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smaller rear tyre effect handling?

Discussion in 'Technical and Troubleshooting Torque' started by Tomcatalex, Aug 12, 2008.

  1. I want to replace my rear tyre with a slightly smaller one

    now 140 70 17

    after 130 70 17

    would this cause any handling problems?

    the front is 110 70 17
  2. Tyre

    The rolling diameter will be slightly lower, but the main problem is the tyre's Load Index. If the tyre you are fitting has a lower L.I. than the original, it is not roadworthy, & can void insurance if an accident happens & a claim is placed. Check the numbers at the end of the tyre size 140/70-17 ##H. They must be the same or greater than standard.
  3. Re: Tyre

  4. Why do you want to do that?
  5. The effect on handling depends a lot on the rim width as well. A Ducati 748 and 996/998 are essentially the same bike (different motor only) but the 998 has a wider tire (190/50-17) on the same rim as a 748 (180/55-17). I believe this was mainly due to marketing (bigger bike needs fatter tire).

    The narrower tire has a taller profile (to keep the same rolling diameter) so drops into corners more easily. Most 998 riders put the narrower tire on as it improves handling.

    In your case a narrower tire with the same profile height will probably give a bigger radius when viewed in profile (to fit the same rim) so may feel like your working harder to get the bike into corners.
  6. I have experienced the exact opposite. The bike is easier to tip in and a bitt less effort required to change line mid corner.
    Someone also told me you actually end up with a slightly larger contact patch -but who knows?
    Easiest way is to simply try it :)
  7. Way back when I was poor my bikes typically were shod with whatever I could afford that had tread. As a result they rarely had OEM sizes on either end, although I didn't try sticking on anything ridiculously wide or narrow. None of the weird and wonderful combinations I tried caused anything particularly dangerous to happen.

    These days I'm affluent enough to keep matched pairs on my ride, but failing to do so never killed me.

    A change of one size on a 15 year old 250? Frankly I'll be surprised if you can detect any real difference. Even if you can I'd say it's very unlikely to be anything you can't get used to.

    I'd echo Loz though. Why?
  8. Have you ever considered washing that thing?
  9. The reason your having issues is you don't wear ATGATT ! LMAO :cool: :LOL:
  10. what's the standard tyre?
  11. 140/70 17-66H
  12. I could be wrong, but is your tyre rubbing on both sides? If not, the rear wheel might not be fitted straight. Might need to adjust the rear wheel so it’s, umm , square.
    Also I personally don’t see anything wrong with going from a 140 70 17 to 130 70 17. The contact patch issue is not an issue for e 250cc 4-stroke. If fact I wouldn’t be surprised if it’s not an issue for a 1000cc sportsbike either, the contact patch issue seems to pop up in MotoGP where they’ve gone to 16inch (diameter) wheels anyway.
    The benefit of handling from a narrower rear tyre will be felt everytime you go around a corner.

    Not sure if this is relevent: Previously I had a Ducati 748 (’98 model) and I changed the ‘size’ of my front tyre, from a 120/60 to a 120/70 profile front tyre. This was to offset that funny ‘falling in’ feeling you get with Ducati superbikes (that old 916 model type) when you lay into corners hard. The the ‘taller’ 70series front tyre had a rounder tread cross section that made the transistion from upright to knee down seem more fluid. Worked for me anyway.

    But all this is achademic if you have comprehencive insurance though.
  13. wouldnt you start by asking why the OEM size is hitting ?. straight ?. seems odd
  14. +1 to that :? if the standard doesn't fit i reckon you have other issues i would be looking into first
  15. unless all the rain a few months back had made it grow i would be making sure everything is hunky dorey in allignment and so on first