Fork Oil Weight

[gonenorth]

Tried 10 weight fork oil on my 2012 Ultra, and while it seemed to smooth out seams in the road it seemed more choppy on rougher roads.  PoorUB thinks it is due to less rebound damping.  We are wondering if anyone has tried 30 wt. and how that worked?

[MaxxV4]

I have used 15 wt. and have since switched back to 10 wt. I would think that 30 wt would be a miserable ride for a touring bike.

JMHO.....

[gonenorth]

Thanks for the insight.  Was concerned with the heavier weight being too stiff and creating a rough ride, but wondered if others had tried it.

[PoorUB]

The big question(s) I have is how much compression damping is there compared to rebound damping and how much does oil weight affect each?

[Admiral Akbar]

The big question(s) I have is how much compression damping is there compared to rebound damping and how much does oil weight affect each?

When you change oil.. You effect both basically the same relative amount.

[PoorUB]

The big question(s) I have is how much compression damping is there compared to rebound damping and how much does oil weight affect each?

When you change oil.. You effect both basically the same relative amount.

I was wondering because I thought I read somewhere that the HD touring forks have very little compression damping compared to rebound dampening.

[Admiral Akbar]

The big question(s) I have is how much compression damping is there compared to rebound damping and how much does oil weight affect each?

When you change oil.. You effect both basically the same relative amount.

I was wondering because I thought I read somewhere that the HD touring forks have very little compression damping compared to rebound dampening.

Most do but the fairing-ed baggers from 2006 up to 2013 use an emulator that HD designed.. I don't know how the damping rates are matched for the 09-up as the damping rod and emulator changed in 2009.   Non emulator forks basically have very little compression damping and all rebound so they rely mostly on rebound only for damping..  HD emulator forks have better compression damping as the emulator provides 2 damping speeds, 1 orifice and 2 spring loaded valve.. The 07 I had did quite well with heavier springs and 10 wt oil but again something changed in 09..

[PoorUB]

Ok, thanks!

[Fatboy128]

I messed with the fork oil on my Fatboy and was never happy with any weight. I installed the monotubes from progressive and now I am very pleased

BTW what ever happened to using ATF??

[88b]

I always use 10w , always surprised how bad the stock oil looks when it comes out and always different amounts in each leg.

[gonenorth]

I appreciate the responses on experience with different weight oil and information on the rebound and compression damping. 

[04 SE Deuce]

Viscosity varies between brands/weights.  Harley type E is 39-40cSt@40C which between a typical 10w and 15w. 

If you want slightly more viscosity try an oil around 45cSt@40C,  Spectro and Maxima 15w are 47cSt@40C. 

Most brands have the viscosity rating on their website under specs,  safety data sheets etc. sometimes you have to scroll a ways...if not a call or email will get specs.  Here's an example:  http://www.spectro-oils.com/wp-content/uploads/2015/06/forkoil.pdf

I mix Red Line med and heavy to get what I want.  Here's a calculator:  http://www.widman.biz/English/Calculators/Mixtures.html

FYI,  went you mix oils you end up with a slightly lower viscosity than expected given the numbers.  For example if you mix equal amounts of 2 oils that are 40cSt@40C and 20cSt@40C the result is 28cSt@40C not 30.   

I tend to adjust oil viscosity based on what temperature I like the performance of the forks the best.  If you like the forks best on a super hot 90/100 degree days go lighter and vise-versa.  -Rick

[gonenorth]

Viscosity varies between brands/weights.  Harley type E is 39-40cSt@40C which between a typical 10w and 15w. 

If you want slightly more viscosity try an oil around 45cSt@40C,  Spectro and Maxima 15w are 47cSt@40C. 

Most brands have the viscosity rating on their website under specs,  safety data sheets etc. sometimes you have to scroll a ways...if not a call or email will get specs.  Here's an example:  http://www.spectro-oils.com/wp-content/uploads/2015/06/forkoil.pdf

I mix Red Line med and heavy to get what I want.  Here's a calculator:  http://www.widman.biz/English/Calculators/Mixtures.html

FYI,  went you mix oils you end up with a slightly lower viscosity than expected given the numbers.  For example if you mix equal amounts of 2 oils that are 40cSt@40C and 20cSt@40C the result is 28cSt@40C not 30.   

I tend to adjust oil viscosity based on what temperature I like the performance of the forks the best.  If you like the forks best on a super hot 90/100 degree days go lighter and vise-versa.  -Rick

Thanks for the good information about the wts and mixing oil.   

[Nowhereman]

A fork needs just a tiny amount of compression dampening.
Spring weight needs to be dialed in to your riding style and weight that you carry.
Stay away from progressive spring designs and go with a straight weight spring.
Rebound dampening is the factor that you tune for and costs money depending on what you need to do.
Those monotube dampers are nice because all the engineering is done for you.
Emulators can work great but, you need to tune oil weight and amount to dial it in.
The emulator mfgs have done a lot of set up work for you and can get you in the ballpark quickly.
Kinda depends on what your looking for from a front end.

