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  • Different cranks on a 24in uni

    Hi All,
    I think the topic on how different crank lengths effect Speed has been worked to death. However my question is very slightly different.
    What I was hoping to find out how many more mph can get from switching from a 150mm to a 100 or 125 on my 24in muni.
    The hope being is my current financially strapped time I can use my 24inch for 5-10miles rides and make this possible by swapping back and forth from the normal 150 to a smaller size depending on whether Iím riding for distance or my usual woodland/hill rides

  • #2
    Based on this video I'd say going from 150 to 127 would give about 7% increase in speed and from 150 to 102 about 22% increase.

    On my 24" (actual wheel OD 25.5") with 125 cranks I get about 6mph at a very relaxed road speed.

    Of course this handy chart gives a great comparison of crank lengths:

    Comment


    • #3
      Originally posted by nickgauntlett View Post
      Hi All,
      I think the topic on how different crank lengths effect Speed has been worked to death. However my question is very slightly different.
      What I was hoping to find out how many more mph can get from switching from a 150mm to a 100 or 125 on my 24in muni.
      The hope being is my current financially strapped time I can use my 24inch for 5-10miles rides and make this possible by swapping back and forth from the normal 150 to a smaller size depending on whether Iím riding for distance or my usual woodland/hill rides
      Just thought I'd throw in, riding will be a heap easier if you use a dedicated road tyre, and better with a bigger diameter. Muni wheels are very tiring for road if you compare it to a road specific tyre.
      If you are female please join the ďFemale Unicyclists!Ē group on Facebook!

      Comment


      • #4
        Originally posted by JimT View Post
        Based on this video I'd say going from 150 to 127 would give about 7% increase in speed and from 150 to 102 about 22% increase.

        On my 24" (actual wheel OD 25.5") with 125 cranks I get about 6mph at a very relaxed road speed.

        Of course this handy chart gives a great comparison of crank lengths:



        Thank you for the graph and your personal experience, found it hugely helpful

        Comment


        • #5
          Speaking as a 65 year old pensioner, who regularly rides 10 miles on a 26" muni with 165 cranks and has recently managed 10 miles on a 20" giraffe, may I suggest that, as you are on a budget, rather than spend your money on different cranks, you use whatever equipment you have and work on improving your fitness, technique and stamina

          Wouldn't cost anything but your time


          But I must thank you, as you have just given me an idea for my next ride - 10 miles on my 20" uni - just need storm Ciara to die down & it'll be my next ride - can't wait!
          Last edited by Nasher; 2020-02-09, 11:08 PM.

          Comment


          • #6
            Originally posted by Gockie View Post
            Just thought I'd throw in, riding will be a heap easier if you use a dedicated road tyre, and better with a bigger diameter. Muni wheels are very tiring for road if you compare it to a road specific tyre.
            Very true, need to find a middle ground in regards of tyres as donít really want to keep swapping tyres over every other day or so. At least cranks you can get with three different holes 100,125 and 150

            Comment


            • #7
              Originally posted by Nasher View Post
              Speaking as a 65 year old pensioner, who regularly rides 10 miles on a 26" muni with 165 cranks and has recently managed 10 miles on a 20" giraffe, may I suggest that, as you are on a budget, rather than spend your money on different cranks, you use whatever equipment you have and work on improving your fitness, technique and stamina

              Wouldn't cost anything but your time


              But I must thank you, as you have just given me an idea for my next ride - 10 miles on my 20" uni - just need storm Ciara to die down & it'll be my next ride - can't wait!
              WOW 10miles in a 20Ē thatís amazing!!
              I should look into my fitness as you rightly stated the winter weather and the storm over the last few days hasnít helped

              Comment


              • #8
                Originally posted by JimT View Post
                Based on this video I'd say going from 150 to 127 would give about 7% increase in speed and from 150 to 102 about 22% increase.

                On my 24" (actual wheel OD 25.5") with 125 cranks I get about 6mph at a very relaxed road speed.

                Of course this handy chart gives a great comparison of crank lengths:

                This also assumes that he can spin his legs faster with the shorter cranks. If he cant increase his RPM on the 102, potentially due to fear of crashing through lack of control, then he wouldnt travel any faster with shorter cranks.

                Comment


                • #9
                  Numbers don't tell the whole story

                  Extra leverage and speed is great, but only if you can "stay on".
                  Have you actually swapped pedals on a unicycle, yet?

                  If you haven't get ready for a big change. My experience:
                  1.) I went from a 125mm to 150mm on my 24" muni, and it felt like shit!!!
                  I couldn't ride. Damn. Felt like a total beginner. Took me a long 3-4 weeks to finally get it. Why? The extra length affects leverage, response timing, and stability. Did I go faster or slower?(...I didn't even think about that).

                  a.) Forces you to change seat height. The crank put's the pedal lower to the ground, so your inseam length get's longer. Riding lower is a minor thing to get used to, but it is a change.

                  b.) Forces you to raise your knees higher. The longer crank brings the pedal up higher at 12 o'clock. Strange feeling. More bent knee mass increases cause more unicycle wobbling. Must learn to engage your core and calibrate your left and right leg motion to be dead even for less wobbling.

                  c.) Extra force applied "faster". Not what you want. Throw's off your whole pedal force and timing. You actually need to "slow down" to catch up to the action. Hard to explain but anyone who has gone from short to long cranks knows this very very well. It sounds like an oxymoron but, basically you have to trust yourself and "slow down" your whole body action to ride.

                  d.) Benefits? Actually, in the case going from shorter to longer. Yes, I gained tremendous leverage to go up hills. The reduction in speed was slightly noticeable.

