measuring sit bones

[lattae]

Can you ladies tell me how you measure your sit bones, and once you have this info, how can you determine the correct width that a saddle should be?

[sundial]

Well.......the easiest way is to go to your local bike shop and ask them if they have a butt-o-meter. It's a cool device that you sit on and it measures your sit bones. Then you can determine what saddle is the right width for you.

A more difficult way is to take a piece of typing paper, place it on a stool or chair and see if you can make indentions with your sit bones. One TE'er had luck using Play Do to make her sit bone impressions.

Good luck and let us know what you find out. :)

[velogirl]

whatever you sit on (a little piece of foam would work), you need to elevate your feet to make your sit bones protrude. to do this, just place your feet on a chair at the same height as you are sitting. make sense?

btw, the "saddle measuring tool" is a specialized product, so you need to go to a specialized dealer to use it.

[lattae]

Thank you for the info. Once I obtain my 'sit bone size' is there a certain rule of width that the saddle should be? Should it be a inch or so wider than the sit bone measurement, or exactly the same size?
Hope you understand what I mean. Thank you ladies so much

[velogirl]

measure your sitbones in mm. there are ranges that will be most comfortable for your width and your style of riding.

here's the guideline from the "butt-o-meter" (yes, I have one because I use it for bike fits). the range on the narrow end is intended for those who ride in a more aero position (ie riding forward on the soft tissue), while the range on the wide end is intended for those who ride in a more upright position (ie sitting on their sit bones).

SIT BONE WIDTH -- SADDLE WIDTH RANGE

130-160mm -- 143mm -- 155mm and wider
100-130mm -- 143mm -- 155mm
70-100mm -- 130mm -- 143mm

I've been fitting women (and men) on Specialized saddles for over a year now. I have a saddle demo program with my bike fits. I'd say 60% of the women I fit on a 143mm saddle, 30% on a 155mm and 10% on a 130mm.

[Thorn]

But...that chart doesn't make sense to me. For the narrower measurements, they suggest saddle widths that are wider. If you're built wide, they suddenly switch over and say you can fit a saddle that is narrower than your sit bone width.

I don't mean to be contrary, but do women with wide sit bones actually ride saddles that are narrower than the bone width? By being uninformed I have done so with extremely negative consequences. So, in your experience is that valid or is that marketing from companies that dont' really have non-tractor saddles for wider widths? And I'm not picking on Specialized--I've read this elsewhere. Just curious.

[velogirl]

actually, Specialized has wider saddles in their line-up.

but I'm not sure I understand your question completely. try to remember that these are ranges of sizes and simply recommendations. however, Specialized has done a ton of medical-based biomechanics research, so I believe they know what they're doing in this respect.

Lorri (no, I am not a Specialized employee)

[Thorn]

Sorry, Lorri, confusion is, unfortunately, contagious and I apologize for the thread digression....of course, I'm a statistical outlyer. My sit bones measure at about 140mm. I struggle to find a saddle that is wide enough, firm enough and "gets out of the way" where it needs to "get out of the way".

Anyway, I read the specialized chart and for narrow widths, the saddle widths they recommend are much wider than the sit bone measurements. For example, for 100-130mm, the saddle width (143-155mm) is wider than the widest range. Makes sense. You want to sit on saddle, not the edges.

But then when the sit bone width gets into my range, the saddle width is not always wider than the sit bones. So, I guess my question is, given that you've been fitting people, have you ever fitted someone in the wider sit bone range successfully on a 155mm? My question is more curiousity (e.g., how far of an outlyer am I?) than anything else.

I guess this is the same as lattae's question. The chart gives ranges. Do you start there? Or do you have a rule of thumb you use?

I've toyed with trying one of the 155mm saddles, but I've been unsuccessful on wider Terry's so I'm more than a bit wary.

[Beane]

Couple of things:

1) Trek has a butt-o-meter now too (a friend of a friend was on the design team for their new saddles)

2) I did the specialized measurer thing and was told to buy a 143. I liked it for a while, but no more. The saddle is really uncomfortable. At first I thought it was that there wasn't enough padding for the sit bones, but now I'm thinking that the saddle is a bit too narrow. So I guess my question is: what are the chances that the size they sold me was wrong?

[KnottedYet]

My sits are 170-180mm wide. (depending how forward tilted or "aero" I am)

No kidding.

I work in pelvic rehab, I am friends with many sit bones. Mine are not terribly unusual.

