Bike Forums > Inseam vs. saddle height.
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 Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

09-23-05, 06:17 PM   #2
chipcom
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 Originally Posted by Patriot This is one that kind of rubs me the wrong way. i have tried a few online calculators, and they are very close to giving me the geometry that seems most comfortable for me. However, one measurement still makes me scratch my head. And that is the BB center to top of saddle measurement. Now, I have a 35.5-36" inseam, and every calculator I have tried tell sme the best range for the BB-center to top of saddle is around 33-34". Now, I have both my bikes set up at 32-32.25" saddle height, and for some reason, I feel like I am getting enough extension, even though it almost 1" lower than every calculator suggests. As one would want, with my pedal at the bottom of the stroke, and my foot parallel to the ground, my knee has a slight bend. If I lock my knee, then my heel drops below the pedal spindle. So, what I am wondering is what you all have your saddles set at, to give me a bit of a comparison. What is your inseam, and what is your BB-center to top of saddle measurement in comparison?
Dude, when it comes to saddle height, calculators can only give you a starting point, the fine tuning is up to you and what works best for you.
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 09-23-05, 06:21 PM #3 skinnyone Dude wheres my guads?     Join Date: May 2005 Location: Guess Bikes: Not enough Posts: 2,680 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Dunno much about your problem... Can you give a linky to some of those calculators.. I want to try a few myself... I have a 35 inch inseam... I measured parallel to the seat tube and I get 31.5"... This is after an elaborate fit and a couple of checks to make sure I am ok...
 09-23-05, 06:28 PM #4 NealH Senior Member     Join Date: May 2003 Location: Triangle, NC Bikes: S-Works Tarmac Posts: 1,470 Mentioned: 3 Post(s) Tagged: 0 Thread(s) Quoted: 155 Post(s) I have a 91cm inseam (bare feet on floor) and, ride an 81cm saddle height (Sidi shoes, SPD-SL cleats). I've tried 1/2cm above and below but, the 81 works and feels the best in regards to extension. As "chipcom" mentioned, those on-line calculators only give you a starting point so don't take them to the bank.
 09-23-05, 06:43 PM #6 Patriot Faith-Vigilance-Service Thread Starter     Join Date: Jul 2004 Location: Port Orchard, WA Bikes: Trinity, Paradisus, Centurion, Mongoose, Trek Posts: 8,330 Mentioned: 1 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) I guess what I am saying is, I know the calculator is just a starting point. I have known that for a long time. What raises my curiousity, is what the differential is for the riders on this forum. Comparing it to your riding style, and why you think it works best for you. __________________ President, OCP --"Will you have some tea... at the theatre with me?"--
 09-23-05, 06:44 PM #7 Enthalpic Killing Rabbits   Join Date: Apr 2005 Bikes: Posts: 5,246 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 70 Post(s) Consider this: Having your seat set too high will cause more damage to your knees than having it set too low.
 09-23-05, 07:00 PM #8 patrick07 Senior Member     Join Date: Apr 2005 Location: South Michigan Bikes: 2005 Specialized Langster, 2005 Giant TCR C3, 2006 Bianchi Castro Valley, 2007 Redline Monocog 29er, 2007 Trek 5000 Posts: 517 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 30" pants inseam. 715 mm from saddle to center bottom bracket using SPD-SL pedals and cleats.
 09-23-05, 07:02 PM #9 fixedfiend Senior Citizen Discount     Join Date: Sep 2004 Bikes: Posts: 998 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) sounds right to me. my inseam and seat height are exactly 2" shorter than yours. using 175 cranks.
09-24-05, 01:37 AM   #10
53-11_alltheway
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 Originally Posted by Patriot This is one that kind of rubs me the wrong way. i have tried a few online calculators, and they are very close to giving me the geometry that seems most comfortable for me. However, one measurement still makes me scratch my head. And that is the BB center to top of saddle measurement.

This is where the online calculators are worthless. Besides the crank length modifies the ideal saddle height/position anyway.

