Guest daemontrym Posted September 3, 2011 Share Posted September 3, 2011 Through the search I have found that if I raise oil height the mid/end stroke gets harder and the opposite happens when lowered. One confusing argument I found was with heavier springs many people say use a heavier weight oil to dampen it and some say to stay with stock or use a light weight oil, dunno what to think about that. Awhile back Installed hyperpro progressive springs which came with 15wt oil and instructions to run a 100mm oil height. The ride was harsh no matter how I set the preload in the front and the front tire would follow any small groove, tar snake and bump steer. So I switched to a 10 wt oil (Honda SS8) running the same level that hyperpro recommended. I feel I am in the ball park of a great setup but wan't to soften the forks a little bit more. So I was thinking about running a 120mm oil height so I can fine tune the harshness out. What would you guys suggest? Link to comment Share on other sites More sharing options...
Veefer800Canuck Posted September 3, 2011 Share Posted September 3, 2011 Give it a try and see, that's the only way to know for sure. If that doesn't work, there is always 7.5wt at 100mm Link to comment Share on other sites More sharing options...
VIFFER93 Posted September 3, 2011 Share Posted September 3, 2011 Give it a try and see, that's the only way to know for sure. If that doesn't work, there is always 7.5wt at 100mm +1 All I would add is that suspention takes a lot of time to understand and more experimentation. We have a gentlemen who runs a full day suspension clinic with the track school I go to and the first parts of the morning are nothing more then dial all your settings one way and go ride it, then turn them the other way and go ride just so you have know what it feels like and then they start to dial things in. It sounds like you know how things "feel" and just need to dial things in. Link to comment Share on other sites More sharing options...
Guest Posted September 3, 2011 Share Posted September 3, 2011 I will try to go down about 1/2 Oz in each fork so I don't have to take it all apart. If that doesn't work I am going to try the 7.5Wt The main problem I have with it is in a turn if there is uneven pavement or a bunch of little bumps instead of soaking them up some the front bounces off of them and it bump steers a little. This is even when backing off on the preload, From all the way in to all the way out it is 15 turns and I have them set to 11 turns. The preload feels good, the springs feel good, but just that last little bit of jarring causes alittle of bump steering. Tires are in good condition (PR2) new front and rear has 4k on it with a lot of life left with no flat spots/cupping. Link to comment Share on other sites More sharing options...
Baileyrock Posted September 4, 2011 Share Posted September 4, 2011 I will try to go down about 1/2 Oz in each fork so I don't have to take it all apart. If that doesn't work I am going to try the 7.5Wt The main problem I have with it is in a turn if there is uneven pavement or a bunch of little bumps instead of soaking them up some the front bounces off of them and it bump steers a little. This is even when backing off on the preload, From all the way in to all the way out it is 15 turns and I have them set to 11 turns. The preload feels good, the springs feel good, but just that last little bit of jarring causes alittle of bump steering. Tires are in good condition (PR2) new front and rear has 4k on it with a lot of life left with no flat spots/cupping. IMO the 15wt oil is your issue! Firmer springs with heavier oil is dramatically slowing the forks ability to absorb bumps quick enough! Change out that 15w for either 7.5 or 10w at stock levels, that should greatly improve the forks ability to absorb those bumps. Increasing oil level in the forks will help firm up the entire stroke slightly, but mostly firm up the last part of the stroke/travel(anti-bottoming). It does NOT lighten the damping in the first part of the stroke as mentioned in your first post. Basically whats happening with oil level changes is that the Air trapped in the top of the tube acts as a secondary spring as it's compressed. When you add more oil you decrease the air volume in the tube which is harder to compress so it acts to stiffen the fork to a point. The problem with stock valve and stiffer springs is that ie: A stiffer spring will require Less compression damping and More rebound damping to properly control the spring. In your fork where you added 15w oil with the new springs it had one positive effect; increase rebound damping, but also a negative effect: increased Comp damping slowing Highspeed/Bump damping resulting in your harsh ride! I would go with 7.5w and test your results. You can use my 30 min fork oil change method to do so. BR The only problem with going to the 7.5w is that you may not have enough rebound damping to control the new springs. Link to comment Share on other sites More sharing options...
