Member Contributer ProMed Posted January 18, 2006 Member Contributer Share Posted January 18, 2006 I recently ordered a set of 1.0kg Race Tech Springs for my 02 and am now trying to decide which weight and brand of fork oil to use. My body weight is always around 195-205. After searching the board it seems some guys are going with 10w and others with 5w. Could someone help me decide which would be best to start out with? Thanks! Paul Link to comment Share on other sites More sharing options...
Guest Posted January 19, 2006 Share Posted January 19, 2006 I recently ordered a set of 1.0kg Race Tech Springs for my 02 and am now trying to decide which weight and brand of fork oil to use. My body weight is always around 195-205. After searching the board it seems some guys are going with 10w and others with 5w. Could someone help me decide which would be best to start out with? Thanks! Paul <{POST_SNAPBACK}> Hi Paul, I can offer you some advice, but it can't take credit for it. I recently had the forks on my 98 checked over. The guy that did them was a mechanic for Lindemann for quite some time (Josh Boykin). He now has a shop near me, luckily. I was in the middle of replacing oil when I realized the work previously done was crap. My forks have Race Tech springs and compression valves. Josh revalved (shim adjustments) the forks and set it up with 10W. Race tech will suggest 5W, but as it was explained to me (convincingly), Race Tech isn't all they are cracked up to be. Personal experience also confirms it. There is good reason to use heavier oil if you go to heavier springs if you are not changing the valving. Contrary to some perceptions, heavier springs are not "stiffer". "Stiffer" is misleading, they simply require more force to compress (duh). BUT, a bit more damping is needed because the springs will compress and rebound at a higher frequency. Just because they don't move as much at a given force doesn't mean they aren't bouncing you all over the road. Like strings on a guitar or the difference between a weak spring and a strong spring on a pogo stick. Start with the 10W, since I assume you are going from stock to 1kg, and no valve change. Going to 7.5W or 5W will reduce damping while adding springs that actually require more control. All this is based on my most recent research and conversation with Josh. In fact, I just brought the reworked forks home today :thumbsup: Link to comment Share on other sites More sharing options...
Member Contributer ProMed Posted February 22, 2006 Author Member Contributer Share Posted February 22, 2006 Thanks for the reply Rick. Very good information, keep up updated on how your bike turns out. I also seem to remember Slammer saying somewhere that he upgraded his springs and went from 5w to 10w or vice-versa? Link to comment Share on other sites More sharing options...
Forum CEO HispanicSlammer Posted February 22, 2006 Forum CEO Share Posted February 22, 2006 , they simply require more force to compress (duh). BUT, a bit more damping is needed because the springs will compress and rebound at a higher frequency Your bike was re-valved for 10w oil simple as that. The stock VFR is valved for 10w oil but uses .75kg springs stock. Add in heavier springs and the whole thing is overdamped. I know I had them that way for 3 months before I revalved them myself. Race tech is mainly a Racing suspension company and so make up a very stiff racing suspension, some find it too stiff for street riding I am sorry but that quote does not make sense to me. If it takes more energy to compress these heavier springs than it would need less energy to damp that movement as most of the energy is absorbed by the spring and not the oil now. You will find a very harsh ride with 1kg springs and 10w oil. I did anyway, 5w oil worked to some extent to make it feel much less harsh - I would strongly recommend revalving the forks too. Honda VFR forks have always been undersprung and overddamped, the oil does a large portion of absorbing the shock in honda forks, small little holes in the valves and tiny shims make for a wider host of rider wieghts than big holes and big shims for a resonably good ride. Go changing the spring wieght and your all out of whack. If you plan to keep 10w oil I would then consider backing off the oil level a smidge so that the air pocket is a bit more than stock, air is the other natural spring in the fork, and it is progressive. To use your guitar analogy the heavy strings are the low frequency bass strings and the lighter strings are the higher pitch. so I think the opposite is true of that quote. Link to comment Share on other sites More sharing options...
Member Contributer ProMed Posted February 22, 2006 Author Member Contributer Share Posted February 22, 2006 Was there any change to the valves in the 6th gen forks? Link to comment Share on other sites More sharing options...