Got to have a nice talk with a very popular brand division head for road bikes this week at a seminar in San Francisco: their widest women's performance saddle isn't even going to be as wide as my sits, let alone give me 1-2 cm wiggle room to each side. Their idea is that women should be sitting on the rami, not the sit bones. Ummm, lets talk about soft tissue damage, shall we? (pelvic rehab training will scare you right out of the idea of weightbearing on your rami, if you can possibly help it!)

I'll be sticking with my 210mm wide Brooks B67.

[velogirl]

I don't think Specialized is recommending you fit on a saddle narrower than your sit bones. You'll note, the top right of the scale indicates "and wider."

I honestly have never measured a woman who had sit bones wider than 160mm. Most have been in the 130-140mm range.

And yes, these are only guidelines. For example, Specialized would fit me on a 143mm saddle. I've been riding a 130mm saddle since 2004. I like it. When I tried the 143mm saddle I ended up with saddle sores.

The fit process doesn't end when someone leaves my office. I guarantee my fit so if someone isn't happy with their fit or satisfied with their saddle, I will see them again until I can make them happy. And in all the years I've been performing fit, I've only ever needed to see someone again twice.

BTW, I've only been demo-ing Specialized saddles for a year but I've been performing bike fit for the past six years.

Now Knotted, tell me more about pelvic rehab. I sit firmly on my soft tissue (not my sit bones) and have been since I started riding about 10 years ago. I've noticed no negative issues.......what should I be looking for?

[KnottedYet]

If you are comfy on your soft tissues it's likely you are on the rami, which is exactly what the new saddles I saw are designed for. They are curved (top surface) to match the "ideal" rami angle for each sitbone width. (in their case, the sitbone width is only used as an indicator of rami angle)

The guy didn't have their widest new saddle for me to try, to see if it did match my rami angle, darn. (my rami are going to have a VERY shallow angle) It isn't in production yet.

There are an awful lot of important muscle attachments and nerves and blood vessels running around in the rami's neighborhood. If the seat top curve doesn't match the rami right, someone will be weightbearing on just a portion of the rami (not the whole thing, just a small contact point) and battering that point and yanking on the soft stuff. Or if it's completely off, they will be off the rami and into the tender goodies or even the pubic bone.

This weekend I rode a borrowed bike with a different brand women's saddle, which was way too narrow. I was definitely weightbearing on the rami, mostly on just one little spot. I'm a hurtin', and it was only a 10 mile ride. If someone tried one of the newer saddles and didn't know what it should feel like (comfy, like you are VG) I would worry about things like pudendal nerve entrapment and blood flow.

The guy was demo-ing with a female pelvis model and a sample of the 146mm saddle, and I was cringing at the thought of damage to those of us who don't match the statistics.

I was impressed that saddle designers are finally getting away from the oat-bran trendiness of over padded saddles and cut outs for women.

[OakLeaf]

I was impressed that saddle designers are finally getting away from the oat-bran trendiness of over padded saddles and cut outs for women.

Do you think that cutouts are always inappropriate? Or just for some women? (I have a hard time picturing where I'd put my very large, um, parts on a saddle without a cutout.)

[KnottedYet]

Do you think that cutouts are always inappropriate? Or just for some women? (I have a hard time picturing where I'd put my very large, um, parts on a saddle without a cutout.)

Oh, no! There are definitely folks and riding styles who need cut outs! What was starting to drive me up the wall was the way the women's saddles were getting gratuitiously over padded and over-cutoutted.

Like some company exec said "here, copy this Terry saddle for me, but make it more padded cuz it looks uncomfortable."

[KnottedYet]

Oh, and as far as statistics and sitbone widths I see; my sample is biased in that I'm seeing the women who have pelvic problems already. The ones who've always been miserable on a bike and never got into riding because it hurt too much.

They couldn't find equipment to fit them, so they never fell in love with riding, never got into a group like Velo Girls, never went to a coach for a fit, AND since they weren't serious bikers they never got included in the statistical samples used to design saddles.

It drives me nuts.

[velogirl]

this is interesting, Knotted. one of the participants @ the Women's Leadership Conference @ USA Cycling shared some information with us about her recent prolapse and the Manchester Procedure and basically told us that pelvic floor failure is more common with cyclists than we think. I don't really have any information about that, but I do know some women who've ridden for extended periods (8-10 years) who have suffered some sensory loss, incontinence, etc.

Hypothetically, do you think there's a relationship here?

Lorri

ps -- I can't ride a saddle without a cutout....

