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  1. #1
    Senior Member broomhandle's Avatar
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    tire sizing 700c x 20/25

    i picked up a old raleigh, and i just noticed the person before had 700c 25's on the front and a 20c on the back.

    i dont notice anything, but i was gonna take this thing on a 200 mile ride.

    would this setup make me feel like im always going uphile or somehting? haha

    any disadvantage?

  2. #2
    'Mizer Cats are INSANE Mentor58's Avatar
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    Most folks do it the other way around, put the wider tire on the back. I can't believe that you would feel any difference, too lazy to figure out the difference in dimensions and figure the actual angle, I'm going to swag it and say "You'd never know the difference". I'd swap them around so they would wear better, but don't lose any sleep over it.

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  3. #3
    ctp
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    I'd think with the speed advantage of the narrower tire, the back might get to going faster than the front and the bike would have a tendency to spin out.


  4. #4
    Senior Member broomhandle's Avatar
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    well, it does make me do a constant wheelie, is that wrong? or normal?

  5. #5
    cycles per second Gonzo Bob's Avatar
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    Quote Originally Posted by ctp
    I'd think with the speed advantage of the narrower tire, the back might get to going faster than the front and the bike would have a tendency to spin out.

    Or, in NASCAR lingo, he'll be loose in the corners

  6. #6
    Senior Member grolby's Avatar
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    If you're doing a wheelie all the time, that's not because of the tires, though 5mm is a pretty significant difference between the two.

    There are a couple of reasons to put a wider tire on the front, those being improved traction and somewhat softer ride over bumpy for the front end. The previous owner may have had some slight hand or wrist discomfort, and ran the wider tire in front to take the jolts out.

    Sheldon's advice: DO NOT rotate the tires unless they are unused or almost unused: http://sheldonbrown.com/tire-rotation.html

  7. #7
    ctp
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    Quote Originally Posted by broomhandlde
    well, it does make me do a constant wheelie, is that wrong? or normal?
    Constant wheelies are normal with some of the crowd I ride with. http://www.cyclecide.com/beer/photos/

    Oh, and no matter what kind of tires I have on, I'm always a bit "loose in the corners"



    ps - no, I don't actually ride with them, but we are local to each other

  8. #8
    Senior Member DieselDan's Avatar
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    I bet it looks like one of those fart can "tuner" cars.
    Bikes use brakes to stop.

    If your bike has breaks, don't ride it.

  9. #9
    Ferrous wheel
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    I would release 5 PSI from the back tyre and replace it with nitrous oxide.
    One thing about living in Santa Carla I never could stomach -- all the damn vampires.

  10. #10
    Senior Member RockyMtnMerlin's Avatar
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    Some of the best responses of any recent thread Nitrous oxide

  11. #11
    ctp
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    Quote Originally Posted by spider-man
    I would release 5 PSI from the back tyre and replace it with nitrous oxide.
    nitrous oxide?

    that makes me laugh for some reason.

  12. #12
    Senior Member Deanster04's Avatar
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    Tires are cheaper than a trip to the emergency room. Sheldon Brown's advice is really the best. Change the front to the rear if you must and buy a new front tire unless there is almost no wear on the tires. You might not even notice.

  13. #13
    Senior Member ken cummings's Avatar
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    Quote Originally Posted by spider-man
    I would release 5 PSI from the back tyre and replace it with nitrous oxide.
    Really Nitrous oxide? Plain N2 or Nitrogen gas makes sense. Nitric oixide maybe would react with and weaken the tire rubber. What are we missing here?

  14. #14
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by broomhandlde
    i picked up a old raleigh, and i just noticed the person before had 700c 25's on the front and a 20c on the back.

    i dont notice anything, but i was gonna take this thing on a 200 mile ride.

    would this setup make me feel like im always going uphile or somehting? haha

    any disadvantage?
    Personally I use the opposite configuration since the rear-wheel has more weight. Then I would use 110psi on both tyres for roughly the same amount of feel. Tyre-wear is more even. Smaller tyre in front also gives quicker and more nibble handling; the steering responds instantly.

    With the bigger tyre in front, I'd have to use 120psi on the 20mm rear and 100psi in front. This ends up giving lazier steering and a more twitchy back end. Hitting bumps in mid-corner at maximum-cornering speed will have the back end be too loose, it'll bounce around more and skip across the tops of the bumps...

    If the 20mm rear tyre hasn't worn in a flat center section, then you can swap them.

  15. #15
    me have long head tube TallRider's Avatar
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    I'd also recommend you swap them and put the narrower tire in front, provided that its tread isn't worn down too much. As Danno said, the steering is more responsive with a narrower tire in front, but I'm thinking more about the ride being more comfortable with a wider tire underneath you, that you can run at slightly lower pressure and will cushion you a touch more, both because it's wider and because it's at lower pressure.

    On a related note, your front tire should always have thick enough tread on it. Basically, it's much more dangerous if your front tire flats while riding than if your rear tire flats while riding. Because the steering depends on the front wheel, you're much more likely to go down if your front tire blows than if your rear tire blows. This is why it's important that you make sure whatever tire is on the front, doesn't have the tread worn through.

  16. #16
    ctp
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    Quote Originally Posted by ken cummings
    What are we missing here?
    the joke?

  17. #17
    Senior Member broomhandle's Avatar
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    yeah, i was going to put the 20 in the front and the 25 in the back. i was thinking the same thing, for handleing. and i just noticed my peugeot that i ride everyday has a 28 on the back and a 23 on the front. im all over the place.

  18. #18
    ctp
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    Quote Originally Posted by broomhandlde
    yeah, i was going to put the 20 in the front and the 25 in the back. i was thinking the same thing, for handleing. and i just noticed my peugeot that i ride everyday has a 28 on the back and a 23 on the front. im all over the place.
    So wait - you could pair up the 20 and the 23 on one bike and the 25 and the 28 on the other bike. Your choice which in front and which in back

  19. #19
    Senior Member broomhandle's Avatar
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    haha, i think every bike i own has mis matched tires. except my 88 trek 100 with conti ultra 2000's both 25's!!! haha

  20. #20
    Ferrous wheel
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    The bike I rode to work today has mismatched tyres, rims, hubs, brake calipers and derailleurs.
    One thing about living in Santa Carla I never could stomach -- all the damn vampires.

  21. #21
    Senior Member broomhandle's Avatar
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    you win. haha

  22. #22
    ctp
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    Quote Originally Posted by spider-man
    The bike I rode to work today has mismatched tyres, rims, hubs, brake calipers and derailleurs.
    good god, you're a wild man!!! You do have life insurance, right?????


  23. #23
    meb
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    Quote Originally Posted by ken cummings
    Really Nitrous oxide? Plain N2 or Nitrogen gas makes sense. Nitric oixide maybe would react with and weaken the tire rubber. What are we missing here?
    But N2 is so inert it doesn't react as well with the rider.

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