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  1. #1
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    Mountain biking tires

    I don't know if going to a 2.25 tire will be OK because my bike originally came with a 1.85. And does it matter if they are kevlar or wire beaded and what's the difference?

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    Senior Member Chumley360's Avatar
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    I can't tell you if the new width will fit or not. You'll probably have to do some measuring to figure that out. But the kevlar bead tires are lighter and foldable. That's really nice if you're planning an extended bike trip you can keep a tire or two in your pack.

  3. #3
    unofficial roadie DirtPedalerB's Avatar
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    1.85 to 2.25 hmmmmm. If the 2.25 tires fit between the stays I guess they would work, but those are going to feel HEAVY when you make the switch. If it came with 1.85's I bet it is an XC bike I'd stick around 1.95 to 2.1 at the max. Tire widths vary between brands, also allow some frame clearance in the back for mud and warped wheels. You may consider a 2.25 on the front with something narrower in the rear as there is usually more room on the fork and more traction up front is a good thing.

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    Check the documentation that came with the bike. You'll be able to find maximum wheel sizes there. I'm thinking tho, if it came with 1.85, that was what it was made for

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    Fitting a larger tyre on the front shouldn't be a problem as there is usually always plenty of space. All you need to do is grab a tape measure!

    However, the rear wheel fitting through the frame may be a problem with a 2.25" tyre. Again, get out your tape measure!

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    Oh please ...

    Quote Originally Posted by DirtPedalerB
    1.85 to 2.25 hmmmmm. If the 2.25 tires fit between the stays I guess they would work, but those are going to feel HEAVY when you make the switch. If it came with 1.85's I bet it is an XC bike I'd stick around 1.95 to 2.1 at the max. Tire widths vary between brands, also allow some frame clearance in the back for mud and warped wheels. You may consider a 2.25 on the front with something narrower in the rear as there is usually more room on the fork and more traction up front is a good thing.
    An entire wheel assembly with rear cassete and 2.25 tire can be moved with your pinkie finger. The difference between a 2.25 and 2.1 or 1.85 tire is irrelevant when compared to you body and frame mass. If you perceive a difference in acceleration, it's likely the loss of mechanical advantage from using a larger diameter wheel.

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    unofficial roadie DirtPedalerB's Avatar
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    Quote Originally Posted by willtsmith_nwi
    An entire wheel assembly with rear cassete and 2.25 tire can be moved with your pinkie finger. The difference between a 2.25 and 2.1 or 1.85 tire is irrelevant when compared to you body and frame mass. If you perceive a difference in acceleration, it's likely the loss of mechanical advantage from using a larger diameter wheel.
    I would think the diameter is around the same if not exactly the same. A heavier tire will take more energy to spin up to speed and I'm sure most 2.25 tires weigh more than most 1.85 ties. Also the wide tires will have bigger contact patch which adds more friction again increasing preceived weight. Wheel weight is the most important to the response of the bike, body and frame mass can't really be changed as a variable when we are discussing changing between tires. So I say he will feel like he is riding a slug .. especially if he goes with a more knobby tread pattern than he has allready. But I seriously doubt they fit.

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    I'm assuming it came with a 1.85, that's what the website had for a like model. I bought it used so I have no manuals or anything for it. It currently has 2.0 on it. Basically I'm in need of some new tires, and I found some maxxis that got really good ratings, but only comes in 2.35.

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    Rotate this ...

    Quote Originally Posted by DirtPedalerB
    I would think the diameter is around the same if not exactly the same. A heavier tire will take more energy to spin up to speed and I'm sure most 2.25 tires weigh more than most 1.85 ties. Also the wide tires will have bigger contact patch which adds more friction again increasing preceived weight. Wheel weight is the most important to the response of the bike, body and frame mass can't really be changed as a variable when we are discussing changing between tires. So I say he will feel like he is riding a slug .. especially if he goes with a more knobby tread pattern than he has allready. But I seriously doubt they fit.
    A carpenter ant weighs more than a mound ant. Which one takes more effort to pick up?

