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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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Dr C.,would I be right in thinking that you have calculated your efficiency at various trochanteric heights?
If so,what's the variation over the percentages?

If greater height is accomodated by change in ankle angle, mainly, and not the knee or hip,does it matter?

Would it be better to measure trochanteric height whilst wearing cycling shoes?
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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This is what a saddle set at 96% of greater trochanteric height looks like when one is not pedaling - note that the bottom of the sole of my shoe is almost, but not quite, parallel to the ground. If I raised my saddle to the maximum of the optimal range (i.e., 100% of greater trochanteric height), my foot would be angled down more, but still not nearly to the same degree as seen in most pics posted here.
What's your inseam (using the back-to-the-wall and bookspine-to-the-scrotum method), and what's your distance from BB axle to top of the saddle, measured along the seat tube/seat post?
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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Andrew, thanks for the thread.

I had actually raised my seat 20mm the other day and took my normal 30 mile ride. It was strange but my back sure hurt. So, this thread was perfect timing.
Got the info from Ves on my bike and where he said I should be fitted with 180 cranks. I then did a rough angle and saw with the new bike seat I was way high compared to
both comments. So, lowered my seat back to where I had it, the angle now seems to be around 150, and will do give my ride a try again this afternoon.

Dave

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Last edited by: h2ofun: Jan 20, 07 12:25
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Re: a saddle that isn't too high [h2ofun] [ In reply to ]
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[reply]I had actually raised my seat 20cm the other day and took my normal 30 mile ride. It was strange but my back sure hurt. [/reply]

The pain was probably the saddle hitting your liver.



Lewis
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Re: a saddle that isn't too high [h2ofun] [ In reply to ]
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I'll assume you meant 20 mm.
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Re: a saddle that isn't too high [Uncle Phil] [ In reply to ]
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Just got back from my ride with my seat lower. Back did not hurt at all. Amazing how just a little change can impact things.

Dave

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
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Re: a saddle that isn't too high [rmur] [ In reply to ]
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half-serious :) I didn't realize the Velodyne 'interfaced' with the rear tire .... that being so it must suffer a little from the small drift I see with the CT (versus PT) in ergo mode. I originally thought it was 100% due to the electric generator heating up but can also see the decrease in rolling resistance as the tire heats up being an issue. I thought the Velodyne eliminated that interface.

The Velodyne has a warm-up mode that applies full current to the brake for as long as you leave it on. That reduces the drift in power to ~5 W in the first hour, and essentially none thereafter. If you calibrate it "stone cold", though, the drift can be ten times as great.

Based on repeated coast-down calibrations, the tire-roller interface seems to heat up quite quickly, i.e., w/in a couple of minutes max.
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Re: a saddle that isn't too high [docfuel] [ In reply to ]
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So, should I assume that, in a steep TT/Tri, position, and the whole set up is rotated 8-12 degrees, the feet would also be pointed down by a similar amount?

First, I don't know where you get 8-12 deg. Compared to almost anyone else, I ride w/ more setback in my road position vs. my aero position (i.e., 8 cm vs. 0 cm at a saddle-to-b.b. distance of 72.5 cm), and even for me it's only a 6 deg difference.

In any case, Price and Donne measured minimal and maximal ankle angle as a function of seat tube angle (over the range of 68 to 80 deg) and found very little difference.
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Re: a saddle that isn't too high [Superman] [ In reply to ]
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I can locate the greater trochanter. Are we measuring the distance from the ground to the trochanter while standing? Bottom of the foot while supine?

Thanks.
Again, the values I mentioned (i.e., 96-100% of greater trochanteric height) are based on how Price and Donne defined the measurement, which is from the greater trochanter to the ground when standing erect in cycling shoes.
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Re: a saddle that isn't too high [sciguy] [ In reply to ]
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1. Are we measuring in bare feet?

No, in cycling shoes.

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2. To the bottom, middle or top of greater trochanter?

They don't say.
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Re: a saddle that isn't too high [kevinkeegan] [ In reply to ]
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Dr C.,would I be right in thinking that you have calculated your efficiency at various trochanteric heights?

No, I just rely on the published literature.

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If so,what's the variation over the percentages?

Raising your saddle from 96% to 104% reduces efficiency by about 1% in absolute terms, i.e., for a given VO2 (and RER) your power would be ~5% lower.

Note that having a saddle that is too high is worse than having one that is too low, i.e., the relationship is not symmetrical around the minima.

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If greater height is accomodated by change in ankle angle, mainly, and not the knee or hip,does it matter?

See above.

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Would it be better to measure trochanteric height whilst wearing cycling shoes?

That is how Price and Donne did it.
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Re: a saddle that isn't too high [Greg66] [ In reply to ]
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What's your inseam (using the back-to-the-wall and bookspine-to-the-scrotum method)[/quote]
I don't know.

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and what's your distance from BB axle to top of the saddle, measured along the seat tube/seat post?

72.5 cm
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Re: a saddle that isn't too high [AlanShearer] [ In reply to ]
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Looks like you need to hit the weights.
Nah - I'm already married.
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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You have nice legs and I don't see any fat on you. Is chocolate part of your diet? :-)

_________________
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
half-serious :) I didn't realize the Velodyne 'interfaced' with the rear tire .... that being so it must suffer a little from the small drift I see with the CT (versus PT) in ergo mode. I originally thought it was 100% due to the electric generator heating up but can also see the decrease in rolling resistance as the tire heats up being an issue. I thought the Velodyne eliminated that interface.

The Velodyne has a warm-up mode that applies full current to the brake for as long as you leave it on. That reduces the drift in power to ~5 W in the first hour, and essentially none thereafter. If you calibrate it "stone cold", though, the drift can be ten times as great.

