measuring sit bones

[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?

[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.

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

[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?
I guess I belong to the minority!!! My saddles are 124 and 130...

[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.