fork oil viscosity-suspension guru's chime in please

[greg the pole]

So I recently did my fork oil on my ST.
Some of you pointed out that I may of cocked up by
a: listening to the dealer in telling me that Yamaha 01 oil is basically 10W
b: going to a slightly lighter oil 7.5 Bel ray, which is still heavier than the Yamaha 01
c: going for a couple of rides in the last few days that confirm my cock up. Hard as a rock the front is.
here's a couple of charts I found,
I have the bike on the stand and will drain the 7.5W oil.

what oil weight do you recommend, as I want to soften up the ride a bit, with the stock springs, and set up.
would a good quality BEL RAY HVI 3W do the trick?

I was reading somewhere that a higher # Viscosity Index shows a good oil that reacts well to changing temps, is this correct?


http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid
http://mahonkin.com/~milktree/motorcycles/fork-oil.html

any thoughts?

Greg

 

[RED CAT]

Greg. Can't go wrong with 5W. Thats what I used and it feels fine. Good ride yesterday but too short.

 

[avc8130]

Have you ridden the bike with the 7.5? Going into the warmer weather I wouldn't worry too much. Ride it. Set the suspension. Then come winter swap it out if you can't get a good performance with the heavier oil in the cold.

ac

 

[greg the pole]

i have ridden it with the 7.5 mind you for a short time (150KM)
I do agree that with the cold weather rides (friday was 8-10 deg C), yesterday was 2-3 deg C) the fluid will flow slowly.
I backed preload all the way out, and will most likely do the same to compression.
Got a 3000km california trip at the end of the month, that will be the real test.

but the more I think about it the more I will leave it till next winter.

 

[greg the pole]

Greg. Can't go wrong with 5W. Thats what I used and it feels fine. Good ride yesterday but too short.

I hear ya, but now that I'm on the right path, for a guy my size, my next oil will be a 3.5W with a high Viscosity index
Indeed good ride, and short.
You got a new tire going on for Utah? or you going to stick with that rear slick you run?
I still can't belive that you can put all the power down with it, had a tough time keeping up with you yeasterday

 

[mcrider007]

Stick with 5wt oil unless you have your high speed compression damping re-valved. If you want to see the effect that temperature has on the viscosity of any given oil you can use graph paper to plot the cSt points at 100C and 40C and extend the line to lower temperatures. The lighter the oil, the flatter the curve.

 

[greg the pole]

Stick with 5wt oil unless you have your high speed compression damping re-valved. If you want to see the effect that temperature has on the viscosity of any given oil you can use graph paper to plot the cSt points at 100C and 40C and extend the line to lower temperatures. The lighter the oil, the flatter the curve.

can you elaborate on that.
For a rider my weight (180LB) would a good quality oil, with a high VI not do with stock internals?
I found the original forks from the factory stiff, and I did fiddle with pre-load, and compression.
I pulled the forks this afternoon, drained out the 7w.
Will pick up the new oil tomorrow, and re-assemble everything.
question is, 5w or 3.5w?

 

[Firefight911]

Again, do not singularly lot a number on a bottle to being a weight of oil in the bottle. There is a variance of "weight" as compared to "viscosity" between brands.

Additionally, just changing oil does not resolve the issue of a dual rate (not progressive rate) spring as supplied.

Don't waste any time on oil until getting the right spring in there.

Also, when discussing damping one must clearly differentiate between hi speed and lo speed damping rates. These having absolutely nothing to do with the speed you are riding but, rather, the speed that the fork movement is taking place over differing terrain such as baby head rocks and hard edges on pavement versus undulations or rolling terrain.


Sent from my iPhone using Tapatalk which means there are more than likely spelling errors!

 

[avc8130]

Again, do not singularly lot a number on a bottle to being a weight of oil in the bottle. There is a variance of "weight" as compared to "viscosity" between brands.

Additionally, just changing oil does not resolve the issue of a dual rate (not progressive rate) spring as supplied.

Don't waste any time on oil until getting the right spring in there.

Also, when discussing damping one must clearly differentiate between hi speed and lo speed damping rates. These having absolutely nothing to do with the speed you are riding but, rather, the speed that the fork movement is taking place over differing terrain such as baby head rocks and hard edges on pavement versus undulations or rolling terrain.


Sent from my iPhone using Tapatalk which means there are more than likely spelling errors!

+1

Go back and set your preload to get proper sag. Oil weight and sag/preload have nothing to do with each other.

I wouldn't go crazy and adjust the compression "all the way out". Play with it. See where you wind up.

Trust me, your dual rate stock springs are hurting you a lot more than your 7.5wt oil.

Swap them out for the proper straight rate for ~$100 and you will have the BEST bang for your buck suspension mod.

ac

 

[Duconce]

What was the oil height that you set? You may want to check that first.

 

[greg the pole]

thanks guys,
I thought about the spring, but have not gotten around to buying a new one.
Oil level is set exactly by the book. spring out, compressed all the way down.
book says 150mm from the top (I think)
We had 6-8 inches of snow today, so the bike's not going anywhere soon.
I have some Amsoil 5w sythetic coming, and I may place an order for some new linear springs while on my california trip.
I'm picking up a new rear Yacubar shock from the Bmw shop on the trip, might grab some springs from them as well.

 

[avc8130]

If you are going to pull the forks and swap the oil...as well as buy an aftermarket rear shock...you owe it to yourself to swap out the stock fork springs for a proper straight rate for your weight.

ac

 

[mcrider007]

can you elaborate on that.
For a rider my weight (180LB) would a good quality oil, with a high VI not do with stock internals?
I found the original forks from the factory stiff, and I did fiddle with pre-load, and compression.
I pulled the forks this afternoon, drained out the 7w.
Will pick up the new oil tomorrow, and re-assemble everything.
question is, 5w or 3.5w?

Your damping complements the spring. High speed compression damping , which is not adjustable on the Tenere, acts like a relief valve to let the oil flow and get out of the way so the spring/forks can compress when you hit a bump. Too much viscosity, not enough oil flow, and a harsh ride. Too little viscosity, too much oil flow, and the springs/fork may compress too much. The OEM forks are dual rate and too stiff in most of the range where we ride, I would go with a lighter, linear spring before going to a lighter oil.

You really don't need a high VI for normal street riding, getting the right viscosity oil that matches the valving is more important. If you go to a 3wt oil to have less compression damping you may end up with insufficient rebound damping.

 

[greg the pole]

thanks for all the feedback, and clarification

so who makes a decent progressive spring for the front forks?

 

[Firefight911]

You do not want a progressive spring on this bike.


Sent from my iPhone using Tapatalk which means there are more than likely spelling errors!

 

[greg the pole]

sorry meant to say linear

 

[mcrider007]

It's a long spring and I think I remember someone saying that Traxxion was selling them, another possible source is RaceTech.

 

[Duconce]

I haven't put them in yet, but I got a set of springs from ProMax. They recommend 15 wt, 6in from the top, seems heavy. I guess I will go with what they recommend to start, see how they work

 

[greg the pole]

I haven't put them in yet, but I got a set of springs from ProMax. They recommend 15 wt, 6in from the top, seems heavy. I guess I will go with what they recommend to start, see how they work

unless they got you a much softer spring, 15W is heavy. 7 is heavy for me.
the 6 inch is spot on for distance from the top, with spring out.

 

[avc8130]

PM Sent.

ac