Fork oil options

[squirrel_hunter]

I would ask KTech or experiment myself.

From my experience stock is 10W but is far too soft, so use 15W. I did this on my first SV, transformed the handling. My second SV came with Ohlins front and rear, when the time came to change the fork oil I wasn't sure what to use, so I put 15W in as that is what I'd used for my first SV. Took the bike out for a run and came straight back to the garage and emptied the 15W and put 10W in. It was horrific with the 15W and perfect with the 10W.

My thoughts were that Ohlins springs were designed to work with the stock setup and hence 10W was what I needed, I'd suggest to start with that and then see what it rides like.

[johnnyrod]

I find it hard to believe the difference between 10W and 15W being "horrific"

[squirrel_hunter]

It was a while ago now but yeah the difference was night and day. I thought I'd put something together wrong, it just didn't ride right, the feedback was all wrong. Took the bike out and came straight back, changed the oil to 10W and it was back to how it handled before.

Suspension is something else, get that right and the bike is amazing, get it wrong and its not worth riding, yeah you can ride round a problem but when you do a back to back comparison it really helps. The thing is people often overlook it, things like fork oil, not changing it regularly enough you get used to it, then stick some new stuff in and see what it behaves like. I remember this one time I took a stock SV out, took a roundabout as I would normally on my bike and nearly came off as the rear end couldn't handle the transfer of forces as the road camber changed, the rear end just bounced. I couldn't work out why, as I took it exactly as I would on my bike. Then I remembered I run an Ohlins shock and that one corner showed just how worthwhile it is to have.

[Bibio]

to decide what oil viscosity you need to first have to ask what does the oil do?

[Adam Ef]

Air gap can make a difference too.

[embee]

I once put some Castrol synthetic 10W fork oil in a bike. If you look at the table in the link not only is the viscosity at 40C rather high for a 10W (42cSt compared to typically 35 for most other 10W oils) but also the VI is quite low, at only 150, which means that at lower temps the viscosity will be quite a lot higher. It was like riding with the forks filled with wood, horrible.

Check the table for commercial oils at http://peterverdone.com/wiki/?title=Suspension_Fluid and try to pick something with a viscosity at 40C near what you are after, and try to get as high VI as you can find . Showa SS8 is what I use as a reference, probably what is used in many production bikes I suspect. Suzuki Fork G10 may be what you get in a stock SV650.
A "typical" 10W oil might be expected to be in the region of 35cSt at 40C, Silkolene RSF 10W is nearer to typical 15W values.

[proze]

I am confnoozled: we have people recommending 10w and 15w oil in this thread and 7.5w oil being perfect in this thread: https://forums.sv650.org/showpost.php?p=3114775

Is that due to differences in rider weight? I thought the springs were handling the rider+bike's mass and the oil was handling the damping?

[aesmith]

My understanding is that oil weight will depend on the spring rate. So a heavier spring, as you have, matches thicker oil.

[Adam Ef]

Springs for rider weight / bike sag. Oil to match the valving (or lack of) that it's going through. Start with the right springs for rider and bike. Adjust oil from there. The SV has zero adjustability for oil flow (comp / reb adjusments) so you need to get it more right for how you want the bike to handle. You also need to get it right for the type of use. Getting it spot on for 30 to 50mph riding will be different to the forces put on it at 70mph plus. Same for setting up for road vs track.

In my SV I had 8.5 K-Tech springs (76kg rider + kit) and 12.5wt (approx) oil with YSS emulators set about half way (with welded rebound holes on damper rods). If was firmer than when I got it as stock. Still compliant enough for bad roads and worked well enough for me, but would still show up flaws cornering at 70mph. Not my regular type of riding though, so it didn't worry me.

It's all a bit of a workaround with an SV. If I did one again I'd get the GSXR front end done to have some rebound and compression adjustment. Easier than opening up the forks and pulling emulators out to make adjustments every time.

[embee]

Originally Posted by proze

I am confnoozled: we have people recommending 10w and 15w oil in this thread and 7.5w oil being perfect in this thread: https://forums.sv650.org/showpost.php?p=3114775

If you look at the table of commercial oils in the link, you'll see that the actual viscosity for the various oils doesn't always reflect the label rating. You really need to decide what technical viscosity you want and select a suitable oil, regardless of what the label says (10W, 15W etc).
For example, Silkolene Maintain RSF 7.5W has a true viscosity quite typical of many other 10W oils at around 35cSt at 40C. If you want something heavier than that, look at the oils in the 40-45cSt range and choose one of those.
As said earlier, the viscosity index (VI) shows how the viscosity changes with temperature. The higher the number the less it changes so the more consistent the damping will be. Try to use something with a reasonably high VI, around 300 is good.