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 11:38:36 -0500
Organization: A noiseless patient Spider
Lines: 82
Message-ID: <vq21ic$rf2i$1@dont-email.me>
References: <vpslph$3noh2$1@dont-email.me> <vpsncj$3o02g$1@dont-email.me>
 <gjmwP.3138$SZca.1726@fx13.iad> <vpsrss$3om5n$1@dont-email.me>
 <0jt3sj9iofpo2ru3abmi7ddrt4uk5btc9t@4ax.com> <vpta8s$3rj0t$1@dont-email.me>
 <j2d4sj1ju5h4qj8l64v92jp2pbfg44podl@4ax.com> <vpthh1$3spru$2@dont-email.me>
 <vpv32c$7frp$1@dont-email.me> <vpv5h5$848g$5@dont-email.me>
 <vpvh4i$akr9$3@dont-email.me> <m2gvseFatp4U1@mid.individual.net>
 <vpvkaa$akr9$9@dont-email.me> <m2j0huFk55iU1@mid.individual.net>
Reply-To: frkrygow@gmail.com
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 02 Mar 2025 17:38:37 +0100 (CET)
Injection-Info: dont-email.me; posting-host="a8066decd4ad11c10a7194848a8504e4";
	logging-data="900178"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+hbEiz1Pfq9HVTdl1CMe9asxzdzxGCAXE="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:dBaxjRM+cBWPEFCdfBaiWEswE7M=
In-Reply-To: <m2j0huFk55iU1@mid.individual.net>
Content-Language: en-US

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.

I submit Peter Sagan at about 0:15 in this video:
https://www.youtube.com/watch?v=Viszek1LlpA

-- 
- Frank Krygowski