inadvertent super power

stevenast

Well-Known Member
Any theories as to why this is happening? I changed out my tires from 29 inch to 28 inch. I know the smaller circumference will give me more torque, but does it explain why I can suddenly peg out the power meter so much easier than before?

Note how the magnet position has changed relative to the sensor on the frame.

IMG_20150512_162641.jpg

I know I can adjust the magnet, but I'm not sure I want to!

Photo of one of the new tires, chosen for puncture resistance.
IMG_20150512_161851~2.jpg
 
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NoDTMF

Active Member
Interesting....I think we can assume the sensor is not providing any input and the system goes into "limp home mode" which apparently doesn't include the limp! I'll move the sensor on my bike and see what happens this weekend
 

stevenast

Well-Known Member
It may just be the smoother tire at higher pressure makes it that much easier to pedal. Eco mode still requires a lot of work up hills...
 

Cameron Newland

Well-Known Member
FYI, there is absolutely no difference in size between 28" and 29" tires. I know that may come as a shock to some, but it's a difference in naming only. 28" = 29" = 700c.
 

stevenast

Well-Known Member
Oh, there is a difference in the size of the tires external diameter. But the bead seat diameter is exactly the same, 622mm, that's why I could use the same wheels.

28, 29, 700c are all vague (outer diameter approximate) marketing terms for 622mm.
 

pxpaulx

Well-Known Member
Oh, there is a difference in the size of the tires external diameter. But the bead seat diameter is exactly the same, 622mm, that's why I could use the same wheels.

28, 29, 700c are all vague (outer diameter approximate) marketing terms for 622mm.

Same as a 26 inch rim with an average tire or with a fat tire - obviously different total diameter, same rim diameter!
 

stevenast

Well-Known Member
@Cameron Newland There absolutely IS a difference. It's the outside diameter, and the circumference... absolutely different between 29 and 28.

Here's another illustration: fat tire bike vs 26 inch tire mtb. The outer diameter of that type of mountain bike tire is approximately 26 inches, and the outer diameter of the fat tire bike is approximately 29 inches diameter.

But they are both on a 559mm bead seat rim. that comes out to a WHEEL diameter of about 22 inches. Measure it yourself!

There certainly is a big difference between the tires, and the rolling diameter, but they go on the same diameter wheel (although the one wheel better be a lot wider lol!)
 

stevenast

Well-Known Member
Three major bead-seat wheel diameters in the full-sized bike world.
622mm = 28", 29", 700c
584mm = 27.5", 650b (gaining in popularity)
559mm = 26" & fat tire

Tire width, and to a lesser extent inflation pressure and tread... Those will combine to make a big difference in the actual diameter and circumference of tires fitted on any of these particular three wheel diameters.