Fork oil weight.

Been giving this some thought and wondered what the techies out there thought was the best weight of oil for the SV?

I recently upgraded to Ohlins springs and popped 15W oil in there as I was under the belief that this would compensate for the SV's poor damping. However, I've been thinking was I right to go for heavier oil? Would I have been better opting for a lighter weight oil like 5W to allow the damping to work more efficiently?

Cheers
Jase

[Viney]

Why did you change the oil in the 1st place?

The std is 10w, i find this fine to be honest.

15w is what everyone seems to do becuase that is the norm.

I may try 12.5w when i next change my for oil. (This is a mix of 1L of 15 and 1L of 10w

At the end of the day, oil is there for the damping and nothing else iirc.

I have been playing with my forks recently, so this is very topical for me!!

Short answer, depends on what you want to do??? Do you feel the front is too springy or too stiff/slow?

Ok as a bit of background, your basic premise is that the thicker the oil the more damping you have. The thinner the oil the less damping you have.

If you have put in stiffer springs, then it would be logical to ‘up’ the damping to compensate (else the springs will be stronger than the damping, effectively making the forks under damped). The crude way of doing this is to change the oil viscosity.

So theoretically you have done the right thing going from 10w (stock) to 15w with the, what I presume are stiffer springs. This will keep the damping properties consistent.

But now for the personal preference bit!!! I like a soft, low damped front, I had .85kg/mm springs (stock is ~ .7kg/mm), I did have 20w oil in there, hated it, put 15w in still not much better, finally I have put 7.5w oil in there and am now happy (still think it is over sprung).

Any help?

[northwind]

I used 15W, which was pretty heavy I think... If I'd ever redone it, I'd have tried 12.5W. Going lighter will reduce all the damping- more dive and more pogoing, since SV forks basically work by squeezing the oil through holes. Exactly like a door closer...

Something else to think about.

When considering damping you need to understand the difference between slow and fast damping, where the speed of the damping relates to the speed of suspension travel. Typicaly, when going over a bump high speed damping comes into effect, where as weight tranfser from braking for example, is controlled by slow speed damping.

The SV uses damping rods to restrict fork oil flow to create the damping, which is a rather crude (but cheap) way of doing things.

Now the important part - damping rods create lots of high speed damping but little low speed damping. Result being, the front feels soft under braking, but harsh over sharp bumps. To prevent high speed damping being too stiff (giving a harsh ride over said bumps) Suzuki havn't put a thick oil in.

So whatever you do the front will feel both soft and stiff, you've just got to find a compramise that works for you.

Originally Posted by Viney

Why did you change the oil in the 1st place?

Changed the springs to Ohlins, so was changing the oil anyway and thought along the same lines as Blue_SV650S that heavier oil would go with the stiffer springs.

Right then, reviewing these ever helpful responses, my damping is a little harsh at times (specifically when "giving it some" which is quite un-nerving) so might return to 10W oil and see whether it suits me better.