SADDLE HEIGHT..please try the "bump test"

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sreten
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Re: SADDLE HEIGHT..please try the "bump test"

Postby sreten » 16 Dec 2014, 12:21am

Brucey wrote:I don't disagree with you entirely, far from it. But all you can do is set up for the 'steady state' , and
this is an upthrust centred somewhere near the pedal on the downstroke, not the BB spindle.
cheers


Hi,

I'd argue steady state bimbling along the upthrust is near the spindle, and only
somebody like Wiggo going full tilt on a time trial will it be near the pedal axis.

But there is a test, similar to what I said before, but just take your rear foot
off the pedal, and balance on your front foot with the cranks level and no
force on the bars. I'd suggest this is apposite for a rider that can crank out
so much power they are barely if at all sat on the saddle most of the time.
(Sadly, that does not remotely apply to me.)

IMO the reality of limiting the static force on your hands lies between
the two extremes, and the point as you apply power you pull on the bars.

Ideally leaning on the bars and pulling on them oscillates around a neutral point.
The neutral point will vary for everyone, but nearly allways hand discomfort
is too much leaning on the bars, i.e. poor typical balance on the bike.

Its not a concern for racers, like all comfort issues, they don't matter.

rgds, sreten.

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531colin
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Re: SADDLE HEIGHT..please try the "bump test"

Postby 531colin » 16 Dec 2014, 9:48am

sreten wrote:........... but nearly allways hand discomfort is too much leaning on the bars, i.e. poor typical balance on the bike.........


As I wrote 2 pages ago, there is a simple demonstration of this that you can do riding along.....there is no need for complex tests and arcane theories;

531colin wrote:.............. Very many people who buy race bikes end up with too much weight on their hands. After a couple of hours riding their wrists and shoulders are getting sore, I can ride next to them and show that I only need one finger on the bars to support my weight, and they can do it too, if they slide back on the saddle...............


Brucey is right, the sequence of adjustments (and of subsequent re-adjustments and checks) is this...
1) saddle height
2) saddle setback, ie KOPS....not because I believe KOPS has magical powers, but its a proxy for "balance" on the bike, ie weight distribution between bum, feet, and hands.
3) reach

Saddle position back and front can be checked by the "one finger weight on the bars test" : Saddle position is never sacrificed to adjust reach.

andrewjoseph
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Re: SADDLE HEIGHT..please try the "bump test"

Postby andrewjoseph » 16 Dec 2014, 10:29am

sreten wrote:...
But there is a test, similar to what I said before, but just take your rear foot
off the pedal
, and balance on your front foot with the cranks level and no
force on the bars....

rgds, sreten.


to do this you need to have the back brake on hard. you can't do this and not have force on the bars. this is not a normal cycling posture for pedalling, or even for a track stand.
--
Burls Ti Tourer for tarmac
Saracen aluminium full suss for trails.

Brucey
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Re: SADDLE HEIGHT..please try the "bump test"

Postby Brucey » 16 Dec 2014, 11:09am

sreten wrote: Its not a concern for racers, like all comfort issues, they don't matter...


oh but they do! Maybe not so much in a short race perhaps but invariably;

Discomfort = energy (mental and/or physical) expended someplace other than the pedals.

Also... you have to be able to train, too. And do the same thing the next day and the day after that. If you can't be comfortable when training, you won't train well, and if you train in a completely different position to racing, you won't race well, either.

Remember that most keen racers will do many more miles than even the most ardent tourists; the notion that these many hours could be spent in discomfort and that 'it doesn't matter' is commonly held, I grant you, but it is just nonsense. If you look at really great racers, they are at one with the bike, perfectly comfortable, with no stress in their upper body even close to VO2 max.

Re the pedal upthrust;

Image

Image

the first is LA's pedal stroke (power unknown, but assumed 'typical') and the second is taken from another 'elite level rider' when asked to produce ~400W at 90rpm. This latter plot is chosen because it represents the most amount of 'pulling up' that I have seen in published data of this type, and it is unclear if the subject could have sustained this for long even when sat fairly upright (eg when climbing).

The vast majority of riders will produce some kind of abbreviated version (probably of LA's stroke) when 'tapping along'.

Even so, you can see that there is a net upthrust which is well forward of the BB spindle in all cases.

On bikes that are set up best, the perfectly 'neutral' position is when pedalling 'normally', however that happens to be for you. Often this means that when you are just freewheeling, there is some weight on the hands. But for many types of cycling, better this than having an unnecessarily upright riding position, with the added drag this brings.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

LollyKat
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Re: SADDLE HEIGHT..please try the "bump test"

Postby LollyKat » 16 Dec 2014, 11:20am

andrewjoseph wrote:...
to do this you need to have the back brake on hard. you can't do this and not have force on the bars. this is not a normal cycling posture for pedalling, or even for a track stand.