What is probably more important is distance from BB center because that takes into account not only height (verical distance), but set-back (horizontal distance from BB)

09-24-05, 04:48 AM   #11
biker7
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 Originally Posted by 53-11_alltheway This is where the online calculators are worthless. Besides the crank length modifies the ideal saddle height/position anyway. What is probably more important is distance from BB center because that takes into account not only height (verical distance), but set-back (horizontal distance from BB)
Worthless? Disagree. Like all formulas, they put you in the game and they should be used directionally based upon where they came from. Lemond was an elite cyclist so of course his formula will not be directly applicable to lesser cyclists. Would say that for most good recreational if not amateur racers…those I know and respond on this board for example, the Lemond .883 x Cycling Inseam puts the seat up too high. I have known some racers where the formula works for them as well. Even among elite racers this formula is not the holly grail on either side. As to only measuring the vertical difference…not right either...not how the formula was meant to be used which is from BB to the highest point of the seat because what matters is the linear distance from your sit bone contact to the BB. This distance doesn't know or care how much set-back you are running or STA as they are irrelevant, i.e. a bike with small set-back and small STA = a bike with a big set-back and bigger STA...the net result being the rider ends up the same postion relative to the BB.
When you measure, the tape will end up unparallel to the seat tube if running more than 0 set-back which is true in my case for example because I run a fair amount of saddle set-back.

Quote:
Believe this is well said and certainly mimics my experience as well. Patriot we are close to the same size…in height and weight. I have a 35.25” cycling inseam and my seat height per the Lemond method should be 31.125 and I run my seat up around 30.6-30.7” or so or almost ½” below the Lemond method. This is pretty common. I have resisted what I feel is correct and run it higher but I am not as strong or comfortable on the bike and don’t feel both sides of my knees are loaded how I like so I run shorter than the .883” measurement. As to crank size mattering for this convention…it doesn’t affect it much and if you want you can plug in the 2.5-5 mm delta or use the equation of 1.09 X cycling inseam which is the complement of .883 X inseam which results in the same saddle height.

Its been written before in other related threads but because of the variablility of sit bone position on each person's anatomy, seat deflection under load etc, the best teacher aside from just riding the bike and experimenting I believe is amount of knee angle at the bottom of the stroke. Here too accounts for much variablility in what is considered normal or desirable. The generally accepted range is a rather large 10 degrees or 25-35 degrees with nominal target being 30 degrees. Believe many racers run less angle at the bottom to maximize extension or downstroke power but some run a full angle with a bit more emphasis on their quad strength. A simple protractor with a friend on a trainer will tell you how you measure.
George

Last edited by biker7; 09-24-05 at 05:19 AM.

09-24-05, 06:56 AM   #13
EURO
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 What raises my curiousity, is what the differential is for the riders on this forum.
The differential will be determined by the way the rider uses the foot, and sadly most people are unaware of how they use this - hence I think the data would be a bit useless.

FYI my inseam is 91.7 cm and my BB centre to seat top is 80.5 cm

My legs are at a perfect 30 degree angle when the pedal is at the bottom of the stroke, and my knee is over the pedal spindle when the pedal is at 90 degrees.

The irony of this is that I set up my seat by feel rather than a formula.

09-24-05, 08:15 AM   #16
53-11_alltheway
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 Originally Posted by biker7 Worthless?
Yeah it's straight up worthless. You know why? If crank length is not taken into account then it precisely gives you the wrong answer.

EDIT: Like I say in the post a couple down, not only does crank length modify maximum height so does fore/aft.

Last edited by 53-11_alltheway; 09-24-05 at 08:23 AM.

09-24-05, 08:17 AM   #17
53-11_alltheway
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 Originally Posted by Retro Grouch Couple of things. 1. So what's your crank length? If your base measurement is from the center of the bottom bracket spindle, differences in crank length are being ignored.

Exactly, the crank length determines the location of the pedals which is more relevant than the BB center.

BB center measurements are fine if all cranks came as 170mm (for example) and there is no devaition.

 09-24-05, 08:21 AM #18 53-11_alltheway "Great One"     Join Date: Feb 2005 Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though) Bikes: Posts: 4,463 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Is this a saddle height formula that doesn't even take into account fore/aft? The maximum saddle height you can tolerate is also dependent on the seat set-back? Why? Because increasing seat set-back increases distance to the pedals and thus limits maximum saddle height.
 09-24-05, 08:39 AM #19 Patriot Faith-Vigilance-Service Thread Starter     Join Date: Jul 2004 Location: Port Orchard, WA Bikes: Trinity, Paradisus, Centurion, Mongoose, Trek Posts: 8,330 Mentioned: 1 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) The saddle height formulas are basically a measuement from the center of the BB, straight up the seat tube to the top of the saddle directly above, regardless of how much setback is used. That is adjusted according to personal preferance taking into account your femur length. I know this may seem strange, but I tend to think that crank length is not quite as large a factor as you are eluding to. Mainly because the crank length usually only differs by a 0-5mm (<0.25") from 170 to 175. This, when the saddle height recommendations are given in 1/2" incraments. But like we have all said, it is just a good starting point. Where you go from there is up to you. __________________ President, OCP --"Will you have some tea... at the theatre with me?"--
09-24-05, 08:45 AM   #20
53-11_alltheway
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 Originally Posted by Patriot The saddle height formulas are basically a measuement from the center of the BB, straight up the seat tube to the top of the saddle directly above, regardless of how much setback is used.
Well, this is exactly what I'm talking about. Why be precise with a formula that leaves out 2 critical variables.