[Nokomis]

Like Knotted, I am also riding a Brooks, B68 - and I haven't found any other saddle that actually let me sit On the sit bones. (Okay, I lie - but I'm not about to put a phone book sized cruiser saddle on my road bike.) When I ride a standard saddle, even the wide ol' 155+ from Specialized - ow the pain! It hurts to walk or sit for days after - and introduces significant tailbone pain, plus numb toes & hands. Even tho my Brooks isn't 100% ideal and doesn't always dissapear beneath me, it's unreal the difference to be supported correctly on a saddle. I wish I could buy a saddle with a similar fit from some of the other manufacturers, as I'm a little nervous to abuse the leather in cross season.

[Andrea]

I have to 2nd the motion that cutouts & tons of padding stink!

I have 160mm seatbones (according to the new Trek measurement thing). Most of the saddles in that size are padded to he** and back with some sort of cutout. They are comfy at first until the padding breaks down and starts to squish the cutout closed... with your soft tissue inside :eek:

I need SOME sort of relief up there (which is why the Brooks never worked for me- way too much pressure when in the drops), but having that relief clogged up by excess foam is almost as bad as nothing at all!

I'm still waiting for someone to come out with the perfect saddle- very wide, minimally padded, relatively T shaped, with a channel or cutout for pressure relief. Under 300g would be nice, too since I'm spending so much to make the remaining parts of my bike lighter...

[mimitabby]

Great thread.
I am a brooks b67 rider, my sit bones measure apparently about 140 cm (using paper, ruler and fingers), but i've tried a lot of different saddles only to go back to the old safe and true. Yes, sometimes I get sore (from a deep pothole bump for example) but I can sit for hours without irritating delicate tissues.

[Cindyloo]

Their idea is that women should be sitting on the rami, not the sit bones.


OK, I finally gave up an googled "rami". I wasn't sure if it was a slang term that would pop up something to get me in trouble at work. :eek:

This explains it nicely: http://en.wikipedia.org/wiki/Superior_pubic_ramus

[VeloVT]

OK, I finally gave up an googled "rami". I wasn't sure if it was a slang term that would pop up something to get me in trouble at work. :eek:

This explains it nicely: http://en.wikipedia.org/wiki/Superior_pubic_ramus

Thanks Cindyloo, I tried finding a diagram too but for some reason I couldn't.

I think this must be where I sit. My Fizik Arione is very, very comfortable to me, but I'm quite sure it's narrower than my sitbones. I've never measured them, but I'm a pear shape with a wide pelvis (even when I'm thin :D), and I'm sure they're not on the narrow side. But I find this saddle more comfortable than wider ones I've tried, particularly wider saddles that have less of a smooth transition from nose to rear (if there's a pronounced flare I tend to "run into it"), and wider saddles that are less convex than the Arione from side to side. My bf has a 143mm Specialized Alias, which is both significantly wider and has a cutout, and it's much less comfortable to me. This has puzzled me for a while, but maybe this explains it. The Arione must be the perfect shape for my rami :p!

[Beane]

Andrea: from your description, we are looking for similar things, so if you find anything great, let me know.

Knotted: I had my anterior pubic ramus removed ~8 years ago when I had an aneurysmal bone cyst grow in it and break it. (I'm assuming that anterior p.r. and superior p.r. are the same thing) .. So, what does my asymmetry mean for my seat comfort, do you think?

[mimitabby]

BEANE, and you still ride???? (what kind of saddle??)

[Beane]

Yeah, I was told that it was non-weightbearing and that I wouldn't miss it... but maybe the doc wasn't considering my future cycling. I have run the gamut of saddles and have yet to find anything I'm completely happy with. The closest was the old specialized dolce, but mine starting squeaking and was a little too cushy for real road riding.

In the cartoon on the wikipedia page, the bone I'm missing is part 4, right where the "b" is.

[KnottedYet]

The new saddles I was talkin' to the dude in SF about are meant to weightbear on the area where the "c" is on the wiki picture. When I told the head of our pelvic rehab program about the new saddles, her outraged reaction was pretty classic.

