oil won't matter at all. My stock 1990 springs were .45kg/mm. I needed .85kg/mm. I could bottom out the stock springs in my driveway!
I just did a heavier weight fork oil swap because i could bottom them out simply by bouncing on them in the driveway. i emptied as much of the old fluid as i could using some tubing and a vacuum pump. then i put in about 375ml of 20 weight fork oil in each one, sealed them back up and blam. No bottoming out, way stiffer, and so much better in every way. I only weigh 160lbs so you might want a little stiffer, but i'm really happy with the way it rides now.
Great guys! I really appreciate it. :cheers:
My bike is a 92, and I can't really afford to buy different springs right now, so I will up the oil to maybe a 15w and see where that gets me.
Glad I found this thread! I just bought new seals & covers! I'm going to do the spacer mod off the mod page & change the oil to 15w & see how that works :cheers:
Thanks again :thumb:
Quote from: bandit79 on June 06, 2009, 11:19:16 AM
Great guys! I really appreciate it. :cheers:
My bike is a 92, and I can't really afford to buy different springs right now, so I will up the oil to maybe a 15w and see where that gets me.
$80 from sonic springs.
The manual does *not* say 382ml per fork. The manual says to start with 382ml, and use a fork oil level tool to set the oil level to 99mm (with no spring, and the fork fully compressed.) If you simply pour in 382ml of oil, the level will not be correct, and given that the GS runs a very high oil level to begin with, you're very likely to end up blowing out a fork seal.
Keep in mind that the 99ml level is for the stock spring. If you have an aftermarket spring, that oil level may cause you to enter hydraulic lock, which will blow out a fork seal or two. If you have aftermarket springs, 120mm would be a better starting point.
I believe 15 weight oil is stock. I run 20 weight, but that's with emulators, for race use.
I'm running racetech springs with the oil at 100mm. Seals still holding up fine *crosses fingers*. FWIW these springs are similar in size to the originals with slightly thicker coils. You could get all fancy and measure the volume of both the original and replacement springs. Subtract the difference in volume from the amount of oil you pour in. Not too many people keep graduated cylinders and stuff like that in their garages though
Thanks Deros514. Have you measured your suspension travel? If so, how much are you using?
I have racetech springs and emulators, and just raised my fork oil level from 120mm to 100mm because I was bottoming out.
I had progressive springs put in last year and I was still bottoming out on gutters. I am having the seals replaced and changing to 20w oil. I will get her back tomorrow and let you know how she rides. Its a 94.
Haven't measured. I don't feel like I've ever bottomed out since the change but I'll grab some zip ties and some measuring tape next time I go riding. :thumb:
Mine did bottom out, but I didn't feel it happen.
Just got mine back. Progressive springs and 20w oil. It rides freaking awesome. I had already had the progressives, the 20w oild must be what is making the difference. I have only gone about 6 miles so far but I'm lovin it.
The oil makes a huge difference, especially if the old stuff had been in there for a while. Fork oil brakes down and thins out over time.
My 94 was bottoming pretty easily so when one of the seals began to leak I took the forks in for new seals and 15w oil. Stock oil is 10w for my year at least. It's better but I still need more. Shouldn't have left the stock springs in. They're too soft. I weigh 195 lbs. It seems to me that progressive springs (or stiffer single-rate) with 15 or 20w oil is the answer for this bike depending on how much you weigh.
Well I guess I am bottoming out. After several hard stops I came with a consistent dive of 3.25 inches. I can't imagine going any stiffer unless I got some emulators too. IMO at that point, I'd be trying too hard to make the bike something its not. While its still bottoming, its still a vast improvement above stock and I am content with its performance.
I went racing this weekend with 100mm oil level and Racetech springs and emulators. I didn't blow a seal, so I guess that oil level works okay.
I talked to my suspension guy. He said that 30 weight oil would have been better for this hot weekend, but that I should stick with 20 weight since things will be cooler at the next two races.
Deros514: Your springs might be a little soft. I run .85 at the track, which are on the soft side of things, and I weigh ~175lbs.
I used racetech's calculator for street. It recommended like a .857 so I went with the .85kg springs. I'd say its a fair balance of comfort and performance. Not looking at hitting the twisties with a racetrack pace anyway.
15 weight did wonders! Might even try 20 wt. I weigh 180 lbs. Tried to put some 1/2 spacers in but couldn't get the caps back on myself. so no go. I wonder what that would have been like :dunno_black:
In any case go 15- 20wt. for sure.
Stock, the GS runs 25mm of preload - which is already a lot. Not sure I'd want to add much more than that.
I find that the easiest way to get the caps on is with the fork tubes out of the triples. Push down on the cap, and spin the fork tube.
Also, I think 15 weight oil is stock. The improvement probably came from replacing your used oil with fresh stuff. :)
Glad I saw this thread, I was actually headed out to the garage to replace the fork seals, springs, fluid etc. Like Deros, I used the racetech calculator and it spit out .857's as well. For those running these springs, what kind of preload and fork oil amount did you guys go with? It sounds like 120-100mm, somewhere in that area?
I don't remember the exact length I used for preload. I do remember the sheet had some sort of formula for setting preload. I followed those and rider sag is around 20mm, static is about 5mm.
For the oil height, I set an aluminum tube attached to some vinyl tubing down to 100mm. I poured in enough oil to almost make it to the top, gave the leg a few pumps to release air bubbles, and sucked out the extra oil through the tube.
Stanfield, once installed, your forks act like a sealed unit, and the volume of air in the fork acts like a secondary spring - as the forks compress, the air is also compressed. The air wants to expand back to atmospheric pressure, and thus resists compression, especially at the extreme end of the fork's travel.
I'd recommend you start at 120mm. Throw a zip-tie around a fork leg and take the bike riding. Afterwords, throw the bike up on a center stand, and measure how much of your suspension travel you're using. If you aren't using all the travel, leave the oil level alone. If you are, you can raise the oil level up.
The stock oil level is 99mm, but that's with stock springs, which are much thinner, and much shorter than the aftermarket parts. At 99mm, the air in the forks is being compressed into a very small volume (~20ml or less) with the forks bottomed out. The higher your oil level, the more stress you put on your fork seals, and the more likely you are to blow them out.
FYI: The GS500 has 103mm of suspension travel. I generally measure from the edge of the dust seal to the bottom of the zip-tie I keep wrapped around the fork leg.
For preload, cut your spacers so that they match stock (25mm. In my case, 1mm of pre-load spacer was visible above the fork tube with the forks fully extended.)
Then, assemble the bike, and measure your static sag, and rider sag. If they are within range, you're fine. If not, add or subtract preload to get the sag in range. In another thread, I post comprehensive instructions on how to measure pre-load.