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Another rule of thumb

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Another rule of thumb

Old 08-11-13, 07:24 PM
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Another rule of thumb

Hi,

Well the last one went down so well .....
(Centre of crank to seat height is near clothing inside leg).

Get the pedals level and hover over your bike. Move your body
so there is no pressure on your hands. Your butt will be where
your saddle should be be for your handlebar position.

Turns out on my folder, (the seat is all the way back and right
height), that my hands are around the end of the bar ends
to achieve this, I'd already ascertained its the fastest position.

rgds, sreten.

Given the above my road bike fits very well. My folder could
do with further forward bars but not easy to do at all.

Last edited by sreten; 08-11-13 at 07:35 PM.
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Old 08-12-13, 06:52 AM
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Umm... is this like for a MTB(AM, XC, trail, DH?)
Or a road bike (crit, long distance stage, tour, recreational?)
Or a TT or a tri
Hybrid?

Also doesn't this method give wildly differeng results depending where your handlebar is located
(Like on a crit bike one might prefer a more forward saddle position and longer reach. With you method he would have to push the seat back to compensate the reach and that would overly lengthen the cockpit and we all know where this is going)

Also using only one contact point to fit one of the three seems a bit funky to me...
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Old 08-12-13, 07:31 AM
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It's a not unusual rule of thumb, usually with the reasoning that your natural balance crouched above the seat is the best position for keeping weight off of your hands. It may work for other reasons, but I can't agree with the weight reasoning. The saddle, bearing part of your weight, changes the balance so - to my mind - taking it out of the picture to find the right balance is illogical.
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Old 08-12-13, 07:49 AM
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Some people never learn.
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Old 08-12-13, 06:31 PM
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Originally Posted by rebel1916
Some people never learn.
Hi, very true, rgds, sreten.

Learning requires curiousity.

Last edited by sreten; 08-12-13 at 06:52 PM.
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Old 08-12-13, 06:43 PM
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Originally Posted by wphamilton
It's a not unusual rule of thumb, usually with the reasoning that your natural balance crouched above the seat is the best position for keeping weight off of your hands. It may work for other reasons, but I can't agree with the weight reasoning. The saddle, bearing part of your weight, changes the balance so - to my mind - taking it out of the picture to find the right balance is illogical.
Hi,

It is not illogical. Tanking along a good racer has very little weight on the seat or the bars.
Their weight is mainly supported by the pedals they are balanced over and pushing hard
through. Of course if you don't pedal hard there is weight on your hands and butt.

Can you come up with a more logical analysis ? It seems to be right for my road bike.

rgds, sreten.
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Old 08-12-13, 07:20 PM
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Originally Posted by elcruxio
Umm... is this like for a MTB(AM, XC, trail, DH?)
Or a road bike (crit, long distance stage, tour, recreational?)
Or a TT or a tri
Hybrid?

Also doesn't this method give wildly differeng results depending where your handlebar is located
(Like on a crit bike one might prefer a more forward saddle position and longer reach. With you method he would have to push the seat back to compensate the reach and that would overly lengthen the cockpit and we all know where this is going)

Also using only one contact point to fit one of the three seems a bit funky to me...
Hi,

It uses two contact points to look at the other one. My folder it only works with
my hands around the ends of the bar ends. On the bar ends or the bars it
shows that they should be more forward or my saddle further back.

Interestingly it also indicates for my folder if it didn't have barends I should
lift the bars 2" to take some weight off my hands. I will play with that a bit.
(Have far more numb hand issues on the folder than the road bike).

rgds, sreten.
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Old 08-13-13, 06:54 AM
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Originally Posted by sreten
Hi,

It is not illogical. Tanking along a good racer has very little weight on the seat or the bars.
Their weight is mainly supported by the pedals they are balanced over and pushing hard
through. Of course if you don't pedal hard there is weight on your hands and butt.

