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Rvf 400 suspension setup

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by nicka9x, Jul 17, 2011.

  1. i am trying to setup the suspension on this new bike. Taking measurements of the static sag and rider sag I have big difference between front and rear. The rear had static sag of 5mm and rider sag of 30mm which is around what is standard but the front has static sag of 37mm and rider sag of 42mm which is too soft. I have adjusted the preload but makes little difference. The first step I was going to do was change the oil and make sure the level is right. Could not enough oil cause this problem or could it be somthing else. I dont think i need a firmer spring because i only wiegh 76 kg and the rear is fine.


     
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  2. Have you wound the pre load adjusters all the way in? Usually one turn of preload = 1mm of sag (Usually).

    I'd probably start by putting a zip tie on one of your fork legs. See if you're bottoming out your forks. If you're not then it's probably alright. Then you can move onto damping to stop dive.

    If you are bottoming out then you need to look at preloading or spring rates if you've got no more adjustment.

    Typically, oil wont change the amount of sag you have. It'll change damping only unless there's way too much oil then you'll get no movement at all.
     
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  3. Oil only affects the damping, not the spring rate, you need to get springs with the correct rate for your weight & style, until you do that, you will just be chasing your tail.

    Racetech have a calc on their site, http://racetech.com/ChooseVehicle.aspx

    Springs will cost less than $200 for the pair.
     
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  4. sag measurements deal with spring rates. i would be going stiffer in the front fork springs first then doing some more measurements. a stiffer fork spring will mean more weight on the back.

    set your sags correctly first, then you can concentrate fully on dampning. do you know what sort of fork internals they have? do they have damper rods or cartridges?

    oil level only really effects bottoming resistance. not ride height.
     
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  5. Pretty much it. If your near or over 80kg front springs will be on the cards.
    If it's not screwing with your enjoyment then don't bother.
    You can run more sag in the front. 10mm more is a big difference though.
    The oil works with shimms to slow the rate of depression. It wont help in the sag.
    How old are the springs or bike?
    Your close to 80 and with all your kit on. Do you have all your kit on when you set your sags ?
     
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  6. This suggests your standard spring rates could be on the soft side:

    http://old.racetech.com/evalving/Sp...400R&formuse=form1&SpringType=Fork&bikeid=289

    But I'd be playing with preload first.

    The zip tie method is a good method of setting front preload. Put it on. Go for a vigorous ride and the right pre-load is where you have about 10mm up your sleeve. If you are finding you can't wind on anymore preload and the cable tie is bottoming out, then you need to look at new springs.

    It actually looks like the rear is set up with a too much preload.
     
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  7. im going to have to disagree with your way of getting the right springs. but im happy to be corrected. i feel that springs will set the ride height of the bike (sags etc) and it is more of a compression dampning thing of how much of the travel it uses. but yes having a bit of travel leftover is what you want. just for those times when you're hard underbrakes and you hit a bump etc.

    i basically measure the sag, and if its in the ballpark i will go for a ride and see how it feels. i run the ziptie and then come back and write down what it felt like and how much travel it used. if it bottomed out and the sag is sweet i will go for more compression damping. once you're at the limit of the clickers you will want to get it revalved to suit you.

    did some oooooggooogleing and found that the rvf has cartridge forks. thats a relief. you will be able to get this thing sorted well.
     
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  8. Thanks for the feedback. I agree that the rear is a bit on the hard side .I had the preload all the way in on the front and it still bottom out when braking using a zip tie. For example when the bike is on the side stand and then is moved upright there is a 20mm movement down on the fork using the zip tie. Some bike have some movement but 20mm this is excessive.
     
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  9. what is your compression dampning set at?
     
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  10. didnt make much difference in or out, a little better when in, more damping.
     
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  11. They only have rebound as far as I know. The VFR/RVF carry quite a bit of weight over the front wheel, so you can afford to have a bit more than the generally recommended 30% loaded. I went to 0.9 kg springs on my VFR, but when I tried to get 30% sag it just got too skitish on choppy mid corner bumps. So I just backed off the preload till it behaved nicely without bottoming out. Went a little heavier on the oil, and run the damping around the middle of the adjustment range.
    You can afford to raise the rear ride height quite a bit. I went nearly 35mm on my VFR without any ill effects at all. The RVF is a lot easier to adjust as you can make shims to slip under the shock mount. The VFR requires welding of the dogbone and redrilling.
     