I do this with the front wheel up against a wall (as if I had ridden into it) - no need for the brake. I lean against a table or another wall for balance.

andrewjoseph
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Re: SADDLE HEIGHT..please try the "bump test"

Postby andrewjoseph » 16 Dec 2014, 4:45pm

LollyKat wrote:
andrewjoseph wrote:...
to do this you need to have the back brake on hard. you can't do this and not have force on the bars. this is not a normal cycling posture for pedalling, or even for a track stand.

I do this with the front wheel up against a wall (as if I had ridden into it) - no need for the brake. I lean against a table or another wall for balance.


With one foot off the pedals? And no weight on the bars?

My impression is that streten is telling us this can be done riding along with the rider not sitting on saddle but putting pressure on pedals.
--
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531colin
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Re: SADDLE HEIGHT..please try the "bump test"

Postby 531colin » 16 Dec 2014, 5:10pm

LollyKat wrote:
andrewjoseph wrote:...
to do this you need to have the back brake on hard. you can't do this and not have force on the bars. this is not a normal cycling posture for pedalling, or even for a track stand.

I do this with the front wheel up against a wall (as if I had ridden into it) - no need for the brake. I lean against a table or another wall for balance.


For setting up Tri bars, or something like that? Not for setting up a tourer?

LollyKat
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Re: SADDLE HEIGHT..please try the "bump test"

Postby LollyKat » 16 Dec 2014, 5:26pm

Wot's Tribars? :roll: :)

All I meant was that I don't need the back brake on when doing the initial set-up. One shoulder or hip leans slightly against a wall or table for balance. With the pedals level I can put as much pressure as I like on the front one because the bike can't go through the wall in front. I find it a good way of getting very close to my desired position, which I then fine tune on the road if necessary.

Yes, touring bikes. Done it this way for years.

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531colin
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Re: SADDLE HEIGHT..please try the "bump test"

Postby 531colin » 16 Dec 2014, 6:00pm

For setting up a touring bike, you can also put as little pressure as you like on the front pedal.

LollyKat
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Re: SADDLE HEIGHT..please try the "bump test"

Postby LollyKat » 16 Dec 2014, 10:12pm

:lol:

samsbike
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Re: SADDLE HEIGHT..please try the "bump test"

Postby samsbike » 5 Apr 2015, 8:57pm

I have just been watching the cycle racing on youtube and it does not appear as though there is that much extension of the knee as I assumed.

The almost seem to have quite a bend at the low point, more than I would expected given my earlier link to the tri fitting/ Colin's pic.

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NATURAL ANKLING
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Re: SADDLE HEIGHT..please try the "bump test"

Postby NATURAL ANKLING » 5 Apr 2015, 10:27pm

Hi,
Racing - Max power at very high cadence will mean that the leg will not straighten as much as your average bod on a TDF copy pushing 53 x 11 with inferior power.
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531colin
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Re: SADDLE HEIGHT..please try the "bump test"

Postby 531colin » 6 Apr 2015, 10:44am

samsbike wrote:I have just been watching the cycle racing on youtube and it does not appear as though there is that much extension of the knee as I assumed.

The almost seem to have quite a bend at the low point, more than I would expected given my earlier link to the tri fitting/ Colin's pic.


Sam....this is still the best I can do.......
531colin wrote:I suppose I shouldn't be surprised that this has all got a bit complicated.
The best thing to come out of it so far, for me, is Brucey reminding me that I used to slide back on the saddle for a bit more power. I don't seem to do that any more, either I'm really old, or my saddle is higher than it was, or I "push and pull" on the cleats instead. I will have to go for a ride.......

This is how it looks to me at the moment.
Set the saddle so with your knee locked your heel is "down a bit" at the bottom, and mark the seatpost.
If you are "forcing a gear" and you get more power by sliding back a bit, its probably about right.
If you are off the back of the saddle and still pedalling, its too low.
If sliding back robs you of power, making you point your toes or dip your hips, you are too high.

A couple of notes....
When "forcing a gear" (low cadence/high force) you are looking for maximum power, which comes when the knee is nearest straight.
At a normal/high cadence, your body is looking for a smooth pedalling action through the bottom of the stroke....even if the saddle is much too high you will point your toes and dip your hips to keep that all-important bend in the knee at the bottom.