Can you come up with a more logical analysis ? It seems to be right for my road bike.

rgds, sreten.
I think if you have very little or no weight on your saddle, it doesn't matter much where it is.

I don't know about you, but I seldom ride with my rear hovering over the seat other than for short distances. When I do sprint my position changes. When I'm not sprinting but at a brisk pace I may stay on top of the gear which pushes me backwards and changes the pressure at both hands and butt. Yet most of the time I have some weight on the saddle - and I don't dawdle around.

Any weight on the saddle changes the balance picture. The pedal stroke changes the picture. I think that crouching still over the saddle does not reflect the riding dynamics.
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Old 08-13-13, 05:08 PM
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Originally Posted by wphamilton
I think if you have very little or no weight on your saddle, it doesn't matter much where it is.

I don't know about you, but I seldom ride with my rear hovering over the seat other than for short distances. When I do sprint my position changes. When I'm not sprinting but at a brisk pace I may stay on top of the gear which pushes me backwards and changes the pressure at both hands and butt. Yet most of the time I have some weight on the saddle - and I don't dawdle around.

Any weight on the saddle changes the balance picture. The pedal stroke changes the picture. I think that crouching still over the saddle does not reflect the riding dynamics.
Hi,

That is like saying only the saddle matters and your hands take no weight, which is not true.

My conjecture is with the pedals level, if you lift off the seat a little on your legs and there
is very little force on your hands this indicates your CofG is basically over the crank spindle.

Of course for climbing and sprinting you pull on the bars, in or out of the saddle.

YMMV, but for my folder, which I ride mostly in the saddle, it indicated lifting the bars
would be better, I tried it today, and it definitely is in terms of hand comfort. It may
be a gross simplification, or a good rule of thumb, I'm not claiming to be an expert.

However I will mention coasting downhill I have the pedals level and lift off the seat a
little for bumps. The amount of adjustment you make when you reseat is what I'm
on about. If it's a little, nothing to worry about. If its a lot and your not riding a
bike intended for extreme riding positions IMO you have some cause for concern.

I agree that crouching over the saddle is not typical. But if you do it indicates
how your typical riding postions CofG relates to the crank spindle. It's a very
logical preposition your CofG should be over the crank spindle, why not ?

rgds, sreten.

I changed the bar height on my one size fits all folder from minimum, level
with the saddle (set as far back as it will go and the right height for leg
extension) using this method, lifting them by about 2".

No doubt the real problem is the bars to saddle is too short, but the bars
have no stem for adjustment, and surprisingly for me the higher bars
were a lot more comfortable, with all the aero of a flying vertical brick.

Last edited by sreten; 08-13-13 at 07:37 PM.
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Old 08-14-13, 09:43 AM
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A conjecture and a rule are two different things. That is my objection to these threads of yours.
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Old 08-14-13, 02:14 PM
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Originally Posted by rebel1916
A conjecture and a rule are two different things. That is my objection to these threads of yours.
Agree w/ rebel,

Bike fitting is not a Secret Society dark art or sudden flash of individual insight. This path has been well trodden by serious folk who have quantified that process into several Fitting Systems that are well proven over decades of application. You do not have to re-invent the wheel as it were, that would pretty much be a waste of time, effort and $ with a yield of dubious results at best.

Several fitting systems are available on-line and in print form in English. Understanding a system, applying it's methodology and adapting the rider and bike will yield a predictable base line fit. Riding miles/hours to adapt are necessary. Or just make it up as you go along.

As Sponge Bob Square Pants once said:
"Well, good luck with that".

-Bandera
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Old 08-14-13, 03:38 PM
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Originally Posted by rebel1916
A conjecture and a rule are two different things. That is my objection to these threads of yours.
Hi, A mindnumbingly banal comment, like I don't know the difference, rgds, sreten.

