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How do you measure your sit bones??

post #1 of 18
Thread Starter 
How exactly do you measure your own sit bones??
post #2 of 18

Re: How do you measure your sit bones??

There are two boney protrusions in you backside, one to the left and one to the right. They are called your Ischial Tuberosities, but most people call them your "sit bones". They support nearly all of your weight when you are sitting. They are located to the left and right of your anus. They are usually farther apart on a female than on a male to accomodate the birth canal. You should be able to feel them if you sit on a hard surface and rock slightly to the right and the left. You will feel the increased pressure on them as you rock in that direction.

The easiest way to measure them is with a tailor's tape measure. Bend over and place the tape on one of the areas where you felt the pressure and pull the tape taunt to the other area that you felt the pressure. Place your finger over the spot on the tape to mark it where it passes over the area where you felt the increased pressure. Then just read the tape where you have it marked with your finger.

If you have a chunk of memory foam like what some of the newer bed matresses are made of, sit on it and before it springs back, measure between the two deepest indentations. Or if you have some thick corrugated cardboard, you can substitute it for the memory foam, but it does not work as well.

As a last resort, visit your LBS and get a fitting. This is usually included in a full fitting for a bike.
post #3 of 18
Thread Starter 

Re: How do you measure your sit bones??

Thanks.
post #4 of 18

Re: How do you measure your sit bones??

Put a piece of printer paper on a carpeted stair, sit on it. Your sit bones will make a clear impression on it. Mark them with a pencil and then you have a pattern you can put on top of a saddle.

This method seems more dignified than trying to measure your **** with a tape measure :-)
post #5 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by longfemur View Post
Put a piece of printer paper on a carpeted stair, sit on it. Your sit bones will make a clear impression on it. Mark them with a pencil and then you have a pattern you can put on top of a saddle.

This method seems more dignified than trying to measure your **** with a tape measure :-)
Dignity is over rated.
post #6 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by longfemur View Post
Put a piece of printer paper on a carpeted stair, sit on it. Your sit bones will make a clear impression on it. Mark them with a pencil and then you have a pattern you can put on top of a saddle.

This method seems more dignified than trying to measure your **** with a tape measure :-)
But a tape measure is infinitely more dignified--and less messy--than using a T-square.
post #7 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by alienator View Post
but a tape measure is infinitely more dignified--and less messy--than using a t-square.
ouch!
post #8 of 18

Re: How do you measure your sit bones??

Best way I've found is to tear off a piece of aluminum foil, and put that on top of a carpeted stair before sitting down. Raise your feet off the ground until you feel like your sit bones have really dug in. When you get up, you have a perfect mold of your butt. Flip your "mold" upside down and lay a ruler across the two "peaks" to get a perfect measurement.
post #9 of 18

Re: How do you measure your sit bones??

Go to a Specialized dealer and look for their Body Geometry saddle measuring device. Consists of a piece of cardboard with a flat piece of "memory foam" like material on it and a ruler along one edge. Follow instructions on card.
post #10 of 18

Re: How do you measure your sit bones??

Good ideas above, but how about this?

Put maybe a pound of flour in an oversized baggie (sealed), or something like the bottom of a garbage bag, and lay that out kind of flat on your closed toiled seat. Sit on that, maybe rock around a little and also raise your feet, then get up and measure between the indentations.

I guess you could put a layer of pristine aluminum foil on it before you sit down....
post #11 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by frenchyge View Post
Go to a Specialized dealer and look for their Body Geometry saddle measuring device. Consists of a piece of cardboard with a flat piece of "memory foam" like material on it and a ruler along one edge. Follow instructions on card.
I did this recently. Easy, quick & accurate. Plus the notes on the cardboard give general indication as to how wide a saddle you need, given your (very) personal measurements.
post #12 of 18

Re: How do you measure your sit bones??

Any comments on the typical relationship between the measured distance between the sit-bone "peaks" (or depressions), and how this translates to the saddle-width dimension?

Presumably the sit-bone separation distance needs to be somewhat less than the saddle width. But by how much?

Specialized road saddles come in 130mm, 143mm, and for some models, 155mm. I've also been looking at some Selle Italia models - most of which are 130mm wide (or a bit more) - but SI also has a couple models with 144 and wider widths.
post #13 of 18

Re: How do you measure your sit bones??

Besides stinky pancakes guy's idea, my favorite is to simply sit on my upturned palm. Then you have a gauge which you are sure to bring with you when you go shopping for a bike seat.
post #14 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by rschleicher View Post
Any comments on the typical relationship between the measured distance between the sit-bone "peaks" (or depressions), and how this translates to the saddle-width dimension?

Presumably the sit-bone separation distance needs to be somewhat less than the saddle width. But by how much?

Specialized road saddles come in 130mm, 143mm, and for some models, 155mm. I've also been looking at some Selle Italia models - most of which are 130mm wide (or a bit more) - but SI also has a couple models with 144 and wider widths.
I measured my sit-bones with the aluminum foil method, and the separation is basically 110mm. Based on this, and on my prior experience with 130mm saddles, I'm convinced I need at least a 143mm saddle width. But I'm not sure if this warrants going even wider, or not. (I also have another older saddle at home that is somewhere around 150mm wide, which seems plenty wide.)
post #15 of 18

Re: How do you measure your sit bones??

Quote:
Originally Posted by rschleicher View Post
Any comments on the typical relationship between the measured distance between the sit-bone "peaks" (or depressions), and how this translates to the saddle-width dimension?

Presumably the sit-bone separation distance needs to be somewhat less than the saddle width. But by how much?
Specialized's guidelines (due to embedded space between Bike & Patents, you may have to cut & paste link):
i32.photobucket.com/albums/d7/k4drd/Bicycles/Bike Patents/7284336SpecializedSaddleFitMethod.jpg

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