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Hawk GT Frame Geometry and Wheelbase

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    Hawk GT Frame Geometry and Wheelbase

    Ok, I'm planning on reducing the steering axis angle from 27 degrees to 22 degrees. This will also reduce the wheelbase by 52mm. Does anyone know of someone that has done this. I already have a plan, but the more heads the better.

    Finally my hawk will handle like a modern sportbike.
    88 Hawk GT
    86 Suzuki FA50

    #2
    Clax,
    22 degrees sounds like a 250 race bike.
    You sure you want to go that steep?
    Are you planning to do it using offset triple clamps?
    You realise that just jacking up the back will similarly quicken the steering and put a bit more weight over the front? That might be cheaper and easier...

    Comment


      #3
      i was about to say the same thing brewsy just said..

      you may want to raise the rear before you do that...

      Comment


        #4
        Buells are 21 degrees. With a shorter wheelbase than the Hawk.

        2007 CBR 600RR:
        WB - 53.8"
        Head Angle - 23.7

        Stock Hawk:
        WB - 56.3
        Head Angle - 27

        Hawk by me:
        WB - 54.3
        Head Angle - 22

        Also, fork offset does not change the steering axis angle. The only way to change the steering axis angle is to change the angle of the steerer tube. That's what I'm going to do. If I can do it cheap enough I'm going to sell kits afterwards. But it's looking like the whole thing is going to require custom triples....i.e. not cheap

        I already raised the rear, and lowered the front it helps but doesn't change much.

        If you do the calculations lowering the front 10mm, and raising the rear 10mm it pitches the bike by .8 degrees and moves the CG forward by only
        .3 inches. It increases the front weight by .9 lbs. Roughly the change in taking a crap.
        88 Hawk GT
        86 Suzuki FA50

        Comment


          #5
          We did this to a race Hawk back around '93 or so, by modifying the steering neck angle of the frame itself. (cut, measure, tack weld, measure, measure, measure, weld) I don't recall what our final measurement was, but 22 deg sounds close. It steered like a 250 GP bike, very, very quick response. Too much for the street, I'd say. It was also hard on front tires, but that was probably due more Richard's riding style and setup. We took the bike to the WERA championship races at Road Atlanta where Richard started in the second wave and finished sixth. Another two or three laps and he would have been on the box!
          That frame eventually went to a guy named Jerry in Colorado to try out, and may still be around out there somehwere. He loved it and bought it after one race.

          I'm assuming that since you are contemplating this you have the technical expertise to accomplish the frame mods. And your stock Hawk already handles like a modern bike... they just finally caught up!
          1988 Blue Hawk GT, serial no. 1161, 153X cams, 40mm CV carbs, Unis, Supertrapp with competition end cap and 20 discs, Fox Shock, Corbin, F4i forks, CBR1100XX clip ons, ZX12 master cylinder, 954 calipers, wave rotors, Galfer lines, RS250 magnesium wheels, Holeshot Fly Screen, Acewell gauges, Durbhan hugger, Brembo mini GP rear caliper with thru swingarm line and RS250 rotor, mini- LED signals, carbon sidestand, Michelin Pilots, what else am I missing?

          Comment


            #6
            Does this bike really need to be more nimble? I mean whats wet weight around 400 for a stock bike. I only weigh 130lb and I can throw this bike around. Id say you're playing with fire...

            Comment


              #7
              Yeah, I've done a lot of work on other stuff, never this, but I feel completely comfortable with the mod. I'm also going to see if I can make it adjustable. I'm not actually modding the frame itself, It might be possible to make it adjustable. I'm thinking some where between 22 and 24 is the sweet spot.

              Also, I'm kind of a pyro, I like playing with fire
              88 Hawk GT
              86 Suzuki FA50

              Comment


                #8
                Well I have lowered Bikes on the forks by minute millimeter increments and played with tire,dogbone(none on the hawk), and shock sizes to even front and rear out. Im anxious to hear how it goes...

                Comment


                  #9
                  Yeah, I've already messed with everything I can do with the stock chassis. My shock is extended as far as it will go. The front is lowered as much as I want to go (after doing the calculations there isn't a point in doing more) There will be plenty of pics and results up once I get started.
                  88 Hawk GT
                  86 Suzuki FA50

                  Comment


                    #10
                    Good luck but I think you could spend time and $ on better ways to make your Hawk a little more nimble that wouldn't compromise stability.My own NT is the most extreme street one I've ridden in terms of weight reduction and what geometry changes can be done without altering the frame.Some people have commented that it's one of if not the best handling bike they've ever ridden - others have come back saying " that's too much,it's way too twitchy and unstable" - you have to decide if it's what you really want.To be honest,my Hawk SUCKS as a daily ride and that whole friendly,easy going Hawk nature is gone - awesome fun down in N GA but useless pretty much everywhere else.I deffo wouldn't bother unless you have some more motor-not knowing what you might have currently and assuming stock- as there's not much more frustrating than having a bike that really wants to run but starts wheezing out of breath.I guess if I had total ninja skills I could manage that trick of keeping up enough corner speed everywhere that GSXR's would never catch me but even at ~ 330lbs and 74hp last time I checked,I've still wished for more go =0)

                    Comment


                      #11
                      I'm not worried about the streetability of mine. It's going to be primarily track with the occasional street ride. I thought about just starting out with an 07 600RR (already correct geom.) but that's faster than I want. I just go to the track to have fun, and the fun for me is the corners. I don't feel a need in going 150 down the straight. And granted, I wouldn't have to twist the grip all the way if I had an RR, but it's a lot more fun to have the bike on boil the entire time. Right now, it should be making around 50 at the rear wheel. I'm planning on doing the hordpower 700 kit, with some head work, and mild cams. I figure I can probably get the weight down to around 325 so that should be about the right amount of fast (well, the amount that I want)

                      What did you do to yours?

                      I'm not completely set on what I'm going to do, pretty close though
                      88 Hawk GT
                      86 Suzuki FA50

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