Those variables are far more important than you think. I know this because I have messed around with 170-180mm cranks. I can also tell you that a few cms difference in set-back has a bigger impact on saddle height than you think (distance in the X plane is not independent to distance in the y plane)

The biomechanics are what you need to be thinking about because that is really what matters. Try visualizing this stuff in your mind because that helps a lot when dialing this in. That and using your own feedback you notice when turning the pedals in a circle.

Retrogrouch was right when he also recommended someone get behind you to watch your hips (that can help detect too much ankling or downward pull by the pedals)

Just my two cents (as usual)

Last edited by 53-11_alltheway; 09-24-05 at 08:54 AM.

09-24-05, 09:06 AM   #22
53-11_alltheway
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 Originally Posted by Patriot This is why my thought are moving in the direction of needing to lower my saddle, because I sit back so far on the saddle, so my saddle height is effectively increased when doing so.
This makes sense.

Your legs are only so long, so if you had long femurs and short tibia for example you could make an argument that ***relative to your riding position*** more distance would have to be in the form of set-back vs saddle height. (ie, distance in horizontal plane vs vertical plane)

Of course we all know that you can rotate about the BB too which modifies things, but the relationship as a series of levers and pivots still remains essentially the same biomechanically.

Last edited by 53-11_alltheway; 09-24-05 at 09:12 AM.

 09-24-05, 09:57 AM #23 55/Rad Form*r Ho*rd*r     Join Date: Jan 2004 Location: Portland, OR Bikes: Seven Axiom, Dave Moulton Fuso Posts: 11,712 Mentioned: 1 Post(s) Tagged: 0 Thread(s) Quoted: 9 Post(s) I do it by feel and my "feel" can change from ride to ride, depending on how I feel. this is why I have QR's on my seatpost clamp. I will often alter saddle height (by as much a foot or 2) on any given ride. OK, maybe a MM or 2. 55/Rad __________________
09-24-05, 09:57 AM   #24
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 Originally Posted by 53-11_alltheway Yeah it's straight up worthless. You know why? If crank length is not taken into account then it precisely gives you the wrong answer. EDIT: Like I say in the post a couple down, not only does crank length modify maximum height so does fore/aft.
I am pretty astounded by what you wrote 53-11. I frankly expected you to be a bit more on board...well...maybe not especially the part about how set-back is not taken into account with Lemond's formula. 53...it is an acute right triangle. Set-back from the BB is the horizontal leg, vertical height from BB to top of saddle is the vertical leg and Greg Lemond's formula i.e. .883 X inseam is the hypotenuse which takes into account set back....it is a function of set-back. Will say it again...the Lemond formula is a function of set back for distance from top of saddle where you measure to the BB. Of course where Patriot sits on his seat affects distance to the BB...it is part of the Lemond formula. If Patriot sits on the far rear of the seat, you measure to where his sit bones contact…which includes how much set-back he is using. As to crank length affecting the formula...not much. If you don't like Lemond's formula, then use Harnley's formua of 1.09 X inseam which takes into account crank length. You end up with virtually the same result give or take a few millimeters...that is...a seat height higher than most cyclists ride except elite racers....1.05 is a more typical norm.

You heard it here first. 53-11 thinks that the TDF champion Greg Lemond’s formula is bunk.
George

Last edited by biker7; 09-24-05 at 10:04 AM.

09-24-05, 10:10 AM   #25
53-11_alltheway
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 Originally Posted by biker7 53-11 thinks that the TDF champion Greg Lemond’s formula is bunk.
It is bunk because it is too simplistic. Crank length/pedal stack height/ shoe sole thickness isn't accounted for. WTH?!?!? (Hint the saddle height difference between a 170mm and 180mm is huge in relative terms for any given leg length)

Besides Patriot claims the formula he is using doesn't even take into consideration seat set-back. (adjustment on the seat rails is independent of the formula WTH?!? again! )

Last edited by 53-11_alltheway; 09-24-05 at 10:32 AM.