    Indy tires are wider than Nascar tires. Which car is faster?


    These facts have nothing to do with the questions that are asked. And they are exactly the same as the things you are saying. I can take two ball bearings from the same line on the same day and I GUARANTEE that their mass is not the same. The reason is simple, the statement makes no sense because there is no parameters on what equality means. An engineer will define a precision with with equality can be assessed. But real objects that exist in the real world cannot be measured EXACTLY so we must define thresholds for the sake of making conversations meaningfull.

    You say that it will take "more energy". You have failed to define what levels of energy is relevant and perceptable. You say wider tires are "slower" because there is "more friction". But had you looked at your physics more carefully you would have discovered that the frictional force is the mass times the coefficient of friction (Ff=m&#181. And the coefficient of friction for a material is independent of surface areas since the increased surface area decreases pressure. Did you know that the low pressures that racers so desperately seek in their tires also increases the surface area?

    Like I said before, increasing the wheel diameter (the tire is the outermost portion of the wheel) changes the effective gearing ratio. This is probably explains the "sluggishness" you perceive. This is no different than the "sluggishness" you feel when shifting from 7th to 8th gear. Put a 2.5" tire on your rim and you will still be able to push it with your pinky. Just imagine how relevant such a mass is to the largest muscle groups in your body in and around your hips and thighs?

    As an afterthought, I am well aware of changes of moment in inertia as the mass in a rotating body increases in radius. I am trying to convince you that it is pretty much irrelevant unless you are a serious endurance racer.

    In general for off road, wider tires are often better as they more easily conform to terrain. The benefit of this is two fold. First, you get increased traction as more of the tire is actually in contact with the trail and you are more likely to be in contact with a surface that will hold. Second, the yielding nature of the pneumatic tire is beneficial as deflect from irregular trail features. The alternative is bouncing the bike up and down. That bouncing is no good. It is a translation of perfectly useful forward kinetic energy into heat energy from flexing the tires. When one conserves kinetic energy, we are not so blindly eager generate it with promises of lesser inertia moments that have never been calculated with reference to the overall inertia of rider mass plus non-rotating bike mass plus rotating mass to determine whether it's even remotely relevant.

  10. #10
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    willsmith - dont be a complete ****, because your just making a fool of yourself.

    Tell me this, if weight on the wheel mattered nothing, why do XC riders use 2.0tyres? Why do we use light tubes? If weight at the wheel mattered nothing, why wouldn't all XC riders use thorn proof downhill tubes for example? Its a combination of weight and contact with the ground (aka friction).

    You say that it will take "more energy". You have failed to define what levels of energy is relevant and perceptable. You say wider tires are "slower" because there is "more friction". But had you looked at your physics more carefully you would have discovered that the frictional force is the mass times the coefficient of friction (Ff=m&#181. And the coefficient of friction for a material is independent of surface areas since the increased surface area decreases pressure. Did you know that the low pressures that racers so desperately seek in their tires also increases the surface area?
    Who care's? We all know Wider tyre = more contact with the ground. Ever wonder why road racers use very thin tyres? YES its called FRICTION! They go FASTER believe it or not with the same pedal efficeincy! You really shouldn't have brought this 'technical' stuff into it as we all know a thinner tyre will roll faster then a wider tyre, and we all know that if you have a 2.35" tyre and the same tyre in 1.90", say a Kenda Nevegal with a nice and nasty tread pattern...you sure are going to feel a difference in weight and that WILL be noticeable when riding. Even if its only a small difference when climbing, still noticeable.

    I'm sure there are many people on here who have noticed this over there long years of riding...

    Last edited by blue_neon; 08-19-06 at 02:32 AM.

