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Front Suspension Upgrade - FZR

Discussion in 'Yamaha 250cc In-Line 4's' started by GreyImport, Jan 4, 2014.

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  1. Willrcr15

    Willrcr15 Well-Known Member

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    I can laugh at that, I'm over 110kg & that'd be a sight.
    Hit a bump in the road recently & with the soft suspension & my fat arse I bent the front rim when she bottomed out, lucky to have survived it, should send the council the bill for the repairs, it was in a new industrial estate.
    I don't know about the others but the FZR brakes are awesome, the rear has big pull.
    And she's all in standard kit by the look of it.
     
    Willrcr15, Jan 7, 2014
    #21
  2. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Im in the 100kg+ club also and Im not looking forward to hitting a major bump/pothole.

    Yea the brakes seem fine but I havnt given them a massive squeeze at speed because of the dive problem.
     
    GreyImport, Jan 7, 2014
    #22
  3. Willrcr15

    Willrcr15 Well-Known Member

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    Yeah, I'd be a bit reluctant to go too far with the suspension, I suspect it'd be a bit like mucking around blind with carby jets, another black art.
    We've just finished racing karts after 10 yrs & chassis tune is everything equal to suspension adjustments & 1 to 3mm changes can make or break the setup chasing tenths of a second around a 54sec one km track.
     
    Willrcr15, Jan 7, 2014
    #23
  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    I guess the ultimate test would be to get some NOS 250 springs and rear shock to see what 'off the assembly line performance' is like..... well as close as u could get with other factors thrown in.
     
    GreyImport, Jan 7, 2014
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  5. Willrcr15

    Willrcr15 Well-Known Member

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    Sounds like they are soft from factory.
    I might try some heavier oil first & stiffen up the rear shock till it matches the front.
    If I could loose about 40kg I wouldn't have to do anything, maybe have a leg taken off or some other part.
    My daughter is learning on the NSR150 & it flies with her 45kg, can't wait to get her on the FZR, she'll love it, she'll have trouble keeping the front wheel down.
     
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    Willrcr15, Jan 7, 2014
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  6. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    How about Race Tech fork springs?
     
    maelstrom, Jan 7, 2014
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  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Jan 7, 2014
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  8. Willrcr15

    Willrcr15 Well-Known Member

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    My Bike:
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    I had a look & only the FZR400 is listed.
    Interestingly the spring rates are double for their recommended calc compared to the stock factory ones.
    Nothing listed for the rear, It'll be soft as well.
    I'm sure there's an answer, probably need to start with the specs for the front & rear springs if they can be found or measured.
    Maybe I'll just stop eating, gunna be easier.
     
    Willrcr15, Jan 7, 2014
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  9. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    maelstrom, Jan 7, 2014
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  10. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    If you do a google for
    "calculating spring rate", you will find lots of online calculators that may allow you to get a ballpark figure for your standard springs. Then you could use Race Tech's online spring calculator to work out what you need for your weight.

    You might find that you can get your own custom springs made. Call Chessels in Brisbane
    07- 3252 2517 and see what they say. Or try a search for custom springs in Oz. (http://www.sssprings.com.au/pro_compression_springs.htm) Could be cheaper than you think. I know a very, very long time ago, when dinosaurs roamed the Earth, we use to get Chessels to make all sorts of weird stuff.
     
    maelstrom, Jan 7, 2014
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  11. Willrcr15

    Willrcr15 Well-Known Member

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    Ok good to know, She'd be a lot nicer a bit stiffer & probably a lot more grip.
    Also ,I used the Zeal site part number to order the clutch cover gasket & expect it this week ready to go on when the new clutch kit arrives, fingers crossed for friday.
    The fork seals are also to suit the zeal so we'll see.
     
    Willrcr15, Jan 7, 2014
    #31
  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Cant remember seeing any specs for the suspension for a 3LN1

    Thanx Mr Green ... will do some further reading .... buying in Oz would make a nice change.

    Stop eating might be a good move ..... my leather jacket might fit then also.

    Can u do a bit of a write up thread and a few pix with those Zeal parts and the clutch overhaul? ..... would be a handy reference.
     
    GreyImport, Jan 7, 2014
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  13. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    As always I am a bit vague, but my understanding is this:
    After you follow the FZR400 link, you just choose the calc spring rate for my weight link.
    Input your weight and the weight of the bike
    For 110 kg (is that true Mr Grey?) you will get a result like this.
    Recommended Fork Spring Rate: 0.931 kg/mm (use closest available)

    So now you can search through their spring database or ask some of the local spring makers to make you some springs that have the length and diameter that you want but with 0.931 kg/mm
    Your springs may have sagged a little, but check the manual it may have the correct length.

    The kg/mm value is independent of what model of bike. It is just calculated for a road going sport bike with an all up weight of x.
    cheers
    Blair
     
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    maelstrom, Jan 7, 2014
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  14. mboddy

    mboddy Well-Known Member Premium Member Contributing Member

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    When I was getting some made up for the TZR I was told that short springs are the way to go for race bikes these days.
    The spacers can be made from PVC tubing or aluminium tubing.
    I used aluminium instead of PVC because the thinner wall allows more air volume in the fork.
     
    mboddy, Jan 8, 2014
    #34
  15. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    That explains it ..... those I linked are definately aimed at the track.
    Heres a pic from another ebay listing ..... spacers included!

    race tech.JPG


    And Mr Green , yes sadly over 100kgs these days ...... and to think a few years ago I was down to 85 :help:
     
    GreyImport, Jan 8, 2014
    #35
  16. Willrcr15

    Willrcr15 Well-Known Member

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    Well that's simplified the front springs so which rear shock to fit ?
    Same physical dimensions & strength to carry 150kg bike + rider weight with some adjustment left either way ??
    Can't help wondering how the linkage geometry / dogbone lengths effect the load on the shock absorber & how the loads & shocky are calculated ??
     
    Willrcr15, Jan 8, 2014
    #36
  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Whereas the front forks are direct, the rear shock system has the swingarm acting as a lever (much heavier spring required) that is made much more complicated by the linkage geometry. So you are going to need a lot more maths to work that one out. I know Tony Foale had some simple software for calculating rising rate etc but I don't know if it covered springs.
    In any case, one of the members has already fitted an R6 shock and sounds very happy, it sounds like a good place to start.
     
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    maelstrom, Jan 8, 2014
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  18. Willrcr15

    Willrcr15 Well-Known Member

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    Might start by asking some of the shock companies how it's calculated, should be simple enough, they have to know how its done.
    What is the suspension like on the Zeals, soft like the FZR's ?? Do they run a single mono shock ?
     
    Willrcr15, Jan 8, 2014
    #38
  19. kiffsta

    kiffsta Senior Member

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    Im looking for a set for my Cibby and have contacted these guys... http://www.mpesuspension.com.au
    I will ask if they can supply some for the fizzer as well.
     
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    kiffsta, Jan 8, 2014
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  20. Willrcr15

    Willrcr15 Well-Known Member

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    They look like the ones that'll know.
    I didn't have any plans to do the suspension but after all the discussion it looks like a necessary mod for a vast improvement.
    Trouble is the kids will never get a go, I'll want it all the time.
     
    Willrcr15, Jan 8, 2014
    #40
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