| Author | Message | ||
     Bsulysses |
Is there a mathematical or scientific equation to do as to finding the right mixture for the two different weights and a certain number of millimeters i have to be exact to from top down? Anybody running there own 12.5wt? Going to be able to get to my forks today dust and oil seals are in and I have 10wt in a 1Liter bottle and 20wt in a 16oz (same brand). I know the oil level I'm trying to achieve may be preference based, but I'm just looking to get somewhere around the right mm from the top down. I'm not doing the spring swap. - avg 250lbs every ride, 200's me and give or take around 50lbs of needs and tools - looking for less brake dive but not so stiff a crack in the road feels like a speed bump - according the the suspension specialist, 10wt and 20wt will get me to 12.5 with the right equation, If that's wrong let me know. I'm hoping with the custom weight and the right levels I will have a better progressive performance in my single rate springs? any input is greatly appreciated! Brandon | ||
| Hughlysses |
Brandon- The final viscosity will just be an proportional average of the mixture. Example: Mix 1 quart of 10W and 0.5 quarts of 20W. What is final viscosity? (1)(10) + (0.5)(20) / (1+0.5) = 13.3 So, if you mix 1 quart of 10W and half a quart of 20W, you wind up with 13.3W fork oil. In your case, you want to wind up with 12.5, so you can solve for how much 20W you need. (1)(10) + (X) (20)/ 1+X = 12.5 I'm not gonna type out all the algebra, but X works out to 0.3333, so you need 1 part of 10 weight fork oil plus 1/3 part of 20 weight fork oil to get 12.5 weight fork oil. All that said, note that actual fork oil viscosity compared to claimed fork oil viscosity varies wildly from manufacturer to manufacturer. (There's a webpage that documents this- I don't have the link handy.) Fork oil labeled 10W may be actually 5W or 15W when measured accurately in a lab. So if you're experimenting, use one brand of fork oil for your experiments. (Message edited by Hughlysses on January 30, 2015) (Message edited by Hughlysses on January 30, 2015) | ||
| Bsulysses |
Thank you Hughlysses! The mm from top down measurement is going to come from me accurately mixing the two and pouring in, once filled the mm from top down will show me how high to fill the next fork? basically does the air pocket measured in mm from top down matter or do I focus on getting all old oil and debris drained and just put the right amount of oil in. If I run 12.5 is there a specific mm I should be within running that viscosity, ex: around 18oz in one fork with regular type e HD oil so maybe less ounces with a heavier viscosity? | ||
| Bluzm2 |
A bit more complex than that unfortunately. The oil level determines the air volume above the oil. This air space it also part of the equation as it acts as part of the "spring". A lower viscosity oil will feel different than the same oil with more in each leg. This comes into play at as the fork starts reaching maximum compression, the smaller volume of air doesn't compress as much therefore providing less air spring action.. Actually as simple as that either, the air volume determines the air spring "rate" too. Basically, its an art and a science! | ||
| Arcticktm |
I can't give you specific recommendations for your intended oil (I run lighter oil than that), but I can say just measure (without the spring) the distance from top of fork to oil level, and that is the number you set oil height to. That elminates the variable of not knowing how much oil you got our, what is trapped, measurement error, etc. I'd start with the oil level in the book (or seach on here for chart) for your year. Or in my case I use '07 numbers, because I swapped to the '07 triple rate springs, as many have done. If you then need stiffer, add more oil to each. softer, take same amount out. I think I would go in roughly 5mm increments. This does not need to be done down to crazy levels of precision, so don't kill yourself being accurate within less than 1mm or something like that. | ||
| Arry |
Harley E type oil = 5wt. Bel Ray 20wt. = Haley E type So, obviously, 5 = 20 .....? | ||
| Mark_weiss |
No need to change oil viscosity, use the suspension's damping adjusters. If you wish to slow down the suspension's movement, just screw in an adjuster a couple of turns. To slow down front end dive, tighten the compression adjusters at the bottom of each fork. Slowing down the rear rebound will help this as well. Just keep in mind that slowing down the suspension (by changing the adjusters or switching oil viscosity) will affect ride quality at all times, not just during braking. Also, slowing down the suspension's movement will not reduce front end dive, it will just allow it to happen more slowly. If you want to change the bike's dive characteristics you need to change the spring rate. A relatively simple way to do this, with minimal affect on general ride quality, is to decrease the air space inside the fork. This is done by raising the height of the oil. Less air space, more spring effect as the forks compress and squish the air. Try raising the oil level by about 10mm at a time. I'm sure that somewhere online there is a geometry site with a formula for volume. | ||
| Pontlee77 |
White at that who not up grade to 2007 Springs that are progresive | ||
| Johnshore |
+1 on the spring upgrade. Reasonably priced and effective upgrade. | ||
| Tootal |
Hugh and Mark are right. You can't compare fork oil weights from brand to brand. I found the ride too harsh and switched to 5 wt. Amsoil and use my fork adjustments to dial it in. Adding more oil will will help with dive. Using thicker oil will effect ride but still allow dive, only slower. I have the 07 springs also and they were an improvement for me. | ||
| Danair |
I showed Al something I came across when doing my forks. I have an 06 and a 07. Did all 4 at once. 07 had progressives in it. Got all done and 07 rode like hell. Usual head scratching and mental replay. Did everything by the book. So I read it again and thought "that's not where I set the level" Well, I was in the 07 book which I keep on my desk, but I used the 06 book cuz its all dirty and lives on the bench. There is a huge difference in the level between 06 and 07 and reducing that airspace, at least by this delta, had a drastic affect....so sneak up on that one if you go that route. |
