Unsprung weight

Discussion in 'Australian Motorcycles' started by jlittler, Jul 25, 2005.

  1. jlittler

    jlittler Guest

    Stolen from MC-Chassis-design email list - practical example of
    reducing unsprung mass - 4 seconds a lap !!

    "This is lifted from the Burge racing website - the brothers who have
    running Norman Hossack's original Yamaha chassis (number 3?) for the
    few seasons

    "I rebuilt my Harris Rotax for the 2004 ACU Supermono Series, fitting
    exhausts and generally tidying and rationalising a few bits and pieces.

    I had some problems at the first rounds at Pembrey, where I crashed out
    the second race. Otherwise I've finished every race and had a great

    I've been pondering the whole Supermono v Minimono question for a long
    and considering whether, because the current minimum weight limit of
    there's a middle way? So, by way of experiment I decided to run GP125
    wheels on my Harris to see what would happen.

    Big investment? Not really. I was able to take the 3.5" rim off my
    Astralite and mate it to the existing rear hub. Then I dusted off the
    complete TZR front end from my 250 single racer, together with it's
    forks and single 300mm disk.

    The result? An instant 4s reduction in lap times at Castle Combe and
    Cadwell!! Who says performance costs money?! The bike was very light
    steering and nimble and I could run and turn into corners sooo much
    The reduction in weight and reciprocating mass made a big difference to

    acceleration and braking too. I moved up from 8th to 4th in the
    series in those two meetings and now seem to be running with a whole
    different group of people. I'd say that was a successful experiment and
    great way of making a 14 year old bike competitive. "
    jlittler, Jul 25, 2005
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  2. The last line sums it up.
    Hamish Alker-Jones, Jul 25, 2005
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  3. jlittler

    jlittler Guest

    If you're implying it was because he put new tech on an old bike, not
    true. The 125 kit in question was of the same vintage as the original
    rims and front end (I think the "dusted off the complete TZR front end"
    sums it up well).

    In short, lighter sprung components made it quicker - not just power to
    weight (although taking 5Kg off a 100Kg bike isn't trivial) but it also
    gave him better cornering

    jlittler, Jul 26, 2005
  4. jlittler

    Nev.. Guest

    The great thing about Hammo's almost indecipherable vagueness is that it
    almost certainly never means what you think it means, unless that's what you
    think it means. Win-win situation every time.

    '03 ZX12R
    Nev.., Jul 26, 2005
  5. jlittler

    John Littler Guest

    <chuckle> Yeah, OK. True, it could mean anything.

    John Littler, Jul 26, 2005
  6. jlittler

    Nev.. Guest

    not a racetrack.. was IoM :)

    '03 ZX12R
    Nev.., Jul 27, 2005
  7. jlittler

    John Littler Guest

    Ahh, OK then, apology accepted.

    <wanders off whistling in blithe ignorance of any sarcasm>

    John Littler, Jul 27, 2005
  8. jlittler

    John Littler Guest

    Geez they're clever buggers these pommies, moving a whole island to the
    midlands - impressive.

    (caldwell and mallory park actually)
    John Littler, Jul 27, 2005
  9. jlittler

    John Littler Guest

    No Clem, click the link, not IOM.
    There are people far better qualified to comment than me, but 4secs a
    lap on the average track generally means you're going a lot faster,
    doesn't it ? The funny thing is this is on a bike at an equivalent level
    to the ones you say are all you need because it's max capability isn't
    particularly high...so this is something you could do in the real world
    and get more capability on a bike where you'd notice it.
    Err nothing, he pulled the spare bits out of the back shed and dusted
    them off...

    (and even if he'd bought them, the answer would still be not very much -
    how much do you reckon a pair of 15 yr old TZR125 rims go for ?)
    John Littler, Jul 27, 2005
  10. jlittler

    Moike Guest

    If you really need them, I'd say $800 each?

    If you don't, you could probably get them for nothing......

    Moike, Jul 28, 2005
  11. jlittler

    Knobdoodle Guest

    X-No-archive: yes
    Yeah they're under that pile of TRX850 brake callipers!
    Knobdoodle, Jul 28, 2005
  12. jlittler

    jlittler Guest

    Never owned one myself, don't imagine they sold many here - but I'll
    bet there'll be shitloads in the UK where learners have to have 125s
    and the OP is located


    jlittler, Jul 28, 2005
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