Guest Posted September 5, 2011 Share Posted September 5, 2011 I didnt take the forks apart or anything I just used a small medicine cup and took 15ml out of each fork. It feels a bit better, but I will give it some time through my commute to school and some longer rides. 10w has been in the forks for a few months now, plus I had a bit of work to do to my fiance's Katana 600 too. Thanks for the help I have 1.0KG springs too should I do a quick swap from the hyper pro progessives to them? I tried them with 5w and an oil height of 120mm and the front felt like a pogo stick. Would this be remedied by the 10wt currently in there, the swap takes like 5 minutes. Link to comment Share on other sites More sharing options...
Baileyrock Posted September 6, 2011 Share Posted September 6, 2011 I have 1.0KG springs too should I do a quick swap from the hyper pro progessives to them? I tried them with 5w and an oil height of 120mm and the front felt like a pogo stick. I don't remember what stock setting is on your forks, but 120 seems low. Wonder if that was enough to even work? Think I set mine at 100 last time? Link to comment Share on other sites More sharing options...
Guest Posted September 6, 2011 Share Posted September 6, 2011 The manual states running 13.9Oz of fork oil but does not give the oil height from what I see. I know at 100mm oil height I put in 16.9oz when I put the forks together since I used 2 small bottles of the Honda SS8. I took 15mL out of each fork now leaving me at 16.5oz which softened it up some. I am debating about putting in my straight rate springs and taking another 2oz out of each fork putting me just above stock fork oil levels with 10w oil. I have a hyperpro set of progressive springs in it now and the 1.0kg sonic springs laying around. Do you think with the 10wt and the 1.0 Kg springs that the setup will work better than when I tried it with the 5w? Link to comment Share on other sites More sharing options...
zRoYz Posted September 6, 2011 Share Posted September 6, 2011 The Gen4 oil level measurement is 177mm that is without spring & forks compressed & from factory they has 7W oil. To install 15W & a level of 100mm your forks would not even react & you would be asking for a front end lose if your into a corner & hit some bumps. You might get away with that if you weighted over 200kgs but then you would be over the load rating of the bike & the rear shock would be at the bump stop. Few points most use heavier fork oil because there to cheap to have valving adjusted for the flow rates needed for the heavier spring they install, it is simply a quick fix but not a wise one because you lose responsiveness which for motorbike suspension is the most important thing. With the VFR we don't have remote adjustable rebound so you need to more or less try to get a compromise setting with the internal parts, then you can fine tune with changing oil level you should only add max 20mm more height & really not go under standard height but you can get away with 5mm if you have to. If you need to adjust outside that limit of fine tuning then you need valve adjustment to suit your needs. I'm also not a fan of progressive springs for the simple reason the spring rate changes as they compress, which means your rebound also has to work with a variable spring rate which just doesn't happen, so you can be using 1/3rd of fork travel & the rebound is perfect, start using 2/3rds the front starts bouncing because the rebound can't handle the higher spring rate so 1/3rd of the return stroke is coming back to fast. Link to comment Share on other sites More sharing options...
Guest Posted September 6, 2011 Share Posted September 6, 2011 Great info there zRoYz and Br I am going to try putting in the 1.0kg springs and lower the height to stock levels. If that doesn't work it will be a weekend project to move to a 7.5 weight. I ran a 5wt with the springs and a 115/120mm oil height as perscribed from jamie daughtery but the forks felt like a pogo stick. Valving I will take care of in a couple of months because I have a wedding to pay for first.. Thanks guys Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted September 7, 2011 Member Contributer Share Posted September 7, 2011 this is what the manual (downloadable form Files section here on VFRD) says airpocket height mm (in) Link to comment Share on other sites More sharing options...
Guest Posted September 8, 2011 Share Posted September 8, 2011 Appreciate it Dutchy.. Friday I will pull the forks off and change the fluid since I have a 60 mile commute to class tomorrow. I changed springs today real quick and everything feels a lot better and I purchased the lighter fork oil today. I will go with what was recommended because it feels close to where I want it. Link to comment Share on other sites More sharing options...
Guest Posted September 10, 2011 Share Posted September 10, 2011 I had fork seals, all the bushings, and new O rings laying around that I bought while deployed last year. I decided to pull the forks completely apart, replace all service parts with new ones, and filled them each with 14oz of a Motorex 7.5W/ Honda Hp 5w mix. The motorex was the only 7.5w I could find locally and looked up the CST chart online to find that it was actually almost as thick as Honda SS8. I had the honda HP 5w laying around from my last experiment and decided to split the difference Once everything was back together I took it for a test ride over by my school on a road filled with tar snakes, warped pavement, and bumpy curves. The forks are much more compliant now and the bumps are soaked up nicely in the turns. Thanks guys Link to comment Share on other sites More sharing options...
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