  11. #11
    unofficial roadie DirtPedalerB's Avatar
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    Quote Originally Posted by willtsmith_nwi
    Like I said before, increasing the wheel diameter (the tire is the outermost portion of the wheel) changes the effective gearing ratio. This is probably explains the "sluggishness" you perceive. This is no different than the "sluggishness" you feel when shifting from 7th to 8th gear. Put a 2.5" tire on your rim and you will still be able to push it with your pinky. Just imagine how relevant such a mass is to the largest muscle groups in your body in and around your hips and thighs?
    A 26X2 and a 26X2.5 have the same diameter. the only difference is the width. you can find slight differences in height of tires in any size, but they bulge at the bottom to about the same distance from the rim depending on pressure.

    pushing something with your pinky has no relevance.. I'd imagine you can push a nascar tire with your hand and an indy car as well with about the same force.

    I'll stick to relatively skinny light tires
    Last edited by DirtPedalerB; 08-19-06 at 08:54 PM. Reason: bad wording

  12. #12
    ÖöÖöÖöÖöÖö Dannihilator's Avatar
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    A 26x2 and a 26x2.5 has a contact patch about the same. Also remember, there is no standard for measuring tire width. An IRC Mibro in 26x2.25 actually measures out to be 1.95, while a Michelin XC tire in 2.1 measures out to be 2.2. so I would have to say, it depends on the tire.
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  13. #13
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    Context ...

    Quote Originally Posted by blue_neon
    willsmith - dont be a complete ****, because your just making a fool of yourself.

    Tell me this, if weight on the wheel mattered nothing, why do XC riders use 2.0tyres? Why do we use light tubes? If weight at the wheel mattered nothing, why wouldn't all XC riders use thorn proof downhill tubes for example? Its a combination of weight and contact with the ground (aka friction).

    Why do some baseball players wear the same unwashed jock strap when they're on a streak? People conjure up all types of faulty reasoning to explain phenomenon they have experienced.

    For DirtPedlarB, the casing of a bicycle tire is not rigid enough to hold a fixed height. If you take a tire and put it on a narrow rim, it will increase the diameter. If you put it on a wider rim, the tire will increase in width and decrease in height. And yes, lower air pressure will increase the size of the contact patch and lower the mean effective diameter of the tire.

    I point out the relative ease of moving the tire absent the rider to give you some reference to what you are talking about. The pinky is virtually a vestigal limb with barely any strength whatsoever. Yet you can easily move the wheel with one of those big old nasty 2.5" tires on wide downhill rims. You could not even remotely do this when the bike is loaded. The reason is that the moment of intertia in the wheel is virtually insignificant compared to your body mass. Furthermore, the energy to get that wheel moving is conserved in it's motion AND once the wheel is up to speed and remains there there is no more penalty for acceleration (which really wasn't significant in the first place).

    In the end, please buy whichever tires you wish. But please realize that their are other factors to tires that are far more significant than weight.

  14. #14
    unofficial roadie DirtPedalerB's Avatar
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    Quote Originally Posted by willtsmith_nwi
    For DirtPedlarB, the casing of a bicycle tire is not rigid enough to hold a fixed height. If you take a tire and put it on a narrow rim, it will increase the diameter. If you put it on a wider rim, the tire will increase in width and decrease in height. And yes, lower air pressure will increase the size of the contact patch and lower the mean effective diameter of the tire.
    So go ride your bike with the rear tire at 40psi and then go ride it at 20psi .. I guarantee it's harder to pedal at 20. But the 20psi tire will have a lower effective diameter so it should be easier according to this logic and what you said about friction not depending on area before.

    I agree that it depends on the specific tire and ride whatever you feel comfortable with, but there is a penalty for big cushy tires.

    weight doesn't matter too much, but the big tires deflect more so I'd say the width is more important than weight. The spacing of the knobs is the main thing I look at though. A tighter spacing will roll better, but may reduce traction. It's all a compromise when it comes to tires.

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