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  12. I think you've pretty well answered your own question. Either there is a problem with the stock springs or they're just not the right spring rate. New springs, some fresh fork oil, set a ballpark preload/sag setting front and rear and go from there.

    Probably doesn't need to be said, but with damping, er on the softer side if you don't really know. You're looking for roughly about a one second stroke, compress and rebound evenly and no pogoing. i.e. one single stroke up and down.
     
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  13. Springs will effect ride height, but preload is basically just a ride height adjustment (contrary to popular belief). By it's nature, it will take away, or give you more travel. You should have the right springs, but short of the expenditure, you should set your preload for the right amount of travel and bike attitude.

    Compression damping isn't meant to restrict the amount of travel, but rather slow the rate of travel. You're are right, however, in that heavier damping will effect total travel, but you shouldn't drive your suspension this way.

    Damping should be used to slow the travel, not restrict the amount of travel

    This confirms your front springs are too soft. Taking off a bit of rear pre-load will give you a bit of front travel back, but probably not enough.

    Not a great measure.
     
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  14. Something probably not mentioned is the reason sag settings exist.

    Springs do all the best work at about half of their travel. So, when you're seated on the bike, you want to be at the top half of that meaty part of the spring travel. If your spring rate is too hard, the spring will only operate in the top part of the travel most of the time. Conversely, if they're too sort, in your case, your springs are only working in the lower half, which is bad. Springs don't work well at all in that portion as well as the risk of hitting the stops on full compression.

    As mentioned, preloading adjusts ride height as well as reducing spring travel so you're always working in the meaty section of the spring travel. Once you get in the right area, you can also use preloading to adjust geometry. More preload on the rear/less on the front will have an effect on reducing rake/trail and enhancing turn in but at the cost of stability. I find it much easier to get your front end sorted and use the rear to adjust geometry changes.

    End of the day, preload settings are individual but the usual 30% rule is a really good ballpark. i.e. set your rider sag to 30% of the forks full travel. This applies to all motorcycles.

    Remember also, with harder springs, you'll need more damping.
     
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  15. At this stage it seems I need harder spring. To check the rating of springs is there a code or is the rating stamped (example 0.9kg) on the springs or do i have to get them tested.
     
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  16. The first thing I would be doing is backing off rear pre-load. This might just get enough travel in the front.

    If it does, check handling. This may slow down the steering too much for you.

    If that fails then you might need new springs. They probably won't be marked and even if they are, they have probably suffered sag over the life of the bike. From there you have to assume the ones you have in there are standard and just get ones that are right for your weight and riding intentions.
     
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  17. Yes.

    As Ibast said, just get the right springs for your weight, the calc has been linked twice for you.
     
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  18. i agree that preload is a way of changing ride height. but it is only a fine tuning device IMO. adding preload wont solve any problems if the spring rate isnt in the ballpark. preload doesnt add or take away suspension travel either, it just changes where the bike sits in the stroke of its suspension. if you measure the topped out length with your preload all the way in and all the way out it should not change, the same with the bottomed out length.

    i should have said damping controls how the stroke of the suspension is used.

    oil level/volume is another way of adjusting the damping, but only in the very last part of the travel of the forks. you usually get a range of volumes that you can use, so if the bike feels good and the sag is good but you want a little more bottoming resistance, you add some oil.

    hey op, can you confirm what adjusters you have on your bike and what they are set at? ive done a bit of googling but i cant find out what you have.
     
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  19. Thanks for the correction on reducing travel. As you said, it'll change where it sits in the stroke, therefore reducing compression travel.
     
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  20. Yep, when setting up suspension I tend to concentrate on the compression event initially.

    Agree that preload is only fine tuning, but I'd experiment with the preload before forking out the money for new springs (pun intended)

    Playing around with oil level is getting into the trickier end of the suspension tuning spectrum. It also effects the rising rate nature of forks. Less air gap will give the forks a quicker rising rate as the given travel produces a higher pressure inside the fork. This can help bottoming problem too.
     
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