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I am in need of a new wheel set for my 29'er, and wondering if 650B's are an option. My current bike handles more like a supertanker than a bike. Great for straight lines once up to speed, but if there is a corner, watch out... The 650's are supposed to more responsive than the 29er and roll better than the 26". Additionally my wife rides a 650B, so we would be able to reduce pare tubes and tires.

Bike has disc brakes so that is not a problem.

Apart from lower BB, hence increased risk of pedal strike, if I were to put 650's on my bike, what disadvantages would I have.

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But you don't know your bike would handle any better with 650. In an earlier post you said you liked your wife's bike. Wheel size is not the only difference unless they are otherwise the same bikes. Put your wife's wheels on your bike and try for yourself. My 29er is better than my old 26 is every way.

The clearance is only 1/2 the difference so a change of about 2 cm. But 2 cm is enough to notice. Not just clearance you change geometry. But that may be a good thing for your supertanker.

Also the weight of the wheel and tire will effect the performance. Even how easily it turns Angular_momentum. A lighter wheel and tire will be more nimble to turn. A lighter 29er might give you (a bit) or what you are looking for. In the end a different frame geometry may be what you need. I think you are putting too much on wheel size alone.

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    +1: They may have different cassettes (which they may not be able to swap due to hubs), but the only way to know if this is a good idea is to actually try it. – Batman Dec 8 '15 at 0:10
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I would be wary. Can you do it? Yes. Will it affect the geometry and handling of the bike? Yes Is there a chance you will pedal strike more frequently? Yes The drop will reduce chainring clearance when doing log overs as well.

One thing you may want to consider is getting wider 650b rims and going for 650b+ (aka 27.5+) tires as they will fit a lot of existing 29ers and will not alter your geometry significantly.

Anything from a 650x2.8 to a 3.0 will be in about the same range of tire size as a 29er wheel/tire combination, but will have a wider / rounder tread profile. A wide rim will be needed, 35mm to 50mm rims are typically used for a 650b+/27.5+ setup.

You'll need to check and be sure you have the frame clearance as well, but if you can fit 29x2.4 tires, you should be good using a smaller tire like the wtb trailblazer which is 27.5x2.8 and should work well with a lot of frames.

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For a given rim design, the larger diameter version will be heavier and weaker.

Lighter wheels have less angular momentum. Although a smaller wheel will be spinning faster, the change in circumference is proportional to the radius, wheras angular momentum is proportional to the square of the distance from the axis.

When rolling over the same rough surface, a larger diameter wheel won't drop as far into holes that are smaller than the wheel, so the larger wheel will follow a shorter path and the force experienced at the new contact point as the tyre bridges the gap will be at a smaller angle from the tangent at that point.

I don't know how to calculate the impact of larger heavier wheels on steering.

650b (584mm) is a compromise between 26" (559mm) and 29"/700c (622mm)

To summarise: The differences in your subjective experience will be too small to outweigh any biasses created by your expectations.

Get a fatbike.

  • Angular momentum not rotational kinetic energy. "Outweigh any biasses created by your expectations" is rude and misspelled. en.wikipedia.org/wiki/Angular_momentum – paparazzo Dec 8 '15 at 17:08
  • Corrected the term. The latter statement isn't meant as an insult, everyone has biasses. My spellchecker doesn't flag anything, maybe your dictionary is different to mine. – Emyr Dec 8 '15 at 17:11

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