Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Getting old is not for sissies
Date: Sun, 2 Mar 2025 20:35:37 -0500
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On 3/2/2025 7:55 PM, Roger Merriman wrote:
> Frank Krygowski <frkrygow@sbcglobal.net> wrote:
>> On 3/2/2025 7:17 AM, Roger Merriman wrote:
>>> Frank Krygowski <frkrygow@sbcglobal.net> wrote:
>>>> On 3/1/2025 12:53 PM, Roger Merriman wrote:
>>>>> Frank Krygowski <frkrygow@sbcglobal.net> wrote:
>>>>>>
>>>>>> I'm puzzled by the video's advice to avoid pulling up on the pedals "as
>>>>>> it's bad technique." I'm pretty sure I do pull up when jumping the bike.
>>>>>> What's bad about it?
>>>>>>
>>>>>> And more on that video. In slow motion as they showed, the physics is
>>>>>> pretty obvious. The rider gets his body mass moving upwards, then
>>>>>> essentially pulls the bike up with him. That's where I think I pull up
>>>>>> using the pedals.
>>>>>>
>>>>> In theory it’s better to have the bike rider spring up, than being pulled
>>>>> up by foot attachments also slight risk of unclipping.
>>>>
>>>> I'm not sure I understand your phrasing. On my road bikes, I "spring up"
>>>> - that is, jump my body upward. I then pull upwards with both hands and
>>>> feet. Since I use toe clips instead of clipless, I don't think I've ever
>>>> unclipped while doing that.
>>>>
>>>>>
>>>>>> What's less obvious, I think, is how a skateboarder with zero foot
>>>>>> attachment can bunny hop a skateboard. It's interesting to think about.
>>>>>>
>>>>>>
>>>>> Lot of folks who jump is a focus do run flats so aren’t pulling up.
>>>>
>>>> I run flat pedals on my mountain bike and my about-town 3 speed. Yes, I
>>>> can jump them, but not as high. On the other bikes, I think the toe
>>>> clips help.
>>>>
>>> I’d refer you to the Don who is a ex downhill racer, and rather technical,
>>> to explain why!
>>>
>>> <https://youtu.be/F7LO1qnm0Xs?si=0p3ONupQJCKONsR4>
>>>
>>> But certainly all of the sane advice for bunny hops are not to being
>>> pulling up with your feet, it can be done but it’s poor technique and will
>>> limit how much you can do.
>>>
>>>> As with the skateboard "ollie" (linked in another post) getting the
>>>> rider's mass up high is easy and obvious, by jumping. Making the bike or
>>>> skateboard levitate is what's tricky.
>>>>
>>>> I think the physics goes this way: You lift the front of the machine,
>>>> raising the machine's center of mass. On the bike, that's by pulling up
>>>> on the handlebars. On the board, that's by kicking down on the tail.
>>>>
>>>> Once the machine center of mass is elevated, then rotate the machine
>>>> about its center of mass. That's  by pushing down on the handlebars or
>>>> by kicking down on the nose of the board.
>>>>
>>>> That rotational action about the center of mass is what causes the rear
>>>> wheel(s) to lift into the air.
>>>>
>>>>
>>> You shouldn’t be lifting either the bar or pedals, it’s about as with all
>>> MTBing weight positions and movement and timing ie push hips back so your
>>> arse is almost brushing the rear tyres.
>>>
>>> And the front will come up, scooping the weight forward to drop the front
>>> down and the rear up.
>>
>> I can accept that the extreme body motions he's describing are needed to
>> get more than, say, a foot into the air. They may or may not have helped
>> the guys who's crashes he shows from 5:34 - 5:45 in the video.
>>
>> And as your man says at 5:49 "... well, it does work, it's not as good."
> 
>>
>> I'm not trying for "big air," as they say. I'm on a road bike, and my
>> objective has been to clear big potholes, railroad tracks or speed
>> bumps. For that I don't think there's a problem with moving one's body
>> straight up then pulling the bike up using handlebars and pedal
>> attachments.
> 
> Kinda depends on your aim, if one wants to learn how to bunny hop for what
> ever reason, it’s a better form and more reliable granted needs practice,
> your method is cheap and dirty hence folks use it, but it inherently has
> limits.
>>
>> I submit Peter Sagan at about 0:15 in this video:
>> https://www.youtube.com/watch?v=Viszek1LlpA
>>
> I’d suggest he probably did more than just pull up, it’s fast ...

It helps to slow it down to half speed or slower as you view it.

> ... but looks
> like he compresses and then springs up, he’s also someone with some MTB
> background and likes to throw the bike about.
> 
> Ie that doesn’t look like just a cheap and dirty pull on the bars.

Reread above, please. What I said is still there:

"On my road bikes, I "spring up"- that is, jump my body upward. I then 
pull upwards with both hands and feet. Since I use toe clips instead of 
clipless, I don't think I've ever unclipped while doing that."

If I want to jump a bit higher and if I have time, I think I do 
"compress" a bit before I spring up.


-- 
- Frank Krygowski