Last edited by sreten; 08-14-13 at 03:43 PM.
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Old 08-14-13, 03:54 PM
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Originally Posted by Bandera
Agree w/ rebel,

Bike fitting is not a Secret Society dark art or sudden flash of individual insight. This path has been well trodden by serious folk who have quantified that process into several Fitting Systems that are well proven over decades of application. You do not have to re-invent the wheel as it were, that would pretty much be a waste of time, effort and $ with a yield of dubious results at best.

Several fitting systems are available on-line and in print form in English. Understanding a system, applying it's methodology and adapting the rider and bike will yield a predictable base line fit. Riding miles/hours to adapt are necessary. Or just make it up as you go along.

As Sponge Bob Square Pants once said:
"Well, good luck with that".

-Bandera
Hi,

So your basic comment is what I'm saying is meaningless
because your not even going to try to understand it.

"Well, good luck with that".

Exactly.

rgds, sreten.
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Old 08-14-13, 04:04 PM
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Originally Posted by sreten
Hi, A mindnumbingly banal comment, like I don't know the difference, rgds, sreten.
Originally Posted by sreten


My conjecture is...
And, of course, the title of this thread is "Another Rule of Thumb".

So you can see my confusion
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Old 08-14-13, 04:43 PM
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Originally Posted by sreten
So your basic comment is what I'm saying is meaningless
because your not even going to try to understand it.
No, my "basic comment" is that if you are interested in properly fitting a rider to a bicycle use a Fitting System.

I do agree that what you are saying is indeed meaningless.

-Bandera
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Old 08-15-13, 06:32 AM
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Originally Posted by sreten
Hi,

It is not illogical. Tanking along a good racer has very little weight on the seat or the bars.
Their weight is mainly supported by the pedals they are balanced over and pushing hard
through. Of course if you don't pedal hard there is weight on your hands and butt.

Can you come up with a more logical analysis ? It seems to be right for my road bike.

rgds, sreten.
I agree with the idea that your center of gravity when riding should be centered over the BB, though not all people do. For me that works well. But I don't see how your suggested technique achieves that.
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Old 08-15-13, 08:58 AM
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Originally Posted by Road Fan
But I don't see how your suggested technique achieves that.
Hi,

If you lift off the seat a little and have a hand position on the bars with no / very little
forces acting on your hands you then must be balanced with your CofG over the BB.

Moving your hands forward will will tip you forwards, and back tip you backwards.
Moving your bars up will tip you back, down tip you forward.

What I'm saying is if when you balance on the pedals if your butt stays in pretty
much the same position, it indicates for your normal riding position your CofG
must be pretty much over the BB, as your body shape is near identical.

If when you balance on the pedals with your normal hand position your butt
moves forward or backwards just above the seat, it indicates for your normal
position your CofG is not above the BB.

My folder has a fixed (too short) effective toptube and stem length. Only
barheight is adjustable, and the geometry doesn't fit any fitting system.
The seat is as far back as it will go and set to the right height. The only
adjustment left is the bar height. It is now much easier on the hands.

rgds, sreten.

To add : balanced over the pedals with your butt hovering over the seat
the CogG is over the bottom bracket. The load of your body weight is
shared by the wheels in proportion to the horizontal distances to the BB.

As long as your body shape remains the same, so does the wheel loads.
Sitting on the saddle doesn't change the wheel loads, it changes the
distribution of the forces at the 3 contact points, and causes some load
on the hands for the whole body position to remain balanced out overall.

Dynamically the forces on the seat, pedals and bars are oscillating, but
the CofG and static vertical loading on the wheels remain near constant.

Last edited by sreten; 08-15-13 at 11:34 AM.
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Old 08-15-13, 08:59 AM
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Originally Posted by Bandera

I do agree that what you are saying is indeed meaningless.

-Bandera
Hi,

Your not interested in what I'm saying,
your comments are negatively meaningless.

rgds, sreten.

Last edited by sreten; 08-15-13 at 05:33 PM.
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