                  What about getting speed from short to longer cranks? You don't automatically go faster. With the shorter cranks now it feels weird. a.) Instead, of the nice smooth round rotation you are used to doing...it feels like your are pumping your legs straight up/down!!! Yes, it feels easier but now your lateral balance is thrown off.
                  b.) Guess what, the longer cranks with more mass going up/down helps to stabilize you. With shorter cranks and lower knee raise you lose that stability. If you are a beginner and need to flail your arms a bit...well you will be flailing them a lot more.
                  c.) Also, you need to raise that seat up, again. However, only after you master the stability issue can you start to apply "more pedal cadence" for extra speed. If you are not rock solid stable, forget about speed.

                  Bottom line the crank length changes some major static and dynamic physics involved. If you are already experienced with different unicycle wheel sizes and cranks it's no big deal, but the first time you do this it is a big deal. Like most of use we "forget" that learning experience. Good luck.
                  Last edited by slamdance; 2020-02-10, 04:43 AM. Reason: ..

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                  • #10
                    I learnt about 1 & 1/2yrs ago on a 20inch with 125s I then once learnt moved on to 24inch still with 125s but because I was doing a lot of muni riding I changed to 150s and found it a lot easier (but again I was new at the time) since then I haven’t changed from 150s although I have riden my sons 20inch uni with 100s on briefly, which like you said feels like a lot of up-down rather than circular movement.
                    Last edited by nickgauntlett; 2020-02-10, 05:07 AM.

                    Comment


                    • #11
                      Originally posted by slamdance View Post
                      If you are already experienced with different unicycle wheel sizes and cranks it's no big deal, but the first time you do this it is a big deal. Like most of use we "forget" that learning experience. Good luck.
                      Experience definitely makes a difference. The better you are at riding the more you adjust easily to the change.

                      I ride two different length cranks between left and right and the only thing I noticed when I made the change was that my seat height felt different. Apart from that didn't feel any different to ride.

                      Comment


                      • #12
                        Originally posted by Pinoclean View Post
                        Experience definitely makes a difference. The better you are at riding the more you adjust easily to the change.

                        .
                        I've always been really bad at swapping between unicycle sizes and even cranks on the same uni. 29 to 36, 36 to 29, 36/150 to 36/127, 29 to 24...., 36 to 19 ahhhhh !! Couldn't ride properly for the first 20 minutes, and then took a week to get accustomed again.

                        Mounting of course suffers, but so does turning, especially tight turns, rough ground and a combination of all. Steep hills require different techniques and feel for different wheels/cranks.

                        The only solution is practice and attention to your weak points.

                        So now I make an effort to swap unicycles and cranks often, try to remember the bits I have trouble with and concentrate on those. One day I'll just jump from one to other without a care, but I suspect by that time I'll be too old to ride.

                        Comment


                        • #13
                          Originally posted by Nasher View Post
                          But I must thank you, as you have just given me an idea for my next ride - 10 miles on my 20" uni - just need storm Ciara to die down & it'll be my next ride - can't wait!
                          I was a pity I got home after dark last night with the family and then we had to eat and all, but I seriously thought of riding around with the storm picking up. Thought it could be cool to see how much side-wind I could take before falling off.

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                          • #14
                            With my 24Ē Muni with stock 145 mm cranks I made hilly road rides up to 13 miles at a speed around 6 mph with a a heavy Duro Wildlife Leopard 3.0 Muni tire.
                            This is without spinning ďfastĒ.
                            Only on my first outing with a group of really experienced riders I have seen what fast spinning is.

                            I tried 125 mm two times and first couple of minutes it felt quite weird but quickly it became clear that I could ride at higher cadence.
                            Since both rides were part of group training with frequent stops I did not get a higher average speed.
                            I switched back to 145mm because I was preparing for a hill climbing event and wanted to train in the correct set up.
                            Since the event Iíve been riding the 27.5 Muni but I did replace the stock 145 mm cranks for 136 mm.

                            IMHO the distance youíre looking after is totally doable without changing to shorter cranks.
                            But shorter cranks will make you faster.
                            And eventually youíll be able to climb at 24.125 mm as well

                            Contrary to what I often read on this forum I found the shorter cranks easier to mount.
                            Perhaps because I have a lousy free mounting technique with too much weight on the back pedal.
                            In my case that means that the lower leverage of the shorter crank is a plus.

                            My local climb that I started uphill practice on:
                            Distance: 0.9 km
                            Avg Grade: 5.6 %

                            Initially at 24-145 I could not make it to the top due to my legs burning up.
                            After some training I could make it several times in a row
                            And eventually I could easily ride it several times in a row at 27.5-136

                            Some math, from the crank ration tables (My own version of the table includes also 27.5Ē wheel size)
                            24-145 has a gain ratio of 2.10
                            24-125 has a gain ratio of 2.44
                            27.5-136 has a gain ration of 2.57
                            The table suggests you can go up to 3.6 for hilly road riding.

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                            • #15
                              Awesome advice on high plus highly encouraging, not too fussed about getting high speed just quick enough to keep up with my 9yr old on a bike with minimum exhaustion
                              Summary is by the sound of things is, anything is possible with enough training

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