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New to me ZX10R race bike

Discussion in 'Tech' started by ilikebass, Nov 15, 2020.

  1. Pneumatico Delle Vittorie

    Pneumatico Delle Vittorie Retired "Tire" Guy

    Huh? here's the specs
    120/70R17 on 3.50 rim
    width 120mm
    diameter 604mm
    125/70R17 on 3.50 rim
    width 124mm
    diameter 610mm

    200/60R17 on 6.00 rim
    width 200mm
    diameter 662mm
    200/65R17 on 6.00 rim
    width 202mm
    diameter 672mm
     
  2. moto316

    moto316 Well-Known Member

    I was referring to the bike geometry with new and old sizes
     
  3. ilikebass

    ilikebass Active Member

    On the tires: so the front/rear radius change is 3mm/5mm but looking at your measurement numbers (assuming these were measured?) there's a very small change in geometry from this. Is that what you were saying?

    DDK, totally get what you're saying on spring rates and preloads. When talking geometry numbers specifically those are the "hard" settings (that are easiest to compare) but of course all those numbers change when the bike is on it's own weight, you're weight is on the bike, you're on the brakes or throttle, you're at some lean angle, etc and what/how much effect those conditions have is dictated by spring rates are preloads. So the hard settings only get you so far, and I understand your point. The more "soft" settings are much harder to talk about in definitive terms so I was kind of focused on the hard geometry settings, but I do see what you're saying. Anyway, my interest in talking numbers specifically is to better understand the useful range so I can try both extremes to form bounding conditions for testing. Your point on balance is a good one, and yes I see that it could be easy to get carried away with the numbers. Working the "soft" settings in (loosely referring to spring rates, preloads, and especially damping) is why this is so difficult but also a fascinating puzzle.

    I do mess around with geometry software to see what effect certain changes make to the rest of the bike. I have been using Tony Foale's software but have a lot of questions and it might be worthwhile to check out Suspact. One change I find pretty interesting is that raising/dropping the forks has much less effect on trail as I thought it would, so the difference in feel must have a lot more to do with things like front weight bias, which is kind of to your point DDK.
     
  4. moto316

    moto316 Well-Known Member

    Yea, the +2mm in extra height in the rear only equates to a tenth of a difference in rake and swingarm angle and half a mm in trail. And all the base geometry numbers/frame measurements are from the zx10r file supplied from motospec.
     

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