# speed comparison

24" 127mm crank vs 26" 150mm crank
on hilly/trails and on paved flat areas

I have 20" with 102mm cranks(do i measure from center of axle to center of pedal?)

Would neither 24"or26" be significantly faster?

Thanks!

edit*
bythe way, I ride ~1mile every day at 7mph
tried 2miles once, taking me 20min
8.6miles today took me 2hrs(had backpack about 15lb, which made me fall of 3 times when trying to mount after crossing crosswalk)

the factors that dictate.speed are

obviously the.more rpm you.can.spin, the faster you will go. the shorter cranks make high rpm pedaling a little easier.

so a 24 inch wheel with 150mm cranks or 110mm cranks, youll likely go.faster with the 110

similarly keep the.cranks.the.same.and change wheel size your speed will change too

however with the need for dynamic fore aft balance, dont expect the change to be simple

before getting a.schlumpf hub i would cruise along at 10mph or so, i thought therfore id cruise along at 15 in high gear same cranks, same wheel size just geared up. not so . im a bit faster in high gear but not 50percent faster

my brain intervenes and says thats fast.enough at about 12mph whatever wheel size im on

Within sensible limits, it is to do with ratios.

Wheel size. Every rotation of the wheel makes you move across the ground by a distance equal to one circumference of your wheel.

Therefore, if you double the size of your wheel, you double how far you travel per revolution.

So if you add 10% to the size of your wheel, you travel 10% further per revolution.

Therefore, all other things being equal, and pedalling at the same cadence (rpm) a 26 will travel 26/24 times as fast as a 24.

26/24 = 1.08333, so a 26 is 8% faster than a 24.

However, all other things are not equal. A bigger wheel will be smoother, and be less affected by minor changes in the surface you are riding over.

A similar ratio thing works with cranks, but only within a fairly narrow range. Add 10% to your cranks and you get 10% more leverage, but your feet have to travel 10% further per revolution, so you tend to pedal slightly more slowly.

However, common sense tells you that you would not go incredibly fast on 10 mm cranks, and you would not do very well on a 36 with 400mm cranks either.

The wheel size ratio effect is fairly consistent as long as you are a confident rider, although big wheels will always go slightly faster than the maths suggests.

The crank size ratio effect is much more dependant on your skill, confidence, leg length, etc.

The only way to find out is to try. As you do more miles, you will find that there are one or two crank sizes that suit you best, and you will find a wheel size that suits you best for the sort of riding you like to do.

You cannot just reduce it to arithmetic, and you cannot learn more than the very basic principles from someone else’s experience.

Yes, crank length is measured center to center between the hub and pedal holes.

Compared a 20" wheel a 24 will be about 20% faster and a 26 will be about 30% faster. These numbers assume that you are pedaling at the same RPM regardless of wheel size.

If you want to get around faster definitely get a bigger wheel. Since you already have a 20 I’d probably skip the 24 and go straight to the 26, or maybe even a 29. As far as your hilly trails; if you already riding these on your 20" with 102s, then you’d probably be OK with 127s on a 26" wheel. If you feel you’ll need more leverage, especially for controlling your speed downhill, then go ahead with the 150s to start.

These are just general suggestions. Like Mike just said it largely comes down to experimentation and personal preference.

Martin