Based on repeated coast-down calibrations, the tire-roller interface seems to heat up quite quickly, i.e., w/in a couple of minutes max.
okay 5W/hr isn't worth sweating over. I'm getting about the same on my CT (with a small cooling fan) now with intervals of 30-50min at FTP. Don't see any drift worth reporting when I'm doing ~2-hr tempo work 320-330W.

I suspect w/o the fan that the drift would be double or triple at L4 power.
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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"In any case, Price and Donne measured minimal and maximal ankle angle as a function of seat tube angle (over the range of 68 to 80 deg) and found very little difference. "

That was my question. Would the steeper TT/Tri position effect the foot position relative to the ground, as opposed the the body? So, by ankle angle you mean foot/shoe to tibia? And that is what stays the same?
_______________________________________

[I just threw a guess of 8-12 deg, when the position on the saddle is considered. It was a total spur of the moment guess. (I guess it varies from 0-15deg difference.)]

_________________
Dick

Take everything I say with a grain of salt. I know nothing.
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Re: a saddle that isn't too high [docfuel] [ In reply to ]
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In Reply To:
"In any case, Price and Donne measured minimal and maximal ankle angle as a function of seat tube angle (over the range of 68 to 80 deg) and found very little difference. "

That was my question. Would the steeper TT/Tri position effect the foot position relative to the ground, as opposed the the body? So, by ankle angle you mean foot/shoe to tibia? And that is what stays the same?

To determine the angle of the ankle with respect to horizontal, Price and Donne placed reflective markers on the lateral malleolus and the lateral aspect of the fifth metatarsal-phalangeal joint. With the saddle set at 100% of trochanteric height, changing the seat tube angle from 74 deg to 80 deg only increased the ankle angle by 4.5 deg.
Last edited by: Andrew Coggan: Jan 22, 07 13:38
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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"with respect to the horizontal..."

Very interesting. I would not have guessed....(especially at 100% of trochanteric height.)

Another question. Are you using 96% on TT bikes, as well as road?

_________________
Dick

Take everything I say with a grain of salt. I know nothing.
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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so if a rider shows up without a bike and asks you to calculate his seat height based on 96% of his greater trochanteric height, what would you measure (step-by-step) on this bare-footed individual?

how would you then generate the seat height no. based on the measurements?

and what instruction would you give to him for him to set up his seat height on his bike to the correct height with the numbers you have given him? (this is assuming you cannot watch him pedal on his bike)

thanks.





Where would you want to swim ?
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Re: a saddle that isn't too high [docfuel] [ In reply to ]
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Are you using 96% on TT bikes, as well as road?
I do on mine (although I do measure to a slightly different point on the saddle to account for the fact that I sit further forward on it).
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Re: a saddle that isn't too high [GregX] [ In reply to ]
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so if a rider shows up without a bike and asks you to calculate his seat height based on 96% of his greater trochanteric height

I'd tell 'em to get lost, as I don't offer my services as a bike fitter. ;-)

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, what would you measure (step-by-step) on this bare-footed individual?

how would you then generate the seat height no. based on the measurements?

and what instruction would you give to him for him to set up his seat height on his bike to the correct height with the numbers you have given him? (this is assuming you cannot watch him pedal on his bike)

Step 1: put on your cycling shoes.

Step 2: measure from the ground up to your greater trochanter.

Step 3: take the desired percentage of this number.

Step 4: subtract the length of the crank arm.

Step 5: set your saddle height as measured from the center of the b.b. to the lowest point on the saddle to this value.

Step 6: adjust as desired/necessary.

(If step 6 sounds too 'unscientific', consider this: for me, optimal saddle height based on, e.g., the approach of Price and Donne actually represents a range nearly 4 cm wide.)
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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mountain bike or road shoes or does it matter?
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Re: a saddle that isn't too high [Andrew Coggan] [ In reply to ]
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"greater trochanter to the ground when standing erect in cycling shoes. "

In realistic terms I'd think this method is easily open to inaccuracy due to the difficulty of palpating an accurate greater trochanter head on many people. The only way to be 100% accurate would be to take full limb lenght x-rays, which is quite impractical.
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Re: a saddle that isn't too high [rmur] [ In reply to ]
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okay 5W/hr isn't worth sweating over. I'm getting about the same on my CT <snip>

ric - have you tried the taxc or conti trainer tires?

On my CT, the tire/roller interface hits stabiliy in ~5minutes (as evidenced by a calbration number that is +/-0.01)


as an added bonus, these tires seem to last a long time - as I mentioned in my blog - I have 40+ hours on a set and I could concievably return them as new. Not so with old road tires....

The only real drawback that I see is my old "am I fit yet" gauge is gone now... I used to know the winter training was going when I had a flat on the trainer...

g


greg
www.wattagetraining.com
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Re: a saddle that isn't too high [cerveloguy] [ In reply to ]
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"greater trochanter to the ground when standing erect in cycling shoes. "

In realistic terms I'd think this method is easily open to inaccuracy due to the difficulty of palpating an accurate greater trochanter head on many people.

Yeah, but I think the greater trochanter is easier to palpate and measure to than the other bony protuberances that have been used (i.e., the symphysis pubis and the ishcial tuberiosity). Besides, I don't think that tremendous accuracy is all that important, i.e., as I see it the point of performing such measurements is just to assure that your saddle height falls w/in a reasonable range (which many here do not). After that, it should be "set it and forget it*".

*Recognizing, of course, that you should keep a record of the measurement, and mark your saddle height on your bike using, e.g., a piece of tape.
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