Comparison of Viscosity (
[email protected]/
[email protected]/VTC)
Ohlins 1309: 19/13/0.32
Showa SS-15: 20/13.4/0.33
BelRay HVI 5wt: 19.5/6.6/0.66 (viscosity index 345)
Shell Advance 7.5: 22/4.9/0.78 (viscosity index 153)
Shell Donax TA: 34.9/7.2/0.79 (viscosity index 141)
I am thinking of using BelRay HVI 5wt as it is available, cheap, and shares comparable numbers between Ohlins and Shell. However, I am concerned about using shock fluid for forks, as you can see the viscosity index is dramatically higher. While a higher VI simply suggest a stable viscosity over a broad range of temperature, I am worried that a shock fluid is not compatible with forks regarding fork internals, fork seals, etc.
Any pros know if using a shock fluid in forks with dramatically higher VI (albeit similar viscosities) is acceptable?
Don't worry about the shock v fork fluid issue.
It's just a name.
As far as seal compatibility goes, it's not an issue. AT ALL. So don't worry about it
Regarding seals, you will almost certainly go through OHLINS seals over time, as they can tend to leak unexpectedly.
So it's good to be able to have a consistent supply of suspension fluid what ever you choose to go with, simply so you can service your forks readily.
Try to select your fluid as close as you can to the factory stuff in accordance with the stated cold viscosity.
The higher the VI of the fluid, the more linear the performance of the fork will be at all times.
The choice of Belray is moving in the right direction regarding it's availability, but IMO it's a compromise.
The Showa fluid is far, far superior.
The OHLINS fluid is the gold standard in terms of performance.
Ideally one needs a fluid that has the most stable viscosity over the operating temperature range of the unit.
What ever you choose, you ideally need to stick to it and set your valving up to suit your application with that fluid. This makes the availability of the Belray fluid a good reason to go with it I suppose.
Also it won't be the same as what comes out of the fork as a factory fill either. So you need to consider that. The Shell stuff is not necessarily what comes out of the fork. It can be a bit of a lottery as to what you get.
The Donax is simply Dexron II spec ATF.
They put that in the manual as a backstop(good old ATF), in case one can't get something else in their market or in case of emergency. It may be fine in a clunker chook chaser on the farm, but really not all that great in your OHLINS.
I totally agree with the previously stated reasons for using the genuine OHLINS fluid.
Actually data I have floating around here somewhere, indicates that the OHLINS fluid has a much higher VI than anything else on the market. This is reflected in the data you have posted.
I don't know what it is, but it certainly can be made of unobtanium at times.
I can either get it from my dealer or another suspension specialist.
Interestingly the 1309 fluid is the only fluid OHLINS are supplying as a "standardised" item these days. They supply it to the race teams.
So on balance, I think that is an indication of how OHLINS themselves regard the 1309 fluid as an essential component in the performance of their forks and how it works with their valving
