A Suspension Tale

[weven]

I thought I would share my suspension findings with our bike.

I bought this FG Gubellini fork kit with valves and rear shock.

http://www.fgspecialparts.it/en/product.asp?maker=FG&model=HONDA+VFR+1200+F&year=2013.

The front can only be bought with their 8wt oil ( they call it race oil).

To save freight cost I asked for a price with no oil, they replied no oil no kit.

I removed the forks, had the springs and valve’s fitted and replaced the rear shock.

The front oil level is 110mm with springs installed. I should add there is an inner nylon guide for the spring which helps keep the spring from touching the inside of the fork under full compression, which of course takes up oil volume.

The standard Honda oil level is 160mm no spring. (Fork oil standard cSt @ 40 deg = 15.3)

I set up the sag as per documents supplied with the front and rear kit.

First off I would say at big speed and big lean angle this setup would handle a large serious of bumps and track straight, unlike the standard suspension which had given me a few scares in the past, one in particular when I hit a large hollow which bottomed out the forks with such force the front slid then gripped and stood me bolt upright, thank god for the unbelievable brakes this bike has I managed to scrub off a enough speed that I made the corner, all be it in the dirt on the edge of the road.

That was when I made the decision to replace the standard setup…………

Here in Australia our roads are a disgrace. I have ridden my area for 30 years and believe me the only work done in that time is when a hole is big enough to hide a Kangaroo in they patch it. Patch being the operative word.

The problem I had the front was just too hard, and was uncomfortable at cruising speeds with the continual bumps just beating the crap out of my arms and neck.

So I had to do something, This is where it became interesting.

I decided the fork oil was too thick/heavy so I replaced the fork oil with Motul 2.5wt.

The result was worse, less compliant/harder WTF ??? I assumed that the 2.5wt must be heavier than the 8wt, how can this be ??

(Clearly Italian roads are in a lot better condition than ours, or 8wt is best suited to a smooth race track.)

It appears that there is no recognised standard for fork oil. ( Unlike Hydraulic Oil )

More study reveals that Motul 2.5wt is nearly twice the viscosity as Redline 2.5wt based on the following rating cSt @ 40 deg.

Motul cSt 2.5 @ 40 deg = 16

Redline cSt 2.5 @ 40 deg = 8.6

So I buy Redline and have it shipped from the US of A. Out with the forks and in with the new oil.

Well F*&^ me the difference is unbelievable. The front end is so compliant, just soaks up the bumps, what a difference !! I have turned the rebound damping up 4 clicks which has compensated for the thinner oil.

As some will understand the air gap is really important, it works in the last 50mm or so of travel with air being the best progressive spring known. I have added oil 3 times (total about 30ml per leg) to get the front to bottom out only on the biggest bumps while braking.

All this experimentation has given me a VFR which is now a pleasure to ride fast or just cruising. Hope this helps others.

Cheers

[cutback]

Weven,

Great write up! I'm sure other suspension tinkerer's will find it helpful....

[weven]

Thanks cutback, one thing I did fail to mention in my story, I have dropped the forks 5ml through the triple clamps which does make the bike turn in quicker.

Trust me that 5ml makes a noticeable difference.

Cheers

[cutback]

^^^^ I agree with you there! I've got a DMR (Jaime) front fork re-valve and dropped mine 4mm. Completely different bike.....

[Baileyrock]

Nice work and investigating on fork oils. Thanks for sharing the info here as that is why were here in the first place, to help fellow owners!

Thanks and glad you love the bike now!

BR

[ggathagan]

Those are odd numbers, but I can't find any specifics on Motul's 2.5w oil on line. I'm assuming you got them from the bottle itself.

The specs on their 5w oil are very close to the specs for Redline's 5w oil:

The following specs are from the respective manufacturers websites:

Motul Factory Line (FL) Light 5w
Vis @ 100°C 4 cSt
Vis @ 40°C 18 cSt

Redline LightWeight 5wt Suspension Fluid
Vis @ 100°C 7.3 cSt
Vis @ 40°C 16.0 cSt

The specs I found for Redline 2.5 differ slightly from yours:

Redline ExtraLight 2.5wt Suspension Fluid
Vis @ 100°C 4.0 cSt
Vis @ 40°C 8.6 cSt

As I said, I can't find anything on the Motul 2.5.

They do have the MSDS sheet for it, but they list the viscosity with a different standard of measurement: 14 mm2/s < v <= 20,5 mm2/s (40°C)

[weven]

My info found here, according to this the

http://mahonkin.com/~milktree/motorcycles/fork-oil.html

ASTM D445 Motul 2.5w Vis @ 40°C 16.1cSt

Or 16 if you look here: http://www.mediaturbo.com/clients/marzocchi/forkoilviscosity.html

And here http://www.qemsc.com.au/documents/suspensionoils.pdf.

Which means the different oils are all over the place.

Based on the different feel from the FG Gubellini 8 wt I would guess Vis @ 40°C 12 to 13 cSt

Cheers

[weven]

Those are odd numbers, but I can't find any specifics on Motul's 2.5w oil on line. I'm assuming you got them from the bottle itself.

The specs on their 5w oil are very close to the specs for Redline's 5w oil:

The following specs are from the respective manufacturers websites:

Motul Factory Line (FL) Light 5w

Vis @ 100°C 4 cSt

Vis @ 40°C 18 cSt

Redline LightWeight 5wt Suspension Fluid

Vis @ 100°C 7.3 cSt

Vis @ 40°C 16.0 cSt

The specs I found for Redline 2.5 differ slightly from yours:

Redline ExtraLight 2.5wt Suspension Fluid

Vis @ 100°C 4.0 cSt

Vis @ 40°C 8.6 cSt

As I said, I can't find anything on the Motul 2.5.

They do have the MSDS sheet for it, but they list the viscosity with a different standard of measurement: 14 mm2/s < v <= 20,5 mm2/s (40°C)

Your correct with Redline just checked their site, will edit.

Cheers