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  1. #1
    accidental tourist
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    It's Gonna Blow!

    I guess I fall into the school of thought that where a little's good, more's better.

    I'm pumping my Continental Top Touring 700X35 tires to 100 lbs psi. It says the max is 70 lbs psi. I pump my Nokia studded tires to about 90 even though it says 65. I don't use the Nokias loaded, though.

    If not, my tires look too flat when the bike is fully loaded. I've never had a problem doing this so far, and have been through several of these tires. should I be worried? I'm thinking of trying Schwalbes also.

    Sheldon Brown seems to pooh pooh that max pressure rating.

  2. #2
    ♋ ☮♂ ☭ ☯ -=(8)=-'s Avatar
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    As a medium mileage commuter I lowered the airpressure on the bikes
    I use to give by aching parts relief fromthe bombed out rural roads of
    PA and VT where I ride and coincedentally stopped having as many flats
    Go figure ?

  3. #3
    Long Distance Cyclist Machka's Avatar
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    Personally, I run my tires with a lower pressure than the recommended max. My contis have a max of 120 psi, I believe, and I run them somewhere between 90 and 100 psi. It makes for a nicer ride.



    Just a word of caution ... if you are going to fill you tires well over the recommended max ... wear safety goggles, and perhaps some other protective gear, while doing so. Tires can, and do, explode.

  4. #4
    Senior Member ken cummings's Avatar
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    I read a report years ago of a man who was killed by a tire blowing out. Of course it was one of those (in biking terms) 4100x1200 mining truck tires
    This space open

  5. #5
    accidental tourist
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    Quote Originally Posted by -=Łem in Pa=-
    As a medium mileage commuter I lowered the airpressure on the bikes
    I use to give by aching parts relief fromthe bombed out rural roads of
    PA and VT where I ride and coincedentally stopped having as many flats
    Go figure ?
    Makes sense, of course. The higher pressure does stiffen the ride a bit and the higher pressure tends to puncture where lower pressure will give more to resist puncturing. My puncture rate may have gone up, I didn't track it, but my snake-bites are gone and I was having them.
    Gotta love the roads these days, and the higher pressure does put me in touch with the road condition. But hit one of those ruts where it reaches the rim.....that'll rattle your fillings!

  6. #6
    accidental tourist
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    Quote Originally Posted by Machka
    Personally, I run my tires with a lower pressure than the recommended max. My contis have a max of 120 psi, I believe, and I run them somewhere between 90 and 100 psi. It makes for a nicer ride.



    Just a word of caution ... if you are going to fill you tires well over the recommended max ... wear safety goggles, and perhaps some other protective gear, while doing so. Tires can, and do, explode.
    Oh no! You mean I have to start packing a face shield and kevlar apron now? 'Cause to be honest, I think the problem's origin already comes from excessive weight.
    I'm a motorcycle mechanic and we sometimes have to pump up tire to double the max to seat them. It's scary sometimes but I've only had a few cheapo tires blow off small chromed rims. It's not a shrapnel issue as much as the shock of the sound.
    I do appreciate your point though. In fact, I try to be cautious whenever I inflate any tire. Everyone should be.

    The thing is, I've been doing this for some time now with no problems. No problems with decents either. I just thought I'd see if anyone had a problem. I would drop pressure if I could, but it appears to me the tires are under inflated then. The tires are struggling under a heavy load, but I don't believe I'm exceeding their carrying capacity. I think the bike loaded (including me) and wet comes to about 350-360 lbs.
    Which tires are you running at the pressure you mentioned? I'm running Conti Grandsports on the Bianchi just at max with no problems. But I wouldn't think to use anything like that on the tourer. Maybe I need to move to different tires. I know it's heavy but the wheels seem to be holding up fine.

    I liked your web page. Did you like cycling in the Cottswolds? I thought it was perfect cycling.

  7. #7
    Long Distance Cyclist Machka's Avatar
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    Quote Originally Posted by spokewrench55
    Which tires are you running at the pressure you mentioned? I'm running Conti Grandsports on the Bianchi just at max with no problems. But I wouldn't think to use anything like that on the tourer. Maybe I need to move to different tires. I know it's heavy but the wheels seem to be holding up fine.

    I liked your web page. Did you like cycling in the Cottswolds? I thought it was perfect cycling.
    I use these ones ... mainly because that's the biggest size that will fit on my bicycle!
    http://www.mec.ca/Products/product_d...=1142836834690

    And thanks. I believe I was only in a little part of the Cotswolds, but I enjoyed cycling everywhere in England and Wales!! I've been over there twice and both times I have had such good experiences. I want to go back!

  8. #8
    Senior Member gregw's Avatar
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    Well here is the more applicable quote from Sheldon Brown;
    "Rolling Resistance
    "Rolling resistance" is the mechanical friction generated as the tire rolls. As a segment of the tire tread rolls into contact with the road, it deforms from its normal curved shape into a flat shape against the road, then back to the curve as the tire rolls onward. The deformation of the rubber in this process is what causes the friction.
    There are two ways to reduce this friction, each subject to trade-offs:

    The thinner and softer the rubber/fabric of the tire are, the more flexible they become.
    The trade-off with this is that the thinner the tire gets, the more fragile it is, and the sooner it will wear out.

    The higher the air pressure, the less the tire will deflect.
    The trade-off with this is that if you pump the tire up too hard, you lose the benefits of pneumatic tires: the ride becomes excessively harsh, and traction will be reduced. In addition, extremely high pressures require a stronger (heavier) fabric and stronger (heavier) rim flanges.

    Rolling resistance does decrease theoretically with any increase in pressure, but with modern, high-quality tires the rolling resistance at correct inflation pressure is already so low that the infinitesimal reductions gained are more than outweighed by the trade-offs. "

    I go for long term comfort on my touring bike, and not concerned with "infinitesimal reductions" in rolling resistance. My Conti's sit at 70 psi, or below if I'm too lazy to pump the tires that day.

    Greg

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