Beane - have you tried one of the really wide and sprung unpadded saddles like the Brooks, or maybe the Selle An-Atomica? Kinda seems like the less mechanical shock you can get into the pelvis, and the more you can weightbear back onto the actual tuberosity, the more stable you'll be. I'm trying to think of ways to compress the area of the missing bone as opposed to forcing it open more (wb on the corner of the triangle rather than on the middle of one of the legs of the triangle. your available wbing corners are the ischial tuberosity and the pubic symphisis. i'd be inclined to try the ischial tub first, but you might consider up near the symphisis) You might also consider trying the new Trek women's saddles when they come out. If you can get one that actually lets you weighbear along the entire length of the inferior ramus, it might be even more stable than anything else. (maybe try a couple sizes and see which works best)

VG - oh, yeah, I think there's a relationship between poor saddle fit and later pelvic issues. The problem from an industry standpoint (as far as I'm concerned) is that once these cyclists are so damaged that they can no longer ride, they fall off the radar of the bike companies. So, no-one is designing the saddle that would have kept my otherwise very healthy 65 year old patient riding. She's old, she's only a woman, she doesn't ride; so she doesn't count in the industry bean-counter's eyes. But a more pear-shaped or more T-shaped or wider cantle or narrower nose or SOMETHING might have kept her from injury and she'd still be riding now.
(and she wouldn't be spending so much quality time with me talking about pee and poop and adult diapers and numbness) (or if she had to anyway because of genetics or posture habits or having birthed 4 kids, she'd at least have a saddle that let her ride despite her pelvic difficulties)

[Thorn]

The new saddles I was talkin' to the dude in SF about are meant to weightbear on the area where the "c" is on the wiki picture.

Owie!!!! Really? That hurts just thinking about it--brings back memories of that original ill-fitting saddle that taught me what it feels like when you ride a saddle that is too narrow. OK, I suppose maybe if they got the angle completely right, but it would definitely need a great cutout...and, just why would I trust them to get all of it right?

But, I digress, thank you very much, Knot, for your explanations. I'm in a forever loop of looking for the right saddle. You've armed me (?saddled me?) with more information as I continue my quest. Always informative and helpful. Thanks.

Any mechanical engineers out there? Perhaps the custom saddle business is prime for the pickin's?

[Andrea]

Beane-

My LBS told me that the new Trek line will have a less poofy saddle available in wider sizes, so I've got my fingers crossed! They have a couple of men's saddles in that look interesting that I may try in the meantime.

[mimitabby]

Knot, can't your patient get a recumbent?

[KnottedYet]

Yup, that option is always out there. But why not keep all options open? Let's start a custom bike saddle business! I'm game! :D

BTW: patient details have been altered to protect patient privacy.

[prm]

Hi Lattae and ladies,

Forgive my intrusion into your forum as a bike tech (male 140lbs) just discovered your posts.
The problem of sit bone anatomy arises daily for women.

Saddle design has improved over the last 5-10 years but remains a problem for certain bum sizes and body weights due to some manufactures adopting a fit-all policy. Where overall construction for safety standards, is measured for rider weights of around 200-220lbs.

I won’t go into detail regarding the differences of male/female saddle designs, soft tissues and cutouts, but a simple test to identify your sit bone dimensions may help with narrowing down your choice of saddles

If you can find a small hard flat topped table (coffee table works well) at a height, where your legs and feet are normally positioned with the pedals at 3 and 9 o-clock.

Sit on the table until you can only feel your sit bones. Rotate your rear end to get the idea of the area needed to be identified.

Place a sheet of non-glossy A4 paper on the table, followed by two layers of tissue on top. Spray a fine water mist to dampen the tissue paper and place another sheet of A4 on top. Sit down and then rotate slightly. If you draw an approximate circle around the two dampened areas on the A4 sheets this should give you a guide to your sit bone centre lines and pressure areas. You can repeat the same test with body angle positioned for bars, hoods and drops, to give an overall picture of the support required.

Hope this may help

[TxDoc]

I've been fitting women (and men) on Specialized saddles for over a year now. I have a saddle demo program with my bike fits. I'd say 60% of the women I fit on a 143mm saddle, 30% on a 155mm and 10% on a 130mm.

10% only? :confused:
I guess I belong to the minority!!! My saddles are 124 and 130...
:D

[dianne_1234]

Found this in my old uni notes and wanted to post it here for easy reference:

Ischial Tuberosity Spacing among women:
5th percentile 112 mm
50th percentile 130 mm
95th percentile 148 mm

Ischial Tuberosity Spacing among men:
5th percentile 100 mm
50th percentile 118 mm
95th percentile 137 mm

I don't remember the population this data was taken from, but I remember being under the impression that it was a very large number of individuals and it was considered "safe" to assume it might represent the whole world.

I've used this info to help narrow the search - once I learned I was wider the 95th percentile(!) I stopped bothering with a lot of narrow saddles.