I have an SV, with the crap "damper rod" forks. As you know, that means I have to use thicker oil than all you guys with cartridge forks. Currently I use either 15W or 20W. And the problem with that is, when it's cold out, the oil gets too thick, hurting the ride. So would it be possible to use synthetic oil instead? Maybe a special single-weight oil like Redline, with no viscosity enhancers?
That's not how it works. Straight weight means it gets thicker when cold. What you want is something with a high viscosity index: Redline and Silkolene pro RSF seem to be the best. Have a look at http://www.peterverdonedesigns.com/motorcycle.htm#oils for some details
Re: Re: Synthetic fork oil? All oils get thicker when they're cold, even multi weights. All I'm saying is that I want a synthetic, because they are more resistant to getting thick.
Re: Re: Re: Synthetic fork oil? Yes dude, but multi-weights do it less, that's what defines them, although in a crude way. The VI is a measure of how much the oil changes visc. with temp: the larger it is, the smaller the variation. Silkolene Pro RSF is up around 300, some other synths nearer 140. Synthetics aint synthetics, Sol...
No, the larger the difference between the 2 numbers, the more able it is to handle high heat. Otherwise it would thin out too much when the engine's hot. If you take a straight-weight 5W oil, and compare it with a 5W-30 oil from the same manufacturer and the same base stock, they will have the same pourability on a 20-degree morning. But the 5W-30 will last longer during high-heat operation, because it has viscosity-building additives. Just my opinion. The second number only indicates its ability to avoid thinning out under high heat loads.
Yes, the second number determined by the viscosity at 100C. Fork oils labelled as 5w are NOT straight, single grade oils, they thin out much less. This is particularly so for synthetics. The labels are essentially arbitrary: for eg Silkolene 7.5 has the same viscosity at 20C as Shell Advance 10wt and MORE than Motul 10wt. In other words, the number on the side of the bottle tells you almost nothing about how the viscosity depends on temp, unlike motor oils for which the SAE standard was worked out. One trick is to use shock oil, which has a higher VI to deal with the much higher temperature range shocks see, relative to forks.
So bottom line, what should I do? I don't think shock fluid will be thick enough for me. I want something that's as thick as your typical 20W fork oil, but that doesn't turn into jello in cold weather. The 20W I have in there now is fine in the summer. It's the winter, and cold mornings, that give me problems.
Try this site for a pretty thorough list of suspension fluids and their specs. You'll have to scroll down the page to get to the list. http://www.traxxion.com/forum/topic.asp?TOPIC_ID=289 Like the above post said the Silkolene Pro RSF and Redline are the best that I've ever used and they last longer before breaking down too.
Wonder what the result would be if you warmed up the forks with a heat gun immediately prior to the session? Just thinking out loud.
Why would you bother doing that? Don't over-dildosize the front end. Hang some fluid in it and ride it.
If you were experiencing a large swing in ambient air temperature on your race/track day (say 40F at 0900 hrs on up to 70F by 1300 hrs) then the theory would be to warm the fork oil up to operating temperature before going out for the 0900 session. This is taking into account that everything feels fine with your setup when it's 70F. Let's just say I got religion real fast one day in the first session of a cold morning trackday at CMP while braking into T1 for the first time that session. The tires were set/warmed correctly and I was going at a reasonable warmup pace. I would not mount the heat gun to the forks btw.
Yeah but how would you do that. Pumping the forks up and down doesn't really create much heat, if any
You wouldn't warp the inner tubes, but do you see any of the factory teams heating their forks with a heat gun?
You're correct. A factory team would probably just have one of their highly paid techs change the fork oil to match the conditions. Not many racers on budget would do that.