[Admiral Akbar]

A fork needs just a tiny amount of compression dampening.

Really?? Interesting..

[Nowhereman]

A fork needs just a tiny amount of compression dampening.

Really?? Interesting..

Yeah it really is...lol
Very little compression damping by hydraulics is required Max but, you already know that don't you..

[Admiral Akbar]

A fork needs just a tiny amount of compression dampening.

Really?? Interesting..

Yeah it really is...lol
Very little compression damping by hydraulics is required Max but, you already know that don't you..

Til you hit a bump, I would guess..

[Nowhereman]

What I would like to see is a version of GM's magna ride suspension for bikes.
Like what their top line cars have; using magnetic fluid to change viscosity dependent on road conditions via electrical stimulus.
I have driven a Cadillac CTS V and a Vette with it and it is the ultimate in boinger technology.

[Hossamania]

What I would like to see is a version of GM's magna ride suspension for bikes.
Like what their top line cars have; using magnetic fluid to change viscosity dependent on road conditions via electrical stimulus.
I have driven a Cadillac CTS V and a Vette with it and it is the ultimate in boinger technology.

Some of the top of the line sport bikes are running similar technology. Plus launch control, wheelie control, side slip control through corners (not just traction control). Pretty amazing tech on them.

[motolocopat]

What I would like to see is a version of GM's magna ride suspension for bikes.
Like what their top line cars have; using magnetic fluid to change viscosity dependent on road conditions via electrical stimulus.
I have driven a Cadillac CTS V and a Vette with it and it is the ultimate in boinger technology.

Some of the top of the line sport bikes are running similar technology. Plus launch control, wheelie control, side slip control through corners (not just traction control). Pretty amazing tech on them.
Yes and have been for sometime. In fact it is getting to be fairly commonplace and being used on midrange.
It never ceases to amaze me that the suspension/Brakes on a $14K-25K Harley are not even up to the level of a 2000 year model midrange jap bike that was 7K new at the time.

[gonenorth]

  Lots of good discussion on this thread.  I did ride with the 10 weight for a while and then switched back to 20 wt.  I took a fairly long ride over some rough roads this afternoon and like the 20 weight over the 10 wt.  While the 20 weight was a little stiffer over the seams, the rebound control was better so I didn't find the ride as choppy on a rough road.  I expect what people like on the oil wt. is like many things - a matter of personal preference.  At this point I'm not going to chase other shock options on the old bagger.  I know there are better shock options out there, but don't want to invest the money at this point.

[fbn ent]

"Stay away from progressive spring designs and go with a straight weight spring."

Really? I ran progressive springs with Bel Ray 20W until I went to Monotubes.

Can you explain that for me Nowhereman? Learning something here.

[Nowhereman]

"Stay away from progressive spring designs and go with a straight weight spring."

Really? I ran progressive springs with Bel Ray 20W until I went to Monotubes.

Can you explain that for me Nowhereman? Learning something here.

Sure, progressive wound rate springs all tend to sack out quickly with the lower spring rate winding portion.
This has been an attempt to give the rider / drivers more suppleness over small undulations.
In theory it sounds good but spring rate life is not that good.
If you have the correct straight wound rate for your riding style, and your "dampening" has been modified to handle faster oil flows for small stuff and slower oil flow for the big stuff, you will have a well handling vehicle.
Ride heights change with progressive rate wound springs over time due to spring sack, which will happen much more quickly than straight weight wound springs.
Air was a good attempt at solving this problem but required much more development in valving to utilize.
We ran air forks for years in MX then dropped em due to set up issues.
Some of us combined straight rate springs and used a little air to set ride height and got some results but later on, the valving became more sophisticated and air preload went away.
My comment on the magnetic fluid shock was due to the state of technology for  dampening.
With that technology, they have fixed the issues of near perfect dampening for any condition.
If you look at that set up, they use straight rate wound springs and not progressive rate wound types.

[Admiral Akbar]

Progressive spring are fine in that they can handle a varying load a little better than a straight wound spring.. They do better then straight wound spring where compression damping is non-existent or low level single speed stuff Like the typical pre emulator Showa shocks on HDs..  The problem with some stock HD progressive springs are that the to rates are far a part so you get the nice plush ride and are into the harder part only near the end of it travel.   

The progressive springs (while still not true progressve) have less of a difference between the 2 rates when compared to HD..

[attach=0]

Here is a good description of the magneto shock..

https://www.youtube.com/watch?v=SBXQ-6uI8GY

[fbn ent]

Thank you gentlemen  .  I don't suppose similar charting is available for the Monotubes......apples 'n oranges?