Different PSI from other tire

Discussion in 'Cycling Equipment' started by Caden, Jul 8, 2006.

  1. Caden

    Caden New Member

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    Confused: I'm replacing my came-with-the-bike Bontrager Select tire (just the rear one for now) with a Continental Ultra Gatorskin. Both are 700x25c. However, the old Bontrager says, "inflate to 100 psi" on the side whereas the new Continental says "max inflation 120 psi". This is an awful big difference. I don't want to pump to 120, get out in the Texas 100-degree heat, and pop it on a descent. Nor do I want to pump to 100 and pinch flat.

    What to do? Why the difference?
     
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  2. gclark8

    gclark8 New Member

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    How heavy is the rider??

    Max Inflation is just that, I run 100 front 110 rear on smooth surfaces, 85 front 95 rear on horrible bitumen, set them for your comfort. :cool:
     
  3. supergrill

    supergrill New Member

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  4. ABG

    ABG New Member

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    Yes, maximum inflation means just to never inflate above that pressure; it does not mean that's the best pressure to be at. In Texas I probably would never inflate it that high. Perhaps you would only want to inflate to 120 psi when you are riding with some damn speed-demons, such as at club cycling events, and need all the speed you can get. Though the difference may really just be superstition, because the difference between a road tire inflated to 100 psi and to 120 psi isn't a helluva lot.

    I actually recently bought a pair of Continental 25 mm tires myself, at REI. Not the expensive Gator ones, but just a pair of regular old slick-tread tires that cost $13 each. They had price-check machines in the store, and when I scanned the tires in there, there was also a detailed description. On the 120 max-psi ones, it said the RECOMMENDED pressure is 100 psi.

    Continental Tire also has a website that describes their tires in detail - it is here. It says that your tires have a max pressure of 120 psi and a recommended pressure of 95 psi. Hope this helps.
     
  5. Caden

    Caden New Member

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    Ah, thanks! I suppose I should have RTFM. :) I'm 145 pounds, btw (for the reader who asked). I may keep it at 100 psi just to match the front, and so as not to get too close to max what with the heat here..
     
  6. gclark8

    gclark8 New Member

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    At 145 you could safely run a bit lower, try to keep the front 5-10 below the rear. Why did you go for 25s and not 23s?
     
  7. Dave80

    Dave80 New Member

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    I've just replaced my Maxxis Detonator tyres (700x28) with Conti Gatorskins. I have to say I wasn't to impressed with the Maxxis tyres I had only done about 1500km and they were well worn, the rear in particular looked very shabby and died with two large holes (both about 3mm triangles). I normally pumped them up to 110psi would this have been a factor? I also ride on a some average roads (i.e. course bitumen) and weigh about 98kg.

    Anyway I'm liking the new gators, i've got a 23 on the front and a 25 on the back (in the hope that it would absorb the bumps a bit better) I'm pumping them also to about 110psi and have noticed that I accelerate a bit quicker and typically go about 3km/h faster. Not a massive difference but I bought them to stop getting bloody punctures. If you heavy should you go on the high or low side of recommended pressure? I've been going higher to prevent the tyre from bulging under my weight :)
     
  8. serenaslu

    serenaslu New Member

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    Your logic is correct. Higher load -> use higher pressure. Same deal as with automobile tires. Usually not as big a consideration, but lighter riders can sometimes get away with lower pressures than heavier riders without risking pinch flats (snakebite punctures), increased sidewall cuts, etc.
     
  9. tetsuryuu

    tetsuryuu New Member

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    I think that the "maximum pressure" listed on the sidewall is usually about half of the actual blow-off pressure that most tires will take. There's a struggle that goes on between the marketing department at manufacturers (who want the max pressure listed as high as possible, since people perceive higher as better for whatever reason) and the legal department (who want to reduce the number of failures/lawsuits). At 145 pounds, using a larger diameter tire like a 25mm, I agree with what's been said so far, in that you probably don't need to run over 100psi. But you could most likely do it safely if you wanted, even in Texas heat.
     
  10. hd reynolds

    hd reynolds New Member

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    Not all bike tires are created equal. The bonty's are durable enuf to take up to the recommended max safe tire pressure of 100psi while the conti's recommended max safe tire pressure is 120psi.

    You dont have to stay within the max, just pump ur tires with whats comfy and durable to you. Just dont exceed the limit.
     
  11. Insight Driver

    Insight Driver New Member

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    Best inflation is based on rider weight balance between front and rear tires. Ideal balance for a perfect fit is 55% rear, 45% front weight distribution. For me, 170 lbs weight I pump my front tire up to 85 psi and the rear to 90 psi. I never get pinch flats and the ride is best at these lower pressures because the tires conform to the roughness of the pavement rather than bouncing over the bumps in the pavement. If I was over 200 lbs then I'd up the pressure to 90 psi front and 105 psi rear. This is using 700-25 tires. For some reason people think higher pressure is better. This is a case of marketing being successful, not right.
     
  12. Ray Dockrey

    Ray Dockrey New Member

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  13. lks

    lks New Member

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    Wrong, maximum pressure does' not mean to never inflate above it. It means never let the tire get above that pressure.
     
  14. ABG

    ABG New Member

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    And the best way to make sure you never get above that pressure is probably to not inflate it that high, right? How are we supposed to know what the tire pressure is at other times? The only times we know the tire pressure are when we measure it with a gauge or when pumping it up with a pump that has a gauge attached.
     
  15. lks

    lks New Member

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    Bike tires, like car tires, have different PSIs depending on how they are built. A car manufacture will specify different PSIs, for the same tire, depending on what vehicle it is going on. They may specify a different PSI for the front and back. The PSI on the side of a tire, is that tire's MAXIMUM PSI. You must allow for a PSI build up do to heat increase. Michelins Pro2 Race 700x23 clincher has a maximum of 120psi. But for a 140lb rider, which I am, they specify 95psi/front and 100psi/rear. Unfortunately, it's hard to find a tire manufacturer's recommended front and rear tire pressure, for a specific combined bike and rider weight.
     
  16. ABG

    ABG New Member

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    Ah OK, thank you for that clarification. So the maximum pressure is not the maximum INFLATION pressure, it's just the maximum operating pressure. Which is something which is hard to determine.

    I have Continental Ultra Sports, and I happen to know that Continental's web site does indeed specify recommended tire pressures, even if it's not listed on the tire. I imagine that Michelin's and many other bicycle manufacturer's web sites will offer the same.

    Thank you for the clarification, I will no longer inflate above the recommended pressure of 95 psi for my tire, since I am 160 pounds, which is probably what the tire manufacturers consider to be about average or slightly above average.
     
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