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Thread: Raising the old tyre size debate, with apologies

  1. #16
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    Quote Originally Posted by Angrybird View Post
    Can you spell Gizbun Eest Khost? :-)
    Haha, good point, hadn't noticed you're locale. Haven't ridden up there but drove it a coupla years back, never in my life have I so wished I had a bike instead. Go the 55's, it'll feel like the big girl has lost 20kg's.

  2. #17
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    Quote Originally Posted by Angrybird View Post
    Thanks sinfull. Going back to my calculator 5% of 190 (ie 55% v 50%) is 9.5mm (not 14.5mm). Even allowing for a bit of squishing of the extra rubber I still see an increased ride height of around 9mm. Hoping to find an exact measurement I emailed Dunlop NZ asking for Sportsmart diameter measurements but have heard nothing back.

    On top of the static measurement tyres also get bigger when they spin (watch the top fuel dragsters) and so the ride height should increase beyond the 9mm when the bike gets up to speed. Not sure of the merits of adding sag to maintain the steering geometry.

    The point you made is exactly the way I had come to see the issue of 180 v 190 tyres. The poster I quoted on the subject of "stretching" disputed this and I even found a quote from Dunlop's website which recommended (180 55s?) for 6 inch rims.

    That sounded dubious to me. As you pointed out the profile of a given 180 must differ between a 5.5 and 6 inch rim. Surely they have optimised it for one or the other. Indeed when they are quoting the profile heights it must be per a given rim size therefore? But no they just bandy around numbers in the way Aiwa quoted wattage for their ghetto blasters.

    I found many subjective comments in favour of both but nothing to say a 180 on a 6" rim is a categoric "no-go." Some highly technical types had actually found a way of measuring maximum theoretical lean angles. If manufacturers were to supply this info in respect of the tyre when fitted to the rims for which it was recommended that might be helpful.
    loving the insight here, but do you really think it's going to make much difference?

  3. #18
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    Quote Originally Posted by Angrybird View Post

    On top of the static measurement tyres also get bigger when they spin (watch the top fuel dragsters) and so the ride height should increase beyond the 9mm when the bike gets up to speed. Not sure of the merits of adding sag to maintain the steering geometry.

    .
    my understanding of this, as it applies to motorcycle tyres, is that you dont get this effect untill >200km/hr.

    fwiw, Im in the pro 55 group too - ive toyed with profiles a bit and have found on bigger bikes it can make the steering a little kinder - noticable on particularly long rides

  4. #19
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    Quote Originally Posted by Angrybird View Post
    Apologies drew.. I am getting to ewe. (Saving the best to larst :-) Thanks for all your thoughts. Nope arms aren't stumpy.. my wingspan is longer than Michael Phelps. Still not long enough to allow me to sit upright on my ZX. Yep I ride feisty roads.. Can you spell Gizbun Eest Khost? :-)
    In that case, 190/55r17 all the way. The 55 has a smaller contact patch when the bike is straight up and down, but more as you lean. The geometry change of the extra 9.5mm would upset a well set up race bike, but on the 14 for the road, it's just gonna tip in quicker with less effort.

  5. #20
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    Quote Originally Posted by sinfull View Post
    The 190 is the way to go, I'd go the 55 but don't think it really makes SFA difference (ie like 5mm profile) I might be corrected on that lol
    Okay, I will correct you....

    The /55 and /50 refer to the PERCENTAGE of the width.
    So it is 55% and 50% of 190 respectivly.
    Thus 104.5mm and 90mm respectivly.

    So OP had it right, 14.5mm difference in side wall height.

  6. #21
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    Quote Originally Posted by quickbuck View Post
    Okay, I will correct you....

    The /55 and /50 refer to the PERCENTAGE of the width.
    So it is 55% and 50% of 190 respectivly.
    Thus 104.5mm and 90mm respectivly.

    So OP had it right, 14.5mm difference in side wall height.
    Bad news, your math is correct, but the designation no longer means exactly as you have said. Manufacturers use that as a guide and then make the tyre whatever size they want really. There are many many tyres on the Market of varying sizes, all using the same carcas.

    The exact dimension of any tyre is relative to rim fitment. All you can be sure of, is that a 55 profile of any given tyre, is taller than the 50 profile in that same model.

  7. #22
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    Quote Originally Posted by Drew View Post
    Bad news, your math is correct, but the designation no longer means exactly as you have said. Manufacturers use that as a guide and then make the tyre whatever size they want really. There are many many tyres on the Market of varying sizes, all using the same carcas.

    The exact dimension of any tyre is relative to rim fitment. All you can be sure of, is that a 55 profile of any given tyre, is taller than the 50 profile in that same model.
    Really????.... Bugger!
    How dare they... they should have consulted me before making a change like that!!!!
    They didn't update me via e-mail... I'm crushed.

