Pre-load or heavier oil?

[Rustyhama]

I am lowering my forks by 50mm, cutting 50mm off the spring & adding a spacer to the damper piston. I know all the ins & outs of this issue -changes the trail & head angle & could effect the handling etc. If anything it may 'quicken' the steering which actually I'm quite happy about as 95% of my riding will be around town and she didn't seem to be that into going around round-a-bouts before anyway. So lets go beyond that issue...

So, I have some rust/pitting on my fork tubes. It probably starts at about 150mm above the dust seal & goes up from there. It's not too bad but I don't want it around my fork seals if possible.
I'm trying to decide between adding some preload by adding a 60mm spacer to the damper or using stiffer oil. Standard is 5w20 so using 10w20. I'm leaning towards preload because I think the stiffer oil will slow the rebound too & I'm not sure I want/need that. BTW I am a very light rider (150lbs in your funny talk);-)

At the end of the day it probably wont make much difference but I'd like a few 'expert' opinions please...

 

[xb33bsa]

changing oil weights will do zero to affect the ride height
but I think you will want the oil to be thicker, because you have less travel and stiffer springing,you will need plenty stiff rebound
one thing about the oil is it is pretty easy to experiment with
I think you will need 30wt
oh and cutting 50mm off the springs makes them stiffer

 

[Rustyhama]

Thank you xb33bsa, I've seen some of your comments on suspension before, I was hoping you might reply as you seem very knowledgeable.
I know the oil won't change the ride height.
Stiffer rebound to match the stiffer springs, yes that makes sense.
Hmmmm from 5 all the way to 30wt? That looks like the stiffest you can get for fork oil. Maybe I'll try 20 but as you say easy enough to change.

I think I'll go with 50mm spacers to match what is cut off the springs therefore no preload but stiffer springs due to being shorter + the thicker oil.
Result should be stiffer overall with good balance between compression & rebound.

Cheers Bro!

 

[xb33bsa]

it wont hurt to have the compression of the fork slowed up by the heavy oil was my thought
mainly on the high speed hits is what you will be concerned with
the shorter travel amount pretty much dictates a stiff ride so that it doesn't bottom too easily

 

[mydlyfkryzis]

The difference between 5W-20 and 10W-20 is only at 0 degree's. At Higher temperatures, only the "20" comes into play.

The "W" in 10W-20 means "Winter", ie: cold weather. So if it is 10 degrees out, the 5W-20 would be softer damping then the 10W-20. Once you are above 70 degrees or so, the "Winter" rating is irrelevant.