Just curious if anyone is running or has tried running a 100 mm rim in the rear and a 65 mm rim in the front with 4" or whatever size tires, and if so what your experience with it was. I'm thinking of doing this as a way to keep the greater float of a wider tire/rim in the rear, but getting a better tire profile from a narrower rim in the front to help eliminate self steer. In snow/sand I'd use 100 on both but for dirt and other surfaces seems like it might be worth switching the front out to 65.
Anyone running 100 mm rim rear and 65 mm rim front?
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That seems the reverse of what would be optimum. Personally, I'd rather have a lighter rim/tire combo in the back for reduced rotational mass and easier pedaling and a wider combo in front for increased float and traction. With what you've described, I would assume that it would be harder to pedal and the front might have a <relative> tendency to plow and push. I know from my experience with motorcycles, you never want more traction on your rear than what you have up front.
Unless you ride around doing wheelies, you're spinning up both wheels when you accelerate. It's not suddenly free just because you move it to the front.
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N8R, I will plan on doing something similar next winter if someone actually produces a 100 mm carbon rim. The front seems to get adequate "float" with the 85mm rims but there seems to be big difference in the rear in terms of being able to ride in marginal snow conditions with the 100mm rim with really low pressures. At really low pressures on narrower rims, the tire seems to move around more and isn't as flat across the tread which affects traction in some snow conditions.
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Like others have said this seems the opposite of what you want. For dirt, you don't need more float in the rear, and the traction of a 3.8 tire on a 65mm rim is more than adequate. Larger tire should go up front for better handling. I've never run a "fat front" but I do like a more aggressive tire up front and a somewhat lighter tire in the rear for the reasons that have been stated. What you describe sounds like it might be better on sand/snow. I know my rear tire almost always is the first to break through crust due to rearward weight bias.
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Not quite. It takes a lot more extra energy to turn a heavier wheel that's being driven in the rear than it does to push that same wheel up front. Up front, the heavier wheel will affect handling but overall, won't have as much of a negative impact on acceleration and power as it would in back.
Umm. I'd love to hear you try to explain this.
You're accelerating both wheels regardless of where the chain attaches.
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I'd love to hear SOMEONE explain it, too, 'cause I've felt what I think Gigantic is talking about. Ahough I'm not certain whether it was the lighter weight/mass of the rear wheel or maybe a difference in tread patterns, tire pressures, atmospheric pressure, or whether I was riding with or against the direction of the earth's rotation. Seriously, it does seem that it takes less effort to accelerate a lighter rear wheel than a heavier one.
Accelerating a lighter wheel does take less energy. But you accelerate both wheels when you ride so swapping front and rear wheels does not reduce he amount of energy it takes to accelerate the bike.
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no. the motor is driving the rear, not the front; that might be true in a 2wd system, but is not necessarily the case in 1wd. Yes, there is extra weight being pushed down the road on the front wheel, but that extra weight is not contributing or detracting from driveline efficiency. Throw a 29er wheel on the back of your bike, you'll find that it is dramatically easier to pedal, easier still if you put on a 700c road wheel.
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facepalm.jpg
Mr. Inertia doesn't care which wheel your chain attaches to, he's still going to do his job.
Wrong. If you're not driving the front.... who is? Can I pour concrete in there and it magically spins up for free?
The motor (you) is driving both wheels. You are spinning both, and that takes energy. Do you really deny that? Come on man.
Run this by some of your engineer friends and let us know how that works out for you.
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There is a difference between the front and the rear. The front is merely rolling and is generally deforming less. The rear absorbs energy output.
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You guys need to go back to middle school science class. When you stomp on the pedals, accelerating your bicycle, unless you're doing a wheelie, you're spinning up BOTH wheels from a dead stop simultaneously and equally. If both the front and rear wheels have the same mass distributed equally, then they are both overcoming the same amount of inertia regardless of where the drive chain is attached. If the rear wheel were to be lighter than the front, the amount of force required to spin the wheels up would be a calculation based on TOTAL wheel mass, front and back. Swapping the two front to back would make no difference.
I've actually done this in real life, too. My Pugsley wheels are swappable front to back. When I swap my lighter fixed hub front wheel to back, and the heavier internal gear hub rear wheel to the front, the laws of physics still apply. It feels the same when spinning up the wheels, because I'm still pushing the same amount of mass.
I've actually done this in real life, too. My Pugsley wheels are swappable front to back. When I swap my lighter fixed hub front wheel to back, and the heavier internal gear hub rear wheel to the front, the laws of physics still apply. It feels the same when spinning up the wheels, because I'm still pushing the same amount of mass.
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so you are saying that running a slick tire on the rear and knobby front is the same effort and efficiency as running knobby in the rear and slick front?
we are talking about bikes, pedal powered.
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