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forum forum Technical Rear shock extenders

This topic contains 5 replies, has 4 voices, and was last updated by doverhay doverhay 2 weeks, 1 day ago.

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  • #13121
    SteveO
    SteveO
    Participant

      Hi,

      A couple of years back I purchased from Alan a modified motto guzzi rear wheel with car rim for my series 1. The original bike wheel overall diameter of the tire was 26 3/4″ the car tire (firestone) I fitted to the new wheel has an overall diameter of 24″. This dropped the rear by 1 3/8″. The look was a little bum dragging. I noted some on the forum have extended their rear shocks and after contemplating various complicated solutions made the simple brackets in the photographs. These were made from 1 1/4″ x 3/16″ black steel as I had some to hand. The bolts are all Grade 8. The top 1/4″ are simply to stop the plates revolving. The brackets can still be removed and the car put back to standard.
      The purpose was to try the higher ride hieght which works well. This leaves the option to either; fit longer shocks to make up the difference, weld the plates to the frame or do nothing. Probably do nothing as working well. I also have several pairs of shocks of the same length from various Guzzis and a pair of new Harley air shocks which I am tempted to fit.
      The box above the shock mounts holds my 3 point seat belts and works well. Only thing to remember is to get the type of seat belt that will work at any angle. I had noticed some rub marks on the back edge of the box, but think that was from the original bike wheel and tire.
      I can highly recommend moving to a car tire as the handling is much better. It always felt as if there back wheel was flexing, but as it is an alloy probably not.
      I did find some shock extenders on Ebay, but these revolve the top half of the shock through 90 degrees which seemed wrong.
      Hope of interest to somebody.

      Regards,

      Steve

    • #13122
      SteveO
      SteveO
      Participant

        did not like photo file type lets try jpg
        works but revolved them.
        Please lay on side to view!

        Steve

        • This reply was modified 2 weeks, 4 days ago by SteveO SteveO.
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      • #13129
        frederick
        frederick
        Participant

          that’s a good simple solution…an alternate is to find a car tire (tyre) closest to the stock width and diameter as possible.

          the build overview posted on the Triking site suggests the 15″ billet rear wheel requires a 125-165 range tire.

          My norge donor bike’s tire (180/55 r17) measures at it’s very widest 7.25″ wide and is 24.8″ dia. (Non-carc bikes may be different)

          Using this calculator https://www.tacomaworld.com/tirecalc?tires=180-55r17-175-70r15
          and trying different combinations of 15″ profiles, double checking a tire source to make sure the size is available, I came up with the closest diameter/widest tire _available_ that would fit:

          https://www.tirerack.com/tires/tires.jsp?tireMake=Vredestein&tireModel=Sprint+Classic&partnum=77HR5SC&vehicleSearch=false&fromCompare1=yes

          your mileage may vary

        • #13134
          SteveO
          SteveO
          Participant

            Frederick,
            I did forget to say I fitted bushes to the top and middle bolts to prevent crushing the original shock mounts.
            Something to be aware of.
            The biggest issue I had with the bike tire was the need to slip the clutch extensively to pull away. Mine had an 18″ rear wheel and the reduction to 15″ plus the car tire has pretty much removed this issue.
            The smaller overall wheel and tire diameter does not significantly increase revs at cruising speed. About 4000 rpm in 5th at 110 km/h (about 70 m/h).

            Steve

          • #13135
            WestEndGuzzi
            WestEndGuzzi
            Keymaster

              I did a similar extension to my Forenales shocks to extend them. I’ve recently extended them by 30mm to give better ride height when 2 up in the car.

              I’ve gone inside the chassis box, holding nuts in position was a problem so tack welded in position.
              Tony

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            • #13140
              doverhay
              doverhay
              Participant

                I was thinking along the same lines; however, it’s good to see a couple of ideas. A job to do when I get back from our tour of Britain! See you all in Norfolk

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