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suspension tuning / spv valve / oil weight

Discussion in 'The Shop' started by nmr8, Jan 26, 2008.

  1. nmr8

    nmr8 Monkey

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    so a few weeks ago under the advisement of local suspension afficionado luca marinelli i modded the spv damper of my '05 nixon super plus spv evole mega turbo edition. ][.

    the mod consisted of removing on of the two shims at the top of the damper, with the understanding that it would liven up the rebound and reduce the spv-ness of the damper.

    what i was really looking for was a fork that felt more like my fox, although the nixon is a 145 and the fox is a 100.

    i had felt, before the mod, that the fork was out of wack, it rebounded really slowly but also had a lot of stiction. the mod definitely made the rebound quicker, and also made the fork sound different, the hissing/scratching noise of high pressure squirting became a lot louder.

    but the stiction was still there, so today i rebuilt the fork. i dumped all the old lubricant and set everything back to factory (lubricant wise, the damper is still modded.) i used motorex 5 weight in the damper as called for, and 50 weight engine oil on top of the air piston, and that's within spec.

    but i didn't have any 5-40 semi bath oil for the lowers, so i used 50 weight there too.

    my questions are these:

    - does anyone have any experience tuning spv dampers and have any pointers to offer?

    -is using 50 weight instead of 5-40 semi bath a really bad thing for the lowers?

    -why are there sometimes two numbers in oil specs?

    -i also used park grease on the top cap threads instead of prep-m, how bad is that? and why?

    -how exactly does semi bath lube work? what does it lube?


    after finishing the rebuild i'm pretty happy with the fork (relative to it's old self, i'm still ordering a fox for the bike :P ) redoing the lubes definitely removed the heinous stiction from before. the rebound adjust still seems to have shockingly little effect on the performance of the fork though.
     

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  2. Tesla

    Tesla Chimp

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    Most of the so called semi-bath forks Ive seen, seem to rely on the oil splashing around to lube, 50 cwt oil is not the way to go IMHO

    I use five weight and change often.
    Grease type on aluminium threads of top cap is not at all critical, use what you got

    multi weight oils are a bit hard to explain, but in fork use just use the first number.....the second number doesnt directly relate to oil viscosity...rather it indicates that the oil has only thinned to the viscosity that an oil of the second number-weight would have thinned to at operating tempreture, its an indication of viscosity stability through tempreture change, and usually only applicable to combustion engine tempretures....ignore it in fork use
     
  3. nmr8

    nmr8 Monkey

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    so i'd be better off using 5 wt fork oil in the lowers? or should i go and get real 5 wt? or real 5-40 semi bath?
     
  4. Marcolino

    Marcolino Chimp

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    about the oil lubrictaion properties appers that a more viscous oil lubricates best moving parts, yet it must reach those parts.

    so manitou uses 5w for lubing the lowers, but rockshox uses 15w...

    in my manitou i use 5w... i also turn it upside down so it gets into the bushings before i start the ride... it helps...

    that oill weight you used may be a bit thick, but try it and see what happens...


    good luck,

    Marcolino

    ps- you should check spv devolve:

    http://forums.mtbr.com/showthread.php?t=64268&highlight=spv+devolve
     
  5. DRAKETHOMAS

    DRAKETHOMAS Chimp

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    I have been rebuilding spv for some time now and there are numerous tricks. I can tune it at 3wt. all the way up to 10wt. based on rider size and conditions. It does require a few tools shoot me an email at isotuned@yahoo.com Thanks Drake As far as the lowers never use over 5wt. unless there are under size bushings being used.