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Discussion Starter #1
I'm going to be ordering some parts and figured I would order the oil for my soon (hopefully) upcoming front suspension upgrade. I searched around but couldn't find a good answer on the best viscosity to use. I'm looking for a high performance street bike at this point. I plan on upgrading the front springs(if I can afford it, otherwise cutting/spacer method until I can) but I don't think cartridge emulators are in my near future(too many other things to buy). I see stock viscosity is 10W20. I would expect a little higher viscosity would help, but have no idea how high would be wise. Any wisdom from those who have done this?

Thanks :)
 

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If you want stiffer front use single weight oil 10w or 15w. You can get it at you local stealer dealer . And know that if you do use 10w20 it is not motor oil , it's fork oil (HUGE DIFFERENCE).
 

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I'm not aware of fork oil available in multi-viscosity. I have always purchased a fixed weight. The manual does call for 10W-20 but I always assumed that was just motor oil. Maybe there is, just not something I ever saw or considered. I have always used fixed weight fork oil... except in a pinch when I have used motor oil. Never did it on purpose. ;)

In the past, many bikes called for ATF which also was 10W.

I'm not sure that I would change to a thicker oil unless you had a specific service in mind. On the street, with the many varying conditions, it may prove too thick.

There's another reason to consider staying with 10W that's not readily evident. That's the rear shock. ??? One thing about suspension tuning that's a standard is maintaining the front working in conjunction with the rear. If one end is acting much different from the other end, even if one is right, the package may feel worse than having both less than optimum, but equally so.

One thing that's nice is it's relatively easy and inexpensive to change fork oil. If you try one and it's not good, it's easy to change.

I would strongly consider the cartridge emulators. Especially for street riding. They really do make a difference. For those who don't understand their purpose, here goes.

The damper rods we have are fixed orifice. That means the damping rate, dictated by the ability of the fixed orifice (drilled hole) ;) to pass oil, are at best a compromise. The dampening is too soft at low speed fork travel, the small bumps, flowing the oil too freely, not dampening much at all. The passage is too large to have much effect on the low volume of the oil passing through them. Somewhere in the middle of that fork speed, caused by a little harsher bump, the restriction of the fixed hole is just right and has the perfect effect, perfect restriction and resistance to flow, perfect dampening rate. Then, when you hit a big bump and the fork needs to travel a large amount quickly, the hole is too small to pass the necessary volume of oil so is therefore too harsh. It's virtually hydraulically locked and unable to move fast enough. Very harsh! It's those errattic responses to varying conditions that the cartridge is designed to fix.

The cartridge is an assembly with a much smaller fixed orifice so it flows a smaller amount of oil at some restriction/pressure, dampening the small bumps perfectly. Then, as the bumps become harsher and a larger volume needs to flow, but still with some resistance to dampen the action, a spring loaded disc in the cartridge is hydraulically lifted by the increased fork oil pressure, affording the larger opening to allow the larger flow required, yet dampening according to how stiff the spring is to resist that lift. The spring in the cartridge is adjustable to vary that effect. It winds up affording the greater amount of dampening for the small bumps that the fixed hole couldn't do, accomodates the middle of the range as the fixed hole did, and then can really open up for the harshest of bumps, letting the fork move over them with the proper resistance, but not hydraulically bound.

If you think that through, does it become clear how that might be very desireable for the WIDE variety of conditions we meet on the highways?

Hope that helps.
 

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Discussion Starter #4
Thanks, dad, that is a good explanation. I know this is a entry level bike, but sometimes I'm surprised that they have not incorporated a basic technology that is found on every car on the road just about. I know it all comes down to money. Cartridge emulators sound great and definitely are on my list, I just need to do rear spring/dogbones, front, and tires first.

I guess I'll try 10W synthetic fork oil then. A 10W-20 should actually be a little thicker than a straight 10W, but if that's what works for folks then it sounds good to me.

Looks like I will have to get it elsewhere anyway, this website is out. At least I know what to look for. Synthetic ATF actually could be a good substitute if it is 10W, and I've already got that on hand.

Thanks again! :)
 

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2001ex500 said:
I know this is a entry level bike, but sometimes I'm surprised that they have not incorporated a basic technology that is found on every car on the road just about. I know it all comes down to money.:)
It may be worth noting that this bike's base design goes back to the late '80's. Guess when the two largest recent advancements in bike technology, the cartridge shock valve and radial tires, came out. About 1990. That will help with a little justification but your point is well taken. :)

I have been known to say that if they fixed the springing on these they may not be as able to demonstrate the marked improvement of their next model up in the line. The dramatic improvement wouldn't be so dramatic. 8)

Ahhh, it still makes a good entry level bike and can be educational in the basics of suspension. ;) Outside of adding a few bucks for cartridges that don't exist in the package, there would be no direct cost to the rest of the fixes. A little tighter valving in the exact same rear shock body, a little stiffer springing, and some cartridges to act well with the springs, would make it a whole new bike.
 

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Along the line of econo fixes. I have heard/seen people silver solder the valve holes in the plunger rods and re drill them smaller for more dampning but I don't know the consequences.
For the non engineers here if you want to try this stunt, be appraised that the flow of an orfice is proportional to it's area not it's diameter. Or an .042 dia hole will flow twice as much as a .030 .

FOG
 

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I am 200+ lbs with full gear on.. I tend to notice a fairly large amount of sag under braking...
My question is this.. are the emulators something that can be done on the stock forks.. without aftermarket springs.. or would i need those also... Or would I be better off to just try a heavier weight oil in my forks.. thanks..

I am not looking for a race suspenion just something that is more confidence inspiring for a weekending romper.. Thanks again
 

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It will dive to bottom until you get the right springs in it. The shock absorber controls the speed of motion but the spring has to handle the dynamic loads of any duration, which braking is. The spring that will be recommended for your weight on the street will be .90 but I wouldn't hesitate to use .85's.

Emulators are nice and highly recommended. They are independent of the springs. One can be changed w/o the other. They will help with the harshness of the shock on hard bumps. If you can only afford one, do the springs. They're the cheaper part anyway. 8) About $100 vs: $150 for the emulators.
 

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So just running the springs would be fine? If just running the springs what weight fork oil would u recommend for me?
Thanks
Josh
 

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One more thing..

When changing out the front springs.. would I have to get all new seals and bearing? my bike only has 3500 on it..

Thanks
 

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Jkrup47 said:
One more thing..

When changing out the front springs.. would I have to get all new seals and bearing? my bike only has 3500 on it..

Thanks
No. If the seals aren't leaking you can leave them alone.

And yes, you can do just springs. I would stay with the 10w fork oil especially for street use. That's due in a small part to the springs but mostly in the interest of matching front to rear and the fact that you're leaving the damper rods in place, not using emulators. Even with emulators I would still leave the 10W in but the reasoning is less dramatic with emulators.

Be aware, it is likely that with the new springs you will run a lower fork oil level than factory recommended. That new recommended level should be available from the spring supplier. I would use Racetech for the springs or maybe Traxxion Dynamics.

Make sure you get the sag right when you install them. They will come with a length of tubing to cut the new spacers from, the method for setting the sag.

Here's a link with a lot more additional background on this stuff. Around page 3 there's front end stuff. It wouldn't hurt to read it all, though. You'll see why you may want to consider the rear with this, too.
http://www.ex-500.com/index.php/topic,702.0.html
 
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