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Tyre profiles

Discussion in 'Technical and Troubleshooting Torque' started by Josh, Jan 9, 2007.

  1. Hi,

    I have a 120/60/17 front tyre. I have seen 120/70/17 on others. What difference will a higher profile make on a tyre, especially a front?


  2. what sort of bike is yours??
    what sort of bike have you seen the other size on??
    what brand / type of tyre were they??

    generaly higher profile if a slightly plusher ride but can squirm around more when pushed but this would only be so for same type/compound on same bikes.
  3. I have a '99 cbr600. I've just seen the other tyres on ebay. Would a tyre that is a "sports tyre" be affected by a slightly higher profile as you suggested?
  4. I doubt you'd notice a 10% change in profile on the road. You may have SLIGHTLY more sedate initial response to countersteering and probably better ride over small irregular bumps.
    The big factor will be the speedo, if it's driven by the front wheel.
    On the GTR, I went up 10% to correct the speedo.

    Regards, Andrew.
  5. Buy the size tyre that the bike is designed for. Most modern sports
    are designed for 120/70/17 front but R6 and some other
    similar are designed for 60 front. Michelin also make a

    Original size is best unless you are very specific about wanting
    the bike to handle in a wierd fashion (eg very nervous for racing
    on tight tracks, you might consider going to a 120/70 even though
    the bike is recommended for a 120/60, but bike will want to fall
    into corners heaps on the street)

    Bigger number will nervous the steering. Smaller number will
    stabilize the steering. Worn out rear tyre will blind you to any
    changes you make, as it will make the bike want to stand up
    no matter what.

    Note... GTRs are too big to be sensitive to profile
    by much, the best way to affect a GTR is to slide the forks up
    through the triple clamps by 10-15mm, lightens the steering nicely.
    Also use plenty of air in the rear shock (not more than 70psi though).
  6. Hmm interesting. After doing alot of reading about my r6 when I got it, I went to a 70 series to help with headshakes from bumps (it actually made the bike more stable in this regard) and yup, it did tend to fall into the corners more but I never noticed this except maybe right hand turns on small roundabouts :)
  7. Yeah, the GTR did tend to turn in a bit easier with the higher profile front, but it was like getting power steering, these things have very narrow handlebars, and the steering is a wee bit heavy when going hard! Mind you, the steering became initially less responsive just off centre too.
    Mind you, they do respond to countersteering very well.
    I don't know about sliding the forks up, the thing is twitchy enough in any sort of breeze. Less caster would make it worse. :shock:

    Regards, Andrew.
  8. Yup, them manufacturers and their million-dollar research departments generally know what's best for their bikes.....
  9. Yes that's another effect, narrower/taller tyres will bumpsteer less
    than wider/lower tyres. There are so many different effects to
    changing tyre size/profile I can't list them all. Also different brands
    with the same sizing will be different profiles (e.g. Pilot Power is more
    triangular than almost anything else Michelin have made for the road).