Sit bones

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Urticaria
Posts: 158
Joined: 21 Jul 2013, 12:02pm

Sit bones

Post by Urticaria »

It's often mentioned that our ischial tuberosities or sit bones should bear our weight when sitting. These are, on average, 12mm closer together in men than in women, and a typical range for men would be 100 to 140mm. We are also told that a reasonable saddle should be slightly wider (perhaps 20mm?) than our sit bone separation, for comfort.

A couple of things are puzzling me:
1) saddles roll downwards towards the edges, so even if the saddle is wider than my sit bone separation, they are unlikely to bearing the full brunt of my weight. So why don't we make saddles that are flat across the back of the seat? Or, with saddles that have a cut out channel, why isn't the separation distance of the peak heights the important measurement rather than saddle width?

2) I've never not sat down on a chair because it was too wide, "Oh, I couldn't possibly be comfortable in that luxurious armchair.Just look at the miniscule size of my bum."
So other than a tiny weight penalty, what harm would there be in just having a 20cm wide saddle, say, for all people and styles of riding?

As far as I can see, nose widths are not scaled to saddle widths by manufacturers, so inter-leg distances and the associated rubbing can't be affecting saddle choice.
axel_knutt
Posts: 2881
Joined: 11 Jan 2007, 12:20pm

Re: Sit bones

Post by axel_knutt »

Urticaria wrote:why don't we make saddles that are flat across the back of the seat? Or, with saddles that have a cut out channel


I bought my WTB Pure V Pro because it does.

Radio 4 Inside Health covered sex and the saddle recently. The link on their website looks like interesting research, but it's rendered a bit pointless by failing to get the punters perched in the correct place on the saddles.

http://www.bbc.co.uk/programmes/b048l0sm
http://www.cdc.gov/niosh/docs/wp-soluti ... 09-131.pdf
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche
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531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Sit bones

Post by 531colin »

yeah, but you don't pedal an armchair.
If a saddle is too wide, or too flat, the corners poke my bum when my leg is at the bottom.
I'm talking about the difference between a B17 narrow and a B17 standard, not monster fat things.
bikepacker
Posts: 2273
Joined: 5 Jan 2007, 7:08pm
Location: Worcestershire
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Re: Sit bones

Post by bikepacker »

Urticaria wrote:It's often mentioned that our ischial tuberosities or sit bones should bear our weight when sitting. These are, on average, 12mm closer together in men than in women, and a typical range for men would be 100 to 140mm. We are also told that a reasonable saddle should be slightly wider (perhaps 20mm?) than our sit bone separation, for comfort.

A couple of things are puzzling me:
1) saddles roll downwards towards the edges, so even if the saddle is wider than my sit bone separation, they are unlikely to bearing the full brunt of my weight. So why don't we make saddles that are flat across the back of the seat? Or, with saddles that have a cut out channel, why isn't the separation distance of the peak heights the important measurement rather than saddle width?

2) I've never not sat down on a chair because it was too wide, "Oh, I couldn't possibly be comfortable in that luxurious armchair.Just look at the miniscule size of my bum."
So other than a tiny weight penalty, what harm would there be in just having a 20cm wide saddle, say, for all people and styles of riding?

As far as I can see, nose widths are not scaled to saddle widths by manufacturers, so inter-leg distances and the associated rubbing can't be affecting saddle choice.


Since my Bursitis problem and the subsequent failure of the treatment I have been using one of these saddles: http://www.sq-lab.com/en/sqlab-products ... 8uU1BNwbcs

It is a saddle similar to what you describe having a flat seat and full width. Using one on my recent coastal tour of Scotland I found it to be comfortable even considering my seat bone problem.
There is your way. There is my way. But there is no "the way".
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Sweep
Posts: 8444
Joined: 20 Oct 2011, 4:57pm
Location: London

Re: Sit bones

Post by Sweep »

Just to say that you should very definitely be putting the weight on your sitbones.

If you encounter serious pain stop and adjust the saddle and if none of that helps change the saddle.

It's a very complicated issue (possibly because different arses and periniums are different) and even cut-out saddles can cause their own problems depending on the interface with different individuals.
Sweep
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