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Info ZXR USD -> FZR fork conversion

Discussion in 'Tech Tips' started by ruckusman, Jul 16, 2016.

  1. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Interested to see what you did with the triple clamps or are you using the ZXR items? The blue spots use steel pistons and the gold spots use alloy pistons (lighter). The Fizzer calipers are 4 piston anyway, yes? I'm going to fit 4 piston onto my Honda. Those opposing pieces of junk belong on a scooter.
     
  2. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    I literally searched the net till I went crosseyed looking for 40mm offset triple clamps for USD forks, and that is before taking fork spacing - stem length or anything else into consideration...

    I was making a rod for my back - potentially Triumph Speed Triple 1050 triple clamps in more recent years have a 40mm offset, but they are not commonly found for cheap - l'll keep looking though

    The ZXR250 triples and their fork tube spacing (200mm) do work out well for the brake caliper adapter plates - another reason to stop obsessing over 40mm offset triples.

    Yes fizzer calipers are 4 piston - they had enough grip to dive the original forks right to the bottom no problems.

    Then I did some calculations, 40mm offset reduced to 35mm takes my trail numbers from 87mm -> ~92.5mm.
    To remedy this I would need to take the rake angle from 24.5 degrees to 23.5 degrees.

    Second set of calculations on what change to get the rake angle to 23.5 degrees is a ~27mm drop of the forks - this calculation was very rough as I was guesstimating some numbers based on the wheelbase.

    Recall that I've already raised the rear slightly when fitting the R6 rear shock and making shorter dogbones than required to regain stock ride height on the rear.

    So till I measure the actual head angle I can deal with any slight increase in trail.
     
    Last edited: May 16, 2018
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    A 5mm increase in trail is going to make the bike feel more stable especially on fast sweeping corners. Any loss of turning ability will be minimal because 92 is still quite short.
     
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  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Try searching for 48Y/25YM bearing's, or 25x48x13, or 25mm x 48mm x 13mm
    https://www.ebay.com.au/sch/i.html?...Loc=2&_osacat=0&_odkw=48Y-25yM#item362a6ab29e

    Cheapest one with freight is this,
    https://www.ebay.com.au/itm/Motorcy...869598?hash=item362a6ab29e:g:zxoAAOxyJX1TF73h

    But it look's like there aren't too many maker's of them
    Same bottom bearing is used in the following model's
    1983-1985 YTM200 TRI-MOTO
    1983-1985 YTM200E YAMAHAULER
    1983-1986 YTM225 TRI-MOTO
    1982-1983 XT550
    1984-1985 FJ600
    1974-1976 RD200
    1973-1975 RD250
    1973-1975 RD350
    1976-1979 RD400
    1984-1985 RZ350
    1987 SRX250
    1980-1982 SR250
    1981 SR250T
    1981-1983 XJ550 MAXIM
    1981-1983 XJ550R SECA
    1976-1977 XS360
    1977-1981 XS400
    1982-1983 XS400 MAXIM
    1988-1990 XV250 ROUTE 66
    2009-2013 XV250 V STAR 250
    1995-2007 XV250 VIRAGO
    1983 XV500 VIRAGO
    1987-1999 XV535 VIRAGO
    1986-1990 YX600 RADIAN
     
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  5. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Mostly I'm pissed that I got charged 200% for a really low grade product via All Balls and I didn't save any time over getting them from the UK - live and learn.

    I will be avoiding All Balls in the future I think

    Going to get the one from ebay :thumb_ups:
     
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  6. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Small update on this...

    Made a new bearing spacer for the wheel, used the original FZR one for length and bought some 25mm diameter 3mm wall aluminium tube - I reamed it out to get it over the 20mm axle. The ZXR250 spacer is too short by several millimetres.

    The tube down the centre of the of the wheel hub is tapered and the 25mm OD tube won't go all the way down, so I needed to remove a small amount of material with a dremel - 5 minute job.

    Spacing is different but not radically so - for test fitting I re-used both of the 20mm ID 42mm OD 12mm wide ZXR bearings, the RHS bearing will stay the same, on the LHS with the 12mm wide bearing I needed ~5.2mm of spacers to get the wheel centred, so I opted for a 20mm ID 42mm OD 16mm wide wheel bearing for the LHS (Speedo).
    This will mean I need a 1.2mm spacer/washer to get it all centred.

    Using the FZR speedo drive as the cable end of the drive is different between the FZR and ZXR, as well as the length differing (shorter) on ZXR. The speedo drive also needed to be reamed out to fit on the axle.

    I've drilled two small recesses into the speedo drive so that the ZXR fork protrusions are untouched and a little filing sees it fit into place in the same orientation as it is on the FZR forks normally.

    I've made a template for the brake caliper adapters which will be out of 5mm stainless. I chose stainless because the forks aren't threaded, so wanted 5mm for the thread for the bolts, same amount of material the ZXR calipers. Then the FZR calipers, which are threaded, will be bolted to the adapter plates from the inside with low profile wide head allen bolts.

    Once they're done it's just bolt it all up once the other steering bearing arrives in the post.

    I'll take some pics once I've got the caliper adapters fabricated.
     
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    Last edited: May 19, 2018

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