  8. #23
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    Quote Originally Posted by quickbuck View Post
    Really????.... Bugger!
    How dare they... they should have consulted me before making a change like that!!!!
    They didn't update me via e-mail... I'm crushed.
    It's rough aye, I wasn't consulted either!

    Put a 190/55r17 supercorsa beside he same sized racetech, (no Poos, they haven't shared the same carcas for a fuckin decade), and the difference is huge. Makes an incredible difference on my old RF to swap from one to the other.

  9. #24
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    Quote Originally Posted by Drew View Post
    It's rough aye, I wasn't consulted either!

    Put a 190/55r17 supercorsa beside he same sized racetech, (no Poos, they haven't shared the same carcas for a fuckin decade), and the difference is huge. Makes an incredible difference on my old RF to swap from one to the other.
    Mmmmm.... That would explane it... I knew different tyres had different shape, but never realised it was because manufacturers stuffed arround with the profile number.
    That would explain why we put a Shinko 100/80 on the front of an FZR250 and it looked like we put a MTB tyre in it.....

    Yeah, I know.... shouldn't buy tyres where the manufacturers name starts with S....

  10. #25
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    Quote Originally Posted by quickbuck View Post
    Mmmmm.... That would explane it... I knew different tyres had different shape, but never realised it was because manufacturers stuffed arround with the profile number.
    That would explain why we put a Shinko 100/80 on the front of an FZR250 and it looked like we put a MTB tyre in it.....

    Yeah, I know.... shouldn't buy tyres where the manufacturers name starts with S....
    I raced the rf at the hill climb with a Shinko on the front, it was fuckin mint! The limiting factor in my times was the bridgestone 016 on the rear.

  11. #26
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    Quote Originally Posted by Drew View Post
    I raced the rf at the hill climb with a Shinko on the front, it was fuckin mint! The limiting factor in my times was the bridgestone 016 on the rear.
    True?
    To be honest I never rode on them. It was the impression they gave me really... I guess if we put a 110/80 on it, then it would have looked better, but looks aren't everything.... The turn in must have been wicked, but never got a chance to find out, sadly.

  12. #27
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    Dunlop say the 180 or 190 are suitable for 5.5 or 6.0 inch rims.

    Each tyre makers actual fitted widths vary a bit too - some 180's are exactly that some a few mm narrower the widest I've measured was actually 185. I must get out more .....

    http://www.dunlopmotorcycle.com/tire...t/sportmax-q2/

  13. #28
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    Another vote for 190/55. Slowpoke's bang on, it'll shed 20kg off your bike in cornering performance. I'm running a Metzeler Z8 on the rear & getting good mileage on the ZX12 too, fwiw.

  14. #29
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    Eest Khost

    Quote Originally Posted by slowpoke View Post
    Haha, good point, hadn't noticed you're locale. Haven't ridden up there but drove it a coupla years back, never in my life have I so wished I had a bike instead. Go the 55's, it'll feel like the big girl has lost 20kg's.
    Hey slowpoke when I told drew our roads were gnarly I wasn't joking. Just rode through the Waioeka Gorge when I brought the bike back from Whakatane (movers dropped it there as Tauranga went quiet on me) and it is covered in loose chip. Many stories of people going down there. The coast road is not conducive to letting your guard down but Morere and Matawai have some decent tracts where you can get into that sense of communing with the tarmac. Funny thing is I am so loving on just being astride a ZX14 having perved at the big Kawasaki since the mid 90s I wouldn't care if it had square tyres. It is just a beautiful machine which talks to your soul every moment you are with it.. the experience is simply profound. I did one quickish stint on a return trip to Matawai but most times I am so immersed in my "secret garden" that it would seem like a travesty not to just take your time and soak up every second of the experience. What was it that Robert Pirsig wrote? "

    “To live only for some future goal is shallow. It's the sides of the mountain that sustain life, not the top.”

    “The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.”

    “We want to make good time, but for us now this is measured with the emphasis on "good" rather than on "time"....”

    Actually those are a few which grabbed my attention at Goodreads. The one I was thinking of still remains in my head from when I read the book as a teenager. Something like, "Sometimes tis better to travel well than arrive.." Think the Buddha said it first in respect of the journey which is life.

  15. #30
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    What's the difference?

    Quote Originally Posted by Dave- View Post
    loving the insight here, but do you really think it's going to make much difference?
    Dave I know what you are saying and I agree. Another quote from Zen and the Art of Motorcycle Maintenance. "The cycle you are working on is a cycle called yourself." Some blokes live on chips and beer.. and Bear Grylls eats scorpion spiders when he is hungry.. does it make a difference?

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