Forum CEO HispanicSlammer Posted February 22, 2006 Forum CEO Share Posted February 22, 2006 Was there any change to the valves in the 6th gen forks? You know I think the cartidge is the same but the 6th gen does have a heavier spring than the 5th gen so I dont really know. I havent seen the valves on a 6th gen I know they are the same but the shim stacks I am not sure of. Honda always lists the cartridge as one part. Link to comment Share on other sites More sharing options...
Member Contributer vfrjim2002 Posted February 22, 2006 Member Contributer Share Posted February 22, 2006 Your bike was re-valved for 10w oil simple as that.? The stock VFR is valved for 10w oil but uses .75kg springs stock.? Add in heavier springs and the whole thing is overdamped.? I know I had them that way for 3 months before I revalved them myself.? Race tech is mainly a Racing suspension company and so make up a very stiff racing suspension, some find it too stiff for street riding... <{POST_SNAPBACK}> Part of the problem that revalving addresses is the imbalance created when you install stiffer springs. The fork's resistance to compression is a function both of spring force and compression damping. If you install higher rate springs and don't change the compression damping of the forks (through lighter oil or revalving), the front end may very well feel overly harsh. The trick is to balance compression damping and spring rate to get controlled, but not harsh movement. The problem with going to lighter fork oil is that, now that you have higher rate springs, you will probably need additional rebound damping to deal with the higher forces the springs feed back into the system. But, since you went to lower viscosity oil to smooth compression out a bit, you are now seriously underdamped on rebound. The only real solution is a revalve by somebody who knows what they're doing. You seem to have a handle on that part of it. I haven't bought springs yet, but my initial take is that RaceTech and others spec springs that are more than little on the heavy side for most street apps. I'll probably go no "stiffer" than .90. Revalve or not? I guess I'll wait and see. Kids in college and all that. :rolleyes: Link to comment Share on other sites More sharing options...
Baileyrock Posted February 22, 2006 Share Posted February 22, 2006 Add in heavier springs and the whole thing is overdamped. I am sorry but that quote does not make sense to me. If it takes more energy to compress these heavier springs than it would need less energy to damp that movement as most of the energy is absorbed by the spring and not the oil now. I think you missed what he was trying to say HS and vfrjim covers it some. From what I understand Rebound damping is the most important one to get right first. If you install higher rate springs and change nothing else it will Rebound faster because the higher spring rate is pushing up harder or faster without increasing rebound damping. You are correct on the compression side with a over dampened stock fork and stiffer springs you will have a harsher fork. Use a lighter oil to improve the compression side and you loose needed rebound damping control. This is why revalving is the best way to solve the issue. All suspension builders I spoke with said that it's better the have rebound adjustments on your forks (like yours) than comp. adjust.. Springs are used to keep the bike off the ground, Damping is used to control spring oscillation(bouncing). Wierd stuff IMO. :rolleyes: Link to comment Share on other sites More sharing options...
Member Contributer ProMed Posted February 24, 2006 Author Member Contributer Share Posted February 24, 2006 Thanks for the great info! A friend of mine that is a Honda mech said that with some oils you can actually mix 10w and 5w fork oil to come up with a 7w oil. He spins wrenches for a pro motocrosser and said they have used this trick to help fine tune for specific tracks. Has anyone ever heard of this? I would like to go with revalving right now, but have already spent too much on the VFR this month. 7w oil sounds like it may be a decent comprimise until I can do it right, or should I just stick with the 10w and drop the level a bit? Link to comment Share on other sites More sharing options...
Member Contributer tok tokkie Posted February 24, 2006 Member Contributer Share Posted February 24, 2006 I read with interest that heavier springs need more re-bound damping. When you hit a bump that causes the suspension to contract. That is a definite amount of energy transferred to the spring. After the bump the energy is released by squirting the oil through the rebound damping system. The same amount of energy went into both springs (set by bike speed & the bump; the spring simply absorbs the energy coming at it) so why should the rebound be different? I am not disputing the fact that a heavier spring needs more rebound damping. I am trying to understand why it needs to be different to a softer spring. Is it just that it would spring back too violently if it is under-damped. (Think I have answered my own question.) Link to comment Share on other sites More sharing options...
Member Contributer johne Posted February 24, 2006 Member Contributer Share Posted February 24, 2006 you can actually mix 10w and 5w fork oil to come up with a 7w oil. Has anyone ever heard of this? <{POST_SNAPBACK}> Why not just buy the 7wt oil?? Link to comment Share on other sites More sharing options...
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