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Speed Rating

Discussion in 'Riding Gear and Bike Accessories/Parts' started by Farab, Mar 10, 2011.

  1. I was looking at the new Michelin Road 3's on the Michelin website, I noticed that they have speed rating "W".
    Just as a matter of interest, I looked it up and apparently its only good up to 270km/h:


    Similarly with what Michelin classes as Sport or Track tyres, are also only "W" rated at 270km/h. (Michelin Powers, etc.)

    Note there is a "(W)" rating that is good for >270km/h.

    Surely they know these tyres are being fitted to 1L Sports (GSXR's, etc.) and Hyper Sports such as Zx14's, Busa's, K1300's, etc., that's well capable of 300km/h. Surely 300km/h is seen on tracks every weekend, all over the world, if only for a brief period.

    So what's the deal? Is there a factor of safety built into this, so that Hans can and indeed gets away with doing 300km/h on his K1300s on the Autobahn?
    Are they just being cautious with their ratings?

    Maybe a race or tyre guru can shed some light on this.

    (Yes, I know 300km/h is an academic discussion for a lot of us, but I'd still like to know why 270km/h tyres are being fitted to +300km/h bikes)
  2. The same reason 150kp rated tyres are commonly fitted to cars capable of 180kph or more. Most people don't understand what the little letter means. The "W" rating means that it is safe for sustained use at 270kph, above that speed you're on your own and dependant on how much they've over-engineered the tyre.

    Failures can happen though. I remember an incident on the Western Highway where a 4wd had been doing 140-150 on 140kph rated remoulds when one of them failed, flipping the vehicle and killing all the occupants. Of course the cops blamed that one on speed, not the cheap-arse tyres on a POS old 4wd. Does make me wonder how many other high-speed fatalities may be linked to people dramatically exceeding tyre speed ratings.
  3. Ooh, ooh, ooh, I can answer this one. :D

    Or at least, give some insight.

    It's not specifically what you're asking, but the 1968 Illinois Tollway Tire Study concluded that 99.96 percent of drivers are successful at coping with a tyre disablement in motorway conditions. That is, less than 0.1% of tyre disablements due to punctures, blowouts, catastrophic tread failure, etc, etc, actually resulted in a crash.

    I've not managed to actually read the contents of the study report; the study and its findings are mentioned a few times in the Northwestern University Crash Investigation coursenotes.
  4. The Metzler's on my Bird are W rated, Thats the highest rating they have,

    The Blackbird stock will do 186 MPH or 300 KPH,

    They probably assume that no one will ride above 270 KPH.
  5. You Tube is littered with people doing 300km/h on the Autobahn, etc.
  6. I did say, Assume, Tongue in cheek, Hahahahahahaha

    The speed limit here is 100 KPH,

    And we dont have an Autobahn, unfortunately.
  7. Yeah, but a 1968 cross-ply handles about the same as a steel rim to begin with. :p

    Besides, people now are driving vehicles with a much higher centre of gravity, and much greater mass, than anything sold in '68. You only have to look at the recent incident involving Firestone tyres and Ford Exploders in the USA to realise drivers are not capable of coping with tyre failure.
  8. Unfortunately there hadn't been a study like it ever before, and there hasn't been one since. :)
  9. Strange. Would have thought there'd have been something given that the USA is making tyre pressure monitoring systems mandatory because of a supposedly high number of injuries/fatalities caused by under-inflated tyres (which we'll more than likely see introduced here as well).
  10. Hrm. I hadn't heard that, TBH. The course material does discuss the advantages and disadvantages of runflat tyres; The advantage being that a puncture won't necessarily compromise tyre performance and the disadvantage being that abnormally low air pressures won't necessarily compromise tyre performance either - which means that vehicles fitted with runflat and other low-pressure tyres need pressure monitors to help the driver tell when they need reinflation.

    Edit: Wikipedia says tyre pressure monitors became mandatory in the US as of 2008 and in the EU 2012.
  11. Hmm, time does go quick.
    Info on the USA's monitoring system is here:

    They're claiming 120 fatalities and 8,500 injuries a year caused by low tyre pressures alone.

    Run flats can be more trouble than they're worth. My dad's BMW has had 3 flats in the last 6 months, though that was down to some idiot leaving the stickers on the inside of the tyre (preventing them sealing properly). He's still waiting to see if the 4th tyre will follow suit.
  12. Over here all those would be because of speed.